Tropical Depression THIRTEEN-E

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TROPICAL DEPRESSION THIRTEEN-E SPECIAL DISCUSSION NUMBER   1
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP132007
1000 AM PDT WED SEP 19 2007
 
EVEN THOUGH THE CLOUD TOPS ARE BEGINNING TO WARM IN INFRARED
SATELLITE IMAGERY....VISIBLE IMAGERY INDICATES THAT THE AREA OF
DISTURBED WEATHER SOUTHWEST OF THE SOUTHERN TIP OF BAJA CALIFORNIA
HAS ACQUIRED ENOUGH ORGANIZATION TO BE CLASSIFIED AS A TROPICAL
DEPRESSION. THE CENTER OF THE DEPRESSION IS LOCATED WITHIN THE
EASTERN PORTION OF THE CONVECTION.  DATA FROM A RECENT QUIKSCAT
PASS AND A DVORAK INTENSITY FROM SAB SUPPORT A 30 KT INITIAL
INTENSITY.

THE DEPRESSION IS MOVING SLOWLY WESTWARD SOUTH OF A MID-LEVEL RIDGE
TO THE NORTH.  THE RIDGE IS FORECAST TO ERODE DURING THE NEXT DAY
OR SO AS A LARGE MID-TO UPPER-LEVEL TROUGH DROPS SOUTHWARD OFF THE
WEST COAST OF THE UNITED STATES.  THIS IS EXPECTED TO LEAVE THE
DEPRESSION IN AN AREA OF WEAK STEERING CURRENTS.  AFTER 48
HOURS...THE DYNAMICAL GUIDANCE SUGGEST THAT THE TROUGH WILL DIG FAR
ENOUGH SOUTH TO INDUCE A NORTHEASTWARD MOTION.  MUCH OF THE
GUIDANCE FORECAST AN ANTICYCLONIC LOOP OF THE CYCLONE...HOWEVER THE
OFFICIAL FORECAST WILL SHOW A SLOW WESTWARD MOTION...WITH A TURN TO
THE NORTHEAST AFTER 48 HOURS.

FUTURE INTENSIFICATION OF THE DEPRESSION LOOKS RATHER BLEAK.  THE
INTENSITY FORECAST ALLOWS FOR STRENGTHENING TO A MINIMAL TROPICAL
STORM IN 24 HOURS...ASSUMING THAT THE CYCLONE DOES NOT INGEST TOO
MUCH OF THE STABLE AIR TO THE NORTH.  THEREAFTER...THE CYCLONE WILL
BE MOVING OVER COOLER WATER...AND SOUTHWESTERLY SHEAR IS EXPECTED
TO INCREASE BEYOND 48 HOURS...WHICH SHOULD INDUCE WEAKENING.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      19/1700Z 17.1N 127.9W    30 KT
 12HR VT     20/0000Z 17.2N 128.5W    30 KT
 24HR VT     20/1200Z 17.2N 129.2W    35 KT
 36HR VT     21/0000Z 17.2N 129.9W    35 KT
 48HR VT     21/1200Z 17.5N 129.9W    30 KT
 72HR VT     22/1200Z 18.5N 128.6W    25 KT
 96HR VT     23/1200Z 19.5N 127.5W    25 KT
120HR VT     24/1200Z 20.5N 126.0W    25 KT
 
$$
FORECASTER BROWN
 
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