ZCZC MIATCDEP3 ALL TTAA00 KNHC DDHHMM TROPICAL DEPRESSION THIRTEEN-E DISCUSSION NUMBER 3 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 2 AM PDT SAT SEP 11 2004 THE DVORAK T NUMBER FROM TAFB IS 3.0 BASED ON THE 0600Z GOES-10 IMAGE...AND FOLLOWING THE GOES-12 ECLIPSE PERIOD...SAB OBTAINED A DVORAK T NUMBER OF 2.5 FROM THE 0645Z IMAGE. WHILE THESE ESTIMATES COULD BE GROUNDS FOR UPGRADING THE DEPRESSION TO A TROPICAL STORM...WE PREFER TO WAIT TO SEE IF THE CONVECTIVE BURST THAT BEGAN DURING THE GOES-12 ECLIPSE PERSISTS...AND PERHAPS WAIT FOR VISIBLE IMAGERY LATER THIS MORNING TO BE MORE CONFIDENT THAT THE LOW LEVEL CENTER IS SUFFICIENTLY INVOLVED WITH THE CONVECTION. SHORTWAVE IR IMAGERY SUGGESTS THE CENTER IS JUST BARELY TUCKED INTO THE NORTHEASTERN PORTION OF THE CONVECTION...INDICATIVE OF THE MODERATE EASTERLY SHEAR OVER THE SYSTEM. THE INITIAL MOTION ESTIMATE IS 280/12...OR JUST NORTH OF WEST...ALONG THE SOUTHERN PERIPHERY OF THE MID/UPPER LEVEL RIDGE CENTERED OVER NORTHERN MEXICO. THE NOGAPS AND GFDN IGNORE THE INITIAL MOTION AND IMMEDIATELY TAKE THE SYSTEM TOWARD THE NORTH OR NORTHWEST...AND THESE SOLUTIONS ARE DISCOUNTED THROUGHOUT THE FORECAST PERIOD. THE INITIAL MOTION IS EXPECTED TO GENERALLY CONTINUE FOR ABOUT THE NEXT 36 HOURS OR SO...AS AGREED UPON BY THE GFS...GFDL...AND UKMET MODELS. BEYOND 36 HOURS...THE OFFICIAL FORECAST STILL RELIES ON A CONSENSUS OF THESE THREE MODELS...ALL OF WHICH FORECAST THE RIDGE TO THE NORTH TO WEAKEN AND FOR THE TROPICAL CYCLONE TO SLOW DOWN AND TURN TOWARD THE NORTHWEST OR NORTH. HOWEVER...WE ARE NOT READY TO FOLLOW A NORTHWARD TURN AS ABRUPT AS THAT SHOWN BY THE GFS AND GFDL...AND RATHER STAY CLOSER TO THE MORE GRADUAL TURN IN THE UKMET. THE OFFICIAL FORECAST IS FASTER THAN THE PREVIOUS ADVISORY AND IS MORE TO THE RIGHT BEYOND DAY THREE...AND NOW INCLUDES A NORTH-NORTHWEST MOTION ON DAYS FOUR AND FIVE. ON THE NEW FORECAST TRACK...SEA SURFACE TEMPERATURES SHOULD REMAIN 28-29C AND THE VERTICAL SHEAR WEAK TO MODERATE IN STRENGTH. THE INTENSITY FORECAST IS JUST AN UPDATE TO THE PREVIOUS ADVISORY...REACHING HURRICANE STRENGTH IN 48 HOURS AND LEVELLING OFF THE INTENSITY AT 75 KNOTS AT DAYS 4 AND 5...GENERALLY IN GOOD AGREEMENT WITH SHIPS. FORECASTER KNABB/JARVINEN FORECAST POSITIONS AND MAX WINDS INITIAL 11/0900Z 11.7N 97.1W 30 KT 12HR VT 11/1800Z 12.0N 98.8W 40 KT 24HR VT 12/0600Z 12.4N 100.8W 45 KT 36HR VT 12/1800Z 12.7N 102.1W 55 KT 48HR VT 13/0600Z 13.2N 103.1W 65 KT 72HR VT 14/0600Z 15.0N 104.5W 70 KT 96HR VT 15/0600Z 16.5N 105.5W 75 KT 120HR VT 16/0600Z 18.0N 106.0W 75 KT $$ NNNN
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Page last modified: Saturday, 11-Sep-2004 09:04:50 UTC