View source for Weather forecasting

{{Short description|Application of science and technology}}
{{Use mdy dates|date=March 2025}}
[[File:Day5pressureforecast.png|thumb|right|250 px|Forecast of surface pressures five days into the future for the North Pacific, North America, and the [[North Atlantic Ocean]]]]
{{Weather}}

'''Weather forecasting''' or '''weather prediction''' is the application of science and technology [[forecasting|to predict]] the conditions of the [[Earth's atmosphere|atmosphere]] for a given location and time. People have attempted to predict the weather informally for thousands of years and formally since the 19th century.

Weather forecasts are made by collecting quantitative data about the current state of the atmosphere, land, and ocean and using [[meteorology]] to project how the atmosphere will change at a given place. Once calculated manually based mainly upon changes in [[atmospheric pressure|barometric pressure]], current weather conditions, and sky conditions or cloud cover, weather forecasting now relies on [[numerical weather prediction|computer-based models]] that take many atmospheric factors into account.<ref>{{cite journal|last1=Dirmeyer|first1=Paul A.|last2=Schlosser|first2=C. Adam|last3=Brubaker|first3=Kaye L.|title=Precipitation, Recycling, and Land Memory: An Integrated Analysis|journal=Journal of Hydrometeorology|date=February 1, 2009|volume=10|issue=1|pages=278–288|doi=10.1175/2008JHM1016.1|bibcode=2009JHyMe..10..278D |hdl=1721.1/52326|s2cid=14539938 |url=https://dspace.mit.edu/bitstream/1721.1/52326/1/Dirmeyer-2009-Precipitation%2c%20Recyc.pdf|hdl-access=free}}</ref> Human input is still required to pick the best possible model to base the forecast upon, which involves pattern recognition skills, [[teleconnection]]s, knowledge of model performance, and knowledge of model biases.

The inaccuracy of forecasting is due to the [[chaos theory|chaotic]] nature of the atmosphere; the massive computational power required to solve the equations that describe the atmosphere, the land, and the ocean, the error involved in measuring the initial conditions, and an incomplete understanding of atmospheric and related processes. Hence, forecasts become less accurate as the difference between the current time and the time for which the forecast is being made (the ''range'' of the forecast) increases. The use of ensembles and model consensus helps narrow the error and provide confidence in the forecast.

There is a vast variety of end uses for weather forecasts. [[Weather warning]]s are important because they are used to protect lives and property. Forecasts based on temperature and [[precipitation (meteorology)|precipitation]] are important to agriculture, and therefore to traders within commodity markets. Temperature forecasts are used by utility companies to estimate demand over coming days. On an everyday basis, many people use weather forecasts to determine what to wear on a given day. Since outdoor activities are severely curtailed by heavy rain, snow and [[wind chill]], forecasts can be used to plan activities around these events, and to plan ahead and survive them.

Weather forecasting is a part of the economy. For example, in 2009, the US spent approximately $5.8&nbsp;billion on it, producing benefits estimated at six times as much.<ref>{{cite book |title=Fostering Innovation, Creating Jobs, Driving Better Decisions: The Value of Government Data |date=July 2014 |publisher=Economics and Statistics Administration Office of the Chief Economist |page=15 |url=http://www.esa.doc.gov/Reports/fostering-innovation-creating-jobs-driving-better-decisions-value-government-data |access-date=December 30, 2018 |archive-url=https://web.archive.org/web/20180829083453/http://www.esa.doc.gov/reports/fostering-innovation-creating-jobs-driving-better-decisions-value-government-data |archive-date=August 29, 2018 |url-status=dead  }}</ref>

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== History ==
{{Main|Timeline of meteorology}}

===Ancient forecasting===
In 650&nbsp;BC, the [[Babylonia]]ns predicted the weather from cloud patterns as well as [[astrology]]. In about 350&nbsp;BC, [[Aristotle]] described weather patterns in ''[[Meteorology (Aristotle)|Meteorologica]]''.<ref>{{Cite web|url=http://teachersinstitute.yale.edu/curriculum/units/1994/5/94.05.01.x.html|title=94.05.01: Meteorology|website=teachersinstitute.yale.edu|access-date=January 14, 2020|archive-date=January 27, 2020|archive-url=https://web.archive.org/web/20200127092756/http://teachersinstitute.yale.edu/curriculum/units/1994/5/94.05.01.x.html|url-status=live}}</ref> Later, [[Theophrastus]] compiled a book on weather forecasting, called the ''Book of Signs''.<ref>{{Cite web|url=https://www.infoplease.com/math-science/weather/weather-forecasting-from-the-beginning|title=Weather: Forecasting from the Beginning|website=InfoPlease|access-date=January 14, 2020|archive-date=January 31, 2017|archive-url=https://web.archive.org/web/20170131030233/http://www.infoplease.com/cig/weather/forecasting-from-beginning.html|url-status=live}}</ref> Chinese weather prediction lore extends at least as far back as 300&nbsp;BC,<ref>[[University of California]] Museum of Paleontology. [http://www.ucmp.berkeley.edu/history/aristotle.html "Aristotle (384-322&nbsp;B.C.E.)] {{Webarchive|url=https://web.archive.org/web/20161120124920/http://www.ucmp.berkeley.edu/history/aristotle.html |date=November 20, 2016 }}". Retrieved January 12, 2008.</ref> which was also around the same time ancient [[Indian astronomy|Indian astronomers]] developed weather-prediction methods.<ref>{{cite web|title=The Indian and Pseudo-indian Passages in Greek and Latin Astronomical and Astrological Texts|author=David Pingree|pages=141–195 [143–4]|url=http://brepols.metapress.com/content/6861608670636388/fulltext.pdf|access-date=March 1, 2010|date=December 14, 2017|author-link=David Pingree}}{{dead link|date=January 2018 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> In the [[New Testament]], Jesus is quoted as referring to deciphering and understanding local weather patterns, by saying, "When evening comes, you say, 'It will be fair weather, for the sky is red', and in the morning, 'Today it will be stormy, for the sky is red and overcast.' You know how to interpret the appearance of the sky, but you cannot interpret the signs of the times."<ref>{{Cite web|url=https://www.biblegateway.com/passage/?search=Matthew+16:2-3&version=ESV|title=Bible Gateway passage: Matthew 16:2–3 – English Standard Version|website=Bible Gateway|access-date=December 1, 2016|archive-date=December 1, 2016|archive-url=https://web.archive.org/web/20161201143801/https://www.biblegateway.com/passage/?search=Matthew+16:2-3&version=ESV|url-status=live}}</ref>

In 904&nbsp;AD, [[Ibn Wahshiyya]]'s ''[[Nabatean Agriculture]]'', translated into Arabic from an earlier [[Aramaic]] work,<ref>{{cite journal|last1=Carrara|first1=A.A|title=Geoponica and Nabatean Agriculture: A New Approach into Their Sources and Authorship|journal=Arabic Sciences and Philosophy|volume=16|issue=1|pages=123–130|doi=10.1017/s0957423906000245|year=2006|s2cid=170931904}}</ref> discussed the weather forecasting of atmospheric changes and signs from the planetary astral alterations; signs of rain based on observation of the [[lunar phase]]s; and weather forecasts based on the movement of winds.<ref>{{Cite book|last=Fahd|first=Toufic|page=842|title=Encyclopedia of the History of Arabic Science}}, in {{Cite book |last1=Rashed |first1=Roshdi |last2=Morelon |first2=Régis |year=1996 |title=Encyclopedia of the History of Arabic Science |volume=3 |publisher=[[Routledge]] |isbn=978-0-415-12410-2 |pages=813–852|title-link=Encyclopedia of the History of Arabic Science }}</ref>

Ancient weather forecasting methods usually relied on observed patterns of events, also termed pattern recognition. For example, it was observed that if the sunset was particularly red, the following day often brought fair weather. This experience accumulated over the generations to produce [[weather lore]]. However, not all{{which|date=April 2015}} of these predictions prove reliable, and many of them have since been found not to stand up to rigorous statistical testing.<ref name=Skywatch>{{cite web |author=Jerry Wilson |url=http://wilstar.com/skywatch.htm#indicators |title=Skywatch: Signs of the Weather |access-date=May 25, 2008 |url-status=dead |archive-url=https://archive.today/20130106041039/http://wilstar.com/skywatch.htm#indicators |archive-date=January 6, 2013 }}</ref>

===Modern methods===
[[File:StateLibQld 1 186783 Royal Charter (ship).jpg|thumb|The ''Royal Charter'' sank in an October 1859 storm, stimulating the establishment of modern weather forecasting.]]
It was not until the invention of the [[Electrical telegraph|electric telegraph]] in 1835 that the modern age of weather forecasting began.<ref name=":0">{{cite web |author=David Hochfelder |year=1998 | url=http://www.si.edu/archives/ihd/jhp/joseph20.htm| title=Joseph Henry: Inventor of the Telegraph? |publisher=Smithsonian Institution | access-date=June 29, 2006 |archive-url = https://web.archive.org/web/20060626163000/http://www.si.edu/archives/ihd/jhp/joseph20.htm |archive-date = June 26, 2006}}</ref> Before that, the fastest that distant weather reports could travel was around 160 kilometres per day (100&nbsp;mi/d), but was more typically 60–120 kilometres per day (40–75&nbsp;mi/day) (whether by land or by sea).<ref name="USPS History">{{cite web|last=Ausman|first=Megaera|title=USPS Historian|url=http://about.usps.com/who-we-are/postal-history/overland-mail.htm|work=About the United States Postal Service|publisher=USPS|access-date=April 28, 2013|archive-date=March 30, 2013|archive-url=https://web.archive.org/web/20130330073121/http://about.usps.com/who-we-are/postal-history/overland-mail.htm|url-status=dead}}</ref><ref name="Royal Mail coaches">{{cite web|last=Mail|first=Royal|title=(UK)|url=http://postalheritage.org.uk/page/Mail-Coaches|work=British Postal Museum|publisher=Postal Heritage Trust|access-date=April 28, 2013|archive-url=https://web.archive.org/web/20130318021542/http://www.postalheritage.org.uk/page/mail-coaches|archive-date=March 18, 2013|url-status=dead}}</ref> By the late 1840s, the telegraph allowed reports of weather conditions from a wide area to be received almost instantaneously,<ref>Encyclopædia Britannica. [http://www.britannica.com/eb/topic-585850/telegraph "Telegraph"] {{Webarchive|url=https://web.archive.org/web/20070929133128/http://www.britannica.com/eb/topic-585850/telegraph |date=September 29, 2007 }}. Retrieved May 5, 2007.</ref> allowing forecasts to be made from knowledge of weather conditions further [[Windward and leeward|upwind]].

The two men credited with the birth of forecasting as a science were an officer of the [[Royal Navy]] [[Francis Beaufort]] and his [[protégé]] [[Robert FitzRoy]]. Both were influential men in [[United Kingdom of Great Britain and Ireland|British]] naval and governmental circles, and though ridiculed in the press at the time, their work gained scientific credence, was accepted by the Royal Navy, and formed the basis for all of today's weather forecasting knowledge.<ref>{{cite web | author = Eric D. Craft |year=2003 | title = An Economic History of Weather Forecasting | archive-url = https://web.archive.org/web/20070503193324/http://eh.net/encyclopedia/article/craft.weather.forcasting.history | archive-date = May 3, 2007 | url = https://eh.net/encyclopedia/an-economic-history-of-weather-forecasting/ | access-date =April 15, 2007}}</ref><ref name="BBC">{{cite news |title=The birth of the weather forecast |url=https://www.bbc.co.uk/news/magazine-32483678 |work=BBC News |date=April 30, 2015 |access-date=April 30, 2015 |archive-date=May 3, 2015 |archive-url=https://web.archive.org/web/20150503001458/http://www.bbc.co.uk/news/magazine-32483678 |url-status=live }}</ref>

Beaufort developed the [[Beaufort scale|Wind Force Scale]] and Weather Notation coding, which he was to use in his journals for the remainder of his life. He also promoted the development of reliable tide tables around British shores, and with his friend [[William Whewell]], expanded weather record-keeping at 200 British [[coast guard]] stations.

[[Robert FitzRoy]] was appointed in 1854 as chief of a new department within the [[Board of Trade]] to deal with the collection of weather data at sea as a service to [[sailor|mariners]]. This was the forerunner of the modern [[Met Office|Meteorological Office]].<ref name="BBC"/> All ship captains were tasked with collating data on the weather and computing it, with the use of tested instruments that were loaned for this purpose.<ref name="Mellersh, H. E. L. 1968">Mellersh, H. E. L. (1968). FitzRoy of the Beagle. Hart-Davis. {{ISBN|0-246-97452-4}}</ref>

[[File:Weather map of Europe MKL Bd. 16 1890 (128535969).jpg|left|thumb|Weather map of Europe, December 10, 1887]]
A storm in October 1859 that caused the loss of the [[Royal Charter (ship)|''Royal Charter'']] inspired FitzRoy to develop charts to allow predictions to be made, which he called "forecasting the weather", thus coining the term "weather forecast".<ref name="Mellersh, H. E. L. 1968"/> Fifteen land stations were established to use the [[telegraph]] to transmit to him daily reports of weather at set times leading to the first gale warning service. His warning service for shipping was initiated in February 1861, with the use of [[electric telegraph|telegraph communications]]. The first daily weather forecasts were published in ''[[The Times]]'' in 1861.<ref name="BBC"/> In the following year a system was introduced of hoisting storm warning cones at the principal ports when a gale was expected.<ref name="Kington">{{Cite book|title=Climates of the British Isles: Present, Past and Future|first=John|last=Kington|editor=Mike Hulme and Elaine Barrow|year=1997|publisher=Routledge|page=147}}</ref> The ''"Weather Book"'' which FitzRoy published in 1863 was far in advance of the scientific opinion of the time.

As the electric telegraph network expanded, allowing for the more rapid dissemination of warnings, a national observational network was developed, which could then be used to provide synoptic analyses. To shorten detailed weather reports into more affordable telegrams, senders encoded weather information in [[Telegraph code|telegraphic code]], such as the one developed by the [[U.S. Army Signal Corps]].<ref>{{cite news |title=A woman bought a vintage dress at an antique store. It had a secret pocket with a mysterious note |first=Faith |last=Karimi |publisher=CNN |date=January 15, 2024 |url=https://edition.cnn.com/2024/01/15/us/antique-dress-maine-encrypted-message-cec/index.html |access-date=January 17, 2024 |archive-date=January 16, 2024 |archive-url=https://web.archive.org/web/20240116233400/https://edition.cnn.com/2024/01/15/us/antique-dress-maine-encrypted-message-cec/index.html |url-status=live }}</ref> Instruments to continuously record variations in meteorological parameters using [[Photography#Science and forensics|photography]] were supplied to the observing stations from [[King's Observatory|Kew Observatory]] – these cameras had been invented by [[Francis Ronalds]] in 1845 and his [[barograph]] had earlier been used by FitzRoy.<ref>{{Cite book|title=Sir Francis Ronalds: Father of the Electric Telegraph|last=Ronalds|first=B. F.|publisher=Imperial College Press|year=2016|isbn=978-1-78326-917-4|location=London}}</ref><ref>{{Cite journal|last=Ronalds|first=B. F.|date=June 2016|title=Sir Francis Ronalds and the Early Years of the Kew Observatory|journal=Weather|volume=71|issue=6|pages=131–134|doi=10.1002/wea.2739 |bibcode=2016Wthr...71..131R|s2cid=123788388 }}</ref>

To convey accurate information, it soon became necessary to have a standard vocabulary describing clouds; this was achieved by means of a series of classifications first achieved by [[Luke Howard (meteorologist)|Luke Howard]] in 1802, and standardized in the ''[[International Cloud Atlas]]'' of 1896.

===Numerical prediction===
{{Main|History of numerical weather prediction}}
[[File:Improved-weather-forecasting 7463.png|thumb|The difference between the forecast and the actual weather outcome for forecasts 3, 5, 7, and 10 days in advance.]]
It was not until the 20th century that advances in the understanding of atmospheric physics led to the foundation of modern [[numerical weather prediction]]. In 1922, English scientist [[Lewis Fry Richardson]] published "Weather Prediction By Numerical Process",<ref>Richardson, Lewis Fry, ''Weather Prediction by Numerical Process'' (Cambridge, England: Cambridge University Press, 1922). Available on-line at: [https://archive.org/stream/weatherpredictio00richrich#page/n7/mode/2up Internet Archive.org].</ref> after finding notes and derivations he worked on as an ambulance driver in World War I. He described therein how small terms in the prognostic fluid dynamics equations governing atmospheric flow could be neglected, and a finite differencing scheme in time and space could be devised, to allow numerical prediction solutions to be found.

Richardson envisioned a large auditorium of thousands of people performing the calculations and passing them to others. However, the sheer number of calculations required was too large to be completed without the use of computers, and the size of the grid and time steps led to unrealistic results in deepening systems. It was later found, through numerical analysis, that this was due to [[numerical instability]].<ref>[[Peter Lynch (meteorologist)|Lynch, Peter]] (2006). The Emergence of Numerical Weather Prediction. Cambridge University Press</ref> The first computerised weather forecast was performed by a team composed of American meteorologists [[Jule Charney]], [[Philip Duncan Thompson]], [[Larry Gates]], and Norwegian meteorologist [[Ragnar Fjørtoft]], applied mathematician [[John von Neumann]], and [[ENIAC]] programmer [[Klara Dan von Neumann]].<ref>{{cite journal|doi=10.3402/tellusa.v2i4.8607|title=Numerical Integration of the Barotropic Vorticity Equation|journal=Tellus|volume=2|issue=4|pages=237–254|year=1950|last1=Charney|first1=J. G.|last2=Fjörtoft|first2=R.|last3=von Neumann|first3=J.|bibcode=1950Tell....2..237C|doi-access=free}}</ref><ref>{{cite magazine |last1=Witman |first1=Sarah |title=Meet the Computer Scientist You Should Thank For Your Smartphone's Weather App |url=http://www.smithsonianmag.com/science-nature/meet-computer-scientist-you-should-thank-your-phone-weather-app-180963716/ |magazine=Smithsonian |date=June 16, 2017 |access-date=July 22, 2017 |archive-date=April 21, 2019 |archive-url=https://web.archive.org/web/20190421001535/https://www.smithsonianmag.com/science-nature/meet-computer-scientist-you-should-thank-your-phone-weather-app-180963716/ |url-status=live }}</ref><ref>{{cite book|last=Edwards|first=Paul N.|title=A Vast Machine: Computer Models, Climate Data, and the Politics of Global Warming|year=2010|publisher=The MIT Press|isbn=978-0262013925|url=http://mitpress.mit.edu/catalog/item/default.asp?ttype=2&tid=12080|url-status=dead|archive-url=https://web.archive.org/web/20120127215929/http://mitpress.mit.edu/catalog/item/default.asp?ttype=2&tid=12080|archive-date=January 27, 2012}}</ref> Practical use of numerical weather prediction began in 1955,<ref>Paul N. Edwards. [http://www.aip.org/history/sloan/gcm/ "Atmospheric General Circulation Modeling"]. {{webarchive|url=https://web.archive.org/web/20080325084036/http://www.aip.org/history/sloan/gcm/ |date=March 25, 2008 }} Retrieved February 16, 2007.</ref> spurred by the development of programmable electronic computers.

===Broadcasts===
{{see also|Weather presenter}}

The first ever daily weather forecasts were published in ''[[The Times]]'' on August 1, 1861, and the first [[weather map]]s were produced later in the same year.<ref>{{cite web |author=Helen Czerski |date=August 1, 2011 |url=https://www.bbc.co.uk/blogs/23degrees/2011/08/150_years_since_the_first_uk_w.html |title=Orbit: Earth's Extraordinary Journey: 150 years since the first UK weather "forecast" |publisher=BBC |access-date=November 5, 2013 |archive-date=March 27, 2023 |archive-url=https://web.archive.org/web/20230327100419/https://www.bbc.co.uk/blogs/23degrees/2011/08/150_years_since_the_first_uk_w.html |url-status=live }}</ref> In 1911, the [[Met Office]] began issuing the first marine weather forecasts via radio transmission. These included gale and storm warnings for areas around Great Britain.<ref>{{cite web|url=http://www.metoffice.gov.uk/media/pdf/1/f/Fact_sheet_No._8.pdf|title=National Meteorological Library and Fact Sheet 8 – The Shipping Forecast|author=Met Office|date=2012|version=1|pages=3–5|access-date=April 10, 2013|archive-date=July 5, 2016|archive-url=https://web.archive.org/web/20160705110246/http://www.metoffice.gov.uk/media/pdf/1/f/Fact_sheet_No._8.pdf|url-status=live}}</ref> In the United States, the first public radio forecasts were made in 1925 by Edward B. "E.B." Rideout, on [[WEZE|WEEI]], the Edison Electric Illuminating station in Boston.<ref name="cyc">{{cite encyclopedia |url=http://www.encyclopedia.com/doc/1G2-3401802621.html |title=meteorology Facts, information, pictures &#124; Encyclopedia.com articles about meteorology |encyclopedia=Encyclopedia.com |access-date=February 21, 2014 |archive-date=March 1, 2010 |archive-url=https://web.archive.org/web/20100301201545/http://www.encyclopedia.com/doc/1G2-3401802621.html |url-status=live }}</ref> Rideout came from the [[National Weather Service|U.S. Weather Bureau]], as did [[WBZ (AM)|WBZ]] weather forecaster G. Harold Noyes in 1931.

[[File:BBC television weather chart - 1936-11-13.jpg|thumb|BBC television weather chart for November 13, 1936]]

The world's first [[Live television|televised]] weather forecasts, including the use of weather maps, were experimentally broadcast by the [[BBC]] in November 1936.<ref name="BBC-60154358">{{cite news |title=BBC Centenary: BBC Weather's most memorable moments - BBC Weather |url=https://www.bbc.co.uk/weather/features/60154358 |access-date=February 12, 2022 |archive-date=February 11, 2022 |archive-url=https://web.archive.org/web/20220211202542/https://www.bbc.co.uk/weather/features/60154358 |url-status=live }}</ref> This was brought into practice in 1949, after [[World War II]].<ref name="BBC-60154358" /> [[George Cowling]] gave the first weather forecast while being televised in front of the map in 1954.<ref>{{Cite news|url=http://news.bbc.co.uk/weather/hi/about/newsid_7833000/7833282.stm |title=BBC – Weather – A history of TV weather forecasts|archive-url=https://web.archive.org/web/20130102193118/http://news.bbc.co.uk/weather/hi/about/newsid_7833000/7833282.stm|website=BBC Weather|archive-date=January 2, 2013}}</ref><ref name="HUNT">{{cite journal|doi=10.1002/wea.81|title=The end of weather forecasting at Met Office London|journal=Weather|volume=62|issue=6|pages=143–146|year=2007|last1=Hunt|first1=Roger|bibcode=2007Wthr...62..143H|s2cid=122103141 |doi-access=}}</ref> In America, experimental television forecasts were made by [[James C. Fidler]] in Cincinnati in either 1940 or 1947{{clarify|date=January 2023}} on the [[DuMont Television Network]].<ref name="cyc" /><ref>{{cite news | url=https://www.usatoday.com/weather/wforund.htm | title=Answers: Understanding weather forecasts | date=February 8, 2006 | work=USA Today | access-date=September 18, 2017 | archive-date=August 13, 2012 | archive-url=https://web.archive.org/web/20120813060637/http://www.usatoday.com/weather/wforund.htm | url-status=dead }}</ref> In the late 1970s and early 1980s, [[John Coleman (news weathercaster)|John Coleman]], the first weatherman for the [[American Broadcasting Company]] (ABC)'s ''[[Good Morning America]]'', pioneered the use of on-screen [[weather satellite]] data and [[computer graphics]] for television forecasts.<ref name=CJR>[https://www.cjr.org/behind_the_news/cjr_rewind_hot_air.php CJR Rewind: Hot Air] {{Webarchive|url=https://web.archive.org/web/20161222183542/http://www.cjr.org/behind_the_news/cjr_rewind_hot_air.php |date=December 22, 2016 }}, ''[[Columbia Journalism Review]]'', reprint, first published in the January/February 2010 issue.</ref> In 1982, Coleman partnered with [[Landmark Media Enterprises|Landmark Communications]] CEO [[Frank Batten]] to launch [[The Weather Channel]] (TWC), a 24-hour cable network devoted to national and local weather reports. Some weather channels have started broadcasting on [[Live broadcasting|live streaming platforms]] such as [[YouTube]] and [[Periscope (app)|Periscope]] to reach more viewers.

== Numerical weather prediction ==
[[File:NAM 500 MB.PNG|thumb|An example of 500 [[millibar|mbar]] [[geopotential height]] and absolute [[vorticity]] prediction from a numerical weather prediction model]]
{{Main|Numerical weather prediction}}

The basic idea of numerical weather prediction is to sample the state of the fluid at a given time and use the equations of [[fluid dynamics]] and [[thermodynamics]] to estimate the state of the fluid at some time in the future. The main inputs from country-based weather services are [[Surface weather observation|surface observations]] from automated [[weather station]]s at ground level over land and from weather buoys at sea. The [[World Meteorological Organization]] acts to standardize the instrumentation, observing practices and timing of these observations worldwide. Stations either report hourly in [[METAR]] reports,<ref>[[National Climatic Data Center]]. [http://www.ncdc.noaa.gov/oa/climate/conversion/swometardecoder.html "Key to METAR Surface Weather Observations"] {{Webarchive|url=https://web.archive.org/web/20021101221848/http://www0.ncdc.noaa.gov/oa/climate/conversion/swometardecoder.html |date=November 1, 2002 }}. Retrieved March 9, 2008.</ref> or every six hours in [[SYNOP]] reports.<ref>[[UNISYS]]. [http://weather.unisys.com/wxp/Appendices/Formats/SYNOP.html "SYNOP Data Format (FM-12): Surface Synoptic Observations"]. {{webarchive|url=https://web.archive.org/web/20071230100059/http://weather.unisys.com/wxp/Appendices/Formats/SYNOP.html |date=December 30, 2007 }} Retrieved May 25, 2008.</ref> Sites launch [[radiosonde]]s, which rise through the depth of the [[troposphere]] and well into the [[stratosphere]].<ref>Gaffen, Dian J. (June 7, 2007). [https://web.archive.org/web/20070607142822/http://www.aero.jussieu.fr/~sparc/News12/Radiosondes.html "Radiosonde Observations and Their Use in SPARC-Related Investigations"]. Retrieved May 25, 2008.</ref> Data from [[weather satellite]]s are used in areas where traditional data sources are not available.<ref>[[NASA]]. [http://wwwghcc.msfc.nasa.gov/GOES/globalir.html "Interactive Global Composite Weather Satellite Images"] {{webarchive|url=https://web.archive.org/web/20080531175530/http://wwwghcc.msfc.nasa.gov/GOES/globalir.html |date=May 31, 2008 }}. Retrieved May 25, 2008.</ref><ref>[[NOAA]]. [http://www.goes.noaa.gov/ECIR4.html Goes Eastern US Sector Infrared Image] {{Webarchive|url=https://web.archive.org/web/20080523192007/http://www.goes.noaa.gov/ECIR4.html |date=May 23, 2008 }}. Retrieved May 25, 2008.</ref><ref>[[Met Office]]. [https://archive.today/20070705213142/http://www.metoffice.gov.uk/research/nwp/satellite/ "Satellite applications"]. Retrieved May 25, 2008.</ref> Compared with similar data from radiosondes, the satellite data has the advantage of global coverage, but at a lower accuracy and resolution.<ref>Tony Reale. [http://cimss.ssec.wisc.edu/itwg/itsc/itsc12/presentations/1a4_T.Reale.ppt "ATOVS Sounding Products (ITSVC-12)"] {{Webarchive|url=https://web.archive.org/web/20080910142825/http://cimss.ssec.wisc.edu/itwg/itsc/itsc12/presentations/1a4_T.Reale.ppt |date=September 10, 2008 }}. Retrieved May 25, 2008.</ref> [[Weather radar|Meteorological radar]] provide information on precipitation location and intensity, which can be used to estimate precipitation accumulations over time.<ref>{{Cite web|url=http://www.csu.edu.au/special/bushfire99/papers/treloar/|date=July 1999|archive-url=https://web.archive.org/web/20090607174157/http://www.csu.edu.au/special/bushfire99/papers/treloar/|archive-date=June 7, 2009|title=The use of accumulated rainfall maps from weather radar systems to assist wildfire detection reconnaissance|author=Andrew Treloar and Peter Brookhouse|url-status=dead}}</ref> Additionally, if a [[Pulse-Doppler radar|pulse Doppler]] [[weather radar]] is used then wind speed and direction can be determined.<ref>University of Washington. [http://www.artsci.washington.edu/news/WinterSpring03/Forecast.htm "An improving forecast"]. Retrieved April 15, 2007 {{webarchive|url=https://web.archive.org/web/20071024112614/http://www.artsci.washington.edu/news/WinterSpring03/Forecast.htm |date=October 24, 2007 }}</ref> These methods, however, leave an in-situ observational gap in the lower atmosphere (from 100 m to 6&nbsp;km above ground level). To reduce this gap, in the late 1990s [[weather drone]]s started to be considered for obtaining data from those altitudes. Research has been growing significantly since the 2010s, and weather-drone data may in future be added to numerical weather models.<ref>{{Cite journal |last1=Pinto |first1=James O. |last2=O’Sullivan |first2=Debbie |last3=Taylor |first3=Stewart |last4=Elston |first4=Jack |last5=Baker |first5=C. B. |last6=Hotz |first6=David |last7=Marshall |first7=Curtis |last8=Jacob |first8=Jamey |last9=Barfuss |first9=Konrad |last10=Piguet |first10=Bruno |last11=Roberts |first11=Greg |last12=Omanovic |first12=Nadja |last13=Fengler |first13=Martin |last14=Jensen |first14=Anders A. |last15=Steiner |first15=Matthias |date=November 1, 2021 |title=The Status and Future of Small Uncrewed Aircraft Systems (UAS) in Operational Meteorology |journal=Bulletin of the American Meteorological Society |language=EN |volume=102 |issue=11 |pages=E2121–E2136 |doi=10.1175/BAMS-D-20-0138.1 |bibcode=2021BAMS..102E2121P |s2cid=237750279 |issn=0003-0007|doi-access=free |url=https://hal-meteofrance.archives-ouvertes.fr/meteo-03450993/file/%5B15200477%20-%20Bulletin%20of%20the%20American%20Meteorological%20Society%5D%20The%20Status%20and%20Future%20of%20Small%20Uncrewed%20Aircraft%20Systems%20%28UAS%29%20in%20Operational%20Meteorology-1.pdf }}</ref><ref>{{Cite web |date=November 14, 2022 |title=Workshop on Use of Unmanned Aerial Vehicles (UAV) for Operational Meteorology |url=https://library.wmo.int/doc_num.php?explnum_id=9951 |access-date=November 14, 2022 |website=World Meteorological Organization |archive-date=October 20, 2022 |archive-url=https://web.archive.org/web/20221020192146/https://library.wmo.int/doc_num.php?explnum_id=9951 |url-status=live }}</ref>

[[File:2005-09-22-10PM CDT Hurricane Rita 3 day path.png|thumb|Modern weather predictions aid in timely evacuations and potentially save lives and prevent property damage]]
Commerce provides [[pilot report]]s along aircraft routes,<ref>Ballish, Bradley A. and V. Krishna Kumar (May 23, 2008). [http://amdar.noaa.gov/docs/bams_ballish_kumar.pdf "Investigation of Systematic Differences in Aircraft and Radiosonde Temperatures with Implications for NWP and Climate Studies"] {{Webarchive|url=https://web.archive.org/web/20110721055504/http://amdar.noaa.gov/docs/bams_ballish_kumar.pdf |date=July 21, 2011 }}. Retrieved May 25, 2008.</ref> and ship reports along shipping routes. Research flights using [[weather reconnaissance|reconnaissance aircraft]] fly in and around weather systems of interest such as [[tropical cyclone]]s.<ref name="Hurricane Hunters">{{cite web|author=403rd Wing|year=2011|url=http://www.hurricanehunters.com/|title=The Hurricane Hunters|publisher=[[Hurricane Hunters|53rd Weather Reconnaissance Squadron]]|access-date=March 30, 2006|archive-date=May 30, 2012|archive-url=https://web.archive.org/web/20120530232904/http://www.hurricanehunters.com/|url-status=live}}</ref><ref name="SunHerald">{{cite news|author=Lee, Christopher|date=October 8, 2007|title=Drone, Sensors May Open Path Into Eye of Storm|url=https://www.washingtonpost.com/wp-dyn/content/article/2007/10/07/AR2007100700971_pf.html|newspaper=The Washington Post|access-date=February 22, 2008|archive-date=November 11, 2012|archive-url=https://web.archive.org/web/20121111093844/http://www.washingtonpost.com/wp-dyn/content/article/2007/10/07/AR2007100700971_pf.html|url-status=live}}</ref> Reconnaissance aircraft are also flown over the open oceans during the cold season into systems that cause significant uncertainty in forecast guidance, or are expected to be of high impact three–seven days into the future over the downstream continent.<ref>{{cite web |date=January 12, 2010 |url=http://www.noaanews.noaa.gov/stories2010/20100112_plane.html |title=NOAA Dispatches High-Tech Research Plane to Improve Winter Storm Forecasts |publisher=[[National Oceanic and Atmospheric Administration]] |access-date=December 22, 2010 |archive-date=January 3, 2011 |archive-url=https://web.archive.org/web/20110103152316/http://www.noaanews.noaa.gov/stories2010/20100112_plane.html |url-status=live }}</ref>

Models are ''initialized'' using this observed data. The irregularly spaced observations are processed by [[data assimilation]] and objective analysis methods, which perform quality control and obtain values at locations usable by the model's mathematical algorithms (usually an evenly spaced grid). The data are then used in the model as the starting point for a forecast.<ref>[[University Corporation for Atmospheric Research]] (August 14, 2007). [https://web.archive.org/web/20070814044336/http://www.mmm.ucar.edu/wrf/WG4/wrfvar/wrfvar-tutorial.htm "The WRF Variational Data Assimilation System (WRF-Var)"]. Retrieved May 25, 2008.</ref> Commonly, the set of equations used to predict the physics and dynamics of the atmosphere are called [[primitive equations]]. These are initialized from the analysis data and rates of change are determined. The rates of change predict the state of the atmosphere a short time into the future. The equations are then applied to this new atmospheric state to find new rates of change, which predict the atmosphere at a yet further time into the future. This ''time stepping'' procedure is continually repeated until the solution reaches the desired forecast time.

The length of the time step chosen within the model is related to the distance between the points on the computational grid, and is chosen to maintain [[numerical stability]].<ref>{{cite book|last=Pielke|first=Roger A.|title=Mesoscale Meteorological Modeling|year=2002|publisher=[[Academic Press]]|isbn=978-0-12-554766-6|pages=285–287}}</ref> Time steps for global models are on the order of tens of minutes,<ref>{{cite book|url=https://books.google.com/books?id=JZikIbXzipwC&pg=PA131|page=132|title=Computational Science – ICCS 2005: 5th International Conference, Atlanta, GA, USA, May 22–25, 2005, Proceedings, Part 1|author1=Sunderam, V. S. |author2=van Albada, G. Dick |author3=Peter, M. A. |author4=Sloot, J. J. Dongarra |year=2005 |publisher=Springer |isbn=978-3-540-26032-5}}</ref> while time steps for regional models are between one and four minutes.<ref>{{cite book|url=https://books.google.com/books?id=UV6PnF2z5_wC&pg=PA276|page=276|title=Developments in teracomputing: proceedings of the ninth ECMWF Workshop on the Use of High Performance Computing in Meteorology|author=Zwieflhofer, Walter; Kreitz, Norbert; European Centre for Medium Range Weather Forecasts |year=2001 |publisher=World Scientific |isbn=978-981-02-4761-4}}</ref> The global models are run at varying times into the future. The [[Met Office]]'s [[Unified Model]] is run six days into the future,<ref name="models">{{cite book|pages=295–296|url=https://books.google.com/books?id=6gFiunmKWWAC&pg=PA297|title=Global Perspectives on Tropical Cyclones: From Science to Mitigation|author1=Chan, Johnny C. L. |author2=Jeffrey D. Kepert |name-list-style=amp |year=2010|publisher=World Scientific|isbn=978-981-4293-47-1}}</ref> the [[European Centre for Medium-Range Weather Forecasts]] model is run out to 10&nbsp;days into the future,<ref>{{cite book|url=https://books.google.com/books?id=fhW5oDv3EPsC&pg=PA474|page=480|author=Holton, James R.|title=An introduction to dynamic meteorology, Volume 1|year=2004|publisher=Academic Press |isbn=978-0-12-354015-7 }}</ref> while the [[Global Forecast System]] model run by the [[Environmental Modeling Center]] is run 16&nbsp;days into the future.<ref>{{cite book|url=https://books.google.com/books?id=mTZvR3R6YdkC&pg=PA121|page=121|title=Famine early warning systems and remote sensing data|author=Brown, Molly E.|publisher=Springer|year=2008 |isbn=978-3-540-75367-4|bibcode=2008fews.book.....B}}</ref> The visual output produced by a model solution is known as a [[prognostic chart]], or ''prog''.<ref>{{cite book|author=Ahrens, C. Donald|page=244|isbn=978-0-495-11558-8|year=2008|publisher=Cengage Learning|title=Essentials of meteorology: an invitation to the atmosphere|url=https://books.google.com/books?id=2Yn29IFukbgC&pg=PA244}}</ref> The raw output is often modified before being presented as the forecast. This can be in the form of statistical techniques to remove known [[bias]]es in the model, or of adjustment to take into account consensus among other numerical weather forecasts.<ref>Daniel Andersson (2007). [http://his.diva-portal.org/smash/record.jsf?pid=diva2%3A2675&dswid=-1516 "Improved accuracy of surrogate models using output postprocessing"] {{Webarchive|url=https://web.archive.org/web/20171012045146/http://his.diva-portal.org/smash/record.jsf?pid=diva2%3A2675&dswid=-1516 |date=October 12, 2017 }}. Retrieved May 25, 2008.</ref> MOS or model output statistics is a technique used to interpret numerical model output and produce site-specific guidance. This guidance is presented in coded numerical form, and can be obtained for nearly all National Weather Service reporting stations in the United States. As proposed by [[Edward Lorenz]] in 1963, long range forecasts, those made at a range of two weeks or more cannot definitively predict the state of the atmosphere, owing to the [[chaos theory|chaotic nature]] of the [[fluid dynamics]] equations involved. In numerical models, extremely small errors in initial values double roughly every five days for variables such as temperature and wind velocity.<ref>{{cite book|title=Storm Watchers|pages=[https://archive.org/details/stormwatcherstur00cox_df1/page/222 222–224]|year=2002|author=Cox, John D.|publisher=John Wiley & Sons, Inc.|isbn=978-0-471-38108-2|url=https://archive.org/details/stormwatcherstur00cox_df1/page/222}}</ref>

Essentially, a model is a computer program that produces [[meteorological]] information for future times at given locations and altitudes. Within any modern model is a set of equations, known as the primitive equations, used to predict the future state of the atmosphere.<ref>{{cite book|last=Pielke|first=Roger A.|title=Mesoscale Meteorological Modeling|year=2002|publisher=[[Academic Press]]|isbn=978-0-12-554766-6|pages=48–49}}</ref> These equations—along with the [[ideal gas law]]—are used to evolve the [[density]], [[pressure]], and [[potential temperature]] [[scalar field]]s and the [[velocity]] [[vector field]] of the atmosphere through time. Additional transport equations for pollutants and other [[aerosol]]s are included in some primitive-equation mesoscale models as well.<ref>{{cite book|last=Pielke|first=Roger A.|title=Mesoscale Meteorological Modeling|year=2002|publisher=[[Academic Press]]|isbn=978-0-12-554766-6|pages=18–19}}</ref> The equations used are [[nonlinear system|nonlinear]] partial differential equations, which are impossible to solve exactly through analytical methods,<ref name="finite">{{cite book|url=https://books.google.com/books?id=SH8R_flZBGIC&pg=PA165|title=Finite difference schemes and partial differential equations|author=Strikwerda, John C.|pages=165–170|year=2004|publisher=SIAM|isbn=978-0-89871-567-5}}</ref> with the exception of a few idealized cases.<ref>{{cite book|last=Pielke|first=Roger A.|title=Mesoscale Meteorological Modeling|year=2002|publisher=[[Academic Press]]|isbn=978-0-12-554766-6|page=65}}</ref> Therefore, numerical methods obtain approximate solutions. Different models use different solution methods: some global models use [[spectral method]]s for the horizontal dimensions and [[finite difference method]]s for the vertical dimension, while regional and other global models usually use finite-difference methods in all three dimensions.<ref name="finite"/>

==Techniques==
===Persistence===
The simplest method of forecasting the weather, persistence, relies upon today's conditions to forecast tomorrow's. This can be valid when the weather achieves a steady state, such as during the summer season in the tropics. This method strongly depends upon the presence of a stagnant weather pattern. Therefore, when in a fluctuating pattern, it becomes inaccurate. It can be useful in both short- and long-range forecasts.<ref>University of Illinois at Urbana-Champaign. [http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/fcst/mth/prst.rxml "Persistence Forecasting: Today equals Tomorrow"] {{Webarchive|url=https://web.archive.org/web/20070220120718/http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/fcst/mth/prst.rxml |date=February 20, 2007 }}. Retrieved February 16, 2007.</ref>

===Barometer===
Measurements of barometric pressure and the pressure tendency (the change of pressure over time) have been used in forecasting since the late 19th century.<ref>[[USA Today]]. [https://www.usatoday.com/weather/wbarocx.htm "Understanding air pressure"] {{Webarchive|url=https://web.archive.org/web/20120701185551/https://www.usatoday.com/weather/wbarocx.htm |date=July 1, 2012 }}. Retrieved May 25, 2008.</ref> The larger the change in pressure, especially if more than {{convert|3.5|hPa|mmHg|lk=on|abbr=on}}, the larger the change in weather can be expected. If the pressure drop is rapid, a [[Low pressure area|low pressure system]] is approaching, and there is a greater chance of rain. [[High pressure area|Rapid pressure rises]] are associated with improving weather conditions, such as clearing skies.<ref>Weather Doctor. [http://www.islandnet.com/~see/weather/eyes/barometer3.htm "Applying The Barometer To Weather Watching"] {{Webarchive|url=https://web.archive.org/web/20080509105153/http://www.islandnet.com/~see/weather/eyes/barometer3.htm |date=May 9, 2008 }}. Retrieved May 25, 2008.</ref>

===Observation===
[[File:marestail.jpg|thumb|Marestail shows moisture at high altitude, signalling the later arrival of wet weather.]]
Along with pressure tendency, the condition of the sky is one of the more important parameters used to forecast weather in mountainous areas. Thickening of cloud cover or the invasion of a higher cloud deck is indicative of rain in the near future. High thin [[cirrostratus cloud]]s can create [[halo (optical phenomenon)|halo]]s around the [[sun]] or [[moon]], which indicates an approach of a [[warm front]] and its associated rain.<ref>{{cite magazine |url=https://books.google.com/books?id=KtkDAAAAMBAJ&pg=PA148|magazine=[[Popular Mechanics]] |page=148 |title=Make Your Own Weather Forecasts |author=Dennis Eskow |date=March 1983 |volume=159 |issue=3 |access-date=April 2, 2011}}</ref> Morning [[fog]] portends fair conditions, as rainy conditions are preceded by wind or clouds that prevent fog formation. The approach of a line of [[thunderstorm]]s could indicate the approach of a [[cold front]]. Cloud-free skies are indicative of fair weather for the near future.<ref>Mark Moore (March 25, 2009). [https://web.archive.org/web/20090325034756/http://www.nwac.us/education_resources/Field_forecasting.pdf "Field Forecasting – A Short Summary"]. Retrieved February 15, 2012.</ref> A [[Bar (tropical cyclone)|bar]] can indicate a coming tropical cyclone. The use of sky cover in weather prediction has led to various [[weather lore]] over the centuries.<ref name=Skywatch />

===Nowcasting===
{{Main|Nowcasting (meteorology)}}
The forecasting of the weather for the following six hours is often referred to as nowcasting.<ref>Glossary of Meteorology. [http://glossary.ametsoc.org/wiki/Nowcast] {{Webarchive|url=https://web.archive.org/web/20150527035615/http://glossary.ametsoc.org/wiki/Nowcast|date=May 27, 2015}} Retrieved May 26, 2015.</ref> In this time range it is possible to forecast smaller features such as individual showers and thunderstorms with reasonable accuracy, as well as other features too small to be resolved by a computer model. A human given the latest radar, satellite and observational data will be able to make a better analysis of the small scale features present and so will be able to make a more accurate forecast for the following few hours.<ref>E-notes.com. [http://www.enotes.com/science-fact-finder/weather-climate/what-nowcasting Weather and Climate | What Is Nowcasting?] {{Webarchive|url=https://web.archive.org/web/20110905132837/http://www.enotes.com/science-fact-finder/weather-climate/what-nowcasting |date=September 5, 2011 }} Retrieved September 8, 2011.</ref> However, there are now [[expert system]]s using those data and mesoscale numerical model to make better extrapolation, including evolution of those features in time. [[Accuweather]] is known for a Minute-Cast, which is a minute-by-minute [[precipitation]] forecast for the next two hours.

===Atmospheric model===
{{Main|Atmospheric model}}
[[File:NAM 500 MB.PNG|thumb|An example of 500 [[millibar|mbar]] [[geopotential height]] prediction from a numerical weather prediction model]]
In the past, human forecasters were responsible for generating the weather forecast based upon available observations.<ref>[[NASA]]. [http://earthobservatory.nasa.gov/Library/WxForecasting/wx2.html "Weather Forecasting Through the Ages"] {{Webarchive|url=https://web.archive.org/web/20050910210732/http://earthobservatory.nasa.gov/Library/WxForecasting/wx2.html |date=September 10, 2005 }}. Retrieved May 25, 2008.</ref> Today, human input is generally confined to choosing a model based on various parameters, such as model biases and performance.<ref name="Klaus">Klaus Weickmann, Jeff Whitaker, Andres Roubicek and Catherine Smith (December 1, 2001). [http://www.cdc.noaa.gov/spotlight/12012001/ "The Use of Ensemble Forecasts to Produce Improved Medium Range (3–15&nbsp;days) Weather Forecasts"]. [[Climate Diagnostics Center]]. Retrieved February 16, 2007. {{Webarchive|url=https://web.archive.org/web/20090827021959/http://www.cdc.noaa.gov/spotlight/12012001/ |date=August 27, 2009 }}</ref> Using a consensus of forecast models, as well as ensemble members of the various models, can help reduce forecast error.<ref name="TBK">Todd Kimberlain (June 2007). [http://www.wpc.ncep.noaa.gov/research/TropicalTalk.ppt "TC Genesis, Track, and Intensity Forecating"] {{Webarchive|url=https://web.archive.org/web/20210227154914/http://www.wpc.ncep.noaa.gov/research/TropicalTalk.ppt |date=February 27, 2021 }}. PowerPoint. Retrieved July 21, 2007.</ref> However, regardless how small the average error becomes with any individual system, large errors within any particular piece of guidance are still possible on any given model run.<ref>Richard J. Pasch, Mike Fiorino, and [[Chris Landsea]]. [http://www.emc.ncep.noaa.gov/research/NCEP-EMCModelReview2006/TPC-NCEP2006.ppt "TPC/NHC'S Review of the NCEP Production Suite for 2006"]. Retrieved May 5, 2008.{{dead link|date=October 2017}}</ref> Humans are required to interpret the model data into weather forecasts that are understandable to the end user. Humans can use knowledge of local effects that may be too small in size to be resolved by the model to add information to the forecast. While increasing accuracy of forecasting models implies that humans may no longer be needed in the forecasting process at some point in the future, there is currently still a need for human intervention.<ref>{{cite journal |last1=Roebber |first1=P. J. |last2=Bosart |first2=L. F. |url=http://cat.inist.fr/?aModele=afficheN&cpsidt=2512901 |title=The complex relationship between forecasting skill and forecast value : A real-world analysis |journal=Weather and Forecasting |issn=0882-8156 |year=1996 |volume=11 |issue=4 |pages=544–559 |access-date=May 25, 2008 |bibcode=1996WtFor..11..544R |doi=10.1175/1520-0434(1996)011<0544:TCRBFS>2.0.CO;2 |s2cid=15191426 |doi-access=free |archive-date=August 16, 2011 |archive-url=https://web.archive.org/web/20110816214902/http://cat.inist.fr/?aModele=afficheN&cpsidt=2512901 |url-status=live }}</ref>

===Analog ===
The analog technique is a complex way of making a forecast, requiring the forecaster to remember a previous weather event that is expected to be mimicked by an upcoming event. What makes it a difficult technique to use is that there is rarely a perfect analog for an event in the future.<ref>[http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/fcst/mth/oth.rxml "Other Forecasting Methods: climatology, analogue and numerical weather prediction"] {{Webarchive|url=https://web.archive.org/web/20070519200402/http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/fcst/mth/oth.rxml |date=May 19, 2007 }}. Retrieved February 16, 2006.</ref> Some call this type of forecasting pattern recognition. It remains a useful method of observing rainfall over data voids such as oceans,<ref>Kenneth C. Allen. [https://web.archive.org/web/20070714214614/http://stinet.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=ADP006190 "Pattern Recognition Techniques Applied to the NASA-ACTS Order-Wire Problem"]. Retrieved February 16, 2007.</ref> as well as the forecasting of precipitation amounts and distribution in the future. A similar technique is used in medium range forecasting, which is known as teleconnections, when systems in other locations are used to help pin down the location of another system within the surrounding regime.<ref>Weather Associates, Inc. [http://www.weatherassociates.com/courses.htm "The Role of Teleconnections & Ensemble Forecasting in Extended- to Medium-Range Forecasting"]. Retrieved February 16, 2007. {{webarchive|url=https://web.archive.org/web/20070622105708/http://www.weatherassociates.com/courses.htm |date=June 22, 2007 }}</ref> An example of teleconnections are by using [[El Niño-Southern Oscillation]] (ENSO) related phenomena.<ref>Thinkquest.org. [http://library.thinkquest.org/20901/teleconnections.htm "Teleconnections: Linking El Niño with Other Places"]. Retrieved February 16, 2007. {{webarchive|url=https://web.archive.org/web/20070420054354/http://library.thinkquest.org/20901/teleconnections.htm |date=April 20, 2007 }}</ref>

=== Artificial intelligence ===
Initial attempts to use [[artificial intelligence]] began in the 2010s. [[Huawei]]'s Pangu-Weather model, [[Google]]'s GraphCast, WindBorne's WeatherMesh model, [[Nvidia]]'s FourCastNet, and the [[European Centre for Medium-Range Weather Forecasts]]' Artificial Intelligence/Integrated Forecasting System, or AIFS all appeared in 2022–2023. In 2024, AIFS started to publish real-time forecasts, showing specific skill at predicting hurricane tracks, but lower-performing on the intensity changes of such storms relative to physics-based models.<ref name=":02">{{Cite web |last=Berger |first=Eric |date=June 3, 2024 |title=No physics? No problem. AI weather forecasting is already making huge strides. |url=https://arstechnica.com/ai/2024/06/as-a-potentially-historic-hurricane-season-looms-can-ai-forecast-models-help/ |access-date=June 6, 2024 |website=Ars Technica |language=en-us}}</ref>

Such models use no physics-based atmosphere modeling or [[large language model]]s. Instead, they learn purely from data such as the [[ECMWF re-analysis]] ERA5.<ref>{{Cite web |last=Setchell |first=Helen |date=February 19, 2020 |title=ECMWF Reanalysis v5 |url=https://www.ecmwf.int/en/forecasts/dataset/ecmwf-reanalysis-v5 |access-date=June 11, 2024 |website=ECMWF |language=en}}</ref> These models typically require far less compute than physics-based models.<ref name=":02" />

[[Microsoft]]'s Aurora system offers global 10-day weather and 5-day air pollution ([[Carbon dioxide|{{chem|CO|2}}]], [[NOx|NO]], [[Nitrogen dioxide|{{chem|NO|2}}]], [[Silicon dioxide|{{chem|SO|2}}]], [[Ozone|{{chem|O|3}}]], and particulates) forecasts with claimed accuracy similar to physics-based models, but at orders-of-magnitude lower cost. Aurora was trained on more than a million hours of data from six weather/climate models.<ref>{{Cite journal |last=Wong |first=Carissa |date=June 4, 2024 |title=Superfast Microsoft AI is first to predict air pollution for the whole world |url=https://www.nature.com/articles/d41586-024-01677-2 |journal=Nature |language=en |doi=10.1038/d41586-024-01677-2|pmid=38834696 |url-access=subscription }}</ref><ref>{{cite arXiv |last1=Bodnar |first1=Cristian |title=Aurora: A Foundation Model of the Atmosphere |date=May 28, 2024 |eprint=2405.13063 |last2=Bruinsma |first2=Wessel P. |last3=Lucic |first3=Ana |last4=Stanley |first4=Megan |last5=Brandstetter |first5=Johannes |last6=Garvan |first6=Patrick |last7=Riechert |first7=Maik |last8=Weyn |first8=Jonathan |last9=Dong |first9=Haiyu|class=physics.ao-ph }}</ref>

In 2024, a group of researchers at Google's [[DeepMind]] AI research laboratories published a paper in ''[[Nature (journal)|Nature]]'' to describe their machine-learning model, called GenCast, that is expected to produce more accurate forecasts than the best traditional weather forecasting systems.<ref>{{Cite journal |last=Price |first=Ilan | display-authors=etal | year=2025 |title=Probabilistic weather forecasting with machine learning  |journal=Nature |volume=637  |issue=8044 |pages=84–90 |language=en |doi=10.1038/s41586-024-08252-9 |pmid=39633054 |pmc=11666454 |bibcode=2025Natur.637...84P }}</ref>

In a study conducted using the AIFS, Lang et al. (2024) presented 30-day ensemble simulations of the [[Madden–Julian oscillation]].<ref>{{Citation |last1=Lang |first1=Simon |title=AIFS-CRPS: Ensemble forecasting using a model trained with a loss function based on the Continuous Ranked Probability Score |date=2024 |arxiv=2412.15832 |last2=Alexe |first2=Mihai |last3=Clare |first3=Mariana C. A. |last4=Roberts |first4=Christopher |last5=Adewoyin |first5=Rilwan |last6=Bouallègue |first6=Zied Ben |last7=Chantry |first7=Matthew |last8=Dramsch |first8=Jesper |last9=Dueben |first9=Peter D.}}</ref>

==Communicating forecasts to the public==
{{main|Weather warning}}
[[File:Newspaper weather forecast - today and tomorrow.svg|frame|right|An example of a two-day weather forecast in the [[Visual language|visual style]] that an American newspaper might use. Temperatures are given in Fahrenheit.]]
Most end users of forecasts are members of the general public. Thunderstorms can create strong winds and dangerous [[lightning]] strikes that can lead to deaths, power outages,<ref>University of Illinois at Urbana-Champaign. [http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/svr/dngr/light.rxml "Lightning"] {{Webarchive|url=https://web.archive.org/web/20070207041842/http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/svr/dngr/light.rxml |date=February 7, 2007 }}. Retrieved February 16, 2007.</ref> and widespread hail damage. Heavy snow or rain can bring transportation and commerce to a stand-still,<ref>[[Associated Press]] (February 10, 2007). [https://www.nbcnews.com/id/wbna17063535 "Upstate N.Y. residents dig out from heavy snow"] . NBC News. Retrieved May 25, 2008.</ref> as well as cause flooding in low-lying areas.<ref>National Flood Insurance Program. [http://www.floodsmart.gov/floodsmart/pages/flooding_flood_risks/flood_scenarios.jsp "Flood Risk Scenarios: Flash Flood"]. Retrieved 2008-05-25. {{webarchive|url=https://web.archive.org/web/20140313115856/https://www.floodsmart.gov/floodsmart/pages/flooding_flood_risks/flood_scenarios.jsp|date=March 13, 2014}} <!-- redirects to https://www.fema.gov/national-flood-insurance-program, maybe there's something useful there, but it's not the same page --></ref> Excessive [[Heat wave|heat]] or [[cold wave]]s can sicken or kill those with inadequate utilities, and droughts can impact water usage and destroy vegetation.

Several countries employ government agencies to provide forecasts and watches/warnings/advisories to the public to protect life and property and maintain commercial interests. Knowledge of what the end user needs from a weather forecast must be taken into account to present the information in a useful and understandable way. Examples include the [[National Oceanic and Atmospheric Administration]]'s [[National Weather Service]] (NWS)<ref>National Weather Service. [http://www.nws.noaa.gov/admin.php About "NOAA's National Weather Service"] {{Webarchive|url=https://web.archive.org/web/20070214052546/http://www.nws.noaa.gov/admin.php |date=February 14, 2007 }}. Retrieved February 16, 2007.</ref> and [[Environment Canada]]'s [[Meteorological Service of Canada|Meteorological Service]] (MSC).<ref>Environment Canada. [http://weather.gc.ca/canada_e.html "Canadian Weather"] {{Webarchive|url=https://web.archive.org/web/20171011182910/http://weather.gc.ca/canada_e.html |date=October 11, 2017 }}. Retrieved February 16, 2007.</ref> Traditionally, newspaper, television, and radio have been the primary outlets for presenting weather forecast information to the public. In addition, some cities had [[weather beacon]]s.  Increasingly, the internet is being used due to the vast amount of specific information that can be found.<ref>Canadian Heritage. [http://www.canadianheritage.gc.ca/progs/ac-ca/progs/ri-bpi/pubs/2005_02/4_e.cfm "Primary Sources of Local Information"]. Retrieved May 26, 2008. {{webarchive|url=https://web.archive.org/web/20080605053120/http://www.canadianheritage.gc.ca/progs/ac-ca/progs/ri-bpi/pubs/2005_02/4_e.cfm |date=June 5, 2008 }}</ref> In all cases, these outlets update their forecasts on a regular basis.

===Severe weather alerts and advisories===
A major part of modern weather forecasting is the severe weather alerts and advisories that the national weather services issue in the case that severe or hazardous weather is expected. This is done to protect life and property.<ref>[[National Weather Service]]. [http://www.weather.gov/mission.shtml National Weather Service Mission Statement]. Retrieved May 25, 2008. {{webarchive|url=https://web.archive.org/web/20131124214601/http://www.weather.gov/mission.shtml |date=November 24, 2013 }}</ref> Some of the most commonly known of severe weather advisories are the [[Severe thunderstorm warning|severe thunderstorm]] and [[tornado warning]], as well as the [[Severe thunderstorm watch|severe thunderstorm]] and [[tornado watch]]. Other forms of these advisories include winter weather, high wind, [[Flood warning|flood]], [[tropical cyclone]], and fog.<ref>[[Environment Canada]]. [http://www.msc-smc.ec.gc.ca/cd/brochures/warning_e.cfm? "Weather watches, warnings and advisories"]. {{webarchive|url=https://web.archive.org/web/20060703204148/http://www.msc-smc.ec.gc.ca/cd/brochures/warning_e.cfm |date=July 3, 2006 }} Retrieved May 26, 2008.</ref> Severe weather advisories and alerts are broadcast through the media, including radio, using emergency systems as the [[Emergency Alert System]], which break into regular programming.<ref>[[Federal Communications Commission]]. [https://www.fcc.gov/general/emergency-alert-system-eas "Emergency Alert System"] {{Webarchive|url=https://web.archive.org/web/20171012055644/https://www.fcc.gov/general/emergency-alert-system-eas |date=October 12, 2017 }}. Retrieved May 26, 2008.</ref>

===Low temperature forecast===
The low temperature forecast for the current day is calculated using the lowest temperature found between 7{{nbsp}}pm that evening through 7{{nbsp}}am the following morning.<ref>[[Weather Channel]] – [http://feedback.weather.com/knowledgebase/articles/32098-weather-com-is-the-low-before-or-after-the-high Calculation of Low Temperature Forecast] {{webarchive|url=https://web.archive.org/web/20150906012055/http://feedback.weather.com/knowledgebase/articles/32098-weather-com-is-the-low-before-or-after-the-high |date=September 6, 2015 }}</ref> So, in short, today's forecasted low is most likely tomorrow's low temperature.

== Specialist forecasting ==
There are a number of sectors with their own specific needs for weather forecasts and specialist services are provided to these users as given below:

=== Air traffic ===
[[File:Plume from eruption of Chaiten volcano, Chile.jpg|thumb|right|Ash cloud from the 2008 eruption of [[Chaitén (volcano)|Chaitén volcano]] stretching across [[Patagonia]] from the Pacific to the Atlantic Ocean]]
{{See also|Terminal aerodrome forecast}}
Because the aviation industry is especially sensitive to the weather, accurate weather forecasting is essential. Fog or exceptionally low [[ceiling (cloud)|ceilings]] can prevent many aircraft from landing and taking off.<ref>[[United States Government Publishing Office|Government Printing Office]]. [http://ecfr.gpoaccess.gov/cgi/t/text/text-idx?c=ecfr;sid=199eb678c4c22b4202e5809c99045c7c;rgn=div7;view=text;node=14%3A2.0.1.3.10.2.5;idno=14;cc=ecfr Title 14: "Aeronautics and Space"]. Retrieved May 26, 2008. {{webarchive|url=https://web.archive.org/web/20110613085006/http://ecfr.gpoaccess.gov/cgi/t/text/text-idx?c=ecfr;sid=199eb678c4c22b4202e5809c99045c7c;rgn=div7;view=text;node=14:2.0.1.3.10.2.5;idno=14;cc=ecfr |date=June 13, 2011 }}</ref> [[Turbulence]] and [[Atmospheric icing|icing]] are also significant in-flight hazards.<ref>Aircraft Owners and Pilots Association. [http://www.aopa.org/asf/publications/sa11.pdf "Aircraft Icing"]. Retrieved May 26, 2008. {{webarchive|url=https://web.archive.org/web/20070202074833/http://www.aopa.org/asf/publications/sa11.pdf |date=February 2, 2007 }}</ref> Thunderstorms are a problem for all aircraft because of severe turbulence due to their [[Vertical draft|updrafts]] and [[Outflow boundary|outflow boundaries]],<ref>[[National Weather Service]] Forecast Office Dodge City, Kansas. [http://www.crh.noaa.gov/ddc/research/bore/HPCtalk.ppt "Aviation Hazards They Didn't Tell You About"]. Retrieved May 26, 2008. {{webarchive|url=https://web.archive.org/web/20080910142824/http://www.crh.noaa.gov/ddc/research/bore/HPCtalk.ppt |date=September 10, 2008 }}</ref> icing due to the heavy precipitation, as well as large [[hail]], strong winds, and lightning, all of which can cause severe damage to an aircraft in flight.<ref>[[Bureau of Meteorology]] (2006). [http://www.caem.wmo.int/_pdf/thunderstorms/thunderstorms_02_effects.pdf "Aviation Hazards: Thunderstorms and Deep Convection"] {{Webarchive|url=https://web.archive.org/web/20080910142826/http://www.caem.wmo.int/_pdf/thunderstorms/thunderstorms_02_effects.pdf |date=September 10, 2008 }}. Retrieved May 26, 2008.</ref> [[Volcanic ash]] is also a significant problem for aviation, as aircraft can lose engine power within ash clouds.<ref>[https://www.usgs.gov/tech-transfer/factsheets/7.html "Volcanic Ash Aviation Hazard"]. Retrieved May 26, 2008. {{webarchive|url=https://web.archive.org/web/20080621085505/http://www.usgs.gov/tech-transfer/factsheets/7.html |date=June 21, 2008 }}</ref> On a day-to-day basis airliners are routed to take advantage of the [[jet stream]] tailwind to improve fuel efficiency.<ref>Ned Rozell. [http://www.gi.alaska.edu/ScienceForum/ASF17/1727.html "Amazing flying machines allow time travel"]. Retrieved May 8, 2008. {{webarchive|url=https://web.archive.org/web/20080605031147/http://www.gi.alaska.edu/ScienceForum/ASF17/1727.html |date=June 5, 2008 }}</ref> Aircrews are briefed prior to [[takeoff]] on the conditions to expect en route and at their destination.<ref>[[National Weather Service]]. [http://www.weather.gov/om/brochures/pilot.htm "A Pilot's Guide to Aviation Weather Services"]. Retrieved May 26, 2008. {{webarchive|url=https://web.archive.org/web/20080624042742/http://www.weather.gov/om/brochures/pilot.htm |date=June 24, 2008 }}</ref> Additionally, airports often change which [[runway]] is being used to take advantage of a [[headwind]]. This reduces the distance required for takeoff, and eliminates potential [[crosswind]]s.<ref>Eric C. King. [http://takeofftools.com/Documents/Crosswind%20Calculator%20Instructions.pdf "Takeoff Tools Crosswind Calculator Instructions"]. Retrieved May 26, 2008. {{webarchive|url=https://web.archive.org/web/20080910142826/http://takeofftools.com/Documents/Crosswind%20Calculator%20Instructions.pdf |date=September 10, 2008 }}</ref>

===Marine===
{{See also|Marine weather forecasting}}
Commercial and recreational use of waterways can be limited significantly by wind direction and speed, [[Ocean surface wave|wave]] periodicity and heights, tides, and precipitation. These factors can each influence the safety of marine transit. Consequently, a variety of codes have been established to efficiently transmit detailed marine weather forecasts to vessel pilots via radio, for example the [[MAFOR]] (marine forecast).<ref>Great Lakes and Seaway Shipping. [http://www.boatnerd.com/facts-figures/mafor.htm "MAFOR Weather Code"] {{Webarchive|url=https://web.archive.org/web/20160616221137/http://www.boatnerd.com/facts-figures/mafor.htm |date=June 16, 2016 }}. Retrieved May 27, 2008.</ref> Typical weather forecasts can be received at sea through the use of [[RTTY]], [[Navtex]] and [[Radiofax]].

===Agriculture===
Farmers rely on weather forecasts to decide what work to do on any particular day. For example, drying [[hay]] is only feasible in dry weather. Prolonged periods of dryness can ruin cotton, wheat,<ref>Blair Fannin. [http://southwestfarmpress.com/news/061406-Texas-weather/ "Dry weather conditions continue for Texas"]. Retrieved May 26, 2008. {{webarchive|url=https://web.archive.org/web/20090703095038/http://southwestfarmpress.com/news/061406-Texas-weather/ |date=July 3, 2009 }}</ref> and [[Maize|corn]] crops. While corn crops can be ruined by drought, their dried remains can be used as a cattle feed substitute in the form of [[silage]].<ref>Dr. Terry Mader. [http://beef.unl.edu/stories/200004030.shtml "Drought Corn Silage"]. Retrieved May 26, 2008. {{webarchive|url=https://web.archive.org/web/20111005203246/http://beef.unl.edu/stories/200004030.shtml |date=October 5, 2011 }}</ref> [[Frost]]s and freezes play havoc with crops both during the spring and fall. For example, [[peach]] trees in full bloom can have their potential peach crop decimated by a spring freeze.<ref>Kathryn C. Taylor. [http://pubs.caes.uga.edu/caespubs/pubcd/C877.htm "Peach Orchard Establishment and Young Tree Care"]. Retrieved May 26, 2008. {{webarchive|url=https://web.archive.org/web/20081224112403/http://pubs.caes.uga.edu/caespubs/pubcd/C877.htm |date=December 24, 2008 }}</ref> Orange groves can suffer significant damage during frosts and freezes, regardless of their timing.<ref>{{cite news |date=January 14, 1991 |agency=[[Associated Press]] |url=https://www.nytimes.com/1991/01/14/us/after-freeze-counting-losses-to-orange-crop.html |title=After Freeze, Counting Losses to Orange Crop |newspaper=The New York Times |access-date=May 26, 2008 |archive-date=June 15, 2018 |archive-url=https://web.archive.org/web/20180615190918/https://www.nytimes.com/1991/01/14/us/after-freeze-counting-losses-to-orange-crop.html |url-status=live }}</ref>

=== Forestry ===

Forecasting of wind, precipitation and humidity is essential for preventing and controlling [[wildfire]]s. Indices such as the ''[[Forest fire weather index]]'' and the ''[[Haines Index]]'', have been developed to predict the areas more at risk of fire from natural or human causes. Conditions for the development of harmful insects can also be predicted by forecasting the weather.

===Utility companies===
[[File:Air handling unit.JPG|thumb|right|An [[air handling unit]] is used for the heating and cooling of air in a central location (click on image for legend).]]
{{Main|Degree day}}
Electricity and gas companies rely on weather forecasts to anticipate demand, which can be strongly affected by the weather. They use the quantity termed the degree day to determine how strong of a use there will be for heating ([[heating degree day]]) or cooling (cooling degree day). These quantities are based on a daily average temperature of {{convert|65|F}}. Cooler temperatures force heating degree days (one per degree Fahrenheit), while warmer temperatures force cooling degree days.<ref>[[Climate Prediction Center]]. [http://www.cpc.noaa.gov/products/analysis_monitoring/cdus/degree_days/ddayexp.shtml "Degree Day Explanation"] {{Webarchive|url=https://web.archive.org/web/20100524040629/http://www.cpc.noaa.gov/products/analysis_monitoring/cdus/degree_days/ddayexp.shtml |date=May 24, 2010 }}. Retrieved May 25, 2008.</ref> In winter, severe cold weather can cause a surge in demand as people turn up their heating.<ref>{{cite news |date=February 26, 1993 |newspaper=[[The New York Times]] |url=https://www.nytimes.com/1993/02/26/business/futures-options-cold-weather-brings-surge-in-prices-of-heating-fuels.html |title=Futures/Options; Cold Weather Brings Surge in Prices of Heating Fuels |access-date=May 25, 2008 |archive-date=June 15, 2018 |archive-url=https://web.archive.org/web/20180615135320/https://www.nytimes.com/1993/02/26/business/futures-options-cold-weather-brings-surge-in-prices-of-heating-fuels.html |url-status=live }}</ref> Similarly, in summer a surge in demand can be linked with the increased use of [[air conditioning]] systems in hot weather.<ref>[[BBC News]] (July 25, 2006) [https://news.bbc.co.uk/2/hi/uk_news/5212724.stm "Heatwave causes electricity surge"] . Retrieved May 25, 2008.</ref> By anticipating a surge in demand, utility companies can purchase additional supplies of power or natural gas before the price increases, or in some circumstances, supplies are restricted through the use of [[Brownout (electricity)|brownouts]] and [[Power outage|blackouts]].<ref>Toronto Catholic Schools. [http://www.tcdsb.org/environment/energydrill/EDSP_KeyMessages_FINAL.pdf "The Seven Key Messages of the Energy Drill Program"]. Retrieved May 25, 2008. {{webarchive|url=https://web.archive.org/web/20120217042744/http://www.tcdsb.org/environment/energydrill/EDSP_KeyMessages_FINAL.pdf |date=February 17, 2012 }}</ref>

===Other commercial companies===
Increasingly, private companies pay for weather forecasts tailored to their needs so that they can increase their profits or avoid large losses.<ref>CSIRO. [http://www.csiro.au/science/pps9c.html#1 "Providing specialized weather forecasts"]. Retrieved May 25, 2008. {{webarchive|url=https://web.archive.org/web/20080419071008/http://www.csiro.au/science/pps9c.html |date=April 19, 2008 }}</ref> For example, supermarket chains may change the stocks on their shelves in anticipation of different [[consumer spending]] habits in different weather conditions. Weather forecasts can be used to invest in the commodity market, such as futures in oranges, corn, soybeans, and oil.<ref>Stephen Jewson and Rodrigo Caballero. [http://search.ssrn.com/sol3/papers.cfm?abstract_id=405780 "The Use of Weather Forecasts in the Pricing of Weather Derivatives"]. Retrieved May 25, 2008. {{webarchive|url=https://web.archive.org/web/20110716125422/http://search.ssrn.com/sol3/papers.cfm?abstract_id=405780 |date=July 16, 2011 }}</ref>

===Military applications===

====United Kingdom====
The British [[Royal Navy]], working with the [[Met Office]], has its own specialist branch of weather observers and forecasters, as part of the Hydrographic and Meteorological (HM) specialisation, who monitor and forecast operational conditions across the globe, to provide accurate and timely weather and oceanographic information to submarines, ships and [[Fleet Air Arm]] aircraft.

A mobile unit in the [[Royal Air Force]], working with the Met Office, forecasts the weather for regions in which British and allied armed forces are deployed. A group based at [[Camp Shorabak|Camp Bastion]] used to provide forecasts for the [[Operation Herrick|British armed forces in Afghanistan]].<ref>[[Met Office]]. [https://www.metoffice.gov.uk/about-us/weather-forecasting-for-military-operations "Weather forecasting for military operations"] {{Webarchive|url=https://web.archive.org/web/20171012094709/https://www.metoffice.gov.uk/about-us/weather-forecasting-for-military-operations |date=October 12, 2017 }}. Retrieved October 23, 2012.</ref>

====United States====
[[File:Npmoc.gif|thumb|right|The emblem of the Joint Typhoon Warning Center (JTWC).]]
Similar to the private sector, military weather forecasters present weather conditions to the war fighter community. Military weather forecasters provide pre-flight and in-flight weather briefs to pilots and provide real time resource protection services for military installations.

Naval forecasters cover the waters and ship weather forecasts. The [[United States Navy]] provides a special service for itself and the rest of the federal government by issuing forecasts for tropical cyclones across the Pacific and Indian Oceans through its [[Joint Typhoon Warning Center]].<ref>[[Joint Typhoon Warning Center]]. [https://web.archive.org/web/20061208162203/http://metocph.nmci.navy.mil/jtwc/menu/JTWC_mission.html "Joint Typhoon Warning Center Mission Statement"].  Retrieved May 27, 2008.</ref>

Within the United States, the [[557th Weather Wing]] provides weather forecasting for the Air Force and the Army. [[United States Air Force|Air Force]] forecasters cover air operations in both wartime and peacetime and provide [[United States Army|Army]] support;<ref>[[United States Air Force]].[https://web.archive.org/web/20070714070133/http://www.af.mil/factsheets/factsheet.asp?fsID=157 "Air Force Weather Agency"]. Retrieved May 26, 2008.</ref> [[United States Coast Guard]] marine science technicians provide ship forecasts for ice breakers and various other operations within their realm;<ref>[[United States Military]]. [https://www.usmilitary.com/coastguardenlistedoccupations.html#engineeringscienceandtechnical "US Coast Guard Jobs – Enlisted Occupations"] {{Webarchive|url=https://web.archive.org/web/20160312201542/http://www.usmilitary.com/coastguardenlistedoccupations.html#engineeringscienceandtechnical |date=March 12, 2016 }}. Retrieved May 26, 2008.</ref> and Marine forecasters provide support for ground- and air-based [[United States Marine Corps]] operations.<ref>Rod Powers. [https://www.thebalance.com/field-meteorology-oceanography-3345698 "United States Marine Corps Enlisted Job Descriptions and Qualification Factors: Field 68 – Meteorology and Oceanography (METOC)"] {{Webarchive|url=https://web.archive.org/web/20170806102458/https://www.thebalance.com/field-meteorology-oceanography-3345698 |date=August 6, 2017 }}. Retrieved 2008-05-26.<!-- as of October 11, 2017, Updated August 13, 2016--></ref> All four of the mentioned military branches have their initial enlisted meteorology technical training at [[Keesler Air Force Base]].<ref>[[Keesler Air Force Base]]. Military officers usually received their education from a civilian institution. [http://www.keesler.af.mil/shared/media/document/AFD-061113-086.pdf "Keesler News: March 9, 2006"] {{webarchive|url=https://web.archive.org/web/20080910142826/http://www.keesler.af.mil/shared/media/document/AFD-061113-086.pdf |date=September 10, 2008 }}. [[United States Air Force]] Retrieved May 26, 2008.</ref> Military and civilian forecasters actively cooperate in analyzing, creating and critiquing weather forecast products.

==See also==
{{Wikisource|Observations upon the Marine Barometer, made during the Examination of the Coasts of New Holland and New South Wales, in the Years 1801, 1802, and 1803|Observations upon the Marine Barometer...}}
* [[Air pollution forecasting]]
* [[Citizen Weather Observer Program]]
* [[Ensemble forecasting]]
* [[Flood forecasting]]
* [[National Collegiate Weather Forecasting Contest]]
* [[National Weatherperson's Day]]
* [[Nonhomogeneous Gaussian regression]]
* [[Surface weather observation]]
* [[Tropical cyclone forecasting]]
* [[Weather and Society Integrated Studies]]
* [[Weather hole]]
* [[WxChallenge]]
* [[Weather forecasting for Operation Overlord]]

==References==
{{Reflist|30em}}

==Further reading==
*{{cite book |last=Blum |first=Andrew |title=The Weather Machine: A Journey Inside the Forecast |location=New York |publisher=HarperCollins |year=2019 |isbn=978-0-062-36861-4 }}
* {{cite book |author1=Ian Roulstone |author2=John Norbury |name-list-style=amp |title=Invisible in the Storm: the role of mathematics in understanding weather |url=https://books.google.com/books?id=qnMrFEHMrWwC|year=2013 |publisher=Princeton University Press|isbn=978-0691152721 }}

==External links==
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{{Commons category|Weather forecasting}}

* [http://earthobservatory.nasa.gov/Features/WxForecasting/wx2.php Weather Forecasting Through the Ages]
* [http://apollo.lsc.vsc.edu/classes/met130/notes/chapter1/history.html Meteorology – A brief history]
* [http://www.slideshare.net/florenceann/history-of-meteorology-6955121 History of meteorology]

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