000 AXNT20 KNHC 010003 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT TUE SEP 30 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2315 UTC. ...SPECIAL FEATURES... TROPICAL STORM LAURA IS CENTERED NEAR 42.3N 48.6W AT 30/2100 UTC OR ABOUT 325 NM SE OF CAPE RACE NEWFOUNDLAND MOVING N AT 12 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 996 MB. MAXIMUM SUSTAINED WIND SPEED IS 50 KT WITH GUSTS TO 60 KT. PLEASE SEE THE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCPAT2/WTNT32 KNHC FOR MORE DETAILS. TROPICAL STORM FORCE WINDS EXTEND OUTWARD UP TO 200 NM FROM THE CENTER OF LAURA. LAURA IS EXPECTED TO ACCELERATE AND TURN TOWARD THE NNE TONIGHT. LAURA WILL BEGIN TO LOSE TROPICAL CHARACTERISTICS TONIGHT AND IS EXPECTED TO BECOME EXTRATROPICAL ON WEDNESDAY. ADDITIONALLY...LAURA IS EXPECTED TO GRADUALLY WEAKEN DURING THE NEXT COUPLE OF DAYS. ISOLATED MODERATE CONVECTION IS FROM 42N-44N BETWEEN 45W-50W. ...TROPICAL WAVES... TROPICAL WAVE IS ALONG 33W/34W S OF 19N MOVING W NEAR 15 KT. SATELLITE IMAGERY DEPICTS INVERTED-V CLOUD PATTERN ALONG WAVE AXIS. ISOLATED MODERATE CONVECTION IS WITHIN 120 NM OF WAVE AXIS N OF 12N...AND SCATTERED MODERATE CONVECTION IS WITHIN 180 NM OF WAVE AXIS S OF 10N. SAHARAN DUST CONTINUES MOVING TO THE W IN THE WAKE OF THE WAVE N OF 15N. TROPICAL WAVE IS ALONG 45W/46W FROM 12N-22N MOVING W 5-10 KT. SATELLITE IMAGERY DEPICTS INVERTED-V CLOUD PATTERN ALONG WAVE AXIS...WITH SURFACE WINDS VEERING UPON WAVE PASSAGE. ISOLATED MODERATE CONVECTION IS FROM 13N-19N BETWEEN 43W-45W. TROPICAL WAVE IS ALONG 61W S OF 16N MOVING W 10-15 KT. SCATTERED SHOWERS ARE OCCURRING WITHIN 150 NM OF WAVE AXIS S OF 15N. SURFACE WIND OBSERVATIONS ACROSS THE LESSER ANTILLES DEPICT WEAK COUNTERCLOCKWISE CURVATURE IN SURFACE FLOW NEAR WAVE AXIS. ...THE ITCZ... THE ITCZ AXIS IS ANALYZED ALONG 11N13W 10N20W 11N31W 9N40W 9N59W. SCATTERED MODERATE CONVECTION IS MOVING TO THE W OVER W AFRICA FROM 7N-13N BETWEEN 10W-17W...AFFECTING GAMBIA AND GUINEA-BISSAU. SCATTERED MODERATE CONVECTION IS FROM 7N-14N BETWEEN 20W-24W. ISOLATED MODERATE CONVECTION IS FROM 5N-9N BETWEEN 41W-49W. ...DISCUSSION... GULF OF MEXICO... DEEP UPPER TROUGH OVER THE E CONUS EXTENDS SOUTHWARD ACROSS MUCH OF THE GULF. STRONG AND MOIST SW FLOW ALOFT E OF THE TROF AXIS IS PROVIDING UPPER SUPPORT FOR NUMEROUS SHOWERS AND THUNDERSTORMS OVER THE FAR SE AND S GULF...FROM S FLORIDA TO THE YUCATAN PENINSULA AND ALSO OVER CUBA. THIS ACTIVITY IS FURTHER BEING ENHANCED BY LOW LEVEL CONVERGENCE ASSOCIATED WITH SEVERAL SURFACE FEATURES INCLUDING A SURFACE LOW JUST OFF THE W COAST OF FL NEAR 26N83W...ANOTHER SURFACE LOW JUST N OF THE YUCATAN PENINSULA NEAR 22N89W...A SURFACE TROUGH THAT CONNECTS THESE TWO LOWS...AND A SURFACE TROUGH THAT TRAILS S FROM THE LOW NEAR THE YUCATAN PENINSULA TO NEAR 17N90W. DEEP DRY AIR IN THE BASE OF THE UPPER TROUGH AND SUBSIDENCE W OF THE UPPER TROUGH AXIS ARE LIMITING CONVECTIVE ACTIVITY IN THE CENTRAL AND W GULF. CARIBBEAN SEA... AN UPPER RIDGE EXTENDS INTO THE CENTRAL CARIBBEAN ANCHORED BY AN UPPER HIGH OVER THE SW ATLANTIC NEAR 22N66W. STABLE CONDITIONS AND DRY AIR BENEATH THIS RIDGE ARE RESULTING IN FAIR WEATHER ACROSS MUCH OF THE CENTRAL AND E CARIBBEAN...WITH ISOLATED SHOWERS FROM 16N-18N BETWEEN 69W-72W APPROACHING S HISPANIOLA. THE UPPER TROUGH OVER THE GULF IS BEGINNING TO BRING MORE UPPER SW FLOW TO THE W CARIBBEAN. THIS FLOW IS DIFFLUENT OVER THE W CARIBBEAN...WHERE ISOLATED MODERATE CONVECTION IS OCCURRING FROM 16N-22N BETWEEN 81W-87W...WITH SCATTERED MODERATE CONVECTION OVER THE ADJACENT LAND AREAS INCLUDING HONDURAS...BELIZE...AND THE YUCATAN PENINSULA. UPPER SUPPORT FROM THE UPPER TROUGH IS ALSO ENHANCING SHOWERS AND THUNDERSTORMS OVER MUCH OF CUBA. SCATTERED MODERATE/ISOLATED STRONG CONVECTION HAS DEVELOPED OVER N COLOMBIA AND N VENEZUELA NEAR THE ITCZ...AND THIS CONVECTION IS PROPAGATING TO THE N NEAR THE ADJACENT CARIBBEAN WATERS. ATLANTIC OCEAN... TROPICAL STORM LAURA IS LOCATED N OF THE REGION...SEE SPECIAL FEATURES SECTION ABOVE. THE DEEP UPPER TROUGH OVER THE E CONUS IS BRINGING STRONG AND MOIST SW FLOW ALOFT TO THE W ATLANTIC. THIS IS PROVIDING THE UPPER SUPPORT FOR SHOWERS AND ISOLATED THUNDERSTORMS OVER THE SW ATLANTIC FROM 25N-32N W OF 72W... INCLUDING S FLORIDA AND THE BAHAMAS. THIS ACTIVITY IS FURTHER BEING ENHANCED BY A SURFACE TROUGH THAT EXTENDS FROM 32N73W TO S FLORIDA NEAR 28N80W. E OF THESE FEATURES...A LARGE UPPER HIGH COVERS THE CENTRAL ATLANTIC AND IS CENTERED NEAR 23N65W. DRY AIR...SUBSIDENCE...AND STABLE CONDITIONS IN THE VICINITY OF THIS HIGH ARE RESULTING IN FAIR WEATHER OVER MUCH OF THE CENTRAL ATLANTIC. HOWEVER...THE CORRESPONDING SURFACE HIGH HAS WEAKENED WITH THE APPROACH OF THE UPPER AND SURFACE TROUGH FURTHER TO THE W. MOISTURE AND CLOUDINESS ARE STREAMING AROUND THE UPPER HIGH N OF 28N BETWEEN 60W-67W. A SURFACE TROUGH EXTENDS FROM 32N58W TO 29N60W AND IS NE OF THE UPPER HIGH...FURTHER ENHANCING SOME OF THE CLOUDINESS. A BROAD UPPER TROUGH WITH LIMITED MOISTURE IS N OF 23N BETWEEN 33W-54W...WHICH SHARPENS FROM 13N-23N BETWEEN 47W-54W. THE TROPICAL ATLANTIC IS DOMINATED BY AN E/W UPPER RIDGE ALONG 16N EXTENDING FROM AN UPPER HIGH NEAR THE CAPE VERDE ISLANDS TO NEAR 48W. A SURFACE RIDGE EXTENDS SOUTHWARD OVER THE E ATLC FROM A 1031 MB SURFACE HIGH NEAR 44N25W. $$ COHEN