Tropical Depression FIFTEEN-E

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TROPICAL DEPRESSION FIFTEEN-E DISCUSSION NUMBER   1
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP152009
200 AM PDT MON SEP 07 2009
 
THERE HAS NOT BEEN MUCH INCREASE IN THE OVERALL COVERAGE OR
INTENSITY OF DEEP CONVECTION ASSOCIATED WITH THE LOW PRESSURE
CENTER WELL TO THE WEST-SOUTHWEST OF CABO SAN LUCAS. 
HOWEVER...OVER THE PAST FEW HOURS WE HAVE OBSERVED A WELL-DEFINED
CURVED BAND OF CONVECTION THAT HAS WRAPPED FAIRLY CLOSE TO THE
CENTER.  DVORAK CURRENT INTENSITY ESTIMATES ARE 25 KT AND 35 KT
FROM TAFB MIAMI AND SAB WASHINGTON RESPECTIVELY.  A QUIKSCAT PASS
FROM 0230 UTC SHOWED A WELL-DEFINED SURFACE CIRCULATION WITH
HIGHEST NON-RAIN-FLAGGED WINDS OF 25 TO 30 KT.  BASED ON THE
INCREASED ORGANIZATION OF THE SYSTEM...IT IS BEING UPGRADED TO A
30-KT TROPICAL DEPRESSION AT THIS TIME.  OVER THE NEXT COUPLE OF
DAYS THE CYCLONE WILL BE MOVING THROUGH AN ENVIRONMENT OF
MARGINALLY WARM SSTS AND WEAK TO MODERATE SHEAR.  MOREOVER THE
SHIPS MODEL OUTPUT AND THE PRESENCE OF A NEIGHBORING STRATOCUMULUS
CLOUD DECK INDICATES THAT THE AIR MASS IS NOT PARTICULARLY
UNSTABLE.  GIVEN THESE FACTORS...ONLY MODEST STRENGTHENING IS
ANTICIPATED... AND THE OFFICIAL INTENSITY FORECAST IS VERY SIMILAR
TO THE CONSENSUS OF THE OBJECTIVE GUIDANCE.  IN THE LATTER HALF OF
THE FORECAST PERIOD...INCREASING SOUTH-SOUTHWESTERLY SHEAR AND
COOLER WATERS SHOULD WEAKEN THE CYCLONE...PERHAPS AT A FASTER RATE
THAN SHOWN HERE.  

INITIAL MOTION IS A RATHER SLOW 285/7.  A WEAKENING MID-LEVEL RIDGE
TO THE NORTH OF THE CYCLONE WILL PROBABLY LEAD TO A LITTLE MORE
SLOWING OF THE FORWARD SPEED DURING THE NEXT 24 TO 48 HOURS. 
THEREAFTER...A MID-LEVEL TROUGH NEAR 130W-140W LONGITUDE IS
EXPECTED TO CAUSE THE SYSTEM TO TURN NORTHWESTWARD AND THEN
NORTH-NORTHWESTWARD.  THE OFFICIAL FORECAST TRACK IS ABOUT IN THE
MIDDLE OF THE OBJECTIVE TRACK MODEL ENVELOPE.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      07/0900Z 15.5N 125.6W    30 KT
 12HR VT     07/1800Z 15.8N 126.7W    35 KT
 24HR VT     08/0600Z 16.2N 128.0W    40 KT
 36HR VT     08/1800Z 16.5N 129.0W    45 KT
 48HR VT     09/0600Z 16.9N 129.8W    45 KT
 72HR VT     10/0600Z 18.5N 131.5W    45 KT
 96HR VT     11/0600Z 21.0N 133.0W    35 KT
120HR VT     12/0600Z 23.5N 134.5W    25 KT
 
$$
FORECASTER PASCH
 
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