000 AXNT20 KNHC 092359 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT SAT SEP 09 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 10/0000 UTC IS NEAR 26.1N 64.6W OR ABOUT 430 MILES...690 KM...SOUTH OF BERMUDA MOVING NORTHWEST AT 12 KT. THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 992 MB. THE MAXIMUM SUSTAINED WIND SPEED IS 55 KT WITH GUSTS TO 65 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 LARGE TROPICAL CYCLONE WITH TROPICAL STORM FORCE WINDS EXTENDING OUTWARD 345 MILES IN THE NE QUADRANT AND NW QUADRANTS. THE OVERALL SATELLITE APPEARANCE INDICATES THAT FLORENCE CONTINUES TO BECOME BETTER ORGANIZED WITH CONVECTION CONSOLIDATING AND BECOMING MORE SYMMETRIC ABOUT THE CENTER WITH CLOUD TOPS CONTINUING TO COOL TO -85 TO -90 C. NEAR THE CENTER OF THE CONVECTIVE MASS. OUTFLOW IS VERY IMPRESSIVE AND IS EXPANDING ESPECIALLY TO THE WEST. HOWEVER REPORTS FROM THE HURRICANE HUNTER AIRCRAFT EARLIER THIS EVENING INDICATE THAT LOW-LEVEL CENTER WAS SEVERELY ELONGATED. STRENGTHENING TO A HURRICANE IS FORECAST AS FLORENCE IS IN A FAVORABLE WARM WATER AND RELATIVELY LOW SHEAR ENVIRONMENT AS IT TRACKS AROUND THE PERIPHERY OF THE SUBTROPICAL RIDGE. ...TROPICAL WAVES... A 1010 MB SFC LOW PRES SYSTEM ASSOCIATED WITH A TROPICAL WAVE IS ANALYZED NEAR 13N24W. THIS LOW IS MOVING TO THE W NEAR 10 KT. MUCH OF THE ASSOCIATED CONVECTION LIES TO THE SOUTHWEST OF THE ANALYZED POSITION FROM 9N-12N BETWEEN 24W-28W. AN E ATLC TROPICAL WAVE IS ALONG 37W S OF 15N MOVING W 10 TO 15 KT. THIS WAVE IS LOW AMPLITUDE AND HAS LITTLE WAVE STRUCTURE ON SATELLITE IMAGES. THE NORTHERN EXTENSION OF THIS WAVE IS EMBEDDED IN SAHARAN DUST. DISORGANIZED SHOWER ACTIVITY HAS INCREASED SLIGHTLY FROM 7N-11N BETWEEN 32W-43W. A 1011 MB LOW IS ADDED TO THE 18 UTC ANALYSIS NEAR 9N45W. THIS CIRCULATION IS EASILY SEEN ON VIS AND SHORTWAVE IMAGES. HOWEVER THE ASSOCIATED SHOWER ACTIVITY IS MINIMAL AND WELL WEST OF THE LOW LEVEL CENTER FROM 8N-12N BETWEEN 49W-51W. IN ADDITION... THIS ACTIVITY IS PROPAGATING AWAY FROM THE CIRCULATION CENTER. A TROPICAL WAVE IS ALONG 50W FROM 9N-25N MOVING W NEAR 10 KT. EARLIER THIS WEEK THIS WAVE LOOKED LIKE IT WAS BECOMING ABSORBED BY THE LARGE CIRCULATION OF FLORENCE. HOWEVER...OVER THE LAST COUPLE OF DAYS IS HAS DEFINITELY SEPARATED ITSELF. A 1013 MB LOW IS ALONG THE WAVE NEAR 22N. THE LOW LEVEL CIRCULATION IS PARTIALLY EXPOSED. SCATTERED MODERATE CONVECTION EXISTS FROM 15N-22N BETWEEN 49W-54W. UPPER LEVEL WINDS COULD BECOME MORE CONDUCIVE FOR FURTHER DEVELOPMENT. A TROPICAL WAVE IS IN THE W CARIBBEAN ALONG 88W S OF 21N MOVING W NEAR 10 TO 15 KT. SLIGHT CYCLONIC TURNING IS SEEN IN THE LOW LEVEL CLOUDS ABOUT THE WAVE AXIS AND A FAINT INVERTED V-PATTERN IS SEEN ON INFRARED IMAGES. THIS WAVE ALONG WITH UPPER DIFFLUENCE AND THE ITCZ IS GENERATING SCATTERED MODERATE CONVECTION FROM 8N-15N BETWEEN 80W-90W. ANOTHER LINE OF SCATTERED MODERATE HAS DEVELOPED OVER THE YUCATAN PENINSULA AND GUATEMALA. A TROPICAL WAVE ALONG 96W S OF 21N MOVING W 10 KT IS MAINLY IN THE E PACIFIC REGION. ASSOCIATED CONVECTION IS MAINLY IN THE ITCZ. ...THE ITCZ... ITCZ IS CENTERED ALONG 15N17W 11N25W 10N37W 8N47W 11N56W. ALL OF THE SIGNIFICANT CONVECTION IS DISCUSSED IN THE TROPICAL WAVES SECTION. ...DISCUSSION... GULF OF MEXICO... AN UPPER LEVEL TROUGH CONTINUES TO MOVE NE AWAY FROM THE AREA AS MID-UPPER LEVEL RIDGING BUILDS FROM THE WEST WITH AN ANTICYCLONE CENTERED OVER MEXICO NEAR 22N100W. AT THE SFC...A STATIONARY FRONT IS LINGERING ACROSS THE N PORTION OF THE REGION EXTENDING FROM CENTRAL FLORIDA WESTWARD ALONG 28N88W 28N95W. UPPER DIFFLUENCE AND SFC CONVERGENCE IS GENERATING SCATTERED SHOWERS AND TSTMS N OF 24N ACROSS THE GULF. THIS MOISTURE ENVELOPE IS SINKING SLOWLY SOUTHWARD STEERED BY THE DOWNWARD BRANCH OF THE UPPER ANTICYCLONE. THERE IS SOME DRY AIR ALOFT IN THE BAY OF CAMPECHE KEEPING SHOWERS RATHER ISOLATED IN THAT AREA. SFC WINDS ARE FAIRLY LIGHT DUE TO THE WEAK PRES GRAD. SHOWERS AND TSTMS APPEAR LIKELY TO CONTINUE IN THE N GULF TOMORROW NEAR THE SFC BOUNDARY. GFS DEVELOPS A WEAK LOW ALONG THE FRONT BUT MANY OF THE OTHER MODELS DO NOT SHOW THIS FEATURE. THIS FRONT WILL BEGIN TO SLOWLY DISSIPATE OVER THE NEXT COUPLE OF DAYS. CARIBBEAN SEA... THE SOUTHERN PORTION OF A LARGE ATLC SUBTROPICAL RIDGE COVERS THE NE CARIBBEAN. A WEAK UPPER HIGH IS CENTERED OVER EASTERN CUBA AND AN ILL-DEFINED WEAKENING UPPER LEVEL LOW IS LOCATED ABOUT 300 NM TO THE N OF HISPANIOLA. THE DEEPEST TROPICAL MOISTURE IS IN THE SW CARIBBEAN WHERE NUMEROUS SHOWERS AND TSTMS ARE FOUND S OF 14N BETWEEN 78W-86W. THIS MOISTURE IS HIGHLY CONTRIBUTED TO THE ITCZ WITH PERHAPS SOME ENHANCEMENT FROM A TROPICAL WAVE TO THE WEST. SHOWERS AND TSTMS HAVE ALSO FIRED UP THIS AFTERNOON OVER JAMAICA AND CUBA ASSOCIATED WITH SOME UPPER DIFFLUENCE AND LOCAL SMALL SCALE EFFECTS. A LINE OF SHOWERS AND TSTMS HAS ALSO DEVELOPED OVER THE YUCATAN PENINSULA AND GUATEMALA FROM 16N-20N BETWEEN 88W-89W. A FAIR AMOUNT OF HIGH LEVEL MOISTURE COVERS THE AREA W OF 75W WITH MUCH DRIER AIR NOTED ON WATER VAPOR IMAGES E OF THERE. SFC WINDS ARE SOUTHWESTERLY ACROSS THE LESSER ANTILLES...DUE TO THE VERY LARGE CIRCULATION OF FLORENCE...WHICH IS LOCATED SEVERAL HUNDRED MILES N OF THE AREA. FAIRLY LIGHT TYPICAL EASTERLIES EXIST IN THE CENTRAL AND WESTERN CARIBBEAN. ATLANTIC OCEAN... AN UPPER LEVEL TROUGH IS TRACKING EASTWARD ALONG AND JUST OFF THE E COAST OF THE U.S. AN ASSOCIATED COLD FRONT ENTERS THE AREA NEAR 32N72W AND EXTENDS TO NEAR MELBOURNE FLORIDA. ONLY ISOLATED SHOWERS ARE NEAR THE FRONT IN THE ATLC LIKELY BECAUSE OF THE DRY AIR ALOFT ABOVE THE AREA. MUCH MORE ACTIVITY EXISTS NEAR THE FRONT IN THE GULF. A LARGE SUBTROPICAL RIDGE COVERS THE REGION BETWEEN 40W-70W. THE UPPER TROUGH ALONG THE E COAST U.S. IS WEAKENING THE WESTERN EXTENSION OF THE RIDGE. THESE ARE THE MAIN STEERING COMPONENT FOR TROPICAL STORM FLORENCE WHICH LIES ON THE W PERIPHERY OF THE RIDGE. A VERY WEAK UPPER LEVEL LOW IS LOCATED JUST AHEAD OF FLORENCE NEAR 26N73W. A SHARP UPPER LEVEL TROUGH LIES TO THE E OF THE RIDGE AND COVERS THE REGION BETWEEN 25W-40W WITH AN UPPER LOW CENTER NEAR 26N33W. THIS UPPER LEVEL FEATURE HAS A SFC REFLECTION AS A TROF ALONG 26N32W 32N29W. THIS TROUGH LOOKS LIKE IT IS BECOMING CUT OFF AS A RATHER LARGE RIDGE BUILDS OFF THE COAST OF AFRICA WITH THE AXIS ALONG 25N. A LARGE AREA OF SCATTERED MODERATE CONVECTION ASSOCIATED WITH FLORENCE LIES FROM 23N-29N BETWEEN 60W-69W. ACCORDING TO THE CIMSS SAL TRACKING PRODUCT AND THE MILKY LOOK ON THE EARLIER VIS IMAGES THE SAHARAN DUST HAS SPREAD TO NEAR 50W...HOWEVER THIS DUST APPEARS TO BE CONSIDERABLY MORE DIFFUSE THAN EARLIER THIS SEASON. A 1024 MB SFC HIGH PRES SYSTEM IS LOCATED NEAR 35N47W. 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