Weather forecasting is the application of science and technology to predict the state of the atmosphere for a future time and a given location. Temperature and layers The temperature of the Earth's atmosphere varies with altitude the mathematical relationship between temperature and altitude varies among five Human beings have attempted to predict the weather informally for millennia, and formally since at least the nineteenth century. The weather is a set of all the phenomena occurring in a given Atmosphere at a given Time. Weather forecasts are made by collecting quantitative data about the current state of the atmosphere and using scientific understanding of atmospheric processes to project how the atmosphere will evolve. Debt AIDS Trade in Africa (or DATA) is a Multinational non-government organization founded in January 2002 in London by U2 's Meteorology (from Greek grc μετέωρος metéōros, "high in the sky" and grc -λογία -logia) is the Interdisciplinary
Once an all human endeavor based mainly upon changes in barometric pressure, current weather conditions, and sky condition, forecast models are used to determine future conditions. Numerical weather prediction uses current weather conditions as input into Mathematical models of the atmosphere to predict the weather. Human input is still required to pick the best possible forecast model to base the forecast upon, which involves pattern recognition skills, teleconnections, knowledge of model performance, and knowledge of model biases. Teleconnection in Atmospheric science refers to climate anomalies being related to each other at large distances (typically thousands of kilometers The chaotic nature of the atmosphere, the massive computational power required to solve the equations that describe the atmosphere, error involved in measuring the initial conditions, and an incomplete understanding of atmospheric processes mean that forecasts become less accurate as the difference in current time and the time for which the forecast is being made (the range of the forecast) increases. In Mathematics, chaos theory describes the behavior of certain dynamical systems – that is systems whose state evolves with time – that may exhibit dynamics that The use of ensembles and model consenses help narrow the error and pick the most likely outcome.
There are a variety of end users to weather forecasts. The most important of the forecasts, weather warnings, are used to protect life and property. Forecasts based on temperature and precipitation are important to agriculture, and therefore to commodity traders within stock markets. Temperature is a physical property of a system that underlies the common notions of hot and cold something that is hotter generally has the greater temperature Agriculture refers to the production of goods through the growing of plants and fungi and the raising of domesticated Animals The study of agriculture Temperature forecasts are used by utility companies to estimate demand over coming days. On an everyday basis, people use weather forecasts to determine what to wear on a given day and what activities are possible to perform on certain days. Since outdoor activities are severely curtailed by heavy rain and snow, forecasts can be used to plan activities around these events, and more importantly, to plan ahead and survive them. Rain is Liquid precipitation. On Earth it is the condensation of atmospheric Water vapor into drops heavy enough to fall often making it to "Snowfall" redirects here For other uses see Snow (disambiguation or Snowfall (disambiguation.
For millennia people have tried to forecast the weather. In 650 BC, the Babylonians predicted the weather from cloud patterns as well as astrology. Babylon was a City-state of ancient Mesopotamia, the remains of which can be found in present-day Al Hillah, Babil Province, Iraq Astrology (from Greek grc ἄστρον astron, "constellation star" and grc -λογία -logia) is a group of Systems  In about 340 BC, Aristotle described weather patterns in Meteorologica. Aristotle (Greek Aristotélēs) (384 BC – 322 BC was a 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 Chinese weather prediction lore extends at least as far back as 300 BC. 
Ancient weather forecasting methods usually relied on observed patterns of events, also termed pattern recognition. For example, it might be 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. Weather lore is the body of informal Folklore related to the Prediction of the Weather. However, not all of these predictions prove reliable, and many of them have since been found not to stand up to rigorous statistical testing. 
It was not until the invention of the electric telegraph in 1835 that the modern age of weather forecasting began. The electrical telegraph is a telegraph that uses electric signals The electromagnetic telegraph is a device for human-to-human transmission  Before this time, it had not been possible to transport information about the current state of the weather any faster than a steam train. The telegraph allowed reports of weather conditions from a wide area to be received almost instantaneously by the late 1840s.  This allowed forecasts to be made by knowing what the weather conditions were like further upwind. 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). Rear-Admiral Sir Francis Beaufort, FRS, FRGS (7 May 1774 &ndash 17 December 1857 was a Hydrographer and officer in Britain 's Royal Navy The Beaufort scale (ˈboʊfət is an Empirical measure for describing Wind speed based mainly on observed sea conditions Vice-Admiral Robert FitzRoy ( 5 July 1805 – 30 April 1865) achieved lasting fame as the captain of HMS ''Beagle'' History The first barometer is thought to have been built unintentionally by Gasparo Berti, sometime between 1640 and 1643 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 Royal Navy, and formed the basis for all of today's weather forecasting knowledge. England is a Country which is part of the United Kingdom. Its inhabitants account for more than 83% of the total UK population whilst its mainland The Royal Navy of the United Kingdom is the oldest of the British armed services (and is therefore known as the Senior Service) 
Great progress was made in the science of meteorology during the 20th century. Meteorology (from Greek grc μετέωρος metéōros, "high in the sky" and grc -λογία -logia) is the Interdisciplinary The possibility of numerical weather prediction was proposed by Lewis Fry Richardson in 1922, though computers did not exist to complete the vast number of calculations required to produce a forecast before the event had occurred. Numerical weather prediction uses current weather conditions as input into Mathematical models of the atmosphere to predict the weather. Practical use of numerical weather prediction began in 1955, spurred by the development of programmable electronic computers. A computer is a Machine that manipulates data according to a list of instructions.
Surface weather observations of atmospheric pressure, temperature, wind speed, wind direction, humidity, precipitation are made near the earth's surface by trained observers, automatic weather stations or buoys. Numerical weather prediction uses current weather conditions as input into Mathematical models of the atmosphere to predict the weather. A weather station is a facility with instruments and equipment to make observations of atmospheric conditions in order to provide information to make weather forecasts A radiosonde ( Sonde is French for Probe) is a unit for use in Weather balloons that measures various atmospheric parameters A weather satellite is a type of Satellite that is primarily used to monitor the Weather and Climate of the Earth. Surface weather observations are the fundamental data used for safety as well as climatological reasons to forecast weather and issue warnings worldwide Temperature is a physical property of a system that underlies the common notions of hot and cold something that is hotter generally has the greater temperature Humidity is the amount of water vapor in the air In daily language the term "humidity" is normally taken to mean Relative humidity. An automatic weather station (AWS is an automated version of the traditional Weather station, either to save human labour or to enable measurements from remote areas Weather buoys are instruments which collect Weather and Ocean data within the world's oceans 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. METAR (METeorological Aviation Report is a format for reporting Weather information SYNOP ( surface synoptic observations) is a numerical Code (called FM-12 by WMO) used for reporting Weather observations made by manned and automated 
Measurements of temperature, humidity and wind above the surface are found by launching radiosondes (weather balloon). A radiosonde ( Sonde is French for Probe) is a unit for use in Weather balloons that measures various atmospheric parameters A weather or sounding balloon is a Balloon (specifically a type of High altitude balloon) which carries instruments aloft to send back information  Data are usually obtained from near the surface to the middle of the stratosphere, about 21 kilometres (69,000 ft). The stratosphere is the second major layer of Earth's atmosphere, just above the Troposphere, and below the Mesosphere.  In recent years, data transmitted from commercial airplanes through the AMDAR system has also been incorporated into upper air observation, primarily in numerical models. Aircraft Meteorological Data Relay (AMDAR is a program initiated by the World Meteorological Organization. 
Increasingly, data from weather satellites are being used because of their almost global coverage. A weather satellite is a type of Satellite that is primarily used to monitor the Weather and Climate of the Earth.  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 infrared (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. Both polar orbiting and geostationary satellites provide soundings of temperature and moisture throughout the depth of the atmosphere. Sounding is a historical nautical term for measuring depth The term probably originated from the expression of sounding the well &mdash the well being a shaftlike structure  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. 
Meteorological radar provide information on precipitation location and intensity, which can be used to estimate precipitation accumulations over time. A weather radar is a type of Radar used to locate precipitation, calculate its motion estimate its type ( Rain  Additionally, if Doppler weather radar is used then wind speed and direction can be determined. A weather radar is a type of Radar used to locate precipitation, calculate its motion estimate its type ( Rain 
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. Applications of data assimilation arise in many geosciences perhaps most importantly in Weather forecasting and Hydrology. 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 models are computer simulations of the atmosphere. A computer simulation, a computer model or a computational model is a Computer program, or network of computers that attempts to simulate an 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. Physics (Greek Physis - φύσις in everyday terms is the Science of Matter and its motion. Fluid dynamics is the sub-discipline of Fluid mechanics dealing with fluid flow: Fluids ( Liquids and Gases in motion The complicated equations which govern how the state of a fluid changes with time require supercomputers to solve them. FLUID ( F ast L ight '''U'''ser '''I'''nterface D esigner is a graphical editor that is used to produce FLTK Source code A supercomputer is a Computer that is at the frontline of processing capacity particularly speed of calculation (at the time of its introduction The output from the model provides the basis of the weather forecast. 
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. Bias is a term used to describe a Tendency or Preference towards a particular perspective, Ideology or result especially when the tendency interferes 
The simplest method of forecasting the weather, persistence relies upon today's conditions to forecast the conditions tomorrow. This can be a valid way of forecasting the weather when it is steady state, such as during the summer season in the tropics. This method of forecasting strongly depends upon the presence of a stagnant weather pattern. It can be useful in both short range forecasts and long range forecasts. 
Using barometric pressure and the pressure tendency (the change of pressure over time) has been used in forecasting since the late nineteenth century.  The larger the change in pressure, especially if more than 3. 5 hPa, or 0. 10 inch, the larger the change in weather can be expected. If the pressure drop is rapid, a low pressure system in approaching, and there is a greater chance of rain. Rapid pressure rises are associated with improving weather conditions, such as clearing skies. 
Along with pressure tendency, use of the sky condition is one of more important weather parameters that can be 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. Morning fog portends fair conditions, as rainy conditions are preceded by wind or clouds, both of which eliminate the formation of fog. The approach of a line of thunderstorms could indicate the approach of a cold front. A cold front defined as the leading edge of a cooler and drier mass of air Cloud-free skies are indicative of fair weather for the near future.  The use of sky cover in weather prediction has led to various weather lore over the centuries. Weather lore is the body of informal Folklore related to the Prediction of the Weather. 
The forecasting of the weather within the next six hours is often referred to as nowcasting.  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. 
In the past, the human forecaster was responsible for generating the entire weather forecast based upon available observations. The bar (symbol bar) decibar (symbol dbar) and the millibar (symbol mbar, also mb are units of Pressure. Geopotential height is a vertical coordinate referenced to Earth's Mean sea level — an adjustment to geometric height ( Elevation above mean sea level using the  Today, human input is generally confined to choosing a model based on various parameters, such as model biases and performance.  Using a consensus of forecast models, as well as ensemble members of the various models, can help reduce forecast error.  However, regardless how small the average error becomes with any individual system, large errors within any particularly piece of guidance are still possible on any given model run.  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 which may be too small in size to be resolved by the model to add information to the forecast. While increasing accuracy of forecast models implies that humans may no longer be needed in the forecast process at some point in the future, there is currently still a need for human intervention. 
A more complicated way of making a forecast, it requires remembering a previous weather event which 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.  Some call this type of forecasting pattern recognition, which remains a useful method of observing rainfall over data voids such as oceans, as well as the forecasting of precipitation amounts and distribution in the future. A variation on this theme is used in Medium Range forecasting, which is known as teleconnections, when you use systems in other locations to help pin down the location of another system within the surrounding regime. Teleconnection in Atmospheric science refers to climate anomalies being related to each other at large distances (typically thousands of kilometers  One method of using teleconnections are by using ENSO-related phenomena. 
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 and the inexactness of the initial observation set which was used to begin the model run. In Mathematics, chaos theory describes the behavior of certain dynamical systems – that is systems whose state evolves with time – that may exhibit dynamics that 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. In Probability theory and Statistics, correlation, (often measured as a correlation coefficient) indicates the strength and direction of a linear
However, looking at a single forecast gives no indication of how likely that forecast is to be correct. Ensemble forecasting entails the production of many forecasts in order to reflect the uncertainty in the initial state of the atmosphere (due to errors in the observations and insufficient sampling). Ensemble forecasting is a numerical prediction method that is used to attempt to generate a representative sample of the possible future states of a dynamical system 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 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 organisation based at Reading, England that was founded in 1975 The United States National Centers for Environmental Prediction (NCEP delivers national and global weather water climate and space weather guidance forecasts warnings and 
Most end users of forecasts are members of the general public, who have interest in such information for several reasons. Thunderstorms can create strong winds and dangerous lightning strikes that can lead to deaths, power outages, and widespread hail damage. Lightning is an atmospheric discharge of Electricity, which typically occurs during Thunderstorms and sometimes during volcanic eruptions or Heavy snow or rain can bring transportation and commerce to a stand-still, as well as cause flooding in low-lying areas. "Snowfall" redirects here For other uses see Snow (disambiguation or Snowfall (disambiguation. A flood is an overflow of an expanse of water that submerges land a deluge  Excessive heat or cold waves can sicken or kill those with inadequate utilities, and droughts can impact water usage and destroy vegetation. A drought is an extended period of months or years when a region notes a deficiency in its water supply Many use forecasts simply to schedule outdoor recreation or to assist in determining daily attire.
Several countries employ government agencies to provide forecasts and watches/warnings/advisories to the public in order 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 United States' National Weather Service (NWS) and Canada's Meteorological Service of Canada (MSC). The National Weather Service ( NWS) once known as the Weather Bureau is one of the six scientific agencies that make up the National Oceanic and Atmospheric Administration The Meteorological Service of Canada (MSC is a division of Environment Canada, which primarily provides public meteorological information and Weather forecasts  Traditionally, newspaper, television, and radio have been the primary outlets for presenting weather forecast information to the public. A newspaper is a written Publication containing News, information and Advertising, usually printed on low-cost paper called Newsprint. Television ( TV) is a widely used Telecommunication medium for sending ( Broadcasting) and receiving moving Images, either monochromatic Radio is the transmission of signals by Modulation of electromagnetic waves with frequencies below those of visible Light. Increasingly, the internet is being used due to the vast amount of specific information that can be found.  In all cases, these outlets update their forecasts on a regular basis, in accordance with their respective publication schedules.
A major part of modern weather forecasting is the severe weather alerts and advisories which the national weather services issue in the case that severe or hazardous weather is expected. This is done to protect life and property.  Some of the most commonly known of severe weather advisories are the severe thunderstorm and tornado warning, as well as the severe weather or the tornado watch. Other forms of these advisories include winter weather, high wind, flood, tropical cyclone, and fog. A tropical cyclone is a storm system characterized by a low pressure center and numerous Thunderstorms that produce strong winds and Flooding  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. The Emergency Alert System (EAS is a national warning system in the U 
The aviation industry is especially sensitive to the weather. Chaitén is a volcanic Caldera in diameter 17km west of the elongated ice-capped Michinmahuida volcano and northeast of Chaitén town in the Llao LLaojpg|thumb|250px| Lake Nahuel Huapi, near Bariloche, Argentina Fog and/or exceptionally low ceilings can prevent many aircraft from landing and taking off. Fog is a cloud that is in contact with the ground Stratus clouds are usually the only clouds that touch the ground  Similarly, turbulence and icing can be hazards whilst in flight. In Fluid dynamics, turbulence or turbulent flow is a fluid regime characterized by chaotic Stochastic property changes Atmospheric icing occurs when Water droplets in the air freeze on objects they contact  Thunderstorms are a problem for all aircraft because of severe turbulence due to their updrafts and outflow boundaries, 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. Hail is a form of precipitation which consists of balls or irregular lumps of ice (hailstones Lightning is an atmospheric discharge of Electricity, which typically occurs during Thunderstorms and sometimes during volcanic eruptions or  Volcanic ash is also a significant problem for aviation, as aircraft can lose engine power within ash clouds. Volcanic ash consists of small Tephra, which are bits of pulverized rock and glass created by volcanic eruptions less than in diameter  On a day to day basis airliners are routed to take advantage of the jet stream tailwind to improve fuel efficiency. Jet streams are fast flowing relatively narrow air currents found at the Tropopause, the transition between the Troposphere (where temperature decreases  Aircrews are briefed prior to take off on the conditions to expect en route and at their destination. Takeoff is the phase of Flight in which an Aircraft goes through a transition from moving along the ground ( Taxiing) to flying in the air usually  Additionally, runway orientation is often changed to take advantage of a headwind to reduce the distance required for takeoff, and to eliminate potential crosswinds. A runway ( RWY) is a strip of land on an Airport, on which Aircraft can take off and land. A headwind is a Wind that blows against the direction of travel of an object Takeoff is the phase of Flight in which an Aircraft goes through a transition from moving along the ground ( Taxiing) to flying in the air usually 
Commercial and recreational use of waterways can be limited significantly by wind direction and speed, 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). MAFOR, an abbreviation of MA rine FOR cast is a code used in the transmission of marine Weather Forecasts to compresses a volume of 
Farmers rely on weather forecasts to decide what work to do on any particular day. A farmer is a person who raises living organisms for food or raw materials For example, drying hay is only feasible in dry weather. Hay is a generic term for grass or Legumes that have been cut dried and stored for use as animal feed, particularly for grazing animals like Prolonged periods of dryness can ruin cotton, wheat, and 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. For the Christian Alternative band please see Silage (band Silage is fermented, high-moisture Fodder that can  Frosts 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.  Orange groves can suffer significant damage during frosts and freezes, regardless of their timing. 
Electricity and gas companies rely on weather forecasts to anticipate demand which can be strongly affected by the weather. A degree day is a measure of Heating or cooling Totalised degree days from an appropriate starting date are used to plan the planting of crops and management of 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). Heating degree day ( HDD) and cooling degree day ( CDD) are quantitative indices designed to reflect the Demand for Energy These quantities are based on a daily average temperature of 65 °F (18 °C). Cooler temperatures force heating degree days (one per degree Fahrenheit), while warmer temperatures force cooling degree days.  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. The term air conditioning refers to the cooling and dehumidification of indoor air for Thermal comfort.  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 brownouts and blackouts. A power outage (also known as power cut, power failure, power loss, or blackout) is the loss of the Electricity supply to an A power outage (also known as power cut, power failure, power loss, or blackout) is the loss of the Electricity supply to an 
Increasingly, private companies pay for weather forecasts tailored to their needs so that they can increase their profits or 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. Weather forecasts can be used to invest in the stock market, such as futures in oranges, corn, soybeans, and oil. 
Similarly to the private sector, military weather forecasters present weather conditions to the war fighter community. They 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. The United States Navy provides a special service to both themselves and the rest of the federal government by issuing forecasts for tropical cyclone across the Pacific and Indian Oceans through their Joint Typhoon Warning Center. The Joint Typhoon Warning Center (JTWC is a joint United States Navy &ndash United States Air Force task force located at Naval Maritime Forecast Center 
Within the United States, four branches of the armed forces have independent weather forecasting techniques tailored for their specific needs: 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; United States Coast Guard marine science technicians provide ship forecasts for ice breakers and other various operations within their realm; and Marine forecasters provide support for ground- and air-based United States Marine Corps operations. An air force, also known in some countries as an air army or historically an army air corps, is in the broadest sense the national military or armed service  All four military branches take their initial meteorology training at Keesler Air Force Base. Keesler Air Force Base is a United States Air Force base located in Biloxi, a city in Harrison County, Mississippi, United  Military and civilian forecasters actively cooperate in analyzing, creating and critiquing weather forecast products.
These are academic or governmental meteorology organizations. Most provide at least a limited forecast for their area of interest on their website.