Tropical Depression SEVEN

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TROPICAL DEPRESSION SEVEN DISCUSSION NUMBER   2
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL072006
500 AM EDT MON SEP 11 2006
 
CONVENTIONAL SATELLITE IMAGERY DEPICTS SOME IMPROVED ORGANIZATION IN
THE CONVECTIVE BANDING THIS MORNING...PARTICULARLY OVER THE
SOUTHEAST PORTION OF THE SYSTEM.  DVORAK INTENSITY ESTIMATES HAVE
INCREASED TO 30 KT FROM ALL AGENCIES WITH THE INITIAL INTENSITY
FOLLOWING SUIT.
 
THE INTENSITY FORECAST CONTINUES TO BE A BIT OF A MYSTERY. THE
LATEST GFDL RUN NOW INDICATES THAT THE DEPRESSION WILL BECOME A
HURRICANE IN 48 HOURS...SIMILAR TO THE SHIPS MODEL. THIS SEEMS
SOMEWHAT AGGRESSIVE CONSIDERING THE CURRENT NORTHWESTERLY
SHEAR...AND THE POTENTIAL FOR STRONG UPPER-LEVEL SOUTHEASTERLY FLOW
IN AROUND 36-48 HOURS...AS THE LARGE SCALE MODELS INDICATE.  IN
FACT...THE GLOBAL MODELS UNANIMOUSLY DISSIPATE THE SYSTEM.  THE
OFFICIAL INTENSITY FORECAST IS QUITE SIMILAR TO THE PREVIOUS
FORECAST... SUGGESTING LITTLE CHANGE IN STRENGTH DURING THE NEXT 48
HOURS. AFTERWARD...IF THE DEPRESSION SURVIVES...THE DYNAMICAL
MODELS INDICATE SOME WEAKENING OF THE UPPER EASTERLIES AND IMPROVED
OUTFLOW WHICH COULD PROVIDE AN OPPORTUNITY FOR SOME
STRENGTHENING...WHICH IS REFLECTED IN THE OFFICIAL FORECAST.
 
INITIAL MOTION IS ESTIMATED AT 290/6...WITHIN THE SOUTHWESTERN
PERIPHERY OF A LOW- TO MID-LEVEL HIGH TO THE NORTHEAST.  THE GLOBAL
MODELS ALL INDICATE A WEAK STEERING CURRENT THAT WOULD EVENTUALLY
TURN THE THE CYCLONE NORTHWESTWARD INTO A BREAK IN THE
SUBTROPICAL RIDGE.  THE BAM MODELS SHOW RECURVATURE INTO THE
MID-LATITUDE WESTERLIES BY DAY 4.  THE GFDL AND THE GLOBAL MODELS
SUGGEST AN ABRUPT NORTHWESTWARD TURN...THEN A MORE NORTHWARD MOTION
AFTER 48 HOURS.  THE OFFICIAL FORECAST IS BASED ON BLEND OF THE
BAMS... THOUGH SLIGHTLY SLOWER...AND CLOSELY FOLLOWS THE PREVIOUS
FORECAST. 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      11/0900Z 20.5N  55.1W    30 KT
 12HR VT     11/1800Z 20.7N  55.9W    30 KT
 24HR VT     12/0600Z 21.3N  57.2W    35 KT
 36HR VT     12/1800Z 22.1N  58.4W    35 KT
 48HR VT     13/0600Z 23.1N  59.6W    40 KT
 72HR VT     14/0600Z 25.5N  61.5W    45 KT
 96HR VT     15/0600Z 28.0N  62.5W    50 KT
120HR VT     16/0600Z 31.0N  62.0W    50 KT
 
$$
FORECASTER ROBERTS/FRANKLIN
 
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