Tropical Depression TWO

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TROPICAL DEPRESSION TWO DISCUSSION NUMBER  10
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022009
1100 AM AST THU AUG 13 2009

TROPICAL DEPRESSION TWO CURRENTLY CONSISTS OF A SWIRL OF LOW CLOUDS
WITH ISOLATED SHOWERS AND THUNDERSTORMS...TOO FEW TO GET A DATA-T
NUMBER USING THE DVORAK TECHNIQUE.  SSMI/DATA AT ABOUT 09Z
SUGGESTED 25 KT WINDS IN THE NORTHERN SEMICIRCLE...AND THAT IS USED
AS THE INITIAL INTENSITY.  SSM/I AND AMSR-E PRECIPITABLE WATER
IMAGERY SUGGESTS THAT A TONGUE OF DRIER AIR HAS WRAPPED ALMOST ALL
THE WAY AROUND THE CIRCULATION...AND WATER VAPOR IMAGERY SHOWS
MID/UPPER-LEVEL DRY AIR IN THE VICINITY OF THE DEPRESSION.  THESE
FACTORS...COMBINED WITH ABOUT 15 KT OF EASTERLY VERTICAL WIND
SHEAR...MAY BE PREVENTING THE SYSTEM FROM MAINTAINING ORGANIZED
CONVECTION.
 
THE INITIAL MOTION IS NOW 270/8.  THERE IS LITTLE CHANGE TO THE
FORECAST PHILOSOPHY FROM THE PREVIOUS FORECAST.  THE DEPRESSION IS
ON THE SOUTH SIDE OF A LOW/MID-LEVEL RIDGE...WHICH SHOULD RESULT IN
A WESTWARD MOTION FOR THE NEXT COUPLE OF DAYS.  AFTER THAT...THE
SYSTEM SHOULD GRADUALLY TURN WEST-NORTHWESTWARD TOWARD A WEAKNESS
IN THE RIDGE OVER THE WESTERN ATLANTIC.  THE OVERALL GUIDANCE
ENVELOPE HAS SHIFTED SOUTHWARD SINCE THE LAST ADVISORY...SO THE NEW
FORECAST TRACK IS ALSO SHIFTED SOUTHWARD.  IT SHOULD BE NOTED THAT
IF THE CYCLONE WEAKENS TO A TROPICAL WAVE...THE REMNANTS WOULD
LIKELY MOVE FARTHER SOUTH THAN CURRENTLY FORECAST...AS SHOWN BY THE
BAMM AND BAMS MODELS.
 
THE SHIPS MODEL CONTINUES TO FORECAST MODERATE TO OCCASIONALLY
STRONG SHEAR OVER THE SYSTEM DURING THE FORECAST PERIOD...AND THUS
THE SHIPS AND LGEM MODELS SHOW LITTLE OR NO STRENGTHENING.  ON THE
OTHER HAND...THE HWRF AND GFDN SHOW SIGNIFICANT STRENGTHENING...
WITH THE HWRF MAKING THE SYSTEM A HURRICANE BY 120 HR.  BASED ON
THE FORECAST SHEAR AND CURRENT TRENDS...THE INTENSITY FORECAST NOW
CALLS FOR LITTLE CHANGE IN STRENGTH DURING THE FORECAST PERIOD IN
BEST AGREEMENT WITH THE LGEM MODEL.  THERE IS A DISTINCT
POSSIBILITY THE CYCLONE COULD WEAKEN TO A REMNANT LOW OR TROPICAL
WAVE DURING THE FORECAST PERIOD...AS FORECAST BY ALL THE GLOBAL
MODELS EXCEPT THE NOGAPS.  
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      13/1500Z 14.0N  37.6W    25 KT
 12HR VT     14/0000Z 14.0N  39.1W    25 KT
 24HR VT     14/1200Z 14.2N  41.3W    25 KT
 36HR VT     15/0000Z 14.4N  43.9W    25 KT
 48HR VT     15/1200Z 14.8N  46.6W    25 KT
 72HR VT     16/1200Z 16.0N  52.5W    25 KT
 96HR VT     17/1200Z 18.5N  59.5W    25 KT
120HR VT     18/1200Z 22.0N  66.0W    25 KT
 
$$
FORECASTER BEVEN
 
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