ZCZC MIATCDAT5 ALL TTAA00 KNHC DDHHMM TROPICAL DEPRESSION FIVE DISCUSSION NUMBER 4 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL052006 1100 AM EDT FRI AUG 25 2006 THE CENTER OF TROPICAL DEPRESSION FIVE IS VERY HARD TO LOCATE THIS MORNING. MICROWAVE SATELLITE IMAGERY SUGGESTS THAT THE CENTER IS LOCATED WEST OF THE LARGE CONVECTIVE MASS THAT HAS PERSISTED THROUGH THE NIGHT...AND CLOSE TO THE PREVIOUS FORECAST TRACKS. HOWEVER...A 12Z OBSERVATION FROM SHIP 6ZXG SUGGEST THE CENTER IS FARTHER TO THE SOUTH AND EAST...WHICH WOULD SUGGEST A MORE WESTWARD MOTION AT A SLOWER FORWARD SPEED. ANIMATION OF VISIBLE IMAGERY HAS NOT YET HELPED RESOLVE THIS...AS IT IS DIFFICULT TO SEE WESTERLY LOW-LEVEL WINDS. THE INITIAL POSITION WILL BE CLOSER TO THAT OF THE MICROWAVE DATA. SATELLITE INTENSITY ESTIMATES REMAIN 35-45 KT... BUT DUE TO THE UNCERTAINTY IN THE CENTER POSITION THE CYCLONE WILL REMAIN A DEPRESSION ON THIS PACKAGE. THE INITIAL MOTION IS A SOMEWHAT UNCERTAIN 280/13...SOMEWHAT SLOWER THAN EARLIER. THERE IS LITTLE CHANGE IN THE SYNOPTIC REASONING OR THE TRACK FORECAST FOR THE FIRST 72-96 HR. THE DEPRESSION IS SOUTH OF A LOW/MID-LEVEL RIDGING OVER THE WESTERN ATLANTIC...WHICH SHOULD KEEP THE SYSTEM MOVING GENERALLY WEST-NORTHWESTWARD. MODEL GUIDANCE SUPPORTS THIS SCENARIO WITH A TIGHT CLUSTERING OF TRACKS THROUGH THE NORTHWESTERN CARIBBEAN...WITH THE EXCEPTION OF THE GFDL WHICH CONTINUES TO CALL FOR A TRACK OVER CUBA. SOME SPREAD APPEARS IN THE GUIDANCE AFTER 96 HR...WITH THE GFS AND NOGAPS BUILDING THE RIDGE ACROSS THE GULF OF MEXICO ENOUGH TO TURN THE CYCLONE WESTWARD...WHILE THE ECMWF AND CANADIAN MODELS HAVING ENOUGH OF A WEAKNESS FOR THE CYCLONE TO TURN NORTHWARD. THE NEW FORECAST TRACK IS AN UPDATE OF THE PREVIOUS PACKAGE FOR THE FIRST 96 HR...THEN SLOWS THE SYSTEM DOWN IN RESPONSE TO THE GUIDANCE SPREAD. THE INTENSITY FORECAST IS PERHAPS BECOMING LESS TRICKY. THE LARGE-SCALE MODELS ARE COMING INTO BETTER AGREEMENT THAT THE UPPER-LEVEL TROUGH OVER THE WESTERN CARIBBEAN WILL MOVE WESTWARD AND ALLOW AN UPPER-LEVEL RIDGE TO DEVELOP OVER THE WESTERN CARIBBEAN. SHOULD THIS HAPPEN...AS SOME OF THE MODELS HAVE BEEN KNOWN TO MOVE UPPER-LEVEL LOWS TOO QUICKLY WESTWARD...IT WOULD REDUCE THE CURRENT 15-20 KT SHEAR AND PRODUCE A MORE FAVORABLE ENVIRONMENT. THE SHIPS MODEL CALLS FOR THE DEPRESSION TO BECOME A HURRICANE IN ABOUT 60 HR AND REACH 87 KT BY 120 HR. GIVEN THE UNCERTAINTIES IN THE INITIAL POSITION AND INTENSITY...THE NEW INTENSITY FORECAST IS THE SAME AS THE OLD FORECAST...CALLING FOR THE CYCLONE TO BECOME A HURRICANE IN ABOUT 72 HR. HOWEVER...IF THE SHEAR DECREASES AS MUCH AS FORECAST...THE CYCLONE COULD BE SIGNIFICANTLY STRONGER THAN CURRENTLY FORECAST AFTER 72 HR. AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT IS SCHEDULED TO INVESTIGATE THE DEPRESSION THIS AFTERNOON. IF THE AIRCRAFT FINDS THE CENTER IN A DIFFERENT LOCATION...SIGNIFICANT CHANGES IN THE FORECAST TRACK COULD BE NECESSARY ON THE NEXT ADVISORY. FORECAST POSITIONS AND MAX WINDS INITIAL 25/1500Z 13.5N 66.4W 30 KT 12HR VT 26/0000Z 14.2N 68.5W 35 KT 24HR VT 26/1200Z 15.0N 71.1W 40 KT 36HR VT 27/0000Z 15.9N 73.6W 45 KT 48HR VT 27/1200Z 16.9N 76.0W 55 KT 72HR VT 28/1200Z 19.0N 80.5W 65 KT 96HR VT 29/1200Z 21.5N 84.5W 65 KT 120HR VT 30/1200Z 23.5N 87.5W 65 KT $$ FORECASTER BEVEN NNNN
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Page last modified: Monday, 11-Sep-2006 11:28:36 UTC