National Weather Service

National Weather Service

Overview
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
National Oceanic and Atmospheric Administration
The National Oceanic and Atmospheric Administration , pronounced , like "noah", is a scientific agency within the United States Department of Commerce focused on the conditions of the oceans and the atmosphere...

 (NOAA) of the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 government
Federal government of the United States
The federal government of the United States is the national government of the constitutional republic of fifty states that is the United States of America. The federal government comprises three distinct branches of government: a legislative, an executive and a judiciary. These branches and...

. It is headquartered in Silver Spring, Maryland
Silver Spring, Maryland
Silver Spring is an unincorporated area and census-designated place in Montgomery County, Maryland, United States. It had a population of 71,452 at the 2010 census, making it the fourth most populous place in Maryland, after Baltimore, Columbia, and Germantown.The urbanized, oldest, and...

.

The NWS is tasked with providing "weather, hydrologic, and climate forecasts and warnings for the United States, its territories, adjacent waters and ocean areas, for the protection of life and property and the enhancement of the national economy." This is done through a collection of national and regional centers, and 122 local weather forecast offices (WFOs).
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Encyclopedia
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
National Oceanic and Atmospheric Administration
The National Oceanic and Atmospheric Administration , pronounced , like "noah", is a scientific agency within the United States Department of Commerce focused on the conditions of the oceans and the atmosphere...

 (NOAA) of the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 government
Federal government of the United States
The federal government of the United States is the national government of the constitutional republic of fifty states that is the United States of America. The federal government comprises three distinct branches of government: a legislative, an executive and a judiciary. These branches and...

. It is headquartered in Silver Spring, Maryland
Silver Spring, Maryland
Silver Spring is an unincorporated area and census-designated place in Montgomery County, Maryland, United States. It had a population of 71,452 at the 2010 census, making it the fourth most populous place in Maryland, after Baltimore, Columbia, and Germantown.The urbanized, oldest, and...

.

The NWS is tasked with providing "weather, hydrologic, and climate forecasts and warnings for the United States, its territories, adjacent waters and ocean areas, for the protection of life and property and the enhancement of the national economy." This is done through a collection of national and regional centers, and 122 local weather forecast offices (WFOs). Since the NWS is a government agency, most of its products are in the public domain and available free of charge.

History


In 1870 the Weather Bureau was established through a joint resolution
Joint resolution
In the United States Congress, a joint resolution is a legislative measure that requires approval by the Senate and the House and is presented to the President for his/her approval or disapproval, in exactly the same case as a bill....

 of Congress
United States Congress
The United States Congress is the bicameral legislature of the federal government of the United States, consisting of the Senate and the House of Representatives. The Congress meets in the United States Capitol in Washington, D.C....

 signed by President Ulysses S. Grant
Ulysses S. Grant
Ulysses S. Grant was the 18th President of the United States as well as military commander during the Civil War and post-war Reconstruction periods. Under Grant's command, the Union Army defeated the Confederate military and ended the Confederate States of America...

 with the mission "to provide for taking meteorological observations at the military stations in the interior of the continent and at other points in the States and Territories...and for giving notice on the northern (Great) Lakes and on the seacoast by magnetic telegraph and marine signals, of the approach and force of storms." The agency was placed under the Secretary of War
United States Secretary of War
The Secretary of War was a member of the United States President's Cabinet, beginning with George Washington's administration. A similar position, called either "Secretary at War" or "Secretary of War," was appointed to serve the Congress of the Confederation under the Articles of Confederation...

 because "military discipline would probably secure the greatest promptness, regularity, and accuracy in the required observations." Within the Department of War, it was assigned to the U.S. Army Signal Corps under Brigadier General Albert J. Myer
Albert J. Myer
Albert James Myer was a surgeon and United States Army officer. He is known as the father of the U.S. Army Signal Corps, as its first chief signal officer just prior to the American Civil War, the inventor of wig-wag signaling , and also as the father of the U.S...

. General Myer gave the National Weather Service its first name: The Division of Telegrams and Reports for the Benefit of Commerce.

The agency first became a civilian enterprise in 1890, when it became part of the Department of Agriculture
United States Department of Agriculture
The United States Department of Agriculture is the United States federal executive department responsible for developing and executing U.S. federal government policy on farming, agriculture, and food...

; it would later be moved to the Department of Commerce
United States Department of Commerce
The United States Department of Commerce is the Cabinet department of the United States government concerned with promoting economic growth. It was originally created as the United States Department of Commerce and Labor on February 14, 1903...

 in 1940. The first Weather Bureau radiosonde
Radiosonde
A radiosonde is a unit for use in weather balloons that measures various atmospheric parameters and transmits them to a fixed receiver. Radiosondes may operate at a radio frequency of 403 MHz or 1680 MHz and both types may be adjusted slightly higher or lower as required...

 was launched in Massachusetts
Massachusetts
The Commonwealth of Massachusetts is a state in the New England region of the northeastern United States of America. It is bordered by Rhode Island and Connecticut to the south, New York to the west, and Vermont and New Hampshire to the north; at its east lies the Atlantic Ocean. As of the 2010...

 in 1937, which went on to replace all routine aircraft observation within two years. The Bureau became part of the Environmental Science Services Administration
Environmental Science Services Administration
The U. S. Environmental Science Services Administration was a United States Federal executive agency created in 1965 as part of a reorganization of the United States Department of Commerce...

 (ESSA), when that agency was formed in August 1966. ESSA, in turn, was renamed the National Oceanic and Atmospheric Administration
National Oceanic and Atmospheric Administration
The National Oceanic and Atmospheric Administration , pronounced , like "noah", is a scientific agency within the United States Department of Commerce focused on the conditions of the oceans and the atmosphere...

 (NOAA) on 1 October 1970, with the enactment of the National Environmental Policy Act
National Environmental Policy Act
The National Environmental Policy Act is a United States environmental law that established a U.S. national policy promoting the enhancement of the environment and also established the President's Council on Environmental Quality ....

. At this time, the Weather Bureau became the National Weather Service.

Forecasting



The NWS issues a comprehensive package of forecast products to support a variety of users, including the general public. Although text forecasts have been the primary means of product dissemination, the NWS has been converting its forecast products to a digital, gridded format. Each of the 122 Weather Forecast Offices (WFOs) send their graphical forecasts to a national server to be compiled in the National Digital Forecast Database (NDFD). This is a collection of sensible weather elements such as: maximum and minimum temperature, humidity, cloud cover, probability of precipitation, amount of precipitation and wintry precipitation, weather type, and wind direction and speed. In addition to viewing gridded weather data via the internet, more advanced users can decode the individual grids using a "GRIB2 decoder" which can output data as shapefiles, netCDF, GrADS, float files, and comma separated variable files. Specific points in the digital database can be accessed using an XML SOAP
SOAP
SOAP, originally defined as Simple Object Access Protocol, is a protocol specification for exchanging structured information in the implementation of Web Services in computer networks...

 service. These capabilities have greatly increased the audience of NDFD data. The NWS has received some criticism from commercial weather vendors for providing graphical forecast data free of charge. They argue that such tailored forecast information compete with their own products. However, a large majority of private weather firms quickly realized its potential benefits and have flourished by using the NDFD as a tool for composing their products.

Aviation



The NWS supports the aviation community through the production of several specific forecast products. Each WFO has responsibility for the issuance of Terminal Aerodrome Forecast
Terminal Aerodrome Forecast
In meteorology and aviation, TAF is a format for reporting weather forecast information, particularly as it relates to aviation. "TAF" is an acronym of Terminal Aerodrome Forecast or, in some countries, Terminal Area Forecast....

s (TAF) for one or more airports in their jurisdiction. TAFs are concise, coded 24-hour forecasts (30-hour forecasts for certain large hub airports) for a specific airport, issued every six hours with amendments as needed. As opposed to a public weather forecast, a TAF only addresses weather elements critical to aviation. These are: wind
Wind
Wind is the flow of gases on a large scale. On Earth, wind consists of the bulk movement of air. In outer space, solar wind is the movement of gases or charged particles from the sun through space, while planetary wind is the outgassing of light chemical elements from a planet's atmosphere into space...

, visibility
Visibility
In meteorology, visibility is a measure of the distance at which an object or light can be clearly discerned. It is reported within surface weather observations and METAR code either in meters or statute miles, depending upon the country. Visibility affects all forms of traffic: roads, sailing...

, weather, sky condition (clouds)
Cloud
A cloud is a visible mass of liquid droplets or frozen crystals made of water and/or various chemicals suspended in the atmosphere above the surface of a planetary body. They are also known as aerosols. Clouds in Earth's atmosphere are studied in the cloud physics branch of meteorology...

, and optional data such as wind shear
Wind shear
Wind shear, sometimes referred to as windshear or wind gradient, is a difference in wind speed and direction over a relatively short distance in the atmosphere...

. The following is an example of a TAF for Will Rogers World Airport
Will Rogers World Airport
Will Rogers World Airport , also known as Will Rogers Airport or simply Will Rogers, is located in southwestern Oklahoma City, Oklahoma 6 miles from downtown and is the principal commercial airport of the Oklahoma City Metropolitan Area...

 in Oklahoma City
Oklahoma City, Oklahoma
Oklahoma City is the capital and the largest city in the state of Oklahoma. The county seat of Oklahoma County, the city ranks 31st among United States cities in population. The city's population, from the 2010 census, was 579,999, with a metro-area population of 1,252,987 . In 2010, the Oklahoma...

:

KOKC 212350Z 220024 10006KT P6SM SCT040 BKN120
TEMPO 2200/2201 VRB15G25KT 2SM +TSRA BKN040CB OVC070
FM220100 10007KT P6SM SCT040CB BKN060 BKN120
TEMPO 2201/2205 2SM +TSRA BKN030CB OVC050
FM220500 07006KT 5SM SHRA BKN030CB OVC050
TEMPO 2205/2208 3SM +TSRA OVC030CB
FM221200 03006KT P6SM -SHRA BKN025 OVC070
FM221600 05007KT P6SM BKN035 OVC100

21 NWS Center Weather Service Units (CWSU) are collocated with the Federal Aviation Administration (FAA)
Federal Aviation Administration
The Federal Aviation Administration is the national aviation authority of the United States. An agency of the United States Department of Transportation, it has authority to regulate and oversee all aspects of civil aviation in the U.S...

 Air Route Traffic Control Centers (ARTCC)
Area Control Center
In air traffic control, an Area Control Center , also known as a Center, is a facility responsible for controlling instrument flight rules aircraft en route in a particular volume of airspace at high altitudes between airport approaches and departures...

. Their main responsibility is to provide up-to-the-minute weather information and briefings to the Traffic Management Units and control room supervisors. Special emphasis is given to weather conditions that would be hazardous to aviation or would impede the flow of air traffic in the National Airspace System
National Airspace System
The National Airspace System of the United States is one of the most complex aviation systems in the world — consisting of thousands of people, procedures, facilities, and pieces of equipment — that enables safe and expeditious air travel in the United States and over large portions of the world's...

. Beside scheduled and unscheduled briefings for decision-makers in the ARTCC and other FAA facilities, CWSU meteorologists also issue two unscheduled products. The Center Weather Advisory (CWA) is an aviation weather warning for thunderstorms, icing, turbulence, and low cloud ceilings
Ceiling (cloud)
- ICAO :The height above the ground or water of the base of the lowest layer of cloud below 6000 meters covering more than halfthe sky.- United Kingdom :...

 and visibilities. The Meteorological Impact Statement (MIS) is a 2-12 hour forecast for weather conditions which are expected to impact ARTCC operations.

The Aviation Weather Center (AWC), located in Kansas City, MO, is a central aviation-support facility operated by the National Weather Service. The AWC issues two primary products:
  • AIRMET
    AIRMET
    An AIRMET, or Airmen's Meteorological Information, is a concise description of weather phenomena that are occurring or may occur along an air route that may affect aircraft safety...

     (Airmen's Meteorological Information): Information on icing
    Icing conditions
    In aviation, icing conditions are those atmospheric conditions that can lead to the formation of water ice on the surfaces of an aircraft, or within the engine as carburetor icing. Inlet icing is another engine-related danger, often occurring in jet aircraft. These icing phenomena do not...

    , turbulence
    Turbulence
    In fluid dynamics, turbulence or turbulent flow is a flow regime characterized by chaotic and stochastic property changes. This includes low momentum diffusion, high momentum convection, and rapid variation of pressure and velocity in space and time...

    , mountain obscuration, low-level wind shear
    Wind shear
    Wind shear, sometimes referred to as windshear or wind gradient, is a difference in wind speed and direction over a relatively short distance in the atmosphere...

    , IMC conditions
    Instrument meteorological conditions
    Instrument meteorological conditions is an aviation flight category that describes weather conditions that require pilots to fly primarily by reference to instruments, and therefore under Instrument Flight Rules , rather than by outside visual references under Visual Flight Rules . Typically, this...

    , and strong surface winds.
  • SIGMET
    SIGMET
    SIGMET, or Significant Meteorological Information, is a weather advisory that contains meteorological information concerning the safety of all aircraft. There are two types of SIGMETs, convective and non-convective...

    s (Significant Meteorological Information)
    • Convective: Issued for an area of thunderstorms affecting an area of 3000 square miles (7,770 km²) or greater, a line of thunderstorms at least 60 nmi (111.1 km) long, and/or severe or embedded thunderstorms affecting any area that are expected to last 30 minutes or longer.
    • Non-convective: Issued for severe or greater turbulence over a 3000 square miles (7,770 km²) area, severe or greater icing over a 3000 square miles (7,770 km²), or IMC conditions
      Instrument meteorological conditions
      Instrument meteorological conditions is an aviation flight category that describes weather conditions that require pilots to fly primarily by reference to instruments, and therefore under Instrument Flight Rules , rather than by outside visual references under Visual Flight Rules . Typically, this...

       over a 3000 square miles (7,770 km²) area due to dust, sand, or volcanic ash.

Fire weather



Supporting national, regional and local land management agencies such as the US Forest Service, the NWS issues a complete Fire Weather Forecast twice daily, with updates as needed. The forecast contains weather information relevant to fire control and smoke management for the next 12–48 hours. The appropriate crews use this information to plan for staffing and equipment levels, the ability to do prescribed burns, and assess the daily fire danger. Once per day, NWS meteorologists issue a coded fire weather forecast for specific USFS observation sites that are then input into the National Fire Danger Rating System
National Fire Danger Rating System
-Background:John J. Keetch, a fire researcher in the southeast, wrote:"One of the prime objectives of the National Fire Danger Rating System is to provide as accurate a measure as possible of the relative seriousness of burning conditions and thereby, NFDRS can serve as an aid to fire control...

 (NFDRS). This computer model outputs the daily fire danger that is then conveyed to the public in one of five ratings: low, moderate, high, very high, or extreme.

The local weather office also, under a prescribed set of criteria, will determine if a Fire Weather Watch or a Red Flag Warning needs to be issued. These products alert not only the public, but other agencies that conditions are creating the potential for extreme fire behavior.

On the national level, the NWS Storm Prediction Center
Storm Prediction Center
The Storm Prediction Center , located in Norman, Oklahoma, is tasked with forecasting the risk of severe thunderstorms and tornadoes in the contiguous United States. The agency issues convective outlooks, mesoscale discussions, and watches as a part of this process...

 issues fire weather analyses for days one and two. These include large-scale areas that may experience critical fire weather conditions including the occurrence of "dry thunderstorms." These are thunderstorms, usually occurring in the western U.S., that are not accompanied by any rain due to it evaporating before reaching the surface.

State and Federal forestry officials sometimes request a forecast from a WFO for a specific location called a "spot forecast." Spot forecasts are used to determine whether it will be safe to ignite a prescribed burn and how to situate crews during the controlling phase. Officials send in a request, usually during the early morning, containing the position coordinates of the proposed burn, the ignition time, and other pertinent information. The WFO composes a short-term fire weather forecast for the location and sends it back to the officials, usually within an hour of receiving the request.

The NWS assists officials at large wildfires or other disasters, including HAZMAT
Hazmat
Hazmat, HazMat and similar terms can refer to:* Hazardous materials and items—see Dangerous goods** Hazchem—a system of hazardous chemical classification and firefighting modes** A hazmat suit is a type of protective clothing...

 incidents, by providing on-site support through Incident Meteorologists (IMET). IMETs are NWS forecasters specially trained to work with Incident Management Teams during severe wildfire outbreaks or other disasters requiring on-site weather support. IMETs travel quickly to the incident site and then assemble a mobile weather center capable of providing continuous meteorological support for the duration of the incident. The kit includes a cell phone, a laptop computer and communications equipment, used for gathering and displaying weather data such as satellite imagery or numerical forecast model output. Remote weather stations are also used to gather specific data for the point of interest. They often receive direct support from the local WFO during such crises. IMETS can be deployed anywhere a disaster strikes and must be capable of working long hours for weeks at a time in remote locations under rough conditions. There are approximately 70 to 80 IMETs nationally.

Public



A significant portion of NWS forecasting is directed toward the general public. Because coded products are very difficult to understand by someone not familiar with the coding, most NWS public products are written using basic meteorological terminology in a sentence format. The main public forecasts products are:
  • Zone Forecast Product (ZFP) – text product issued by all WFOs to explicitly state expected weather conditions within each zone in their area of forecast responsibility through day seven.
  • Surf Zone Forecast (SRF) – a text forecast for local beaches issued by coastal WFOs, including coastal hazard information such as that pertaining to rip currents. These products are issued year-round at the Los Angeles, San Diego, and New York City offices, and seasonally at most other coastal offices.
  • Short Term Forecast (NOW) – a localized, event-driven product used to provide the public with detailed weather information during significant and/or fast-changing hydrometeorological conditions during the next six hours.
  • Area Forecast Matrices (AFM) – displays various weather parameters at 3, 6 and 12 hour intervals for areas specified in the current ZFP.
  • Point Forecast Matrices (PFM) – displays various weather parameters at 3, 6 and 12 hour intervals for significant cities in the WFO area of responsibility.
  • Tabular State Forecast Product (SFT) – general seven-day public forecast of hydrometeorological conditions at specific locations over a WFO's area of responsibility.
  • Area Forecast Discussion (AFD) – a semi-technical product primarily for explaining the scientific rationale behind a forecast and to summarize current watches/warnings/advisories in effect.
  • Graphicast – a forecast picture using basic meteorology descriptions of the weather, and weather map icons. This product has been available since at least mid 2008. It is slowly expanding to most weather forecast office websites.


NWS forecasts are available from their website. Previously, upon clicking a location on the map, the zone forecast for that county would appear. Now that the National Digital Forecast Database is operational, the internet forecasts have become "point-and-click," with the web server instantly composing a narrative text forecast for a particular point on the grid. This capability greatly reduces discontinuities in the forecast and takes full advantage of the detail put into the forecast by NWS meteorologists. Here is one example of a tornado warning issued by the National Weather Service:
THE NATIONAL WEATHER SERVICE IN NORMAN HAS ISSUED A
  • TORNADO WARNING FOR...

CENTRAL LOGAN COUNTY IN CENTRAL OKLAHOMA...
PAYNE COUNTY IN CENTRAL OKLAHOMA...
SOUTHEASTERN NOBLE COUNTY IN NORTHERN OKLAHOMA...
  • UNTIL 630 PM CDT


Hydrologic


The NWS is the primary source for rainfall forecasts, hydrologic watches, warnings, and advisories for the United States of America. While the Hydrometeorological Prediction Center
Hydrometeorological Prediction Center
The Hydrometeorological Prediction Center is one of nine service centers under the umbrella of the National Centers for Environmental Prediction , a part of the National Weather Service, which in turn is part of the National Oceanic and Atmospheric Administration of the U.S. government...

 provides guidance for future precipitation amounts and areas where excessive rainfall is likely, local NWS offices are responsible for issuing: Flood Watches, Flash Flood Watches, Flood Warnings, Flash Flood Warnings and Flood Advisories for their local County Warning Area, as well as the official rainfall forecast for their county warning areas. These products can and do emphasize different hydrologic issues depending on geographic area, land use, time of year, as well as other meteorological and non-meteorological factors. For example, during the early spring or late winter a Flood Warning can be issued for an ice jam that occurs on a river, while in the summer a Flood Warning will most likely be issued for excessive rainfall.
In recent years the NWS has enhanced its dissemination of hydrologic information through the Advanced Hydrologic Prediction Service, more commonly referred to by the acronym (AHPS). AHPS allows anyone to view near real time observation and forecast data for rivers, lakes and streams. AHPS also enables the NWS to provide long-range probabilistic information which can be used for long-range planning decisions.

Daily river forecasts are issued by the 13 River Forecast Centers (RFC) using hydrologic models based on rainfall, soil characteristics, precipitation forecasts, and several other variables. The first such center was founded on September 23, 1946. Some RFCs, especially those in mountainous regions, also provide seasonal snow pack and peak flow forecasts. These forecasts are used by a wide range of users, including those in agriculture, hydroelectric dam
Hydroelectricity
Hydroelectricity is the term referring to electricity generated by hydropower; the production of electrical power through the use of the gravitational force of falling or flowing water. It is the most widely used form of renewable energy...

 operation, and water supply
Water resources
Water resources are sources of water that are useful or potentially useful. Uses of water include agricultural, industrial, household, recreational and environmental activities. Virtually all of these human uses require fresh water....

 resources.

Marine


The NWS's mission to protect life and property and to enhance the national economy includes a suite of products for the water bodies adjacent to the U.S.. The marine forecasting program is aimed at promoting safe and efficient transportation, both commercial and recreational. NWS national centers or WFOs issue several marine products:
  • Coastal Waters Forecast (CWF) – a text product issued by all coastal WFOs to explicitly state expected weather conditions within their marine forecast area of responsibility through day 5. Also addresses expect wave heights.
  • Offshore Waters Forecast (OFF) – a text product that provides forecast and warning information to mariners who travel on the oceanic waters adjacent to the U.S. coastal waters through day 5. Issued by the Ocean Prediction Center
    Ocean Prediction Center
    The Ocean Prediction Center , established in 1995, is one of the National Centers for Environmental Prediction’s original six service centers. Until January 12, 2003, the name of the organization was the Marine Prediction Center. Its origins are traced back to the sinking of the RMS Titanic in...

     (OPC).
  • NAVTEX forecast – a text forecast issued by OPC designed to accommodate broadcast restrictions of the U.S. Coast Guard NAVTEX transmitters. The product is a combination of the CWF and OFF.
  • High Seas Forecast (HSF) – routine text product issued every six hours by OPC to provide warning and forecast information to mariners who travel on the oceanic waters.

Tropical


The National Hurricane Center
National Hurricane Center
The National Hurricane Center , located at Florida International University in Miami, Florida, is the division of the National Weather Service responsible for tracking and predicting weather systems within the tropics between the Prime Meridian and the 140th meridian west poleward to the 30th...

 (NHC) and the Central Pacific Hurricane Center
Central Pacific Hurricane Center
The Central Pacific Hurricane Center of the United States National Weather Service is the official body responsible for tracking and issuing tropical cyclone warnings, watches, advisories, discussions, and statements for the Central North Pacific Basin...

 (CPHC) are responsible for monitoring tropical weather in the Atlantic
Atlantic Ocean
The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...

, and central and eastern Pacific Ocean
Pacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...

. In addition to routine outlooks and discussions, they initiate advisories and discussions on individual tropical cyclone
Tropical cyclone
A tropical cyclone is a storm system characterized by a large low-pressure center and numerous thunderstorms that produce strong winds and heavy rain. Tropical cyclones strengthen when water evaporated from the ocean is released as the saturated air rises, resulting in condensation of water vapor...

s, as needed. If a tropical cyclone
Tropical cyclone
A tropical cyclone is a storm system characterized by a large low-pressure center and numerous thunderstorms that produce strong winds and heavy rain. Tropical cyclones strengthen when water evaporated from the ocean is released as the saturated air rises, resulting in condensation of water vapor...

 threatens the United States or its territories, individual WFOs begin issuing statements detailing the expected local effects. The following tropical weather products are issued by the NWS:
  • Routine Products
    • Tropical Weather Outlook (TWO)
      • Atlantic basin
      • Pacific basin
    • Tropical Weather Discussion (TWD)
      • Atlantic basin
      • Pacific basin
    • Tropical Weather Summary (TWS)
    • Satellite Interpretation Message (SIM)
  • Active Tropical Cyclone Products
    • Tropical/Subtropical Cyclone Public Advisory (TCP)
    • Tropical/Subtropical Cyclone Discussion (TCD)
    • Tropical Cyclone Forecast/Advisory (TCM)
    • Strike Probabilities of Tropical Cyclone Conditions (SPF)
  • Local WFO Products
    • Hurricane Local Statement (HLS)
    • Inland Tropical Storm/Hurricane Watches or Warnings (NPW)
    • Post-Tropical Cyclone Reports (PSH)



Climate


The Climate Prediction Center
Climate Prediction Center
The Climate Prediction Center is one of the National Centers for Environmental Prediction, which are a part of NOAA's National Weather Service. It is located in Camp Springs, Maryland.-Products:...

 (CPC) is responsible for all of the NWS's climate-related forecasts. Their mission is to "serve the public by assessing and forecasting the impacts of short-term climate variability, emphasizing enhanced risks of weather-related extreme events, for use in mitigating losses and maximizing economic gains." Their products cover time scales from a week to seasons, extending into the future as far as technically feasible, and cover the land, the ocean, and the atmosphere, extending into the stratosphere. Most of their products cover the Contiguous U.S. and Alaska.

Additionally, Weather Forecast Offices issue daily and monthly climate reports for official climate stations within their area of responsibility. These generally include recorded highs, lows and other information. This information is considered preliminary until certified by the National Climatic Data Center
National Climatic Data Center
The United States National Climatic Data Center in Asheville, North Carolina is the world's largest active archive of weather data. The center became established in late 1951, with the move into the new facility occurring in early 1952....

.

Data acquisition



Surface observations


The Automated Surface Observing System (ASOS) is a joint effort of the National Weather Service (NWS), the Federal Aviation Administration (FAA), and the Department of Defense (DOD). The ASOS serves as the nation's primary surface weather observing network. It is designed to support weather forecast activities and aviation operations and, at the same time, support the needs of the meteorological, hydrological, and climatological research communities. ASOS was especially designed for the safety of the aviation community, therefore the sites are almost always located near airport runways. The system transmits routine hourly observations along with special observations when conditions exceed preselected weather element thresholds (e.g. the visibility decreases to less than 3 miles). The basic weather elements observed are: sky condition, visibility, present weather, obstructions to vision, pressure, temperature, dewpoint, wind direction and speed, precipitation accumulation, and selected significant remarks. The coded observations are issued as METAR
METAR
METAR is a format for reporting weather information. A METAR weather report is predominantly used by pilots in fulfillment of a part of a pre-flight weather briefing, and by meteorologists, who use aggregated METAR information to assist in weather forecasting....

s and look similar to this:
METAR KNXX 121155Z 03018G29KT 1/4SM +TSSN FG VV002 M05/M07 A2957 RMK PK WND 01029/1143 SLP026
SNINCR 2/10 RCRNR T2 SET 6///// 7//// 4/010 T10561067 11022 21056 55001 PWINO PNO FZRANO

Getting more information on the atmosphere, more frequently, and from more locations is the key to improving forecasts and warnings. Due to the large installation and operating costs associated with ASOS, the stations are widely spaced. Before aviation weather observing began, the Cooperative Observer Program (COOP) was the only means for acquiring daily weather information. This network of approximately 11,000 mostly volunteer weather observers still flourishes today, providing much of the meteorological and climatological data to the country. The program which was established in 1890 under the Organic Act, currently has a twofold mission:
  • Provide observational meteorological data, usually consisting of daily maximum and minimum temperatures, snowfall, and 24-hour precipitation totals, required to define the climate of the United States and to help measure long-term climate changes.
  • Provide observational meteorological data in near real-time to support forecast, warning and other public service programs of the NWS.

Marine observations




NWS forecasters need frequent, high-quality marine observations to examine conditions for forecast preparation and to verify their forecasts after they are produced. These observations are especially critical to the output of numerical weather models
Numerical weather prediction
Numerical weather prediction uses mathematical models of the atmosphere and oceans to predict the weather based on current weather conditions. Though first attempted in the 1920s, it was not until the advent of computer simulation in the 1950s that numerical weather predictions produced realistic...

 because large water bodies have a profound impact on the weather. Other users rely on the observations and forecasts for commercial and recreational activities. To help meet these needs, the NWS's National Data Buoy Center
National Data Buoy Center
The National Data Buoy Center is a part of the National Oceanic and Atmospheric Administration's National Weather Service...

 (NDBC) operates a network of about 90 buoys and 60 land-based coastal observing systems (C-MAN). All stations measure wind speed, direction, and gust; barometric pressure; and air temperature. In addition, all buoy stations, and some C-MAN stations, measure sea surface temperature and wave height and period. Conductivity and water current are measured at selected stations. All stations report hourly.

Supplemental weather observations are acquired through the United States Voluntary Observing Ship (VOS) program. It is organized for the purpose of obtaining weather and oceanographic observations from transiting ships. An international program under World Meteorological Organization (WMO) marine auspices, the VOS has forty-nine countries as participants. The United States program is the largest in the world, with nearly 1,000 vessels. Observations are taken by deck officers, coded in a special format known as the "ships synoptic code", and transmitted in realtime to the NWS. They are then distributed on national and international circuits for use by meteorologists in weather forecasting, by oceanographers, ship routing services, fishermen, and many others. The observations are then forwarded for use by the National Climatic Data Center (NCDC) in Asheville, North Carolina.

Upper air observations



Upper air weather data is essential for weather forecasting and research. The NWS operates 92 radiosonde
Radiosonde
A radiosonde is a unit for use in weather balloons that measures various atmospheric parameters and transmits them to a fixed receiver. Radiosondes may operate at a radio frequency of 403 MHz or 1680 MHz and both types may be adjusted slightly higher or lower as required...

 locations in North America and 10 sites in the Caribbean. A small, expendable instrument package is suspended below a 2 metres (6.6 ft) wide balloon filled with hydrogen
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...

 or helium
Helium
Helium is the chemical element with atomic number 2 and an atomic weight of 4.002602, which is represented by the symbol He. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas that heads the noble gas group in the periodic table...

, then released daily at or shortly after 11 UTC
Coordinated Universal Time
Coordinated Universal Time is the primary time standard by which the world regulates clocks and time. It is one of several closely related successors to Greenwich Mean Time. Computer servers, online services and other entities that rely on having a universally accepted time use UTC for that purpose...

 and 23 UTC
Coordinated Universal Time
Coordinated Universal Time is the primary time standard by which the world regulates clocks and time. It is one of several closely related successors to Greenwich Mean Time. Computer servers, online services and other entities that rely on having a universally accepted time use UTC for that purpose...

. As the radiosonde rises at about 300 meters/minute (1,000 ft/min), sensors on the radiosonde measure profiles of pressure, temperature, and relative humidity. These sensors are linked to a battery powered radio transmitter that sends the sensor measurements to a ground receiver. By tracking the position of the radiosonde in flight, information on wind speed and direction aloft is also obtained. The flight can last longer than two hours, and during this time the radiosonde can ascend above 35 km (114,829.4 ft) and drift more than 200 km (124.3 mi) from the release point. When the balloon has expanded beyond its elastic limit and bursts (about 6 m or 20 ft in diameter), a small parachute slows the descent of the radiosonde, minimizing the danger to lives and property.

Data obtained during the flights is coded and disseminated, at which point it can be plotted on a Skew-T
Skew-T log-P diagram
A Skew-T Log-P diagram is one of four thermodynamic diagrams commonly used in weather analysis and forecasting. In 1947, N. Herlofson proposed a modification to the emagram which allows straight, horizontal isobars, and provides for a large angle between isotherms and dry adiabats, similar to that...

 or Stuve diagram for analysis.

In recent years, the National Weather Service has begun incorporating data from AMDAR
AMDAR
Aircraft Meteorological Data Relay is a program initiated by the World Meteorological Organization.AMDAR is used to collect meteorological data worldwide by using commercial aircraft....

 in its numerical models (however, the raw data is not available to the public).

Event-driven products


The National Weather Service has developed a multi-tier concept for forecasting or alerting the public to all types of hazardous weather. These are:

Outlook – A Hazardous Weather Outlook is issued daily addressing potentially hazardous weather or hydrologic events that may occur in the next seven days. The outlook will include information about potential severe thunderstorms, heavy rain or flooding, winter weather, extremes of heat or cold, etc. It is intended to provide information to those who need considerable lead time to prepare for the event. Other outlooks are issued on an event-driven basis, such as the Flood Potential Outlook and Severe Weather Outlook.

Watch – A watch is used when the risk of a hazardous weather or hydrologic event has increased significantly, but its occurrence, location or timing is still uncertain. It is intended to provide enough lead time so those who need to set their plans in motion can do so. A watch means that hazardous weather is possible, but not imminent. People should have a plan of action in case a storm threatens and they should listen for later information and possible warnings especially when planning travel or outdoor activities.

Warning – A warning is issued when a hazardous weather or hydrologic event is occurring, imminent or likely. A warning means weather conditions pose a threat to life or property. People in the path of the storm need to take protective action.

Advisory – An advisory is issued when a hazardous weather or hydrologic event is occurring, imminent or likely. Advisories are for less serious conditions than warnings, that cause significant inconvenience and if caution is not exercised, could lead to situations that may threaten life or property.

Special Weather Statement – A special weather statement is issued when something rare or unusual is occurring. These are usually triggered by sudden changes in meteorological conditions. The statements are to be taken as warnings for residents of a specific area. The warning generally states that an area might be at risk for a slight weather danger. Not all weather statements are warnings, though. Other times, statements describe informative facts about a weather system; such as local snowfall.

Product dissemination


NOAA Weather Radio All-Hazards (NWR), sometimes called Weatheradio (though this is actually a trademark of receiver manufacturer Tandy
Tandy Corporation
Tandy Corporation was a family-owned leather goods company based in Fort Worth, Texas. Tandy was founded in 1919 as a leather supply store, and acquired RadioShack in 1963. The Tandy name was dropped in May 2000, when RadioShack Corporation was made the official name.-History:Tandy began in 1919...

), is a special radio system that transmits weather warnings and forecasts 24 hours a day across most of the United States. The system, owned and operated by the NWS, consists of more than 900 transmitters, covering all 50 states, adjacent coastal waters, Puerto Rico
Puerto Rico
Puerto Rico , officially the Commonwealth of Puerto Rico , is an unincorporated territory of the United States, located in the northeastern Caribbean, east of the Dominican Republic and west of both the United States Virgin Islands and the British Virgin Islands.Puerto Rico comprises an...

, the U.S. Virgin Islands
United States Virgin Islands
The Virgin Islands of the United States are a group of islands in the Caribbean that are an insular area of the United States. The islands are geographically part of the Virgin Islands archipelago and are located in the Leeward Islands of the Lesser Antilles.The U.S...

, and the U.S. Pacific Territories. NWR requires a special radio
Radio
Radio is the transmission of signals through free space by modulation of electromagnetic waves with frequencies below those of visible light. Electromagnetic radiation travels by means of oscillating electromagnetic fields that pass through the air and the vacuum of space...

 receiver or scanner capable of picking up the signal. It is broadcast on seven frequencies centered around 162 MHz in the VHF frequency band. In recent years, national emergency response agencies such as FEMA and the Department of Homeland Security
United States Department of Homeland Security
The United States Department of Homeland Security is a cabinet department of the United States federal government, created in response to the September 11 attacks, and with the primary responsibilities of protecting the territory of the United States and protectorates from and responding to...

 have begun to take advantage of NWR's ability to efficiently reach a large portion of the population. The system is now used to broadcast civil and natural emergency information in addition to that relating to weather.

NOAA Weather Wire Service (NWWS) is a satellite data collection and dissemination system operated by the National Weather Service. Its purpose is to provide state and federal government, commercial users, media, and private citizens with timely delivery of meteorological, hydrological, climatological, and geophysical information. All products in the NWWS datastream are prioritized, with weather and hydrologic warnings receiving the highest priority (watches are next in priority). NWWS delivers severe weather and storm warnings to users in 10 seconds or less from the time they are issued, making it the fastest delivery system available. Products are broadcast to users via the AMC
SES Americom
SES Americom was a major commercial satellite operator based in the United States. Formerly RCA Americom and GE Americom, the company became one of the principal parts of SES S.A.....

-4 satellite.

EMWIN is the Emergency Managers Weather Information Network, a system designed to provide the emergency management community with access to a set of NWS warnings, watches, forecasts, and other products at no recurring cost. Its can receive data via radio, internet, or a dedicated satellite dish, depending on the needs and capabilities of the user.

The NOAAPORT broadcast system provides a one-way broadcast communication of NOAA environmental data and information in near real time to NOAA and external users. This broadcast service is implemented by a commercial provider of satellite communications utilizing C-band.

The Weather.gov website is a data rich website operated by NWS that serves as a portal to hundreds of thousands of webpages and more than 300 different NWS websites. From the homepage, it is possible to enter a city and state to get a local forecast page, view a rapidly updated map of active watch and warnings, and select areas related to graphical forecasts, national maps, radar displays, rivers, air quality, satellite images and climate. Also offered are xml data feeds of active watch and warnings, ASOS observations and digital forecasts for 5x5 kilometer grids.

The Interactive Weather Information Network (IWIN) was an internet site operated by the NWS that has been superseded by the weather.gov site.

Since 1983, the NWS has provided external user access to U.S. Government obtained or derived weather information through a collection of data communication line services called the Family of Services (FOS). FOS is accessible via dedicated telecommunications access lines in the Washington, D.C., area. All FOS data services are driven by the NWS Telecommunication Gateway computer systems located at NWS headquarters in Silver Spring, MD. Users may obtain any of the individual services from NWS for a one-time connection charge and an annual user fee.

Every NWS office operates its own web page with access to current products and other information specific to the local area.

Technology


The WSR-88D
NEXRAD
NEXRAD or Nexrad is a network of 159 high-resolution Doppler weather radars operated by the National Weather Service, an agency of the National Oceanic and Atmospheric Administration within the United States Department of Commerce...

 Doppler
Doppler effect
The Doppler effect , named after Austrian physicist Christian Doppler who proposed it in 1842 in Prague, is the change in frequency of a wave for an observer moving relative to the source of the wave. It is commonly heard when a vehicle sounding a siren or horn approaches, passes, and recedes from...

 weather radar
Weather radar
Weather radar, also called weather surveillance radar and Doppler weather radar, is a type of radar used to locate precipitation, calculate its motion, estimate its type . Modern weather radars are mostly pulse-Doppler radars, capable of detecting the motion of rain droplets in addition to the...

 system, also called NEXRAD
NEXRAD
NEXRAD or Nexrad is a network of 159 high-resolution Doppler weather radars operated by the National Weather Service, an agency of the National Oceanic and Atmospheric Administration within the United States Department of Commerce...

, was developed by the NWS during the mid 1980s and fully deployed by the early 1990s. There are 158 such radar
Radar
Radar is an object-detection system which uses radio waves to determine the range, altitude, direction, or speed of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. The radar dish or antenna transmits pulses of radio...

 sites in the United States and selected overseas locations. This technology, because of its high resolution and ability to detect intra-cloud motions, is now the cornerstone of NWS severe weather warning operations.

NWS meteorologists use an advanced information processing, display, and telecommunications system called AWIPS to complete their work. These workstations allow them to easily view a multitude of weather and hydrologic information, as well as compose and disseminate products.

The NWS Environmental Modeling Center
Environmental Modeling Center
The Environmental Modeling Center , improves numerical weather, marine and climate predictions at the National Centers for Environmental Prediction , through a broad program of research in data assimilation and modeling...

 was one of the early users of the ESMF
ESMF
The ESMF is open source software for building climate, numerical weather prediction, data assimilation, and other Earth science software applications. These applications are computationally demanding and usually run on supercomputers...

 common modeling infrastructure. The GFS
GFS
There are three distributed file systems that share the initials GFS:* Global File System, a cluster file system for Linux released under GPL license* GlusterFS, a cluster file system...

 system is one of the applications that is built on the framework.

Organization



  • National Weather Service (NWS)
    • Chief Information Officer
    • National Centers for Environmental Prediction
      National Centers for Environmental Prediction
      The United States National Centers for Environmental Prediction delivers national and global weather, water, climate and space weather guidance, forecasts, warnings and analyses to its Partners and External User Communities...

       (NCEP)
      • Aviation Weather Center (AWC)
      • Climate Prediction Center
        Climate Prediction Center
        The Climate Prediction Center is one of the National Centers for Environmental Prediction, which are a part of NOAA's National Weather Service. It is located in Camp Springs, Maryland.-Products:...

         (CPC)
      • Environmental Modeling Center
        Environmental Modeling Center
        The Environmental Modeling Center , improves numerical weather, marine and climate predictions at the National Centers for Environmental Prediction , through a broad program of research in data assimilation and modeling...

         (EMC)
      • Hydrometeorological Prediction Center
        Hydrometeorological Prediction Center
        The Hydrometeorological Prediction Center is one of nine service centers under the umbrella of the National Centers for Environmental Prediction , a part of the National Weather Service, which in turn is part of the National Oceanic and Atmospheric Administration of the U.S. government...

         (HPC)
      • Ocean Prediction Center
        Ocean Prediction Center
        The Ocean Prediction Center , established in 1995, is one of the National Centers for Environmental Prediction’s original six service centers. Until January 12, 2003, the name of the organization was the Marine Prediction Center. Its origins are traced back to the sinking of the RMS Titanic in...

         (OPC)
      • NCEP Central Operations
      • Space Weather Prediction Center (SWPC)
      • Storm Prediction Center
        Storm Prediction Center
        The Storm Prediction Center , located in Norman, Oklahoma, is tasked with forecasting the risk of severe thunderstorms and tornadoes in the contiguous United States. The agency issues convective outlooks, mesoscale discussions, and watches as a part of this process...

         (SPC)
      • Tropical Prediction Center (TPC)
        • National Hurricane Center
          National Hurricane Center
          The National Hurricane Center , located at Florida International University in Miami, Florida, is the division of the National Weather Service responsible for tracking and predicting weather systems within the tropics between the Prime Meridian and the 140th meridian west poleward to the 30th...

           (NHC)
        • Tropical Analysis and Forecast Branch (TAFB)
        • Technical Support Branch (TSB)
    • Chief Financial Officer
    • Operational Systems
    • Hydrologic Development
    • Science and Technology
      • Programs and Plans
      • Meteorological Development Laboratory (MDL)
    • Climate, Water and Weather Services
    • 6 Regions
      • 122 Weather Forecast Offices (WFOs)
      • 21 Center Weather Service Unit
        Center Weather Service Unit
        A Center Weather Service Unit is a National Weather Service unit located inside each of the Federal Aviation Administration's 21 Air Route Traffic Control Centers .- Overview :...

        s (CWSU)
      • 13 River Forecast Centers (RFC)
      • Pacific Tsunami Warning Center
        Pacific Tsunami Warning Center
        The Pacific Tsunami Warning Center is one of two tsunami warning centers that are operated by NOAA in the United States. Headquartered in Ewa Beach, Hawaii, the PTWC is part of an international tsunami warning system program and serves as the operational center for TWS of the Pacific issuing...

         (PTWC)
      • West Coast and Alaska Tsunami Warning Center (WCATWC)
    • Spaceflight Meteorology Group
      Spaceflight Meteorology Group
      The Spaceflight Meteorology Group is a U.S. weather forecasting unit staffed by the National Weather Service for the National Aeronautics and Space Administration which provides pertinent information on the current and expected state of the atmosphere during human spaceflight operations. It is...

       (SMG)

Controversy


While generally respected as one of the premier weather organizations in the United States, the National Weather Service has been perceived by some, particularly commercial weather services such as AccuWeather
AccuWeather
AccuWeather is an American media company that provides for-profit weather forecasting services worldwide.AccuWeather was founded in 1962 by Joel N. Myers, then a Penn State graduate student working on degrees in meteorology. His first customer was a gas company in Pennsylvania. While running the...

, as competing unfairly with the private sector. In 2005, Senator Rick Santorum
Rick Santorum
Richard John "Rick" Santorum is a lawyer and a former United States Senator from the commonwealth of Pennsylvania. Santorum was the chairman of the Senate Republican Conference -making him the third-ranking Senate Republican from 2001 until his leave in 2007. Santorum is considered both a social...

 (R-PA) introduced the National Weather Service Duties Act of 2005
National Weather Service Duties Act of 2005
The National Weather Service Duties Act of 2005 was a legislative proposal forwarded in April 2005 by now former United States Senator Rick Santorum to curtail perceived government competition with commercial weather services from the National Weather Service...

, a bill intended to limit the NWS's ability to provide data that could be given by commercial outlets, but at cost to generate private profit. The bill was widely criticized by users of the NWS's services, especially by Emergency Management Officials, who rely on the NWS for information during situations such as fires, flooding or severe weather. The bill died in committee during the 2005 session.

See also


  • NOAA's Environmental Real-time Observation Network
    NOAA's Environmental Real-time Observation Network
    NOAA's Environmental Real-time Observation Network , is a project to establish a nationwide network of weather monitoring stations across the United States. A 20-mile by 20-mile grid has been established, with the hopes of having one observation system within each cell...

  • Meteorological Service of Canada
    Meteorological Service of Canada
    The Meteorological Service of Canada , also known as "The Canadian Weather Service", is a division of Environment Canada, which primarily provides public meteorological information and weather forecasts and warnings of severe weather and other environmental hazards...

     – founded 1876
  • Reginald Fessenden
    Reginald Fessenden
    Reginald Aubrey Fessenden , a naturalized American citizen born in Canada, was an inventor who performed pioneering experiments in radio, including early—and possibly the first—radio transmissions of voice and music...

     – Known for proving the practicality of using a network of coastal radio stations to transmit weather information
  • National Weather Service Employees Organization
    National Weather Service Employees Organization
    The National Weather Service Employees Organization, known as the NWSEO, is the labor organization and professional association that represents 4,000 employees of the National Oceanic and Atmospheric Administration in the U.S...



External links