000 AXNT20 KNHC 122358 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT SAT SEP 12 2009 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 2330 UTC. ...SPECIAL FEATURES... TROPICAL STORM FRED HAS BEEN DOWNGRADED TO A TROPICAL DEPRESSION AS OF 12/2100 UTC. TROPICAL DEPRESSION FRED IS CENTERED NEAR 17.7N 33.7W OR ABOUT 565 NM W OF THE CAPE VERDE ISLANDS DRIFTING N NEAR 1 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1005 MB. MAXIMUM SUSTAINED WINDS HAVE DECREASED TO 30 KT WITH GUSTS TO 40 KT. ONLY A SMALL AREA OF SCATTERED MODERATE/ISOLATED STRONG CONVECTION REMAINS TO THE N OF THE CENTER FROM 20N-22N BETWEEN 33W-34W. FRED IS FORECAST TO BE A REMNANT LOW IN LESS THAN 24 HRS. SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT2/WTNT22 KNHC FOR MORE DETAILS. ...TROPICAL WAVES... TROPICAL WAVE IS ALONG 21W/22W S OF 19N MOVING W NEAR 10 KT. A 1010 MB LOW IS ANALYZED ALONG THE WAVE AXIS NEAR 13N. SATELLITE IMAGERY AND SATELLITE DERIVED WINDS INDICATE A BROAD AREA OF LOW/MID-LEVEL CYCLONIC TURNING IN THE VICINITY OF THE WAVE AXIS. THE WAVE ALSO COINCIDES WITH A DEEP LAYER MOISTURE MAXIMUM OBSERVED IN TOTAL PRECIPITABLE WATER IMAGERY. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS NEAR THE LOW CENTER FROM 12N-14N BETWEEN 21W-23W. SCATTERED STRONG CONVECTION IS FROM 15N-18N BETWEEN 23W-25W. TROPICAL WAVE IS ALONG 87W S OF 19N MOVING W NEAR 15 KT. THE WAVE COINCIDES WITH A BROAD AREA OF DEEP LAYER MOISTURE OBSERVED IN TOTAL PRECIPITABLE WATER IMAGERY. MODERATELY DRY AIR ALOFT IS CURRENTLY INHIBITING ANY DEEP CONVECTION NEAR THE WAVE. ...ITCZ... THE ITCZ AXIS IS CENTERED ALONG 15N17W 10N23W 9N40W 10N51W 11N63W. ISOLATED MODERATE/STRONG CONVECTION IS WITHIN 180 NM EITHER SIDE OF THE AXIS BETWEEN 55W-63W. ...DISCUSSION... GULF OF MEXICO... SCATTERED SHOWERS/THUNDERSTORMS REMAIN ACROSS THE WRN GULF TONIGHT W OF 87W WITH ISOLATED SHOWERS/THUNDERSTORMS IN THE N CENTRAL GULF. AS OF 2100 UTC...THE SHOWER ACTIVITY IS ENHANCED BY LOW-LEVEL CONVERGENCE NEAR A 1005 MB SURFACE LOW OFF THE TEXAS COAST NEAR 28N96W...AND A STATIONARY FRONT HUGGING THE GULF STATES COASTLINE EXTENDING FROM THE LOW CENTER ALONG 29N93W 29N88W 30N83W AND ACROSS N FLORIDA TO A WEAKER 1011 MB SURFACE LOW NEAR 30N80W. A WEAK TROUGH EXTENDS FROM THE LOW OFF THE TEXAS COAST EXTENDING FROM 28N96W TO 22N96W. THE LOW/FRONTAL SYSTEM IS SUPPORTED UP AN UPPER LEVEL TROUGH ACROSS THE SW UNITED STATES EXTENDING INTO THE WRN GULF. AN UPPER LEVEL HIGH COVERS THE CENTRAL AND ERN GULF CENTERED NEAR 25N85W. UPPER LEVEL DIFFLUENCE BETWEEN THESE FEATURES IS ALSO ENHANCING THE SHOWERS/THUNDERSTORMS ACROSS THE BASIN. CARIBBEAN SEA... MOST OF THE CARIBBEAN REMAINS CALM THIS EVENING DUE TO MID/UPPER LEVEL DRY AIR...EXCEPT FOR ISOLATED SHOWERS/THUNDERSTORMS ACROSS THE NRN ISLANDS N OF 17N FROM BETWEEN ERN HISPANIOLA TO WRN CUBA. THE SHOWER ACTIVITY IS ENHANCED BY UPPER LEVEL DIFFLUENCE BETWEEN THE UPPER LEVEL RIDGE ACROSS THE GULF AND WRN ATLC AND AN UPPER LEVEL LOW N OF PUERTO RICO NEAR 21N65W. HIGH LEVEL CLOUDS ARE ACROSS THE BASIN S OF 13N DUE TO SLY FLOW ALOFT SHIFTING TO WLY FLOW ALOFT DRAWING TROPICAL MOISTURE N AND E. SURFACE CONVERGENCE NEAR THE ITCZ IS SUPPORTING SCATTERED SHOWERS/THUNDERSTORMS S OF 12N W OF 78W AFFECTING COSTA RICA AND PANAMA. SURFACE CONVERGENCE NEAR A 1009 MB LOW OVER NRN COLOMBIA NEAR 9N75W IS SUPPORTING SCATTERED SHOWERS/THUNDERSTORMS S OF 11N BETWEEN 70W-75W. A FEW ISOLATED SHOWERS ARE ALSO AFFECTING THE SRN LESSER ANTILLES. MODERATE TO FRESH TRADEWINDS ARE ACROSS MUCH OF THE BASIN. EXPECT THE TROPICAL WAVE ALONG 87W TO MOVE W OF CENTRAL AMERICA LATER TONIGHT. ATLANTIC OCEAN... A FEW ISOLATED SHOWERS/POSSIBLE THUNDERSTORMS REMAIN ACROSS THE WRN ATLC W OF 72W TO THE FLORIDA COAST IN ASSOCIATION WITH A WEAK 1011 MB LOW OFF THE N FLORIDA COAST NEAR 30N80W...AND A STATIONARY FRONT EXTENDING ALONG THE GULF COAST ACROSS N FLORIDA TO THE WEAK LOW CONTINUING TO 31N77W. THE SHOWERS ARE ALSO ENHANCED BY UPPER LEVEL DIFFLUENCE BETWEEN AN UPPER LEVEL RIDGE OVER THE GULF EXTENDING OVER THE WRN ATLC W OF 72W...AN UPPER LEVEL TROUGH N OF THE RIDGE CENTERED OVER NEW ENGLAND...AND AN UPPER LEVEL LOW N OF PUERTO RICO NEAR 21N65W. A WEAK 1018 MB SURFACE HIGH IS TO THE E NEAR 27N62W. FARTHER E...A STATIONARY FRONT DIPS INTO THE DISCUSSION AREA NEAR 32N60W CONTINUING ALONG 29N49W 32N36W EXTENDING NE OUT OF THE AREA. ISOLATED SHOWERS ARE ALONG THE FRONT WITH AN AREA OF SCATTERED SHOWERS/THUNDERSTORMS FROM 29N-31N BETWEEN 55W-58W. THIS ACTIVITY IS ALSO ENHANCED BY UPPER LEVEL DIFFLUENCE BETWEEN AN UPPER HIGH NEAR 27N55W AND AN UPPER LEVEL TROUGH N OF 20N WITH AXIS ALONG 40W. THE UPPER LEVEL TROUGH IS ALSO SUPPORTING A SURFACE TROUGH THAT HAS BECOME EMBEDDED IN THE ITCZ ALONG 19N51W TO 10N52W. AN UPPER LEVEL RIDGE COVERS THE ERN ATLC CENTERED OFF THE COAST OF AFRICA NEAR 19N20W ENHANCING CONVECTION NEAR THE TROPICAL WAVE ALONG 21W/22W. $$ WALTON