000 AXNT20 KNHC 090006 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT FRI SEP 08 2006 TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHEASTERN SECTIONS OF SOUTH AMERICA...AND THE ATLANTIC OCEAN TO THE AFRICAN COAST FROM THE EQUATOR TO 32N. THE FOLLOWING INFORMATION IS BASED ON SATELLITE IMAGERY...WEATHER OBSERVATIONS...RADAR... AND METEOROLOGICAL ANALYSIS. BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2315 UTC. ...SPECIAL FEATURE... THE CENTER OF TROPICAL STORM FLORENCE AT 09/0000 UTC IS NEAR 24.1N 60.9W OR ABOUT 615 MILES...990 KM...SOUTH-SOUTHEAST OF BERMUDA MOVING NORTHWEST AT 13 KT. THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 1000 MB. THE MAXIMUM SUSTAINED WIND SPEED IS 45 KT WITH GUSTS TO 55 KT. PLEASE READ THE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT1/WTNT21 KNHC AND THE PUBLIC ADVISORY UNDER MIATCPAT1/WTNT31 KNHC FOR MORE DETAILS. FLORENCE IS A VERY LARGE TROPICAL CYCLONE WITH TROPICAL STORM FORCE WINDS EXTENDING OUTWARD 325 NM IN THE NE QUADRANT AND 250 NM IN THE NW AND SE QUADRANTS. FLORENCE APPEARS TO BE ON THE ORGANIZING TREND AS THE CLOUD PATTERN AND RAIN FIELD IS CONSOLIDATING AND BECOMING MORE SYMMETRIC ABOUT THE CENTER. SCATTERED MODERATE CONVECTION EXISTS FROM 22N-26N BETWEEN 58W-64W. THIS OVERALL STRUCTURE IS MUCH IMPROVED THAN YESTERDAY AT THIS TIME WHEN THE SYSTEM LOOKS SHAPELESS AND ELONGATED. FLORENCE IS IN A FAVORABLE WARM WATER AND LOW SHEAR ENVIRONMENT FOR STRENGTHENING AS IT TRACKS NORTHWESTWARD AROUND THE PERIPHERY OF THE SUBTROPICAL RIDGE. ...TROPICAL WAVES... A SFC LOW PRES AREA ASSOCIATED WITH A TROPICAL WAVE DEVELOPED THIS MORNING OFF THE COAST OF AFRICA. THIS LOW PRES SYSTEM IS LOCATED NEAR 14N20W MOVING W NEAR 10 KT ANALYZED AT 1008 MB. SCATTERED MODERATE CONVECTION IS WITHIN 180 NM OF THE LOW. AN E ATLC TROPICAL WAVE IS ALONG 32W S OF 13N MOVING W 10 TO 15 KT. THIS WAVE IS LOW AMPLITUDE AND HAS LITTLE WAVE STRUCTURE ON SATELLITE IMAGES. SHOWER ACTIVITY HAS INCREASED SOMEWHAT OVER THE PAST 24 HOURS BUT IS MAINLY AHEAD OF THE ANALYZED AXIS EMBEDDED IN THE ITCZ. A TROPICAL WAVE IS ALONG 47W S OF 17N MOVING W NEAR 10 KT. LAST NIGHT THIS WAVE LOOKED LIKE IT WAS BECOMING ABSORBED BY THE LARGE CIRCULATION OF FLORENCE. HOWEVER...SATELLITE IMAGERY NOW SUGGEST THAT IT IS A SEPARATE FEATURE. AN AREA OF LOW PRES HAS ALSO FORMED ON THIS WAVE NEAR 21N/22N. THIS WAVE WILL LIKELY BE MADE HIGHER AMPLITUDE ON THE 00 UTC ANALYSIS TO REFLECT THIS. FURTHER DEVELOPMENT...IF ANY...SHOULD BE SLOW TO OCCUR AS UPPER LEVEL WINDS ARE UNFAVORABLE. A TROPICAL WAVE IS IN THE W CARIBBEAN ALONG 83W S OF 21N MOVING W NEAR 15 KT OVER THE PAST 24 HOURS. A FAINT INVERTED V-PATTERN IS SEEN ON SATELLITE IMAGES. THIS WAVE ALONG WITH UPPER DIFFLUENCE IS GENERATING SCATTERED SHOWERS AND TSTMS BETWEEN 67W-77W FROM 16N-20N. THE STRONGEST ACTIVITY IS OVER HISPANIOLA WHERE CONVECTION HAS INTENSIFIED AND EXPANDED OVER THE LAST FEW HOURS. SIMILAR WEATHER IS ALONG THE BASE OF THE WAVE ENHANCED BY THE ITCZ FROM 8N-11N BETWEEN 72W AND 78W. A TROPICAL WAVE ALONG 92W HAS MOVED INTO THE E PACIFIC. ...THE ITCZ... ITCZ IS CENTERED ALONG 13N21W 9N37W 8N43W THEN DISCONTINUOUS ALONG 13N62W 11N79W 10N83W. THE INTERRUPTION IN THE ITCZ IS CAUSED BY TROPICAL STORM FLORENCE. BESIDES FOR THE CONVECTION ASSOCIATED WITH THE TROPICAL WAVES....SCATTERED MODERATE LIES WITHIN 180 NM EITHER SIDE BETWEEN 36W-49W. SIMILAR ACTIVITY IS WITHIN 200 NM S OF THE AXIS OVER N SOUTH AMERICA W OF 65W. ...DISCUSSION... GULF OF MEXICO... AN UPPER LEVEL TROUGH LIES ACROSS THE EASTERN U.S. AND N PORTIONS OF THE GULF. THIS TROUGH HAS BECOME WEAKER AND MORE ZONAL IN THE REGION THAN IT WAS YESTERDAY. A NARROW RIDGE LIES TO THE S OF THE TROUGH STRETCHING FROM S MEXICO TO THE CARIBBEAN WITH A MID-UPPER LEVEL ANTICYCLONE CENTERED NEAR 21N98W. A FAIR AMOUNT OF MOISTURE EXISTS ACROSS THE AREA N OF 24N. THE DEEPEST MOISTURE IS IN THE NE GULF WHERE SCATTERED TO NUMEROUS SHOWERS AND TSTMS ARE FOUND FROM 26N-30N E OF 86W ACROSS N CNTRL FLORIDA. THIS ACTIVITY IS BEING ENHANCED BY AN ASSOCIATED STATIONARY FRONT WHICH EXTENDS FROM N CENTRAL FLORIDA SW ALONG 29N86W 27N93W. SCATTERED SHOWERS AND ISOLATED TSTMS ARE WITHIN 180 NM EITHER SIDE OF THE SFC BOUNDARY. NUMEROUS SHOWERS AND TSTMS HAVE BLOSSOMED OVER THE PAST FEW HOURS OVER S FLORIDA. THERE IS SOME DRY SLOTS NEAR THE CORNERS OF THE GULF WITH MODERATE TO STRONG SUBSIDENCE NOTED OVER THE FLORIDA PANHANDLE AND SOME DRY AIR ALOFT S OF 23N. SFC WINDS ARE LIGHT DUE TO THE WEAK PRES GRAD. THE UPPER TROUGH WILL LIFT TO THE NE AND THE STATIONARY FRONT WILL BEGIN TO DISSIPATE. WEAK SFC HIGH PRES WILL LIKELY FORM IN THE E GULF THIS WEEKEND AND GFS SUGGESTS THAT THE GREATEST CHANCE OF PRECIP WILL BE IN THE W GULF AIDED BY MOIST RETURN FLOW. CARIBBEAN SEA... THE SOUTHERN PORTION OF THE LARGE ATLC SUBTROPICAL RIDGE COVERS THE NE CARIBBEAN. MODERATE TO STRONG SUBSIDENCE LIES E OF 68W. A WEAK NARROW RIDGE EXTENDS FROM THE GULF INTO THE W CARIBBEAN. A WEAKENING UPPER LEVEL LOW IS LOCATED ABOUT 300 NM TO THE N OF THE MONA PASSAGE. UPPER DIFFLUENCE BETWEEN THESE FEATURES IN ADDITION TO SOME INFLUENCE FROM A NEARBY TROPICAL WAVE AND UPSLOPE FLOW OVER MOUNTAINOUS TERRAIN IS PRODUCING SCATTERED SHOWERS AND TSTMS ACROSS HISPANIOLA...JAMAICA AND CUBA. SCATTERED MODERATE CONVECTION EXISTS ALONG THE N PORTIONS OF S AMERICA AND THE SW CARIBBEAN HIGHLY CONTRIBUTED TO THE ITCZ. SIMILAR WEATHER IS ALSO FOUND OVER NICARAGUA...HONDURAS AND COSTA RICA ENHANCED BY THE TROPICAL WAVE IN THE REGION. ISOLATED SHOWERS COVER THE REMAINDER OF THE AREA NOT OUTLINED. DUE TO THE ABNORMALLY LARGE CIRCULATION OF FLORENCE SFC WINDS ARE WESTERLY ACROSS THE LESSER ANTILLES. IN THE CENTRAL AND WESTERN CARIBBEAN TYPICAL TRADES ARE FAIRLY LIGHT. ATLANTIC OCEAN... A FLATTENING UPPER LEVEL TROUGH IS TRACKING EASTWARD ACROSS THE CENTRAL U.S. AND N GULF. AN ASSOCIATED STATIONARY FRONT ENTERS THE AREA NEAR 32N74W AND EXTENDS TO N CENTRAL FLORIDA. UPPER DIFFLUENCE ON THE E SIDE OF THE TROUGH AXIS AND SFC CONVERGENCE NEAR THE BOUNDARY IS GENERATING SCATTERED SHOWERS AND TSTMS OVER FLORIDA. SHOWERS ARE MORE ISOLATED IN THE ATLC AND MOSTLY N OF THE DISCUSSION AREA. A LARGE SUBTROPICAL RIDGE COVERS THE REGION BETWEEN 40W-70W. THIS IS THE MAIN STEERING COMPONENT FOR TROPICAL STORM FLORENCE WHICH LIES ON THE SW PERIPHERY OF THIS RIDGE. FLORENCE IS FORECAST TO TURN TO THE N IN THE NEXT 24-36 HOURS AS IT ROUNDS THE CORNER OF THIS RIDGE AND INTERACTS WITH THE TROUGH OVER THE E U.S. A WEAK UPPER LEVEL LOW NEAR 23N68W HAS WEAKENED THE RIDGE SLIGHTLY. A LARGE DEEP UPPER LEVEL TROUGH LIES TO THE E OF THE RIDGE AND COVERS THE REGION BETWEEN 25W-40W. A LARGE SHIELD OF SCATTERED SHOWERS AND TSTMS ASSOCIATED WITH FLORENCE LIES FROM 20N-27N BETWEEN 50W-65W. DEBRIS MOISTURE FROM FLORENCE CARRIED SOUTHEASTWARD BY THE UPPER RIDGE AND ENHANCED BY UPPER DIFFLUENCE NEAR THE BASE OF THE E ATLC TROUGH HAS PRODUCED SCATTERED SHOWERS WITHIN 120 NM OF A LINE ALONG 21N48W 17N36W 21N28W. ACCORDING TO THE CIMSS SAL TRACKING PRODUCT AND THE MILKY LOOK ON THE EARLIER VIS IMAGES THE SAHARAN DUST HAS SPREAD TO NEAR 45W...HOWEVER THIS DUST APPEARS TO BE MORE DIFFUSE THAN EARLIER THIS SEASON. AT THE SFC...A 1025 MB HIGH PRES SYSTEM IS LOCATED NEAR 35N48W. THE TIGHTEST PRES GRAD IS IN THE CENTRAL ATLC NEAR T.S. FLORENCE WHICH IS PRODUCING A LARGE AREA OF TROPICAL STORM FORCE WINDS TO THE N OF THE CYCLONE. $$ CANGIALOSI