National Weather Service

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 (NOAA) of the United States government. It is headquartered in Silver Spring, Maryland.

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.

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 service. These capabilities have greatly increased the audience of NDFD data.

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 Forecasts (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, visibility, weather, sky condition (clouds), and optional data such as wind shear. The following is an example of a TAF for Will Rogers World Airport in Oklahoma City:

Fire weather

See also: Wildfire

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 (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 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.

Public

Map of regions covered by the 122 Weather Forecast Offices.

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.

History

In 1870 the Weather Bureau was established 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 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. General Myer gave the National Weather Service its first name: The Division of Telegrams and Reports for the Benefit of Commerce.

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, as competing unfairly with the private sector. In 2005, Senator Rick Santorum (R-PA) introduced the National Weather Service Duties Act of 2005, 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.