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TROPICAL DEPRESSION ELEVEN-E DISCUSSION NUMBER   7
NATIONAL WEATHER SERVICE MIAMI FL
2 AM PDT SAT SEP 07 2002
 
THE CENTER OF THE DEPRESSION IS DIFFICULT TO LOCATE WITH 
CONVENTIONAL SATELLITE IMAGERY...BUT IT APPEARS THAT THE CYCLONE HAS 
SLOWED DOWN CONSIDERABLY DURING THE PAST 6 HOURS. EARLIER MICROWAVE 
DATA INDICATED A TIGHT CIRCULATION WHEN THE SYSTEM PROBABLY PEAKED 
BETWEEN 21Z AND 00Z. HOWEVER...CONVECTION HAS DECREASED MARKEDLY 
SINCE THEN. THE PREVIOUS INTENSITY OF 30 KT IS MAINTAINED FOR THIS 
ADVISORY BASED ON SATELLITE INTENSITY ESTIMATES OF 30 KT...35 KT... 
AND 25 KT FROM TAFB...SAB...AND AFWA...RESPECTIVELY. THE CENTRAL 
PRESSURE WAS LOWERED TO 1006 MB BASED ON SHIP REPORTS LOCATED 
NORTHEAST AND SOUTHWEST OF THE CENTER REPORTING 1007.2 MB AT 00Z.

THE INITIAL MOTION ESTIMATE IS 320/03. DUE TO THE UNCERTAINTY IN THE 
CENTER POSITION...I DID NOT WANT TO MAKE ANY SIGNIFICANT CHANGES TO 
THE PREVIOUS FORECAST TRACK OTHER THAN TO SLOW DOWN THE FORWARD 
SPEED. THE OUTER CIRCULATION IS FAIRLY WELL-DEFINED...BUT THE 
INNER-CORE WIND FIELD REMAINS POORLY DEFINED DUE TO THE LACK OF DEEP 
CONVECTION. THE NHC MODEL GUIDANCE IS IN STRONG AGREEMENT ON THE 
CYCLONE TRACKING NORTHWESTWARD FOR 24 TO 36 HOURS AND THEN MORE 
NORTHWARD AFTER THAT...EXCEPT FOR THE GFDL MODEL WHICH DISSIPATES 
THE SYSTEM WITHIN 12 HOURS. THE OFFICIAL FORECAST TRACK IS JUST AN 
UPDATE OF THE PREVIOUS TRACK...ALBEIT SLOWER...AND IS IN THE MIDDLE 
OF THE TIGHTLY PACKED MODEL SUITE.
 
IT APPEARS THAT THE DEPRESSION HAS MISSED ITS OPPORTUNITY FOR 
SIGNIFICANT INTENSIFICATION TO OCCUR. WHILE SSTS ARE WARM...AROUND 
28C...AND THE SHEAR IS LOW...AROUND 5 KT...THE PRESENCE OF DRY 
MID-LEVEL AIR SURROUNDING THE CYCLONE IS THE LIKELY CULPRIT THAT HAS 
CAUSED THE CONVECTION TO SIGNIFICANTLY WEAKEN. THERE MAY BE 
INTERMITTENT BURSTS OF CONVECTION THAT WILL SPIN UP THE INNER-CORE 
WIND FIELD OVER THE NEXT 24 TO 36 HOURS...BUT THAT WILL LIKELY JUST 
RESULT IN THE MORE DRY AIR BEING ENTRAINED CAUSING THE CONVECTION TO 
WEAKEN AGAIN. HOWEVER...OUT OF RESPECT FOR THE SHIPS INTENSITY MODEL 
AND THE FACT THAT THE CYCLONE IS FORECAST TO REMAIN OVER WARM SSTS 
FOR ANOTHER 24 HOURS...THE OFFICIAL INTENSITY FORECAST CALLS FOR 
SOME SLIGHT STRENGTHENING THROUGH 24 HOURS. AFTERWARDS...GRADUAL 
WEAKENING IS EXPECTED SINCE THE SYSTEM WILL BE MOVING OVER MUCH 
COOLER WATER. HOWEVER...IF CONVECTION DOES NOT REDEVELOP NEAR THE 
LOW-LEVEL CENTER WITHIN THE NEXT 12 HOURS OR SO...THEN THE 
DEPRESSION COULD DISSIPATE LATER TODAY LIKE THE GFDL MODEL IS 
FORECASTING.
 
FORECASTER STEWART/BERG
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     07/0900Z 21.7N 111.6W    30 KTS
12HR VT     07/1800Z 22.3N 112.1W    35 KTS
24HR VT     08/0600Z 23.5N 112.8W    40 KTS
36HR VT     08/1800Z 24.8N 113.5W    35 KTS
48HR VT     09/0600Z 26.2N 114.0W    30 KTS
72HR VT     10/0600Z 29.0N 115.0W    25 KTS
 
 
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