ZCZC MIATCDEP1 ALL TTAA00 KNHC DDHHMM 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 $$ NNNN
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Page last modified: Monday, 11-Sep-2006 11:28:39 UTC