The Weather Prediction Center (WPC), located in College Park, Maryland, is one of nine service centers under the umbrella of the National Centers for Environmental Prediction (NCEP), a part of the National Weather Service (NWS), which in turn is part of the National Oceanic and Atmospheric Administration (NOAA) of the U.S. government. Until March 5, 2013, the Weather Prediction Center was known as the Hydrometeorological Prediction Center (HPC). The Weather Prediction Center serves as a center for quantitative precipitation forecasting, medium range forecasting (three to eight days), and the interpretation of numerical weather prediction computer models.
The Weather Prediction Center issues storm summaries on storm systems bringing significant rainfall and snowfall to portions of the United States. They also forecast precipitation amounts for the lower 48 United States for systems expected to impact the country over the next seven days. Advisories are also issued for tropical cyclones which have moved inland, weakened to tropical depression strength, and are no longer the responsibility of the National Hurricane Center. The Weather Prediction Center also acts as the backup office to the National Hurricane Center in the event of a complete communications failure.
Long range climatological forecasts are produced by the Climate Prediction Center (CPC), a branch of the National Weather Service. These include 8–14 day outlooks, monthly outlooks, and seasonal outlooks.
History
From the early days of organized weather collection in the United States, a central facility was used to gather and disseminate data. Originally, this task occupied a single room within the United States Army Signal Service in Washington, D.C. Reports were collected via telegraph and general forecasts were made for the country.
While WPC's roots lie deep in the past, the organization can be most directly traced to the formation of the Analysis Center by Circular Letter 39–42, signed by Weather Bureau director Francis W. Reichelderfer on March 5, 1942. Operations began on March 16, 1942, with the unit collocated with the Weather Bureau Central Office at 24th and M Streets NW in Washington, D.C. Initially the unit was sometimes referred to as the Master Analysis Center.
In 1947, the Analysis Center was combined with the Air Force Master Analysis Center and the Navy Weather Central to create the Weather Bureau-Air Force-Navy (WBAN) Analysis Center. Their operations commenced on June 16, 1947, at 24th and M Streets NW. By early 1950 the WBAN Analysis Center consisted of 150 employees. Medium range forecasting was done nationally to 54 hours in the future.
In July 1954, the Joint Numerical Weather Prediction Unit (JNWPU) was created to test out numerical weather prediction (NWP) techniques by computer. This unit co-located with the WBAN analysis center to form the National Weather Analysis Center, which was located in Suitland, Maryland. When the two units merged, the name changed to the National Meteorological Center (NMC) in January 1958. When the JNWPU dissolved in 1961, NMC became an independent organization from Global Weather Central and Fleet Numerical Weather Central. Research and computer processing abilities increased over the years, which allowed for the first global forecast model to run by June 1966. By January 1975, much of the facility, minus the computers, moved to the World Weather Building, located in nearby Camp Springs, Maryland.
Mission
The mission of the WPC is to provide forecast, guidance, and analysis products and services to support the daily public forecasting activities of the NWS and its customers, and to provide tailored support to other government agencies in emergency and special situations.
Products and services
Quantitative precipitation forecasts (QPF)
thumb|250 px|Five-day QPF for [[Hurricane Rita (2005)]]
The QPF desks prepare and issue forecasts of accumulating (quantitative) precipitation, heavy rain, heavy snow, and highlights areas with the potential for flash flooding, with forecasts valid over the following five days. These products are sent to the National Weather Service forecast offices and are available on the Internet for public use. Heavy snow forecast products, in association with the short-range public forecast products (described below), serve as a coordinating mechanism for the national winter storm watch and warning program.
One desk of the National Environmental Satellite Data and Information Service (NESDIS) is co-located with the WPC QPF desks, which together form the National Precipitation Prediction Unit (NPPU). NESDIS meteorologists prepare estimates of rainfall and current trends based on satellite data, and this information is used by the Day 1 QPF forecaster to help create individual 6-hourly forecasts that cover the next 12 hours. With access to WSR-88D/Doppler weather radar data, satellite estimates, and NCEP model forecast data as well as current weather observations and WPC analyses, the forecaster has the latest data for use in preparation of short-range precipitation forecasts. Meteorological reasoning discussions are regularly written and issued with the forecast packages to explain and support the forecast. and days 3–7 to possible future tropical cyclones, are coordinated between the medium range pressures desk and NHC each day at 1700 UTC during the hurricane season. This coordination call began between the Extended Forecast Section and the Miami Hurricane Warning Office prior to 1959.
Within the WPC tropical program, the lead forecaster on shift, who prepares the day 1 QPF, is to provide the rainfall statement for tropical cyclones that are expected to make landfall. This statement is included in the Public Advisory issued by the NHC, and is a forecast of expected rainfall amounts that will occur with the tropical cyclone.
Finally, the WPC surface analysis desk has the responsibility for issuing Public Advisories whenever a tropical cyclone has made landfall in the U.S. or adjacent parts of Mexico, has weakened below tropical storm status (i.e. to a tropical depression or post-tropical cyclone or low) and is not expected to re-emerge over water as a tropical cyclone, yet the system is still capable of producing flooding type rains. This WPC Public Advisory will continue to be issued until the flooding rainfall threat is over. The advisory will contain information on how much rainfall has occurred with a particular tropical system, and will also include forecast information on the remnants of the system. Mesoscale discussions (MDs) once were issued by the Storm Prediction Center (SPC) for both convective (MCDs) and precipitation (MPDs) events but WPC now covers this heavy rainfall function.
International desks
The International desks have a variety of responsibilities, primarily the training of foreign visitors in the use of Numerical Weather Prediction products. The International desk routinely hosts visitors from Central and South America and the Caribbean. Visiting meteorologists train, and also generate forecasts for their own national centers, and assist WPC forecasters with QPF related to tropical cyclones in Central America and the Caribbean.