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MDL is responsible for developing and implementing the Trajectory Model.
This model produces forecasts of air-parcel trajectories twice a day
over the contiguous U.S. out to 48 hours in advance.
The three-dimensional wind field from the the 0000 and 1200 UTC
runs of the Nested Grid Model (NGM) is used as input to the Trajectory Model.
By integrating the vertical motion of the air parcels over a
period of time, the Trajectory Model is able to forecast the net
vertical displacement of air parcels during 12-hour periods.
Forecasters have found that this information is very useful in
predicting heavy snowfall, occurrence of thunderstorms and
severe weather, and air pollution episodes.
Trajectory model forecast products are avialable in both
alphanumeric and graphical format and are usually disseminated around 0400 and 1600 UTC.
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Operational Products
The current operational products
are produced by the NGM version of the trajectory model.
Raw GRIB files
are available on the NWS ftp server.
Text Products
These text products were discontinued as of 1200 UTC on January 11, 2005.
Eight alphanumeric bulletins based on trajectory model output are
transmitted twice a day over AFOS, the Family of Services, military, and FAA
lines. The bulletins are divided by geographic regions and are given the
headers of FOUS50 - FOUS57. They contain 24-hour forecasts of temperature,
dew point, and the K stability index for selected stations, along with
six-hourly positions for trajectories terminating at the surface, 850 mb, and
700 mb. On AFOS they can be found under the product identifiers
NMCFTJ50 - NMCFTJ57. For a sample product see FOUS50
Graphic Products
The Redbook graphics of temperature and dew point at the surface, 850 mb, and 700 mb and the K stability index were removed as of 1200 UTC January 11, 2005.
Forecast fields from the trajectory model are also transmitted
twice a day in graphical format over AFOS and the Family of Services. These
forecast fields include the 24-hour parcel trajectores terminating at the
A
surface, 850 mb, and 700 mb for the eastern U.S. and the western U.S.; the
temperature and dew point at the surface, 850 mb, and 700 mb; the K stability
index; and finally the net vertical displacement for parcels terminating at
700 mb for the 12-24 h, 24-36 h and 36-48 h periods.
References
Reap, R. M. 1992: The Meteorological Development Laboratory
Three-Dimensional Trajectory Model. Technical Procedures Bulletin (TPB) 397
, National Oceanic and Atmospheric Administration (NOAA), U.S. Department of
Commerce, 11 pp. Available from the Office of
Climate, Water, and Weather Services.
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