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| #212153 (Received by flhurricane at: 11:03 PM 31.Aug.2008) TCDAT3 TROPICAL STORM HANNA DISCUSSION NUMBER 16 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082008 1100 PM EDT SUN AUG 31 2008 SINCE THE RECONNAISSANCE AIRCRAFT DEPARTED HANNA THIS AFTERNOON... DEEP CONVECTION HAS BECOME A LITTLE MORE CONCENTRATED JUST SOUTHEAST OF THE CENTER. SEVERAL MICROWAVE IMAGES FROM BETWEEN 2200 AND 0000 UTC HAVE BEEN VERY HELPFUL IN LOCATING THE CENTER. DVORAK INTENSITY ESTIMATES HAVE INCREASED AGAIN TO T3.0 OR 45 KT... AND NOAA BUOY 41046 RECENTLY REPORTED A PEAK ONE-MINUTE WIND SPEED OF 39 KT VERY NEAR THE AREA OF DEEP CONVECTION. THESE DATA SUPPORT INCREASING THE INTENSITY TO 45 KT. BOTH THE SHIPS MODEL AND UW-CIMSS DIAGNOSE ABOUT 20 KT OF NORTHWESTERLY SHEAR OVER HANNA AT THIS TIME. THE SHIPS GUIDANCE AND THE GLOBAL MODELS PREDICT SIMILAR OR SLIGHTLY HIGHER SHEAR VALUES DURING THE NEXT 2-3 DAYS. GIVEN THIS SHEAR...IT IS TEMPTING TO NOT FORECAST ANY STRENGTHENING DURING THIS TIME...BUT MOST OF THE GUIDANCE SHOWS SOME INTENSIFICATION. LATE IN THE FORECAST PERIOD...THERE ARE SOME INDICATIONS THAT THE UPPER-LEVEL ENVIRONMENT COULD BECOME SOMEWHAT MORE CONDUCIVE FOR STRENGTHENING...HOWEVER IT WILL DEPEND ON EXACTLY WHERE HANNA IS LOCATED. THE LGEM MODEL IS AT THE LOW END OF THE SPECTRUM AND FORECASTS VERY LITTLE INTENSITY CHANGE DURING THE NEXT 5 DAYS. THE NEW INTENSITY FORECAST IS VERY SIMILAR TO PREVIOUS ADVISORY THROUGH 36 HOURS...BUT IS A LITTLE MORE CONSERVATIVE THEREAFTER AND USES A BLEND OF THE SHIPS AND LGEM MODELS AT 3 DAYS AND BEYOND. HANNA HAS BEEN MOVING WESTWARD OR 280/7 KT. THE BUILDING DEEP-LAYER RIDGE OVER THE EASTERN UNITED STATES IS FORECAST TO BLOCK HANNA'S FORWARD MOTION VERY SOON...AND THE TRACK GUIDANCE SHOWS VERY SLOW AND ERRATIC MOTION OVER THE NEXT COUPLE OF DAYS. AFTER 48 HOURS...THE RIDGE BEGINS TO WEAKEN OVER THE U.S. WHILE ANOTHER RIDGE BUILDS OVER THE ATLANTIC TO THE NORTHEAST OF HANNA. THE ATLANTIC RIDGE IS EXPECTED TO STEER THE STORM NORTHWESTWARD BY THAT TIME. THE TRACK GUIDANCE GENERALLY AGREES ON THIS SCENARIO...BUT THE SPREAD OF THE GUIDANCE REMAINS QUITE LARGE AT DAYS 4 AND 5. THE UKMET REMAINS THE SOUTHERN OUTLIER WITH A TRACK NEAR CUBA AND SOUTHERN FLORIDA...WHILE THE GFS...HWRF...AND GFDL ARE ON THE EASTERN EDGE OF THE GUIDANCE ENVELOPE WITH A TRACK TOWARDS THE CAROLINAS. THE OFFICIAL FORECAST REMAINS VERY CLOSE TO THE PREVIOUS ADVISORY AND CLOSE TO THE MODEL CONSENSUS WHICH HAS SHIFTED EVER SO SLIGHTLY WESTWARD. FORECAST POSITIONS AND MAX WINDS INITIAL 01/0300Z 23.7N 72.2W 45 KT 12HR VT 01/1200Z 23.5N 72.9W 45 KT 24HR VT 02/0000Z 23.4N 73.5W 45 KT 36HR VT 02/1200Z 23.4N 73.7W 50 KT 48HR VT 03/0000Z 23.7N 74.2W 50 KT 72HR VT 04/0000Z 25.4N 75.8W 55 KT 96HR VT 05/0000Z 29.0N 79.0W 60 KT 120HR VT 06/0000Z 33.5N 82.0W 45 KT...INLAND $$ FORECASTER BROWN |
