Tropical Storm ALETTA

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TROPICAL STORM ALETTA DISCUSSION NUMBER   9
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP012006
200 AM PDT MON MAY 29 2006
 
MICROWAVE SATELLITE IMAGERY AROUND 03Z INDICATED THE CENTER OF 
ALETTA HAD REMAINED WELL-DEFINED AS THE CYCLONE CONTINUED TO
DRIFT SLOWLY NORTHWARD. HOWEVER...SINCE THE LAST MICROWAVE
OVERPASS... INFRARED SATELLITE IMAGERY INDICATES DEEP CONVECTION 
AND POSSIBLY A SMALL CDO HAVE DEVELOPED OVER THE LOW-LEVEL CENTER.
THE INITIAL INTENSITY OF 40 KT IS BASED ON A BLEND OF SATELLITE
ESTIMATES OF 35 KT FROM TAFB AND SAB...45 KT FROM AFWA...AND THE
RECENT DEVELOPMENT OF THE CDO-LIKE CONVECTIVE FEATURE.
 
THE INITIAL MOTION ESTIMATE REMAINS 360/02 KT...BASED ON MICROWAVE
POSITION ESTIMATES BETWEEN 00Z AND 03Z. ALL OF THE NHC MODEL 
GUIDANCE SUGGESTS THAT A GRADUAL TURN TOWARD THE NORTHWEST OR
WEST-NORTHWEST SHOULD OCCUR WITHIN THE NEXT 24 HOURS AS MID-LEVEL
RIDGING TO THE NORTH AND NORTHWEST OF ALETTA SLOWLY DEVELOPS
EASTWARD. THE MODELS ARE IN EXCELLENT AGREEMENT ON THIS EVOLVING
SCENARIO...AND THE ONLY DIFFERENCE BETWEEN THE MODELS LIES IN HOW
FAST THEY MOVE ALETTA WESTWARD AFTER 72 HOURS. THE UKMET APPEARS TO
BE TOO FAST IN THE LATTER PERIODS...WHICH HAS CONTAMINATED THE GUNA
AND GUNS CONSENSUS FORECASTS. AS A RESULT...THE OFFICIAL FORECAST IS
SLOWER THAN GUNA AND IS SIMILAR TO THE PREVIOUS FORECAST TRACK.

THE MUCH ADVERTISED DECREASE IN THE VERTICAL SHEAR OVER THE PAST
COUPLE OF DAYS FINALLY APPEARS TO BE OCCURRING. UPPER-LEVEL OUTFLOW
HAS IMPROVED TO THE WEST...AND THE DEVELOPMENT OF THE CDO-LIKE
FEATURE COULD BE THE ONSET OF MORE SIGNIFICANT INTENSIFICATION...
MAINLY IN THE SHORT TERM. THE SHIPS MODEL DECREASES THE VERTICAL
SHEAR TO ABOUT 5 KT BY 24 HOURS...AND THEN GRADUALLY INCREASES THE
WEST TO SOUTHWESTERLY SHEAR TO 20-25 BY 48 HOURS AND BEYOND.
THEREFORE... THE INTENSIFICATION TREND WAS INCREASED A LITTLE BIT
ABOVE THE SHIPS MODEL FORECASTS THROUGH 48 HOURS...AND THEN IS CLOSE
TO THE SHIPS INTENSITY FORECASTS AFTER THAT.
 
FORECASTER STEWART
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      29/0900Z 16.2N 101.0W    40 KT
 12HR VT     29/1800Z 16.4N 101.2W    45 KT
 24HR VT     30/0600Z 16.4N 102.0W    50 KT
 36HR VT     30/1800Z 16.4N 102.7W    55 KT
 48HR VT     31/0600Z 16.4N 103.4W    55 KT
 72HR VT     01/0600Z 16.3N 104.7W    50 KT
 96HR VT     02/0600Z 16.0N 106.0W    50 KT
120HR VT     03/0600Z 16.0N 107.5W    45 KT
 
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