ZCZC MIATCDEP1 ALL TTAA00 KNHC DDHHMM TROPICAL STORM ALETTA DISCUSSION NUMBER 4 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP012006 800 PM PDT SAT MAY 27 2006 THE FIRST STORM OF THE SEASON IS LOOKING LIKE A TOUGH ONE TO FORECAST. LAST-LIGHT VISIBLE IMAGES DEPICTED A LOW-LEVEL CIRCULATION CENTER MOVING WESTWARD...AWAY FROM THE DEEP CONVECTION. SSM/I AND AMSR-E IMAGES ALSO SHOWED A LOW-LEVEL CENTER DISPLACED TO THE WEST OF THE CONVECTION. UNLESS A NEW CENTER DEVELOPS FARTHER TO THE EAST... ALETTA MAY NOT LAST VERY LONG. GIVEN THAT THE CENTER HAS REFORMED NEAR THE DEEP CONVECTION AT LEAST TWICE ALREADY IN THIS SYSTEM...IT MIGHT NOT BE UNREASONABLE TO EXPECT YET ANOTHER REFORMATION. DVORAK CURRENT INTENSITY ESTIMATES RANGE FROM 35 TO 45 KT. SINCE THE SYSTEM IS NOT WELL ORGANIZED AT THIS TIME...THE INITIAL WIND SPEED IS HELD AT 35 KT FOR THIS PACKAGE. IN SPITE OF THE CURRENTLY DISORGANIZED STATE OF THE TROPICAL CYCLONE...THE GLOBAL MODELS ARE FORECASTING A MORE FAVORABLE UPPER- TROPOSPHERIC ENVIRONMENT OF WEAKER SHEAR AND ANTICYCLONIC FLOW TO DEVELOP OVER THE NEXT DAY OR TWO. THEREFORE...I WILL CONTINUE TO FORECAST SOME INTENSIFICATION...AS IN THE PREVIOUS ADVISORIES. THIS IS ALSO IN GENERAL AGREEMENT WITH THE SHIPS INTENSITY FORECAST. THERE HAS BEEN LITTLE OVERALL MOTION OVER THE PAST SEVERAL HOURS... AND STEERING CURRENTS ARE LIKELY TO REMAIN RATHER WEAK FOR THE NEXT FEW DAYS. THERE ARE NOW NO DYNAMICAL MODELS THAT TAKE THE TROPICAL CYCLONE WESTWARD. THE GFDL AND NOGAPS MODELS FORECAST ALETTA TO MOVE INLAND OVER SOUTHERN MEXICO WITHIN 24-36 HOURS. IT SHOULD BE NOTED THAT THE GFDL'S VORTEX TRACKER...WHICH IS LISTED ON THE STANDARD OUTPUT MESSAGE...LOSES TRACK OF THE SYSTEM AND DOES NOT INDICATE LANDFALL. HOWEVER...INSPECTION OF THE GFDL MODEL OUTPUT FIELDS OF SEA LEVEL PRESSURE CLEARLY SHOWS THE CENTER CROSSING THE COAST. SINCE THERE IS CURRENTLY NO CREDIBLE GUIDANCE TO FORECAST A WESTWARD MOTION LATER IN THE PERIOD...THE OFFICIAL FORECAST TRACK IS SHIFTED EASTWARD FROM THE PREVIOUS ADVISORY...AND KEEPS THE SYSTEM STATIONARY FROM DAYS 3-5. OBVIOUSLY...ALETTA MAY HAVE MOVED INLAND AND DISSIPATED BY THEN. FORECASTER PASCH FORECAST POSITIONS AND MAX WINDS INITIAL 28/0300Z 15.7N 101.0W 35 KT 12HR VT 28/1200Z 16.0N 100.9W 40 KT 24HR VT 29/0000Z 16.3N 100.8W 45 KT 36HR VT 29/1200Z 16.6N 100.7W 50 KT 48HR VT 30/0000Z 16.9N 100.7W 50 KT 72HR VT 31/0000Z 17.0N 101.0W 55 KT 96HR VT 01/0000Z 17.0N 101.0W 55 KT 120HR VT 02/0000Z 17.0N 101.0W 55 KT $$ NNNN
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Page last modified: Monday, 11-Sep-2006 11:28:39 UTC