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| #63783 (Received by flhurricane at: 10:17 PM 31.Dec.2005) TCDAT5 TROPICAL STORM ZETA DISCUSSION NUMBER 7 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 10 PM EST SAT DEC 31 2005 ZETA APPEARED ON THE VERGE OF LOSING ALL OF ITS DEEP CONVECTION A FEW HOURS AGO... BUT SINCE ABOUT 21Z THE CONVECTION HAS BEEN ON SOMEWHAT OF AN INCREASE AGAIN. HOWEVER... THAT CONVECTION IS LIMITED TO THE NORTHEASTERN QUADRANT DUE TO THE PERSISTENT WIND SHEAR. SUBJECTIVE DVORAK T-NUMBERS AT 00Z WERE 2.5 AND THE INTENSITY ESTIMATES WERE 45 TO 55 KT. THE AMSU AND QUIKSCAT OVERPASSES THIS AFTERNOON BOTH MISSED MOST OF THE CIRCULATION... SO THERE IS NOT MUCH BASIS UPON WHICH TO CHANGE THE INITIAL INTENSITY WHICH REMAINS 45 KT. ZETA IS STILL BARELY MOVING... BUT IT APPEARS TO BE DRIFTING WESTWARD. THERE IS NOT MUCH CHANGE TO THE PREVIOUS FORECAST OR REASONING. THE OFFICIAL FORECAST HOLDS ON TO A TROPICAL STORM FOR ANOTHER 24 HOURS... LONGER THAN THE SHIPS GUIDANCE BUT WELL BELOW THE GFDL INTENSITY FORECAST. THE UPPER-TROPOSPHERIC WINDS OVER ZETA ARE NOT FORECAST BY THE DYNAMICAL MODELS TO GET MUCH STRONGER DURING THE NEXT COUPLE OF DAYS. SO IT IS POSSIBLE ZETA WILL REMAIN A TROPICAL STORM LONGER THAN FORECAST... BUT GIVEN HOW MUCH IT STRUGGLED AGAINST THE SHEAR EARLIER TODAY IT COULD ALSO LOSE ITS DEEP CONVECTION FOR GOOD AT JUST ABOUT ANY TIME. THE OFFICIAL FORECAST TRACK REMAINS SLOW AND GENERALLY WESTWARD... PRESUMING THAT SOME CONVECTION WILL REMAIN FOR ANOTHER DAY OR TWO... WHICH WOULD ALLOW THE UPPER-LEVEL WESTERLIES TO RETARD THE STEERING INFLUENCE OF THE EASTERLIES AROUND THE NARROW AND WEAK LOW- TO MID-LEVEL RIDGE TO THE NORTH OF ZETA. THE TROPICAL CYCLONE OR ITS REMNANTS MIGHT BE PULLED NORTHWARD BEYOND ABOUT 48 HOURS AHEAD OF THE NEXT COLD FRONT FORECAST TO TRAVERSE THE ATLANTIC. FORECASTER KNABB FORECAST POSITIONS AND MAX WINDS INITIAL 01/0300Z 25.6N 38.3W 45 KT 12HR VT 01/1200Z 25.5N 39.0W 40 KT 24HR VT 02/0000Z 25.4N 40.0W 35 KT 36HR VT 02/1200Z 25.4N 40.9W 30 KT 48HR VT 03/0000Z 25.6N 41.9W 25 KT...REMNANT LOW 72HR VT 04/0000Z...DISSIPATED |
