Tropical Depression FOUR-E

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TROPICAL DEPRESSION FOUR-E DISCUSSION NUMBER   3
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP042012
200 PM PDT WED JUL 04 2012
 
THE DEPRESSION HAS CHANGED LITTLE DURING THE PAST SIX HOURS.
HOWEVER...THERE ARE SIGNS NOW THAT THE NORTHERLY VERTICAL SHEAR IS
BEGINNING TO ABATE AS MODEST CONVECTION HAS RECENTLY BEGUN TO
DEVELOP IN THE NORTHERN SEMICIRCLE WITH A SMALL BURST OF CONVECTION
ALSO HAVING DEVELOPED NEAR THE CENTER. THE LOW-LEVEL CENTER IS
STILL DIFFICULT TO DETERMINE...BUT A FORTUITOUS 1628Z ASCAT
OVERPASS INDICATED THE CENTER OF THE ELONGATED CIRCULATION WAS
LOCATED VERY NEAR THE PREVIOUS FORECAST TRACK. ALTHOUGH SATELLITE
INTENSITY ESTIMATES ARE A CONSENSUS T2.5/35 KT FROM TAFB AND
SAB...AND T2.4/34 KT FROM UW-CIMSS ADT...THE INITIAL INTENSITY IS
BEING MAINTAINED AT 30 KT BASED ON THE RECENT ASCAT DATA THAT ONLY
SHOWED 25-KT WINDS IN THE NORTHEAST QUADRANT. EVEN ALLOWING FOR THE
LOW BIAS OF ASCAT...THE SURFACE WINDS SHOULD BE NO MORE THAN 30 KT.
 
THE INITIAL MOTION ESTIMATE IS 295/11 KT. THE CYCLONE IS EXPECTED TO
GRADUALLY TURN MORE WESTWARD OVER THE NEXT 2 DAYS AS THE SYSTEM
MOVES ALONG THE SOUTHERN PERIPHERY OF A DEEP-LAYER SUBTROPICAL
RIDGE TO ITS NORTH. NHC MODEL GUIDANCE REMAINS IN EXCELLENT
AGREEMENT ON THIS DEVELOPING TRACK SCENARIO. THE OFFICIAL FORECAST
TRACK IS SITUATED IN THE MIDDLE OF THE TIGHTLY PACKED GUIDANCE
ENVELOPE AND LIES CLOSE TO THE CONSENSUS MODELS TVCN AND TV15.
 
MODERATE NORTHERLY TO NORTHEASTERLY VERTICAL WIND SHEAR THAT HAS
BEEN HINDERING DEVELOPMENT OVER THE PAST COUPLE OF DAYS IS FORECAST
BY ALL OF THE GLOBAL AND REGIONAL MODELS TO GRADUALLY SUBSIDE...AND
AFTER 24 HOURS THE SHEAR IS EXPECTED TO BE LESS THAN 10 KT. THIS
SHOULD ALLOW FOR AT LEAST MODEST STRENGTHENING THROUGH 72 HOURS
WHILE THE CYCLONE REMAINS OVER WARM SSTS AND IN MOIST MID-LEVEL
CONDITIONS. HOWEVER...BY 96 HOURS AND BEYOND...THE SYSTEM IS
FORECAST TO MOVE OVER SUB-25C SSTS AND INTO A MORE STABLE
THERMODYNAMIC ENVIRONMENT...WHICH SHOULD INDUCE STEADY WEAKENING.
THE OFFICIAL INTENSITY FORECAST IS SIMILAR TO THE PREVIOUS ADVISORY
AND REMAINS ABOVE THE STATISTICAL GUIDANCE AND CLOSE TO A BLEND OF
THE HWRF AND GFS MODELS...WHICH INDICATE A HURRICANE BY 72 HOURS.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  04/2100Z 13.5N 107.8W   30 KT  35 MPH
 12H  05/0600Z 14.0N 109.3W   35 KT  40 MPH
 24H  05/1800Z 14.5N 111.3W   40 KT  45 MPH
 36H  06/0600Z 14.8N 113.3W   45 KT  50 MPH
 48H  06/1800Z 14.9N 115.4W   55 KT  65 MPH
 72H  07/1800Z 15.0N 119.4W   65 KT  75 MPH
 96H  08/1800Z 15.3N 123.7W   55 KT  65 MPH
120H  09/1800Z 16.1N 128.4W   45 KT  50 MPH
 
$$
FORECASTER STEWART
 
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