Modern weather predictions aid in timely evacuations and potentially save lives and property damage

Weather map of Europe, 10 December 1887

Weather forecasting is the application of current technology and science to predict the state of the atmosphere for a future time and a given location. The history of weather forecasting goes back millennia, however the techniques used have changed significantly since then. Today, weather forecasts are made by collecting as much data as possible about the current state of the atmosphere (particularly the temperature, humidity and wind) and using understanding of atmospheric processes (through meteorology) to determine how the atmosphere evolves in the future. However, the chaotic nature of the atmosphere and incomplete understanding of the processes mean that forecasts become less accurate as the range of the forecast increases. Image File history File links Download high resolution version (895x716, 27 KB) Summary Three-day cone of uncertainty for the path of Hurricane Rita as of 10 PM CDT, September 22, 2005. ... Image File history File links Download high resolution version (895x716, 27 KB) Summary Three-day cone of uncertainty for the path of Hurricane Rita as of 10 PM CDT, September 22, 2005. ... Image File history File links Download high resolution version (800x1275, 376 KB) Weather map for Europe (09. ... Image File history File links Download high resolution version (800x1275, 376 KB) Weather map for Europe (09. ... World map showing Europe A satellite composite image of Europe Europe is one of the seven traditional continents of the Earth. ... December 10 is the 344th day (345th in leap years) of the year in the Gregorian calendar, 21 days before the next year. ... 1887 (MDCCCLXXXVII) is a common year starting on Saturday (click on link for calendar) of the Gregorian calendar or a common year starting on Monday of the Julian calendar. ... Weather is a term that encompasses phenomena in the atmosphere of a planet. ... Layers of Atmosphere (NOAA) Air redirects here. ... In general, data consist of propositions that reflect reality. ... Fig. ... Humidity is the concentration of water vapor in the air. ... Wind is the roughly horizontal movement of air (as opposed to an air current) caused by uneven heating of the Earths surface. ... Satellite image of Hurricane Hugo with a polar low visible at the top of the image. ... A plot of the trajectory Lorenz system for values r = 28, σ = 10, b = 8/3 In mathematics and physics, chaos theory describes the behavior of certain nonlinear dynamical systems that under certain conditions exhibit a phenomenon known as chaos. ...

History of weather forecasting

Many people's livelihoods and indeed lives are strongly influenced by the weather. For millennia people have tried to predict what the weather would be like a day or a season in advance. In 650 BCE, the Babylonians predicted the weather from cloud patterns. In about 340 BCE, Aristotle described weather patterns in Meteorologica. The Chinese were predicting weather at least as far back as 300 BCE. Aristotle (Greek: Aristotélēs) (384 BC – March 7, 322 BC) was an ancient Greek philosopher, a student of Plato and teacher of Alexander the Great. ... Meteorology (or Meteorologica) is a text by Aristotle which contains his theories about the earth sciences. ...

Ancient methods of weather forecasting usually relied on experience to spot patterns of events. For example, they noticed that if the sunset gave a particularly red sky, then the following day brought fair weather. This experience accumulated over the generations to produce weather lore. However, not all of these predictions prove reliable and many of them have since been found not to stand up to rigorous statistical testing. Cumulus humilis indicates a good day ahead. ...

It was not until the invention of the telegraph in 1837 that the modern age of weather forecasting began. Before this time, it had not been possible to transport information about the current state of the weather any faster than a steam train, however the telegraph allowed reports of weather conditions from a wide area to be received almost instantaneously. This allowed forecasts to be made by knowing what the weather conditions were like further upwind. Optical Telegraf of Claude Chappe on the Litermont near Nalbach, Germany Telegraph and telegram redirect here. ...

The two men most credited with the birth of forecasting as a science were Francis Beaufort (remembered chiefly for the Beaufort scale) and his protégé Robert Fitzroy (developer of the Fitzroy Barometer). Both were influential men in British Naval and Governmental circles, and though ridiculed in the press at the time, their work gained scientific credence, was accepted by the British Navy and formed the basis for all of today's weather forecasting knowledge. Bob Ryan is the Prophet of the Golden Sun, fortold by the Sage Zarmatha in the year 1230 in the Emerald Palace, it was there that Zarmatha gazed into the sphere of Oberona and exclaimed to the Council of 9, Behold, in the year 2010 the chosen meteorologist, Bob Ryan... The American Meteorological Society (AMS) promotes the development and dissemination of information and education on the atmospheric and related oceanic and hydrologic sciences and the advancement of their professional applications. ... Sir Francis Beaufort (May 7, 1774 - December 17, 1857) was a British naval officer and hydrographer and was born in Ireland. ... The Beaufort scale is an empirical measure for describing wind intensity based mainly on observed sea conditions. ... Robert FitzRoy Vice Admiral Robert FitzRoy (July 5, 1805 - April 30, 1865) achieved lasting fame as the captain of HMS Beagle and as a pioneering meteorologist who made accurate weather forecasting a reality, also proving an able surveyor and hydrographer as well as Governor of New Zealand. ...

Great progress was made in the science of meteorology during the 20th century which allowed understanding of atmospheric processes. The idea of numerical weather prediction (NWP) was presented by Lewis Fry Richardson in 1922. However, computers fast enough to complete the vast number of calculations required to produce a forecast before the event had occurred did not exist at that time. It was not until the 1970’s that NWP became operational in forecasting agencies across the world. Satellite image of Hurricane Hugo with a polar low visible at the top of the image. ... (19th century - 20th century - 21st century - more centuries) Decades: 1900s 1910s 1920s 1930s 1940s 1950s 1960s 1970s 1980s 1990s As a means of recording the passage of time, the 20th century was that century which lasted from 1901–2000 in the sense of the Gregorian calendar (1900–1999... Numerical weather prediction is the science of predicting the weather using models of the atmosphere and computational techniques. ... Lewis Fry Richardson (October 11, 1881 - September 30, 1953) was a mathematician, physicist and psychologist. ...

Modern day weather forecasting system

A modern day weather forecasting system consists of five components:

• Data collection
• Data assimilation
• Numerical weather prediction
• Model output post-processing
• Forecast presentation to end-user

Data collection

Traditional observations made at the surface of atmospheric pressure, temperature, wind speed, wind direction, humidity, precipitation are collected routinely from trained observers, automatic weather stations or buoys. The World Meteorological Organization acts to standardize the instrumentation, observing practices and timing of these observations worldwide. Stations either report hourly in METAR reports, or every six hours in SYNOP reports. Diurnal (daily) rhythm of air pressure in northern Germany (black curve is air pressure) Atmospheric pressure is the pressure at any point in the Earths atmosphere. ... Fig. ... An AWS in Antarctica An automatic weather station (AWS) is an automated version of the tradition weather station, either to save human labour or to enable measurements from remote areas. ... A seal on a buoy in San Diego Harbor A buoy is a stationary floating device that can have various purposes: sea mark - aids pilotage by marking a maritime channel, hazard and administrative area to allow boats and ships to navigate safely. ... The World Meteorological Organization (WMO) is an intergovernmental organization with a membership of 187 Member States and Territories. ... METAR is a format for reporting weather information. ... SYNOP (surface synoptic observations) is a numerical code (called FM-12 by WMO) used for reporting marine weather observations made by manned and automated weather stations. ...

Additionally, information about the temperature, humidity and wind above the surface are found by launching a radiosonde (weather balloon). Data up to the tropopause are usually transmitted to the surface. In recent years, data transmitted from commercial airplanes through the AMDAR system has also been incorporated into upper air observation, primarily in numerical models. radiosonde with measuring instruments A radiosonde (Sonde is German for probe) is a unit for use in weather balloons that measures various atmospheric parameters and transmits them to a fixed receiver. ... Rawinsonde weather balloon just after launch. ... The tropopause is a boundary region in the atmosphere between the troposphere and the stratosphere. ...

Increasingly, data from weather satellites are being used due to their (almost) global coverage. Although their visible light images are very useful for forecasters to see development of clouds, little of this information can be used by numerical weather prediction models. The infra-red (IR) data however can be used as it gives information on the temperature at the surface and cloud tops. Individual clouds can also be tracked from one time to the next to provide information on wind direction and strength at the clouds steering level. Polar orbiting satellites provide soundings of temperature and moisture throughout the depth of the atmosphere. Compared with similar data from radiosondes, the satellite data has the advantage that coverage is global, however the accuracy and resolution is not as good. A weather satellite is a type of artificial satellite that is primarily used to monitor the weather and/or climate of the Earth. ... Sounding - The historical nautical term for measuring depth. ...

Meteorological radar provide information on precipitation location and intensity. Additionally, if doppler radar are used then wind speed and direction can be determined. To meet Wikipedias quality standards, this article or section may require cleanup. ... It has been suggested that Pulse-Doppler radar be merged into this article or section. ...

Data assimilation

Main article Data assimilation Data assimilation (DA) is a method used in the weather forecasting process in which observations of the current (and possibly, past) weather are combined with a previous forecast for that time to produce the meteorological `analysis; the best estimate of the current state of the atmosphere. ...

During the data assimilation process, information gained from the observations is used in conjunction with a numerical model's most recent forecast for the time that observations were made (since this contains information from previous observations) to produce the meteorological analysis. This is the best estimate of the current state of the atmosphere. It is a three dimensional representation of the distribution of temperature, moisture and wind.

Numerical weather prediction (NWP)

Main article: Numerical weather prediction

Numerical weather prediction models are computer simulations of the atmosphere. They take the analysis as the starting point and evolve the state of the atmosphere forward in time using understanding of physics and fluid dynamics. The complicated equations which govern how the state of a fluid changes with time require supercomputers to solve them. The output from the model provides the basis of the weather forecast. Numerical weather prediction is the science of predicting the weather using models of the atmosphere and computational techniques. ... Numerical weather prediction is the science of predicting the weather using models of the atmosphere and computational techniques. ... The first few hydrogen atom electron orbitals shown as cross-sections with color-coded probability density. ... Fluid dynamics is the subdiscipline of fluid mechanics that studies fluids (liquids and gases) in motion. ... A fluid is defined as a substance that continually deforms (flows) under an applied shear stress regardless of the magnitude of the applied stress. ... A supercomputer is a device for turning compute-bound problems into I/O-bound problems. ...

Model output post processing

The raw output is often modified before being presented as the forecast. This can be in the form of statistical techniques to remove known biases in the model, or of adjustment to take into account consensus among other numerical weather forecasts. A bias is a prejudice in a general or specific sense, usually in the sense for having a preference to one particular point of view or ideological perspective. ...

In the past, the human forecaster used to be responsible for generating the entire weather forecast from the observations. However today, for forecasts beyond 24hrs human input is generally confined to post-processing of model data to add value to the forecast. Humans are required to interpret the model data into weather forecasts that are understandable to the end user. Additionally, humans can use knowledge of local effects which may be too small in size to be resolved by the model to add information to the forecast. Increasing accuracy of forecast models continues to decrease the need for post-processing and human input, mostly in areas with a low variation in terrain.

Presentation of weather forecasts

The final stage in the forecasting process is perhaps the most important. 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.

Public information

Weather forecasting is a common feature in newspapers, as shown here in the back pages of The Observer and Le Monde.

One of the main end users of a forecast is the general public. Thunderstorms can cause strong winds, dangerous lightning strikes leading to power outages, and widespread hail damage. Heavy snow or rain can bring transportation and commerce to a stand-still, as well as cause flooding in low-lying areas. Excessive heat or cold waves can kill or sicken those without adequate utilities. The National Weather Service provides forecasts and watches/warnings/advisories for all areas of the United States to protect life and property and maintain commercial interests. Environment Canada is responsible for dispensing similar forecasts and warnings to the public in Canada. Traditionally, television and radio weather presenters have been the main method of informing the public, however increasingly the internet is being used due to the vast amount of information that can be found. Image File history File linksMetadata Download high resolution version (1760x1168, 490 KB) Summary Weather forecasting is a common feature in newspapers, as shown here in the back pages of The Observer and Le Monde. ... Image File history File linksMetadata Download high resolution version (1760x1168, 490 KB) Summary Weather forecasting is a common feature in newspapers, as shown here in the back pages of The Observer and Le Monde. ... Wikipedia does not yet have an article with this exact name. ... Le Monde is a French daily evening newspaper with a circulation in 2002 of 389,200. ... A rolling thundercloud over Enschede, The Netherlands. ... Animation of snowcover changing with the seasons. ... A flood (in Old English flod, a word common to Teutonic languages; compare German Flut, Dutch vloed from the same root as is seen in flow, float) is an overflow of water, an expanse of water submerging land, a deluge. ... The National Weather Service (NWS) is one of the six scientific agencies that make up the National Oceanic and Atmospheric Administration (NOAA) of the United States government. ...

Air traffic

The aviation industry is especially sensitive to the weather. Fog and/or exceptionally low ceilings can prevent many aircraft landing and taking off. Similarly, turbulence and icing can be hazards whilst in flight. Thunderstorms are a problem for all aircraft, due to severe turbulence and icing, as well as large hail, strong winds, and lightning, all of which can cause fatal damage to an aircraft in flight. On a day to day basis airliners are routed to take advantage of the jet stream tailwind to improve fuel efficiency. Air crews are briefed prior to take off on the conditions to expect en route and at their destination. Evening fog obscures Londons Tower Bridge from passers by. ... In fluid dynamics, turbulence or turbulent flow is a flow regime characterized by chaotic, stochastic property changes. ... The effect of atmospheric icing on a tree. ... This does not cite its references or sources. ... Lightning is an atmospheric discharge of electricity, usually, but not always, during a rain storm. ... Jet streams are fast flowing, relatively narrow air currents found in the atmosphere at around 12 km above the surface of the Earth, just under the tropopause. ... A Ryanair Boeing 737 takes off from Bristol International Airport, England Take off is the phase of flight where an aircraft transitions from moving along the ground (taxiing) to flying in the air (see flight), usually from a runway. ...

Marine

Commercial and recreational use of waterways can be limited significantly by weather in that wind direction and speed, wave periodicity and heights, tides, and precipitation 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). MAFOR, an abbreviation of MArine FORcast, is a code used in the transmission of marine weather forecasts to compresses a volume of meteorological and marine information into shorter code for convenience during radio broadcasting. ...

Utility companies

Electricity and gas companies rely on weather forecasts to anticipate demand which can be strongly affected by the weather. In winter, severe cold weather can cause a surge in demand as people turn up their heating. Similarly, in summer a surge in demand can be linked with the increased use of air conditioning systems in hot weather. 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. Note: in the broadest sense, air conditioning can refer to any form of heating, ventilation, and air-conditioning. ...

Private sector

Increasingly, private companies pay for weather forecasts tailored to their needs so that they can increase their profits or to avoid large losses. For example, supermarket chains may change the stocks on their shelves in anticipation of different consumer spending habits in different weather conditions. State Departments of Transportation and private road maintenance companies also use their forecasts to demonstrate a 'best effort' in defending against lawsuits as a result of traffic accidents.

Military applications

Similarly to the private sector, Military weather forecasters present weather conditions to the war fighter community. Equally provide pre-flight weather briefs and flight weather briefs from take off to terminal location. Including updates throughout the flight path. Also, military weather forecasters provide real time resource protection services for military installations, not covered by the National Weather Service. Three military branches have independent weather forecasting techniques tailored for their specific needs. For example, Naval Forecasters cover the waters and ship weather forecasts; Air Force Forecasters cover air operations in both wartime and peacetime operations and provide Army support; Coast Guard Forecasters provide ship forecasts for ice breakers and other various operations within their realm; And Marine Forecasters forecast for their troops and local aviation assets. There is a silent cooperative agreement between civilian forecasters and military forecasters, both working in unison for the improvement of weather forecasting in general.

Ensemble forecasting

Although a forecast model will predict realistic looking weather features evolving realistically into the distant future, the errors in a forecast will inevitably grow with time due to the chaotic nature of the atmosphere. The detail that can be given in a forecast therefore decreases with time as these errors increase. There becomes a point when the errors are so large that the forecast is completely wrong and the forecast atmospheric state has no correlation with the actual state of the atmosphere. A plot of the trajectory Lorenz system for values r = 28, σ = 10, b = 8/3 In mathematics and physics, chaos theory describes the behavior of certain nonlinear dynamical systems that under certain conditions exhibit a phenomenon known as chaos. ... Linear correlations between 1000 pairs of numbers. ...

However, looking at a single forecast gives no indication of how likely that forecast is to be correct. Ensemble forecasting uses lots of forecasts produced to reflect the uncertainty in the initial state of the atmosphere (due to errors in the observations and insufficient sampling). The uncertainty in the forecast can then be assessed by the range of different forecasts produced. They have been shown to be better at detecting the possibility of extreme events at long range. Ensemble forecasting is a method used by modern operational forecast centers to account for sensitive dependency on initial conditions. ...

Ensemble forecasts are increasingly being used for operational weather forecasting (for example at ECMWF, NCEP, and the Canadian forecasting center). The European Centre for Medium-Range Weather Forecasts (ECMWF) is an international intergovernmental organization based at Reading, England that was founded in 1975. ... The National Cholesterol Education Program is a program managed by the National Heart, Lung and Blood Institute, a division of the NIH. Its goal is to reduce increased cardiovascular disease rates due to hypercholesterolemia (evelated cholesterol levels) in the United States of America. ...

Nowcasting

The forecasting of the weather in the 0-6 hour timeframe is often referred to as nowcasting. It is in this range that the human forecaster still has an advantage over computer NWP models. In this time range it is possible to forecast smaller features such as individual shower clouds with reasonable accuracy, however these are often 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.

Below is a sample nowcast, issued by the National Weather Service in Mount Holly, New Jersey: The National Weather Service (NWS) is one of the six scientific agencies that make up the National Oceanic and Atmospheric Administration (NOAA) of the United States government. ... Mount Holly Township highlighted in Burlington County. ...

 000 FPUS71 KPHI 240805 NOWPHI 

 SHORT TERM FORECAST NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 405 AM EDT FRI JUN 24 2005 DEZ002>004-MDZ015-019-020-NJZ013-014-020-022>027-241200- ATLANTIC NJ-ATLANTIC COASTAL CAPE MAY NJ-CAPE MAY NJ-CAROLINE MD- COASTAL ATLANTIC NJ-COASTAL OCEAN NJ-DELAWARE BEACHES DE- EASTERN MONMOUTH NJ-INLAND SUSSEX DE-KENT DE-OCEAN NJ- QUEEN ANNE'S MD-SOUTHEASTERN BURLINGTON NJ-TALBOT MD- WESTERN MONMOUTH NJ- INCLUDING THE CITIES OF...ATLANTIC CITY AND DOVER 405 AM EDT FRI JUN 24 2005 

 .NOW... 

 AREAS OF FOG AND LOW CLOUDS WILL BE OVER SOUTHERN DELAWARE AND PORTIONS OF THE NORTHEASTERN MARYLAND SHORE EARLY THIS MORNING, AS WELL AS ALONG THE NEW JERSEY COAST. THE PATCHY DENSE FOG MAY REDUCE THE VISIBILITY TO A QUARTER MILE OR LESS AT TIMES. IF YOU WILL BE DRIVING THIS MORNING, BE SURE TO LEAVE PLENTY OF ROOM BETWEEN YOUR VEHICLE AND THE ONE AHEAD OF YOU. YOUR VISIBILITY COULD DROP QUICKLY IF YOU DRIVE INTO A DENSE PATCH OF FOG. WATCH ESPECIALLY FOR PEDESTRIANS. THE FOG SHOULD DISSIPATE AN HOUR OR TWO AFTER SUNRISE. $$ 

Punctuation

Written weather forecasts use an idiosyncratic punctuation style, employing heavy use of three-dot ellipses (e.g.: "light rain...strengthening through the night"). It takes the place of a comma and is derived from legacy computer systems (some of which are still active), which did not include a comma in their character sets. The term punctuation has two different linguistic meanings: in general, the act and the effect of punctuating, i. ... It has been suggested that Elliptical construction be merged into this article or section. ...

See also

• Trend estimation
• Forecasting
• Weather wars
• Weather control
• Weather report
• National Collegiate Weather Forecasting Competition
• WxChallenge

A series of measurements of a process may be treated as a time series, and then trend estimation is the application of statistical techniques to make and justify statements about trends in the data. ... Look up forecast in Wiktionary, the free dictionary. ... This article may contain original research or unverified claims. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... Weather Report was a influential jazz fusion band of the 1970s and 1980s, pitting jazz with R&B, funk, and rock elements while still retaining an extremely high level of compositional and improvisational skills. ... The National Collegiate Weather Forecasting Competition or NCWFC is a yearly competition between colleges in the US. The competition is run by Penn State. ...

Websites providing forecasts

Meteorological agencies

These are academic or governmental meteorology organizations. Most provide at least a limited forecast for their area of interest on their website.

• The World Meteorological Organization
• NOAA weather page

  NOAA satellite images

  National Weather Service

• The Met Office of the UK
• European Centre for Medium Range Weather Forecasting (ECMWF)
• Environment Canada Weather Office
• Australian Bureau of Meteorology
• New Zealand MetService
• Meteo Suisse (Swiss Weather Agency, in English
• Afghanistan Meteorological Authority
• Finnish Meteorological Institute
• Instituto Nacional de Meteorología. INM
• Royal Meteorological Institute of Belgium
• Korea Meteorological Administration

Afghanistan Meteorological Authority is located in Kabul, Afghanistan. ...

Commercial organisations

These are high profile commercial sites of varying quality. Most of these companies get their forecasts from the same source, namely the NOAA's GFS model. The National Oceanic and Atmospheric Administration (NOAA) is a scientific agency of the United States Department of Commerce focused on the conditions of the oceans and the atmosphere. ... The Global Forecast System (GFS) is global numerical weather prediction model run by NOAA. This model is run four times a day and produces forecasts up 16 days in advance, but with decreasing spatial and temporal resolution over time (although it is widely accepted that beyond 7 days the forecast...

• UK Weather Services - Long range weather forecast - 14 day weather forecast - Supplied by Cross Media Technologies www.weathersys.com
• Weather Underground — Provides a wide variety of US and international weather information
• Unisys Weather Site — Provides meteorological data, analysis, and forecasts for the US
• Verizon's Weather Forecasts - Provides weather briefs & extended outlook for the U.S. Also powers weather on 20,000 other websites
• United States Weather Center - Free and easy to use weather reports, forecasts, message boards and archives.
• Accuweather — Weather forecasts and weather-related news (US and international)
• The Weather Channel — Weather forecasts and weather-related news mainly for the US, but also has world forecasts.
• BBC Weather — Weather forecasts for the UK and climate overviews for the whole world
• TheWeatherOutlook - A UK based site providing long range forecasts for much of Europe.
• Wetterzentrale - A German language site displaying a large range of high quality weather charts.
• The Weather Network - A Canadian weather forecaster
• Weatherzone - Provides a wide variety of Australian weather information.
• Weather.com.au - Australian weather forecasts.
• Weather News, Inc. (WNI) - Provides weather forecasts to a global audience. Pioneer of mobile weather content.
• Weather Bonk - Google maps mashup offering worldwide interactive realtime temperature maps, forecasts, webcams, satellite overlays, monthly averages and more.

Weather Underground is a commercial organization that provides free, real-time weather information via the Internet. ... AccuWeather is a large American company that provides weather forecasting services. ... For the Australian Weather Channel with the same name, see The Weather Channel, Australia The Weather Channel (TWC) is a cable and satellite television network that broadcasts weather and weather-related news 24 hours a day. ...

Other external links

• Weather prediction blog
• Article on the economic history and impact of weather forecasting from EH.NET
• General descriptions of weather forecasting technology The Science of Meteorology Online
• Learn about calculating weather forecast accuracy Compare how weather forecast accuracy differs between forecasters and between different areas of the United States at ForecastAdvisor.com
• Make your own weather forecast! Download this powerpoint presentation from Lis Cohen's Weather Outreach to learn how.