TROPICAL DEPRESSION #4
ISSUED: 10:00 P.M. – WEDNESDAY – 8/15/01

TD#4 CONTINUES TO MOVE QUICKLY TOWARD THE WEST.  CURRENT MOTION IS WEST (270) AT 20 KTS. 

MOST SIGNIFICANT CHANGE OVER THE LAST 6 HOURS HAS BEEN THE MUCH IMPROVED OUTFLOW OVER THE NORTHERN SEMI-CIRCLE.  LATEST IR SAT PICS AS WELL AS WV LOOPS SHOW THIS IMPROVING OUTFLOW.  LATEST IR IMAGES ALSO SHOW INCREASE IN CONVECTION OVER THE WESTERN SEMI-CIRCLE OF THE OVERALL CIRCULATION WITH CLOUD TOPS ON THE ORDER OF –70/-75C.  THE CENTER OF CIRCULATION HOWEVER IS TO THE EAST OF THE DEEPEST CONVECTION.   IN SHORT, T.D. #4 CONTINUES TO BECOME SLOWLY BUT STEADILY BETTER ORGANIZED.  AN UPGRADE TO TROPICAL STORM STATUS IS LIKELY WITHIN THE NEXT 1-2 ADVISORIES FROM TPC.  RAPID FORWARD MOTION IS THE ONLY FACTOR I SEE HINDERING/SLOWING DEVELOPMENT.

TRACK:  ONCE AGAIN I’M IN AGREEMENT WITH LATEST TPC TRACK PACKAGE.  SYSTEM IS EMBEDDED IN DEEP EASTERLIES TO SOUTH OF STRONG RIDGE TO THE NORTH.  RIDGE IS FCST TO BUILD WEST NEXT 24-48 HOURS AND THUS GENERAL WEST TO MORE WEST-NORTHWEST MOTION BY 48-72 HOURS IS EXPECTED.  A GRADUAL REDUCTION IN FORWARD SPEED IS EXPECTED BEYOND 18-24 HOURS.  UNTIL THEN A BRISK 20 MPH+ PACE IS EXPECTED.  LATEST CIMSS LOWER LEVEL WIND ANALYSIS SUPPORTS A SLOWING OF FORWARD SPEED STARTING IN THE NEXT 18-24 HOURS.  ONCE SYSTEM BECOMES MORE VERTICALLY STACKED IT WILL BE GUIDED MORE BY THE UPPER LEVEL WINDS.  CYCLONE SHOULD ENTER INTO THE CARIBBEAN SOMEWHERE BETWEEN 13-15 NORTH DURING FRIDAY MORNING OR EARLY AFTERNOON.

INTENSITY: TOUGH CALL HERE.  FOR SEVERAL RUNS IN A ROW SHIPS HAS PERSISTED IN A 90-100 KT. HURRICANE BY 72 HOURS.  LATEST GFDL HAS NOW FOLLOWED SUIT AND IS NO LONGER DISSIPATING THE SYSTEM.  WATER TEMPS ARE INCREASINGLY WARMER AHEAD OF THE DEPRESSION….UPPER LEVEL WINDS ARE FAVORABLE AND ARE FORECAST TO REMAIN THAT WAY.  WILL GO ALONG WITH LATEST TPC FCST OF 70 KTS. BY 72 HOURS.  STILL BELIEVE THE ONLY THING HINDERING MORE RAPID DEVELOPMENT IS FAST FORWARD SPEED.  ONCE THE FORWARD SPEED SLOWS INTENSIFICATION SHOULD FOLLOW RATHER QUICKLY.

INTENSITY FORECASTING IS A VERY DIFFICULT AND IS NOT AN EXACT SCIENCE BY ANY MEANS.  RESIDENTS OF THE ISLANDS ESPECIALLY THE CENTRAL AND NORTHERN ISLANDS SHOULD BE AWARE OF THIS AND REALIZE THEY MAY HAVE TO DEAL WITH A HURRICANE DURING THE NEXT 36-48 HOURS.  WATCHES WILL LIKELY BE ISSUED LATER TONIGHT.

LONGER RANGE TRACK:  LATEST NCEP MANUAL PROGS TRACKS THE SYSTEM OVER THE DOMINICAN REPUBLIC BY MONDAY…THEN TOWARD THE S.E. BAHAMA ISLANDS…THEN TO VCTY 35N/72 WEST BY NEXT WEDNESDAY.  I BELIEVE THIS IS NOT THE RIGHT IDEA.  ALTHOUGH THERE WILL BE A WEAKNESS DEVELOPING NEAR THE WESTERN EXTENSION OF THE SUB-TROPICAL RIDGE I DO NOT BELIEVE IT WILL BE NEARLY ENOUGH TO DRAW THE SYSTEM NORTH ACROSS THE DOMINICAN REPUBLIC.  OVER TIME A MORE NW TRACK IS LIKELY AND I BELIEVE THE SYSTEM IS DESTINED FOR THE GULF OF MEXICO EITHER BY WAY OF NORTH OR SOUTH OF CUBA.  THIS IMPLIES SYSTEM TILL TANGLE WITH THE CUBAN LAND MASS…EITHER THE EASTERN END OR THE WESTERN END.  IN SHORT…AT THIS TIME I DO NOT SEE THIS AS A RECURVING STORM OVER THE WESTERN ATLANTIC….NOR DO I SEE IT AS A THREAT TO THE EASTERN UNITED STATES WITH THE SOLE EXCEPTION OF THE SOUTHERN ONE HALF OF FLORIDA…AT THIS EARLY VANTAGE POINT THERE IS SOME THREAT THERE.  THAT IS DAYS AWAY SO THE WORD FOR NOW IS MONITOR AND FOLLOW FUTURE UPDATES.