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This is where all forecasts for the area are made for land, air, and water, using the Advanced Weather Interactive Processing System (AWIPS), which is our mainframe computer system. AWIPS was installed at Sterling in the Spring of 1999. It allows the forecast staff to analyze computer forecast guidance, otherwise know as "computer models", in 4 dimensions (along the Earth's surface as well as with respect to height and time), and overlay this data with satellite, radar, and local weather reports.  An example of a typical AWIPS graphic workstation screen can be seen on the right (except the resolution normally is much better).  In the big pane is computer model data.  The screen is interactive, allowing the forecaster to load and display the desired fields, or compare the same parameters among several computer models.  There are four smaller panes in which any item or combination of items can be stored for later viewing.  For instance, on the left is an enhanced, infrared satellite picture with surface observations overlaid.

In the image to the left is the forecast operations center.  The forecast position on the left is the short term, or aviation, forecast desk. At this desk terminal forecasts (called TAFs) and route forecasts (TWEBs) are composed for aviation purposes. These products are issued every 6 hours, and updated as needed. This forecaster is also responsible for writing the marine forecast (Coastal Waters Forecast)...also done 4 times a day and updated as necessary, fire weather forecasts and spot briefings, and Short Term Forecasts as the weather requires. "Short fused" warnings, such as for Severe Thunderstorms, Tornadoes, Flash Floods, and marine warnings, would be the decision of this person as well. On active weather days, additional staff would be on hand or called in to assist with all these duties.  The warning process is explained in greater detail under the radar operations section of this tour.

On the right is the long term, or public, forecast desk. This person composes the 7-day forecast traditionally distributed via radio and other media sources. "Longer fused" items, such as winter storm watches/warnings, windchill or heat advisories/warnings, and flood watches-- to name a few-- would be the responsibility of this person.

All of the forecast products are generated by the forecaster using AWIPS.   The forecaster interaction with the system is performed through a set of matrices.  Counties or areas are grouped based on similar forecast weather conditions.  Then, each group gets a matrix with the various weather fields and time steps.  This interface can be seen below right.  AWIPS assigns first guess variables to each matrix position.  These fields are then adjusted by the forecaster based on meteorological principles and forecaster experience.  As the parameters are adjusted in the matrix on the lower left, he/she can compare the values in the group being worked on with the other groups via the small windows on the map, and can also view the proposed wording in the window along the lower right part of the display.  Once complete, this sets the foundation for all generated products as the individual forecast products are composed by AWIPS based upon this matrix.  The forecaster does have the option to adjust the wording of the final product to best explain details before the products are transmitted.


When "long fused" warnings, watches, or advisories need to be issued, AWIPS contains a program to accomplish this task as well.  These items are then displayed on a map, an example of which can be seen to the left.  This map displays not only the area served by our forecast office, but also areas covered by surrounding offices.  This way, offices can more readily coordinate with each other.  AWIPS software can recognize any watches, warnings, or advisories in effect, and will break apart groups, if necessary, and insert the appropriate headline in the forecast products.
Interested in the end result?  Click here to view the latest weather info


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National Weather Service
Weather Forecast Office Baltimore/Washington
43858 Weather Service Rd.
Sterling, VA 20166
Phone: (703) 996-2200
Page last modified: Aug 17, 2011 2:30 PM EDT
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