Tropical Storm ALETTA

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TROPICAL STORM ALETTA DISCUSSION NUMBER   5
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP012006
200 AM PDT SUN MAY 28 2006
 
A BURST OF COLD-TOPPED CONVECTION HAS DEVELOPED EAST OF THE LOW-LEVEL
CENTER...AND HAS BEEN PROPAGATING SLOWLY SOUTHWARD. THE INITIAL
POSITION WAS PLACED A LITTLE SOUTH OF THE LAST ADVISORY POSITION
BASED ON A 28/0045Z QUIKSCAT OVERPASS. THE INTENSITY OF 40 KT IS
BASED ON A BLEND OF SATELLITE INTENSITY ESTIMATES OF 45 KT FROM TAFB
AND 35 KT FROM SAB...AND THE LATEST UW-CIMSS AMSU ESTIMATE OF 40 KT.

IT IS DIFFICULT AT THIS TIME TO DETERMINE IF THE LOW-LEVEL CENTER IS
MIGRATING SOUTHWARD ALONG WITH THE CONVECTION. IT IS POSSIBLE THAT
THE CONVECTION HAS JUST SHIFTED SOUTHWARD AS AN EASTWARD MOVING
MID-LEVEL TROUGH PASSES JUST NORTH OF THE SYSTEM CAUSING THE
MID-LEVEL FLOW TO SHIFT FROM WESTERLY TO NORTHERLY. DUE TO THIS
UNCERTAINTY...HOWEVER...THE INITIAL MOTION WILL REMAIN STATIONARY.
NONE OF THE NHC MODELS ARE INDICATING LANDFALL ANY LONGER. WITH THE
EXCEPTION OF THE BAM MODELS...THE REST OF THE NHC MODEL GUIDANCE
KEEPS THE CENTER WELL OFFSHORE THE MEXICAN COAST AND EITHER KEEP IT
STATIONARY OR DRIFT IT SOUTHWARD FOR THE NEXT 48 HOURS... AND THEN
TAKE IT WEST OR WEST-SOUTHWARD AFTER THAT AS MID-LEVEL RIDGING
BUILDS IN TO THE NORTH OF THE CYCLONE. THE OFFICIAL FORECAST IS
SIMILAR TO THE PREVIOUS ADVISORY...ONLY SLOWER. IF THE SLOW
NORTHWARD MOTION INDICATED IN THIS ADVISORY DOES NOT DEVELOP LATER
TODAY...THEN THE TROPICAL STORM WARNING AND WATCHES FOR THE MEXICAN
COAST WILL NEED TO BE DISCONTINUED.
 
THE AFOREMENTIONED MID-LEVEL TROUGH NOTED IN WATER VAPOR IMAGERY IS
FORECAST TO PASS NORTHEAST OF ALETTA DURING THE NEXT 12 HOURS. THIS
SHOULD CAUSE THE MID-LEVEL FLOW TO VEER AROUND MORE TO THE NORTH AND
NORTHEAST...RELAXING THE SHEAR THAT HAS BEEN HINDERING DEVELOPMENT.
THE SHIPS MODEL DECREASES THE UPPER-LEVEL SHEAR TO LESS THAN 5 KT BY
48 HOURS...WHICH SHOULD ALLOW FOR SOME ADDITIONAL STRENGTHENING TO
OCCUR DESPITE THE RELATIVELY DRY ENVIRONMENT SURROUNDING ALETTA.
 
FORECASTER STEWART
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      28/0900Z 15.4N 101.0W    40 KT
 12HR VT     28/1800Z 15.6N 100.9W    40 KT
 24HR VT     29/0600Z 15.9N 100.9W    45 KT
 36HR VT     29/1800Z 16.2N 100.8W    50 KT
 48HR VT     30/0600Z 16.4N 100.9W    55 KT
 72HR VT     31/0600Z 16.3N 101.2W    55 KT
 96HR VT     01/0600Z 16.2N 101.5W    55 KT
120HR VT     02/0600Z 16.0N 102.0W    55 KT
 
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