Tropical Depression Ten Discussion Number 8

Statement as of 11:00 PM EDT on September 17, 2002

Satellite imagery indicate that the cloud pattern is definitely
becoming better organized. Convection has increased near the center
with developing banding features and the outflow is rapidly
expanding. It appears to be a tropical storm on satellite.
However...an Air Force plane just finished investigating the
depression and found that the minimum pressure has not changed and
it remains about 1006 mb. Max flight level winds are 41 knots
confined to a small area to the northeast of the center.
Therefore...the system is kept at 30 knots. A new plane will be
there at 6 UTC.
IR images still show some patches of cirrus undercutting the outflow
blowing from the southwest. This was confirmed by data from the
dropsondes launched by the NOAA high altitude jet. These winds have
been producing shear. However...most of the numerical models have
been very persistent in developing a 200 mb ridge over the western
Caribbean for the past few days. In fact...latest NCEP global run
has a 200 mb anticyclone over the system in 48 hours...perfect for
strengthening. With such a good upper-level environment and the
fact that the tropical cyclone is heading toward an area of
very high upper-oceanic heat content...strengthening is indicated.
The system is expected to be a hurricane by the time it approaches
western Cuba. The GFDL continues to be aggressive...bringing the
presure to 939 mb just north of western Cuba.
The depression has been moving toward the northwest or 315 degrees
at 5 or 6 knots during the past few hours. Steering currents are
weak but there is enough ridging to keep the cyclone on a general
slow northwest track through 72 hours. Thereafter...steering
currents are forecast to collapse and the cyclone will move very
little over the southeastern Gulf of Mexico or western Cuba. The
official forecast track is in the middle of the ensemble but is
biased toward the latest NCEP Global Model run. The latter makes
the cyclone nearly stationary over western Cuba or the southeastern
Gulf of Mexico in 4 or 5 days.
Forecaster Avila

forecast positions and Max winds

initial 18/0300z 16.9n 77.9w 30 kts
12hr VT 18/1200z 17.5n 78.7w 35 kts
24hr VT 19/0000z 18.9n 80.0w 45 kts
36hr VT 19/1200z 20.0n 81.0w 55 kts
48hr VT 20/0000z 21.5n 82.5w 65 kts
72hr VT 21/0000z 23.0n 84.0w 75 kts