COAMPS 2.0

On the synoptic scale, COAMPS consistently performs as well as other models
(NOGAPS/NORAPS/ECMWF) in forecasting synoptic scale events. On the
mesoscale, COAMPS frequently outperforms other models in predicting
mesoscale meteorological events, particularly close to land in the littoral
zone.

The strongest feature of the COAMPS 27-km nest is its ability to capture
localized winds and small-scale effects. The Mistral, for example, is well
depicted in shape, size and duration.

     a. COAMPS EUROPE (Nest2 27 km resolution)

     Nest2 develops spurious lows in data sparse maritime areas with weak
     cyclonic flow at 500 mb. Gale force winds are generated by these
     fictitious systems.

     Bora events in the Adriatic and Aegean Seas tend to be over forecast
     by 5 - 10 kts, at other times are under forecast.

     Sea breezes are well depicted in the Adriatic and upper Aegean Seas.

     Nest2 demonstrates poor skill in most narrow straits, such as the
     Straits of Bonifacio and Gibraltar. Specifically, Nest2 tends to under
     forecast the funneling effect by 5 -15 kts.

     Precipitation guidance is generally good as far as shape of the
     precipitation area but is low on the amount. Nest2 is very good at
     depicting orographic induced precipitation, however remains light on
     convective or stratiform types.

     A cold bias exists over Europe with the least being at tau 12 at the
     surface and the greatest at tau 48 at 250 mb.

     A warm bias exists on the African continent, but is less than the
     European cold bias.

     b. COAMPS SOUTHWEST ASIA (Nest2 27 km resolution)

     Nest2 develops storm force winds in the mountains along the eastern
     shore of the Red Sea when winds are perpendicular to the terrain. This
     feature may or may not exist. Verification is a problem.

     Nest2 develops wind maximums in the Gulf Of Oman and the Strait of
     Hormuz during the southwest monsoon. SSMI imagery and coastal reports
     indicate light and variable winds.

     Nest2 has a problem handling the Shamal by underestimating winds by 5
     to 10 kts. It also tends to decrease wind velocities approximately 6 -
     12 hours early.

     During periods of weak pressure gradients over the Arabian Gulf, Nest2
     does not handle the surface flow well, i.e. sea and land breezes.
     Fleet forecasters have noted that in gentle wind fields, the wind
     directions were off as much as 90 degrees. During these periods Nest3
     should be used if available.

     Precipitation guidance is generally good as far as shape of the
     precipitation area but is low on the amount.

     Synoptic lows which develop over interior Saudi Arabia and which
     subsequently track eastward are usually forecast to have southeasterly
     flow followed by an increasing northwesterly flow after system
     passage. However, many of the systems affecting the Gulf region have
     not shown that particular wind pattern. Prior to passage, winds are
     generally light and variable. After passage, winds become
     northwesterly.