000 AXNT20 KNHC 041759 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT THU SEP 04 2008 TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHERN SECTIONS OF SOUTH AMERICA...AND ATLANTIC OCEAN TO THE AFRICAN COAST FROM THE EQUATOR TO 32N. THE FOLLOWING INFORMATION IS BASED ON SATELLITE IMAGERY...METEOROLOGICAL ANALYSIS...WEATHER OBSERVATIONS...AND RADAR. BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1715 UTC. ...SPECIAL FEATURES... AT 04/1800 UTC...TROPICAL STORM HANNA IS CENTERED NEAR 25.1N 74.2W OR ABOUT 180 NM EAST OF NASSAU AND ABOUT 580 NM SOUTH-SOUTHEAST OF WILMINGTON NORTH CAROLINA MOVING NW AT 12 KT. THIS MOTION IS EXPECTED TO CONTINUE DURING THE NEXT DAY OR SO WITH A GRADUAL INCREASE IN FORWARD SPEED. A TURN TO THE NORTH IS EXPECTED BY LATE FRIDAY. THE CENTER OF HANNA WILL PASS JUST EAST OF THE CENTRAL AND NORTHWESTERN BAHAMAS TODAY...AND WILL BE NEAR THE SOUTHEAST COAST OF THE UNITED STATES BY LATE FRIDAY. HOWEVER...RAINS AND WINDS ASSOCIATED WITH HANNA WILL REACH THE COAST WELL IN ADVANCE OF THE CENTER. ESTIMATED MINIMUM CENTRAL PRESSURE IS 989 MB. MAXIMUM SUSTAINED WIND SPEED IS 55 KT WITH GUSTS TO 65 KT. LITTLE CHANGE IN STRENGTH IS FORECAST TODAY...HOWEVER...HANNA COULD BECOME A HURRICANE ON FRIDAY PRIOR TO REACHING THE COASTLINE. SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT3/WTNT23 KNHC FOR MORE DETAILS. CONVECTION ASSOCIATED WITH HANNA HAS DIMINISHED SUBSTANTIALLY OVER THE PAST 6-12 HOURS. VERY DRY AIR ASSOCIATED WITH AN UPPER-LEVEL LOW OVER CENTRAL CUBA IS CHOKING OFF CONVECTION NEAR THE CORE OF HANNA... AND THE CYCLONE HAS A VERY SUBTROPICAL APPEARANCE. HANNA COULD PRODUCE RAINFALL TOTALS OF 2 TO 4 INCHES OVER THE NORTHERN BAHAMAS. SWELLS FROM HANNA ARE EXPECTED TO INCREASE THE RISK OF DANGEROUS RIP CURRENTS ALONG PORTIONS OF THE SOUTHEASTERN UNITED STATES COAST DURING THE NEXT COUPLE OF DAYS. AT 04/1500 UTC...HURRICANE IKE IS CENTERED NEAR 23.2N 57.0W OR ABOUT 455 NM...845 KM...NORTHEAST OF THE LEEWARD ISLANDS MOVING W-NW AT 14 KT. A GRADUAL TURN TOWARD THE WEST AND WEST-SOUTHWEST IS EXPECTED OVER THE NEXT 48 HOURS AS A HIGH BUILDS IN TO THE NORTHWEST OF IKE. THE HURRICANE WILL CONTINUE TO MOVE OVER THE OPEN WATERS OF THE WEST-CENTRAL ATLANTIC DURING THE NEXT COUPLE OF DAYS. IT IS TOO EARLY TO DETERMINE WHAT LAND AREAS MIGHT EVENTUALLY BE AFFECTED BY IKE BUT INTERESTS IN THE SOUTHEASTERN BAHAMAS AND THE TURKS AND CAICOS ISLANDS SHOULD MONITOR THE PROGRESS OF THIS SYSTEM. ESTIMATED MINIMUM CENTRAL PRESSURE IS 938 MB. MAXIMUM SUSTAINED WIND SPEED IS 120 KT WITH GUSTS TO 145 KT. IKE IS A EXTREMELY DANGEROUS CATEGORY FOUR HURRICANE ON THE SAFFIR-SIMPSON HURRICANE SCALE. SOME WEAKENING IS FORECAST DURING THE NEXT DAY OR SO BUT IKE IS EXPECTED TO REMAIN A POWERFUL HURRICANE FOR THE NEXT SEVERAL DAYS. SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/ WMO HEADERS MIATCMAT4/WTNT24 KNHC FOR MORE DETAILS. IKE CONTINUES TO DISPLAY A WELL-DEFINED EYE WITH VERY COLD CLOUD TEMPERATURES IN THE EYEWALL. HOWEVER THE CLOUD PATTERN IS NOW ASYMMETRIC DUE TO SOME NORTHERLY SHEAR AFFECTING THE CYCLONE. AT 04/1500 UTC...TROPICAL STORM JOSEPHINE IS CENTERED NEAR 14.5N 32.2W OR ABOUT 450 NM...840 KM...WEST OF THE SOUTHERNMOST CAPE VERDE ISLANDS MOVING W-NW AT 9 KT...AND THIS MOTION IS EXPECTED TO CONTINUE FOR THE NEXT COUPLE OF DAYS. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1000 MB. MAXIMUM SUSTAINED WIND SPEED IS 45 KT WITH GUSTS TO 55 KT. UPPER-LEVEL WINDS ARE CURRENTLY NOT FAVORABLE FOR SIGNIFICANT STRENGTHENING...AND LITTLE CHANGE IN STRENGTH IS FORECAST DURING THE NEXT COUPLE OF DAYS.SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT5/WTNT25 KNHC FOR MORE DETAILS. THE DEEP CONVECTION THAT WAS PRESENT EARLY THIS MORNING HAS DISSIPATED...LEAVING AN EXPOSED LOW-LEVEL CENTER WELL TO THE SOUTHWEST OF SMALL AREAS OF DISORGANIZED CONVECTION. ...TROPICAL WAVES... A TROPICAL WAVE HAS ALREADY PUSHED WEST OF DAKAR PER RECENT OBSERVED SOUNDING. THE WAVE AXIS IS CENTERED ALONG 18W S OF 18N...MOVING W NEAR 10 KT. SATELLITE IMAGERY DEPICTS MODERATE CURVATURE IN THE SURFACE WIND FIELD AROUND 12N. HOWEVER...MOST OF THE SHOWER ACTIVITY IS ACROSS THE NORTHERN END OF THE WAVE...COVERING THE AREA FROM 15N TO 20N EAST OF 22 W TO THE AFRICAN COAST. THE LEADING EDGE OF THE SHOWER ACTIVITY HAS REACHED THE EASTERNMOST CAPE VERDE ISLANDS. A NEW LOW AMPLITUDE TROPICAL WAVE HAS BEEN ADDED ON THE 12Z SURFACE MAP BASED SATELLITE IMAGERY AND TPW PRODUCT FROM CIMMS. THE WAVE AXIS IS ALONG 43W S OF 16N...MOVING W 10 TO 15 KT. THIS TROPICAL WAVE IS PRODUCING A LARGE AREA OF SCATTERED MODERATE CONVECTION FROM 11N TO 16N BETWEEN 42W AND 50W...WITH THE STRONGEST ACTIVITY WELL AHEAD OF THE WAVE AXIS. IN ADDITION...A ASCAT PASS FROM AROUND 12Z ALSO SHOWED A WIND SHIFT IN ASSOCIATION WITH THE WAVE AXIS. ...THE ITCZ... THE ITCZ AXIS IS ANALYZED ALONG 9N14W 10N24W 8N37W 8N50W 10N62W. ISOLATED MODERATE CONVECTION IS MAINLY SOUTH OF THE ITCZ AXIS FROM 6N TO 9N BETWEEN 40W AND 51W. ...DISCUSSION... GULF OF MEXICO... THE EXTRATROPICAL REMNANT LOW ASSOCIATED WITH THE FORMER T.D. GUSTAV IS CURRENTLY CENTERED OVER MISSOURI. RAINFALL TOTALS OF UP TO 20 INCHES HAVE BEEN REPORTED IN LOUISIANA. A SURFACE TROUGH TRAILS FROM THE LOW TO THE NORTHWEST GULF...EXTENDING FROM SOUTHWEST LOUISIANA TO DEEP SOUTH TEXAS. A NARROW BAND OF SHOWERS WITH EMBEDDED THUNDERSTORMS IS WITHIN 75 NM AHEAD OF THE TROUGH....PARTICULARLY NORTH OF 27N. ANOTHER SURFACE TROUGH IS LOCATED OVER THE BAY OF CAMPECHE...RESULTING IN SCATTERED SHOWERS AND THUNDERSTORMS SOUTH OF 20N...NEAR MINATITLAN MEXICO. A WEAK SURFACE RIDGE EXTENDING FROM THE SOUTHEAST CONUS TO THE EASTERN GULF SEPARATES THE SURFACE TROUGHS OVER THE WESTERN GULF FROM THE LARGE CIRCULATION ASSOCIATED WITH TROPICAL STORM HANNA. AN UPPER LEVEL HIGH OVER SOUTHERN BAJA PENINSULA AND ITS ASSOCIATED RIDGE ARE IMPACTING MUCH OF THE GULF. A STRONG UPPER LEVEL LOW CENTERED OVER CENTRAL CUBA IS PRODUCING DRY NORTHERLY UPPER LEVEL FLOW OVER THE FAR EASTERN GULF. CARIBBEAN SEA... AN UPPER LEVEL RIDGE EXTENDING SOUTHWESTWARD FROM AN UPPER LEVEL HIGH OVER THE WEST CENTRAL ATLANTIC...COMBINED WITH THE AFOREMENTIONED UPPER LEVEL LOW OVER CUBA...IS RESULTING IN A LARGE AREA OF SCATTERED MODERATE CONVECTION OVER THE CENTRAL CARIBBEAN. SOME SHOWER AND THUNDERSTORM ACTIVITY IS IMPACTING HISPANIOLA...THE ABC ISLANDS AND WESTERN VENEZUELA...INCLUDING THE LAKE MARACAIBO AREA. THE SAN JUAN DOPPLER RADAR ALSO SHOWS A LINE OF SHOWERS AND TSTMS AFFECTING THE WESTERN PORTION OF THE ISLANDS. DUE TO THE RECENT HEAVY RAINFALL ACROSS THE ISLANDS ASSOCIATED WITH HANNA'S CIRCULATION...THE TERRAINS REMAINS SATURATED...AND ANY ADDITIONAL RAIN WILL CAUSE LOCALIZED FLOODING OF RIVERS...SMALL STREAMS AND CREEKS. AS A RESULT...A FLASH FLOOD WATCH WILL REMAIN IN EFFECT UNTIL 4 PM AST THIS AFTERNOON. ST THOMAS VI REPORTED 1.35 INCHES OF RAIN IN 24 HOURS THROUGH THIS MORNING. LOW LEVEL CONVERGENCE ALONG THE WEST COAST OF CENTRAL AMERICA IS GENERATING A LARGE AREA OF CLOUDINESS WITH EMBEDDED SHOWERS. DRY EASTERLY UPPER LEVEL FLOW COMBINED WITH MODERATE SUBSIDENCE IS LIMITED CONVECTIVE ACTIVITY OVER THE FAR EASTERN CARIBBEAN. UNUSUAL SOUTHWESTERLY SURFACE WINDS IN ASSOCIATION WITH THE LARGE CIRCULATION OF HANNA CONTINUE IMPACTING THE CENTRAL CARIBBEAN. ATLANTIC OCEAN... CONSISTENT WITH CLIMATOLOGY...THREE TROPICAL CYCLONES ARE LOCATED IN THE DISCUSSION AREA...SEE SPECIAL FEATURES ABOVE FOR DETAILS. FROM EAST TO WEST...THE THREE ARE...TROPICAL STORM JOSEPHINE...HURRICANE IKE...AND TROPICAL STORM HANNA. THE PREVIOUSLY MENTIONED UPPER LEVEL HIGH OVER THE WEST CENTRAL ATLANTIC IS CENTERED NEAR 28N63W. AN UPPER LEVEL LOW IS CENTERED NEAR 19N41W. MODERATE NORTHERLY UPPER LEVEL FLOW CONTINUES OVER THE CENTRAL ATLANTIC NORTH OF 20N. THE REMAINDER OF THE FORECAST AREA IS DOMINATED BY AN UPPER LEVEL RIDGE OVER THE WESTERN COAST OF AFRICA NEAR 20N16W. AT THE SURFACE...A 1027 MB HIGH LOCATED NEAR 35N45W COVERS THE NORTHERN PORTION OF THE EASTERN AND CENTRAL ATLANTIC. DURING THE NEXT 24 HOURS...THE HIGH IS FORECAST TO MOVE WESTWARD. $$ COHEN/RUBIO