Tropical Depression FOUR-E

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TROPICAL DEPRESSION FOUR-E SPECIAL DISCUSSION NUMBER   1
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP042010
530 AM PDT SAT JUN 19 2010
 
INFRARED SATELLITE IMAGERY INDICATES DEEP CONVECTION HAS DEVELOPED
AROUND A LARGE BUT WELL-DEFINED LOW- TO MID-LEVEL CIRCULATION NOTED
IN A 19/0805Z AMSR-E MICROWAVE OVERPASS. ALTHOUGH SATELLITE
INTENSITY ESTIMATES AT 06Z WERE ONLY T1.0/25 KT FROM BOTH TAFB AND
SAB...THE IMPROVED CONVECTIVE ORGANIZATION SINCE THAT TIME SUGGESTS
THAT THIS SYSTEM HAS BECOME A TROPICAL DEPRESSION AT A SLIGHTLY
HIGHER INITIAL INTENSITY THAN THE RECENT SATELLITE ESTIMATES.

THE INITIAL MOTION ESTIMATE IS 255/05 BASED ON MICROWAVE SATELLITE
POSITION ESTIMATES OVER THE PAST 12 HOURS. MOST OF THE NHC MODEL
GUIDANCE MOVES THE CYCLONE IN A WEST-SOUTHWEST TO WESTWARD
DIRECTION THROUGHOUT THE FORECAST PERIOD AS A MASSIVE MID-LEVEL
RIDGE TO THE NORTH BUILDS WEST-SOUTHWESTWARD FROM THE U.S. SOUTHERN
PLAINS ACROSS NORTHERN MEXICO AND INTO THE EASTERN PACIFIC WEST OF
THE BAJA PENINSULA. THE OFFICIAL FORECAST TRACK IS SIMILAR TO BUT
SLIGHTLY SOUTH OF THE CONSENSUS MODEL...TVCN...OUT OF RESPECT FOR
THE MORE LOWER LATITUDE AND SLOWER ECMWF FORECAST TRACK. AS A
RESULT OF THE WESTWARD TRACK AWAY FROM MEXICO...COASTAL TROPICAL
CYCLONE WATCHES OR WARNINGS ARE NOT ANTICIPATED AT THIS TIME.

THE RECENT AMSR-E OVERPASS REVEALED A CLOSED EYE-LIKE FEATURE IN THE
LOW-LEVELS WITH A NEARLY CLOSED MID-LEVEL CIRCULATION NOTED IN THE
89-GHZ CHANNEL. BASED ON THIS IMPROVED VERTICAL STRUCTURE...AT
LEAST STEADY INTENSIFICATION WOULD APPEAR TO BE IN ORDER FOR THE
NEXT 72 HOURS OR SO...WITH THE POSSIBILITY OF RAPID INTENSIFICATION
OCCURRING DURING THIS SAME TIME PERIOD. THE OFFICIAL INTENSITY
FORECAST IS HIGHER THAN THE SHIPS MODEL AND CLOSER TO THE HWRF AND
GFDL...WHICH MAKE THE SYSTEM A HURRICANE WITHIN 48 HOURS.  THE
SHIPS FORECAST IS BASED ON THE MUCH FASTER MEDIUM BAM MODEL TRACK
WHICH BRINGS THIS CYCLONE OVER COLDER WATER AND INTO STRONG
VERTICAL SHEAR CONDITIONS MUCH SOONER THAN THE OFFICIAL FORECAST
TRACK INDICATES.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      19/1230Z 12.8N  97.0W    30 KT
 12HR VT     19/1800Z 12.6N  97.8W    35 KT
 24HR VT     20/0600Z 12.5N  99.2W    40 KT
 36HR VT     20/1800Z 12.5N 100.7W    50 KT
 48HR VT     21/0600Z 12.5N 102.0W    60 KT
 72HR VT     22/0600Z 12.5N 104.0W    65 KT
 96HR VT     23/0600Z 12.5N 106.0W    65 KT
120HR VT     24/0600Z 13.0N 108.5W    65 KT
 
$$
FORECASTER STEWART/BRENNAN
 
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