Tropical Depression FIVE

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TROPICAL DEPRESSION FIVE DISCUSSION NUMBER   3
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL052006
500 AM EDT FRI AUG 25 2006
 
DESPITE WESTERLY SHEAR... THE TROPICAL DEPRESSION APPEARS TO BE
APPROACHING TROPICAL STORM STRENGTH.  DEEP CONVECTION HAS
INTENSIFIED NEAR THE CENTER WITH IMPROVING BANDING FEATURES IN THE
EASTERN SEMICIRCLE.  HOWEVER IT APPEARS THE CENTER IS ON THE
WESTERN EDGE OF THE THUNDERSTORMS... AS SUGGESTED BY A NOTCH IN THE
DEEP CONVECTION PATTERN ON NIGHT-VIS SATELLITE IMAGES.  SATELLITE
CLASSIFICATIONS RANGE FROM 35-45 KT BUT ARE A LITTLE CLOSER TO THE
CENTER OF THE DEEP CONVECTION.  WITH THE UNCERTAINITY IN INITIAL
POSITION.. 30 KT WILL BE KEPT UNTIL VISIBLE IMAGES ALLOW US TO GET
A BETTER HANDLE ON WHERE THE SYSTEM IS LOCATED.
 
THE TRACK FORECAST SEEMS LIKE THE EASIER PART OF THE FORECAST THIS
MORNING. THE DEPRESSION IS SPEEDING WESTWARD AT ABOUT THE SAME
RATE... 280/17. MIDDLE-LEVEL RIDGING SHOULD REMAIN STRONG OVER
THE WESTERN ATLANTIC OCEAN... KEEPING THE SYSTEM MOVING IN A
GENERAL WEST TO WEST-NORTHWESTWARD HEADING FOR THE NEXT COUPLE OF
DAYS. THE NOGAPS/UKMET SHOW STRONGER RIDGING AND A WEAKER
TROPICAL CYCLONE... LEADING TO A TRACK CLOSER TO YUCATAN IN ABOUT 5
DAYS. THE GFS AND GFDL TEMPORARILY WEAKEN THE RIDGE IN A FEW
DAYS... WHICH ALLOW A STRONGER SYSTEM TO MOVE TO THE NORTHWEST
CLOSER TO CUBA. I'M INCLINED TO STICK CLOSER TO THE FIRST OPTION
... LEADING TO A SMALL WESTWARD SHIFT OF THE TRACK FORECAST.
 
THE INTENSITY FORECAST IS TRICKY TO SAY THE LEAST. FIRST OF ALL...
THE SYSTEM HAS TO SURVIVE THE STRONG WESTERLY SHEAR IT WILL BE
EXPERIENCING FOR THE NEXT DAY OR TWO. THIS IS BY NO MEANS CERTAIN
AND IT WOULDN'T BE A HUGE SURPRISE FOR THE DEPRESSION TO DISSIPATE
IN THE "GRAVEYARD" OF THE EASTERN CARIBBEAN SEA... LIKE SOME OF THE
GLOBAL MODELS ARE FORECASTING. HOWEVER...IF THE TROPICAL CYCLONE
SURVIVES...AND THIS IS A BIG IF...GLOBAL MODELS REMOVE THE SHEAR BY
FRACTURING THE MID-OCEANIC TROUGH IN THE WESTERN CARIBBEAN. THIS
PATTERN CHANGE SENDS AN UPPER-LEVEL LOW INTO THE GULF OF MEXICO IN
3 DAYS WHILE BUILDING UPPER RIDGING NEAR THE DEPRESSION. THIS COULD
ALLOW THE SYSTEM TO STRENGTHEN ESPECIALLY AS IT ENTERS THE WESTERN
CARIBBEAN. ON THE OTHER HAND... GLOBAL MODELS HAVE NOTORIOUSLY
WEAKENED UPPER-LEVEL CYCLONES TOO QUICKLY IN THE PAST AND THE
MID-OCEANIC TROUGH HAS BEEN QUITE PERSISTENT AND STRONGER-THAN-
NORMAL IN THAT AREA THIS SEASON.  AFTER SAYING ALL THIS... THE
INTENSITY FORECAST WILL BE QUITE SIMILAR TO PREVIOUS. HOWEVER IF
THE LOW SHEAR ENVIRONMENT THE GLOBAL MODELS ARE FORECASTING
MATERIALIZES IN THE WESTERN CARIBBEAN... TD FIVE COULD BE A LOT
STRONGER THAN SHOWN BELOW IN THE LATER PERIODS. 
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      25/0900Z 13.4N  65.7W    30 KT
 12HR VT     25/1800Z 13.9N  67.8W    35 KT
 24HR VT     26/0600Z 14.8N  70.4W    40 KT
 36HR VT     26/1800Z 15.6N  72.8W    45 KT
 48HR VT     27/0600Z 16.5N  75.0W    55 KT
 72HR VT     28/0600Z 18.5N  79.5W    65 KT
 96HR VT     29/0600Z 21.0N  84.0W    65 KT
120HR VT     30/0600Z 23.5N  87.5W    65 KT
 
$$
FORECASTER BLAKE/AVILA
 
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