1WTNT41 KNHC 281458 2TCDAT1 3TROPICAL DEPRESSION SIXTEEN DISCUSSION NUMBER 1 4NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL162010 51100 AM EDT TUE SEP 28 2010 6 7SURFACE OBSERVATIONS AND SATELLITE IMAGES INDICATE THAT THE LOW 8PRESSURE AREA OVER THE NORTHWESTERN CARIBBEAN SEA HAS ACQUIRED A 9SUFFICIENTLY WELL-DEFINED CENTER OF CIRCULATION AND ORGANIZED DEEP 10CONVECTION TO BE CLASSIFIED AS A TROPICAL CYCLONE. THE SURFACE 11DATA INDICATE THAT THE SYSTEM IS VERY CLOSE TO TROPICAL STORM 12INTENSITY. SOUTH-SOUTHWESTERLY VERTICAL SHEAR ASSOCIATED WITH A 13LARGE UPPER-LEVEL TROUGH MOVING INTO THE SOUTHEASTERN UNITED STATES 14SHOULD LIMIT INTENSIFICATION AS THE SYSTEM MOVES ACROSS CUBA AND 15TOWARD SOUTHEASTERN FLORIDA. THE OFFICIAL INTENSITY FORECAST IS 16SIMILAR TO THE STATISTICAL/DYNAMICAL LGEM GUIDANCE. BY 48 17HOURS...DYNAMICAL GUIDANCE SHOWS THE CYCLONE MERGING WITH A FRONTAL 18ZONE. DISSIPATION SHOULD OCCUR IN 72 HOURS OR SOONER AS THE MODELS 19DEPICT A NEW BAROCLINIC DEVELOPMENT NEAR THE CAROLINAS. 20 21INITIAL MOTION IS ABOUT 020/9. THE CYCLONE IS EXPECTED TO CONTINUE 22A GENERALLY NORTH-NORTHEASTWARD MOTION AHEAD OF THE AFOREMENTIONED 23MID- TO UPPER-LEVEL TROUGH...AND WEST OF A SUBTROPICAL ANTICYCLONE. 24THE OFFICIAL TRACK FORECAST IS NEAR THE WESTERN SIDE OF THE MODEL 25ENVELOPE. 26 27IT SHOULD BE NOTED THAT THE STRONGEST WINDS AND HEAVIEST RAINS 28ASSOCIATED WITH THIS SYSTEM ARE OCCURING WELL TO THE SOUTHEAST OF 29THE CENTER. IF THIS STRUCTURE PERSISTS...THE TRACK OF THE CENTER 30WILL BE RELATIVELY UNIMPORTANT SINCE SIGNIFICANT IMPACTS WILL BE 31CONFINED TO THE EASTERN PORTION OF THE CIRCULATION. 32 33FORECAST POSITIONS AND MAX WINDS 34 35INITIAL 28/1500Z 20.6N 82.5W 30 KT 36 12HR VT 29/0000Z 21.6N 81.8W 35 KT 37 24HR VT 29/1200Z 23.5N 80.7W 40 KT 38 36HR VT 30/0000Z 26.5N 80.0W 40 KT 39 48HR VT 30/1200Z 31.0N 78.5W 40 KT...POST-TROP/EXTRATROP 40 72HR VT 01/1200Z...DISSIPATED 41 42$$ 43FORECASTER PASCH 44 45 46 47WTNT41 KNHC 290242 48TCDAT1 49TROPICAL DEPRESSION SIXTEEN DISCUSSION NUMBER 3 50NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL162010 511100 PM EDT TUE SEP 28 2010 52 53TROPICAL DEPRESSION SIXTEEN CONTINUES TO HAVE A STRUCTURE MORE 54CHARACTERISTIC OF A WESTERN NORTH PACIFIC/NORTH INDIAN OCEAN 55MONSOON DEPRESSION. SURFACE OBSERVATIONS CONTINUE TO INDICATE 56WINDS OF 20 KT OR LESS OVER AN AREA ENCOMPASSING 100 N MI IN 57DIAMETER FROM THE CENTER...AND THAT THE STRONGEST WINDS AND 58CONVECTION ARE 250-300 N MI AWAY FROM THE CENTER IN THE 59SOUTHEASTERN QUADRANT. AN EARLIER AIR FORCE RESERVE HURRICANE 60HUNTER MISSION IN THIS AREA FOUND FLIGHT-LEVEL WINDS SUPPORTING AN 61INITIAL INTENSITY OF 30 KT. SURFACE OBSERVATIONS INDICATE THAT THE 62CENTRAL PRESSURE IS NEAR 997 MB. 63 64THERE ARE MULTIPLE LOW-LEVEL CLOUD SWIRLS PRESENT...AND THE CENTER 65APPEARS TO RE-FORM FROM TIME TO TIME. THE INITIAL MOTION OF 035/7 66IS THUS A BIT UNCERTAIN. OTHER THAN THAT...THERE IS NO CHANGE IN 67THE FORECAST PHILOSOPHY FROM THE PREVIOUS ADVISORY...AND ONLY MINOR 68CHANGES TO THE FORECAST TRACK. A COMBINATION OF A DEEP-LAYER 69TROUGH OVER THE SOUTHEASTERN UNITED STATES AND EASTERN GULF OF 70MEXICO AND A LOW/MID-LEVEL RIDGE OVER THE WESTERN ATLANTIC SHOULD 71STEER THE CYCLONE NORTH-NORTHEASTWARD WITH ACCELERATION FOR THE 72NEXT 12-24 HOURS...FOLLOWED BY A QUICK NORTHWARD MOTION. THERE IS 73SOME SPREAD IN BOTH THE SPEED AND DIRECTION OF MOTION BY 48 HR. 74THE GFS... GFDL...AND HWRF ARE MUCH FASTER AND TO THE LEFT OF THE 75REST OF THE GUIDANCE...WHILE THE NOGAPS...GFDN...AND GFS ENSEMBLE 76MEAN ARE SLOWER AND TO THE RIGHT. THESE DIFFERENCES LIKELY RESULT 77FROM THE MODEL HANDLING OF THE DEPRESSION INTERACTING WITH A 78DEVELOPING BAROCLINIC LOW OVER THE EASTERN UNITED STATES. THE NEW 79FORECAST TRACK IS DOWN THE MIDDLE OF THE GUIDANCE ENVELOPE CLOSE TO 80THE CONSENSUS MODELS. 81 82THE DEPRESSION IS CURRENTLY IN AN ENVIRONMENT OF 15 KT OF 83SOUTHWESTERLY VERTICAL WIND SHEAR...WHICH THE LARGE-SCALE MODELS 84FORECAST TO INCREASE DURING THE NEXT 12-24 HR. THUS...NEITHER THE 85ENVIRONMENT NOR THE CURRENT STRUCTURE ARE CONDUCIVE FOR SIGNIFICANT 86STRENGTHENING. THE INTENSITY FORECAST IS THE SAME AS IN THE 87PREVIOUS ADVISORY...WITH MODEST STRENGTHENING ALONG THE LINES OF 88THE SHIPS AND LGEM MODELS. EXTRATROPICAL TRANSITION IS EXPECTED TO 89BEGIN IN ABOUT 24 HR OR SO AND BE COMPLETE BY 36-48 HR. THE 90CYCLONE IS FORECAST TO BE ABSORBED BY THE EASTERN U. S. BAROCLINIC 91LOW AFTER 48 HR...AS FORECAST BY MOST OF THE DYNAMICAL GUIDANCE. 92 93UNLESS THE STRUCTURE CHANGES RADICALLY IN THE NEXT 12-24 HOURS...IT 94IS LIKELY THAT THERE WILL CONTINUE TO BE A LARGE AREA OF LIGHT 95WINDS NEAR THE CENTER. THE STRONGEST WINDS SHOULD OCCUR IN AREAS 96WELL TO THE EAST OF THE FORECAST TRACK. 97 98FORECAST POSITIONS AND MAX WINDS 99 100INITIAL 29/0300Z 21.9N 81.9W 30 KT 101 12HR VT 29/1200Z 23.3N 81.2W 35 KT 102 24HR VT 30/0000Z 26.3N 80.2W 40 KT 103 36HR VT 30/1200Z 30.6N 79.3W 40 KT...POST-TROP/EXTRATROP 104 48HR VT 01/0000Z 36.3N 78.0W 35 KT...POST-TROP/EXTRATROP 105 72HR VT 02/0000Z...ABSORBED BY EXTRATROPICAL LOW 106 107$$ 108FORECASTER BEVEN 109 110 111 112WTNT41 KNHC 290857 113TCDAT1 114TROPICAL DEPRESSION SIXTEEN DISCUSSION NUMBER 4 115NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL162010 116500 AM EDT WED SEP 29 2010 117 118ALTHOUGH THE SATELLITE APPEARANCE OF TROPICAL DEPRESSION SIXTEEN HAS 119CHANGED LITTLE SINCE THE LAST ADVISORY...DOPPLER RADAR DATA FROM 120KEY WEST AND MIAMI...ALONG WITH RADAR RADAR FROM CUBA INDICATE 121CONVECTION HAS INCREASED IN THE NORTHERN SEMICIRCLE. ALSO...AN AIR 122FORCE RESERVE RECONNAISSANCE AIRCRAFT FLYING BETWEEN FLORIDA AND 123CUBA HAS INDICATED SURFACE WINDS OF 33 KT IN UNCONTAMINATED SFMR 124DATA ABOUT 80-120 NMI EAST-NORTHEAST OF THE CENTER...WHICH IS MUCH 125CLOSER TO THE CENTER THAN SEEN NOTED IN PRIOR SURFACE OBSERVATIONS 126AND RECON DATA. THE LARGEST DOPPLER RADAR VELOCITY VALUES DETECTED 127THUS FAR HAVE BEEN 40-44 KT BETWEEN 6000-12000 FT. THIS INDICATES 128THAT THE DEPRESSION IS VERY NEAR BECOMING A TROPICAL STORM. 129 130THE DEPRESSION IS ON TRACK AND THE THE INITIAL MOTION ESTIMATE IS 131020/12. 00Z UPPER-AIR DATA AND WATER VAPOR IMAGERY INDICATED THE 132MID- TO UPPER-LEVEL FLOW ACROSS THE EASTERN GULF OF MEXICO...THE 133SOUTHEASTERN U.S. AND THE EXTREME NORTHWESTERN CARIBBEAN SEA HAS 134BEEN STEADILY BACKING AROUND FROM THE WEST TO THE SOUTH-SOUTHWEST 135DURING THE PAST 24 HOURS. AS A SERIES OF STRONG SHORTWAVE TROUGHS 136DIG SOUTHWARD DOWN THE WEST SIDE OF THE LONGWAVE TROUGH LOCATED 137ALONG 85W...THE FLOW ACROSS FLORIDA SHOULD BECOME MORE SOUTHERLY. 138THIS FLOW PATTERN SHOULD ACCELERATE THE DEPRESSION TO THE 139NORTH-NORTHEAST ACROSS SOUTHEASTERN FLORIDA AS A TROPICAL CYCLONE 140TODAY...AND INTO THE CAROLINAS AS AN EXTRATROPICAL LOW PRESSURE 141SYSTEM IN 36 HOURS OR SO. ALTHOUGH THE MODEL CONSENSUS HAS SHIFTED 142A LITTLE TO THE EAST IN THE LATEST MODEL RUNS...THE STRONG BACKING 143FLOW PATTERN MENTIONED PREVIOUSLY ARGUES FOR KEEPING THE FORECAST 144TRACK ALONG THE WESTERN OR LEFT SIDE OF THE MODEL GUIDANCE 145ENVELOPE. AS A RESULT...THE OFFICIAL FORECAST TRACK IS JUST AN 146EXTENSION OF THE PREVIOUS ADVISORY TRACK. 147 148THE VERTICAL SHEAR IS EXPECTED TO DECREASE SLIGHTLY DURING THE NEXT 14912 HOURS BEFORE INCREASING TO ABOVE 30 KT IN ABOUT 36 HOURS. AS A 150RESULT...THERE WILL BE A BRIEF WINDOW OF OPPORTUNITY FOR SOME 151STRENGTHENING TO OCCUR PRIOR TO THE CYCLONE MAKING LANDFALL ALONG 152THE SOUTHEASTERN FLORIDA COAST LATER TODAY. EXTRATROPICAL 153TRANSITION IS EXPECTED TO BEGIN IN 24 HOURS OR SO AND BE COMPLETE 154BY 36-48 HR AS THE SYSTEM NEARS THE COAST OF THE CAROLINAS WHERE IT 155IS EXPECTED TO MERGE WITH A FRONTAL SYSTEM. BY 48 HOURS...THE LOW 156IS FORECAST TO BE ABSORBED BY A LARGER U. S. BAROCLINIC OVER THE 157NORTHEASTERN UNITED STATES. THE OFFICIAL INTENSITY FORECAST IS 158SIMILAR TO THE PREVIOUS ADVISORY AND IS A BLEND OF THE SHIPS AND 159LGEM INTENSITY MODELS. 160 161 162FORECAST POSITIONS AND MAX WINDS 163 164INITIAL 29/0900Z 23.3N 81.4W 30 KT 165 12HR VT 29/1800Z 25.2N 80.7W 35 KT 166 24HR VT 30/0600Z 28.9N 79.7W 40 KT 167 36HR VT 30/1800Z 33.8N 78.6W 40 KT...POST-TROP/EXTRATROP 168 48HR VT 01/0600Z 40.0N 77.3W 35 KT...POST-TROP/EXTRATROP 169 72HR VT 02/0600Z...DISSIPATED 170 171$$ 172FORECASTER STEWART 173 174 175 176