000 WTNT45 KNHC 240258 TCDAT5 TROPICAL STORM MATTHEW DISCUSSION NUMBER 3 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL152010 1100 PM EDT THU SEP 23 2010 THE OVERALL ORGANIZATION OF MATTHEW HAS CONTINUED TO GRADUALLY IMPROVE THIS EVENING. A BURST OF DEEP CONVECTION HAS RECENTLY DEVELOPED OVER THE CENTER AND SEVERAL BROKEN BANDS OF THUNDERSTORMS ARE SEEN AROUND THE PERIPHERY OF THE CIRCULATION. THE LATEST SATELLITE INTENSITY ESTIMATES FROM TAFB AND SAB ARE 45 AND 35 KT...RESPECTIVELY. BASED ON THESE ESTIMATES THE INITIAL INTENSITY IS SET AT 40 KT. THE INITIAL MOTION ESTIMATE IS 275/15. FOR THE NEXT 36-48 HOURS... MATTHEW IS EXPECTED TO CONTINUE IN A WEST TO WEST-NORTHWEST DIRECTION TO THE SOUTH OF A SUBTROPICAL RIDGE THAT EXTENDS FROM THE ATLANTIC WESTWARD INTO THE SOUTHEASTERN UNITED STATES. THE TRACK GUIDANCE IS IN GOOD AGREEMENT DURING THAT TIME AND THERE IS FAIRLY HIGH CONFIDENCE IN THAT PART OF THE FORECAST. IN 2-3 DAYS... THE WESTERN PORTION OF THE RIDGE IS EXPECTED TO WEAKEN AS A STRONG MID-LATITUDE TROUGH MOVES INTO THE CENTRAL UNITED STATES. THIS SHOULD RESULT IN A WEAKENING OF THE STEERING CURRENTS AND A DECELERATION OF THE CYCLONE. THEREAFTER...THE MODEL SOLUTIONS DIVERGE SIGNIFICANTLY...WITH SEVERAL OF THEM SHOWING RATHER COMPLEX SCENARIOS. THE GFS...UKMET...AND ECMWF ALL MOVE MATTHEW WELL INLAND OVER THE SOUTHERN PORTION OF THE YUCATAN PENINSULA IN 2-3 DAYS. AFTER THAT TIME...THE GFS AND ECMWF ACTUALLY WEAKEN MATTHEW...THEN DEVELOP A SECOND CYCLONE OVER THE NORTHWEST CARIBBEAN SEA. ON THE OTHER HAND...THE NOGAPS...GFDL....AND HWRF KEEP MATTHEW AS THE PRIMARY SYSTEM AND SHOW IT TURNING NORTHWARD ALONG THE CARIBBEAN COAST OF THE YUCATAN PENINSULA AT DAYS 4 AND 5. NEEDLESS TO SAY...THERE IS A MUCH HIGHER DEGREE OF UNCERTAINTY IN THE 4 AND 5 DAY FORECASTS THAN NORMAL. FOR NOW THE OFFICIAL FORECAST HAS BEEN ADJUSTED CLOSER TO THE MULTI-MODEL CONSENSUS...TVCN...AND IS WEST OF THE PREVIOUS FORECAST BEYOND 72 HOURS. MATTHEW WILL BE IN AN ENVIRONMENT OF LIGHT TO MODERATE EASTERLY SHEAR OVER WARM WATER DURING THE NEXT DAY OR SO. THEREFORE... STEADY STRENGTHENING IS PREDICTED AND THE OFFICIAL FORECAST IS CLOSE TO THE SHIPS/LGEM GUIDANCE DURING THAT TIME. AFTER 24 HOURS...THE INTENSITY FORECAST IS HIGHLY DEPENDENT ON LAND INTERACTION. THE NEW OFFICIAL FORECAST IS SIMILAR TO THE PREVIOUS ADVISORY THROUGH 48 HOURS...ASSUMING THE CENTER STAYS OFFSHORE OF HONDURAS. THEREAFTER...THE INTENSITY FORECAST HAS BEEN ADJUSTED DOWNWARD SINCE THE NEW TRACK FORECAST SHOWS MATTHEW OVER THE YUCATAN PENINSULA AT 72-120 HOURS. BASED ON THE NEW TRACK AND INTENSITY FORECAST...SOME CHANGES WERE REQUIRED TO THE WATCHES AND WARNINGS. FORECAST POSITIONS AND MAX WINDS INITIAL 24/0300Z 14.0N 78.4W 40 KT 12HR VT 24/1200Z 14.5N 80.5W 50 KT 24HR VT 25/0000Z 15.1N 82.9W 65 KT 36HR VT 25/1200Z 15.9N 85.1W 60 KT...INLAND 48HR VT 26/0000Z 16.6N 87.1W 65 KT...OVER WATER 72HR VT 27/0000Z 17.9N 89.2W 50 KT...INLAND 96HR VT 28/0000Z 18.5N 89.5W 40 KT...INLAND 120HR VT 29/0000Z 19.0N 89.5W 35 KT...INLAND $$ FORECASTER BROWN