Tropical Depression TWO

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TROPICAL DEPRESSION TWO DISCUSSION NUMBER   4
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022009
1100 PM AST TUE AUG 11 2009
 
CONVENTIONAL SATELLITE IMAGERY INDICATES A RECENT BURST OF DEEP
CONVECTION OVER THE WESTERN SEMICIRCLE OF THE DEPRESSION...WITH THE
CENTER ON THE EASTERN EDGE OF THIS CONVECTIVE MASS.  EVEN THOUGH
DVORAK T-NUMBERS ARE 1.5 FROM BOTH TAFB AND SAB...A RECENTLY-
RECEIVED ASCAT PASS FROM 0000 UTC SUPPORTS INCREASING THE INTENSITY
TO 30 KT.  EVEN MORE RECENTLY...LATEST SATELLITE IMAGERY SUGGESTS A
FURTHER INCREASE IN ORGANIZATION AND THE DEPRESSION MAY NOW BE
CLOSE TO TROPICAL STORM STRENGTH.
 
WHILE THE CIRCULATION CENTER IS GRADUALLY BECOMING BETTER-
DEFINED...THERE STILL EXISTS SOME UNCERTAINTY IN THE INITIAL
LOCATION.  THE INITIAL MOTION IS ESTIMATED TO BE 275/11...AS THE
CYCLONE IS BEING STEERED BY DEEP-LAYER EASTERLY FLOW ON THE
SOUTHERN PERIPHERY OF A MID-LEVEL SUBTROPICAL RIDGE.  THIS PATTERN
SHOULD FAVOR A GENERAL WEST TO WEST-NORTHWEST COURSE OVER THE NEXT
SEVERAL DAYS...CONSISTENT WITH THE LATEST MODEL GUIDANCE.  A
WEAKNESS IN THE SUBTROPICAL RIDGE ON DAYS 4 AND 5 SHOULD ALLOW THE
CYCLONE TO BEGIN GAINING MORE LATITUDE WITH AN INCREASE IN FORWARD
SPEED.  THE HWRF SOLUTION APPEARS TO BE AN OUTLIER AMONGST THE
MODEL SUITE...IMMEDIATELY TAKING THE CYCLONE ON A MORE
NORTHWESTWARD PATH.  ON THE OTHER HAND...THE SPREAD OF THE
REMAINING GUIDANCE IS RELATIVELY SMALL...EVEN IN THE LONGER
RANGE...WHICH ADDS SOME CONFIDENCE TO THE CURRENT FORECAST.  THE
OFFICIAL FORECAST DISCOUNTS THE HWRF SOLUTION AND LIES BETWEEN THE
MODEL CONSENSUS AND THE PREVIOUS ADVISORY.
 
THE DEPRESSION IS CURRENTLY EMBEDDED IN A LOW SHEAR ENVIRONMENT WITH
MARGINAL SEA SURFACE TEMPERATURES...WHICH SHOULD SUPPORT
INTENSIFICATION.  HOWEVER...SHIPS MODEL GUIDANCE INDICATES MODEST
EASTERLY SHEAR IMPACTING THE CYCLONE SHORTLY THEREAFTER AS A RESULT
OF INCREASING MID-LEVEL HEIGHTS TO THE NORTH.  THIS INCREASE IN
SHEAR SHOULD INHIBIT FURTHER DEVELOPMENT IN THE SHORT-TERM.  LATER
IN THE PERIOD...GLOBAL MODELS SUGGEST THAT THE CYCLONE WILL
INTERACT WITH INCREASING SOUTHWESTERLY FLOW ALOFT...DOWNSTREAM OF A
PRONOUNCED MID- TO UPPER-LEVEL CYCLONE WITHIN THE MID-OCEANIC
TROUGH.  THIS INTERACTION SHOULD INDUCE SUFFICIENT SHEAR TO WEAKEN
THE SYSTEM BEGINNING DAY 4.  SHOULD THE CYCLONE TAKE A MORE
NORTHERLY TRACK...IT WOULD ENCOUNTER AN EVEN MORE HOSTILE
ENVIRONMENT WHICH COULD ACCELERATE THE WEAKENING TREND.  THEN
AGAIN...SHOULD THE CYCLONE MAINTAIN A MORE SOUTHERN TRACK...THE
SHEAR WOULD LIKELY BE LOWER WHICH WOULD SUPPORT A STRONGER SYSTEM.
  
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      12/0300Z 14.8N  31.5W    30 KT
 12HR VT     12/1200Z 14.8N  33.2W    35 KT
 24HR VT     13/0000Z 14.8N  35.4W    35 KT
 36HR VT     13/1200Z 14.9N  37.7W    35 KT
 48HR VT     14/0000Z 15.2N  40.2W    40 KT
 72HR VT     15/0000Z 16.5N  45.0W    45 KT
 96HR VT     16/0000Z 19.0N  51.0W    45 KT
120HR VT     17/0000Z 22.0N  56.5W    40 KT
 
$$
FORECASTER KIMBERLAIN/BROWN/COHEN
 
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