Tropical Depression FOUR-E

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TROPICAL DEPRESSION FOUR-E DISCUSSION NUMBER   1
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP042009
200 AM PDT FRI JUL 10 2009
 
THE CIRCULATION ASSOCIATED WITH THE AREA OF LOW PRESSURE LOCATED
WELL TO THE SOUTHWEST OF MEXICO HAS CONTINUED TO BECOME BETTER
ORGANIZED AND IS BECOMING DETACHED FROM THE INTERTROPICAL
CONVERGENCE ZONE.  SATELLITE INTENSITY ESTIMATES AT 0600 UTC FROM
TAFB AND SAB WERE T1.5 AND T2.0...RESPECTIVELY...ALTHOUGH DATA-T
NUMBERS AT THE TIME WERE 2.0 AND 2.5.  RECENTLY...A CLUSTER OF DEEP
CONVECTION HAS BECOME CONSOLIDATED NEAR THE LOW-LEVEL CENTER AND A
PROMINENT CONVECTIVE BAND HAS FORMED WITHIN THE SOUTHEASTERN
SEMICIRCLE.  THE STRUCTURE OF THE CIRCULATION AND THE CONVECTION
HAVE BECOME WELL-DEFINED ENOUGH TO JUSTIFY THE HIGHER END OF THE
ESTIMATES...AND ADVISORIES ARE BEING INITIATED ON THIS SYSTEM AS A
25-KT DEPRESSION.
 
THE DEPRESSION IS MOVING AT AN INITIAL MOTION OF 275/7.  THE SUITE
OF GLOBAL MODELS SHOWS FAIRLY TIGHT CLUSTERING THROUGH THE ENTIRE
5-DAY FORECAST PERIOD AND INDICATES THAT THE DEPRESSION WILL NOT
MAKE MUCH OF A NORTHWARD DISPLACEMENT.  THE CYCLONE IS CURRENTLY
APPROACHING A WEAKNESS IN THE SUBTROPICAL RIDGE DUE TO THE REMNANTS
OF BLANCA AND A CLOSED UPPER LOW OFF THE OREGON COAST...BUT THE
MODELS QUICKLY RE-BUILD THE RIDGE WESTWARD OVER THE NEXT 48 HOURS.
AS THE RIDGE BUILDS...THE DEPRESSION IS EXPECTED TO ACCELERATE AND
MOVE AT A CONSISTENT 11 OR 12 KNOTS IN ABOUT 24-36 HOURS.  THE
OFFICIAL FORECAST LIES GENERALLY JUST SOUTH OF THE MODEL CONSENSUS
AND SHADES CLOSER TO THE TRACKS OF THE GFDL AND HWRF.
 
OCEAN TEMPERATURES ALONG THE FORECAST TRACK OF THE DEPRESSION ARE
AROUND 28-29C AND VERTICAL SHEAR IS EXPECTED TO REMAIN LOW OVER THE
NEXT 5 DAYS...SO IT DOES NOT LOOK LIKE THERE IS MUCH TO LIMIT
INTENSIFICATION.  HOWEVER...MOST OF THE MODELS SHOW ONLY SLOW
STRENGTHENING THROUGH THE FIRST 24-36 HOURS WITH QUICKER
INTENSIFICATION THEREAFTER.  THE GFDL PRODUCES THE MOST
STRENGTHENING AND BRINGS THE CYCLONE TO NEAR 90 KT WITHIN 5 DAYS
WHILE THE SHIPS AND LGEM MODELS LEVEL OFF THE INTENSITY AROUND 70
KT FROM 84-120 HOURS.  SINCE IT IS NOT APPARENT WHAT WOULD LIMIT
INTENSIFICATION AT DAYS 4 AND 5...THE OFFICIAL FORECAST IS SLIGHTLY
ABOVE THE SHIPS/LGEM GUIDANCE...AND CLOSER TO THE GFDL AND HWRF
MODELS.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      10/0900Z 10.0N 111.5W    25 KT
 12HR VT     10/1800Z 10.2N 112.6W    30 KT
 24HR VT     11/0600Z 10.4N 114.8W    35 KT
 36HR VT     11/1800Z 10.6N 117.2W    40 KT
 48HR VT     12/0600Z 11.0N 119.6W    45 KT
 72HR VT     13/0600Z 12.0N 124.5W    60 KT
 96HR VT     14/0600Z 13.0N 129.5W    70 KT
120HR VT     15/0600Z 13.5N 134.5W    80 KT
 
$$
FORECASTER BERG
 
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