000 AXNT20 KNHC 132340 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT SUN SEP 13 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 2245 UTC. ...SPECIAL FEATURES... AN AREA OF SHOWERS/THUNDERSTORMS TO THE N OF A 1009 MB SURFACE LOW NEAR 18N35W...THE REMNANT CIRCULATION OF FRED...HAS INCREASED OVER THE PAST FEW HOURS. NUMEROUS STRONG CONVECTION IS FROM 19N-23N BETWEEN 34W-36W. UPPER LEVEL WINDS REMAIN UNFAVORABLE FOR REDEVELOPMENT INTO A TROPICAL CYCLONE. HOWEVER...IF CONVECTION CONTINUES TO PERSIST AND BECOMES BETTER ORGANIZED REGENERATION IS POSSIBLE. THERE IS NOW A MEDIUM CHANCE...30 TO 50 PERCENT...OF THIS SYSTEM BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HRS. ...TROPICAL WAVES... TROPICAL WAVE IS ALONG 60W/61W S OF 15N. THIS WAVE HAS PREVIOUSLY BEEN ANALYZED AS A SURFACE TROUGH THAT ORIGINALLY FORMED AS A FRACTURE OF A TROPICAL WAVE SEVERAL DAYS AGO. THE TROUGH STALLED DUE TO THE CIRCULATION OF FRED AND THE PRESENCE OF AN UPPER LEVEL TROUGH BEFORE REGAINING WWD MOVEMENT AND IS NOW RE-ANALYZED AS A TROPICAL WAVE. BASED ON THE PREVIOUS 24 HR TROUGH POSITION THE WAVE IS MOVING W 15-20 KT. THE WAVE COINCIDES WITH A LOW-AMPLITUDE DEEP LAYER MOISTURE MAXIMUM OBSERVED IN TOTAL PRECIPITABLE WATER IMAGERY. SCATTERED MODERATE CONVECTION IS FROM 11N-13N BETWEEN 57W-60W. TROPICAL WAVE IS ALONG 95W S OF 19N MOVING W NEAR 20 KT. WAVE IS MAINLY IN THE E PACIFIC REGION GENERATING SCATTERED SHOWERS/THUNDERSTORMS. NO ASSOCIATED SHOWER ACTIVITY IS IN THE BAY OF CAMPECHE. REFER TO THE TWDEP FOR MORE DETAILS. ...ITCZ... THE ITCZ AXIS IS CENTERED ALONG 18N17W THROUGH A 1012 MB LOW NEAR 14N22W CONTINUING ALONG 9N30W 7N40W 10N50W 12N57W 10N65W. SCATTERED MODERATE CONVECTION IS FROM 14N-16N BETWEEN 23W-25W NEAR THE SURFACE LOW. ISOLATED MODERATE CONVECTION IS WITHIN 150 NM S OF THE AXIS BETWEEN 26W-34W. ...DISCUSSION... GULF OF MEXICO... AS OF 2100 UTC...A STATIONARY FRONT LINES THE N GULF FROM N FLORIDA NEAR 29N83W ALONG 31N87W 30N90W TO A 1005 MB LOW NEAR HOUSTON TEXAS AT 30N96W. A SURFACE TROUGH EXTEND S FROM THE LOW CENTER ALONG 26N93W 21N94W. THE SYSTEM IS SUPPORTED BY A SHORTWAVE UPPER LEVEL TROUGH OVER TEXAS EMBEDDED IN A BROAD UPPER LEVEL TROUGH OVER NRN MEXICO. ISOLATED SHOWERS/ THUNDERSTORMS ARE FROM 22N-26N BETWEEN 90W-93W. RECENT LIGHTNING DATA INDICATES NUMEROUS SHOWERS/THUNDERSTORMS IN THE CENTRAL GULF FROM 25N-29N BETWEEN 87W-90W. ISOLATED SHOWERS/THUNDERSTORMS ARE ALSO ACROSS THE ERN GULF FROM 22N-28N E OF 87W. THIS ACTIVITY IS ENHANCED BY SURFACE CONVERGENCE AHEAD OF THE TROUGH AND FRONT AS WELL AS UPPER LEVEL DIFFLUENCE BETWEEN THE UPPER LEVEL TROUGH OVER MEXICO AND TEXAS AND AN UPPER LEVEL RIDGE DOMINATING THE ERN GULF CENTERED OVER WRN CUBA NEAR 23N83W. BEHIND THE SURFACE TROUGH...STRONG SUBSIDENCE AND DRY AIR ALOFT ARE SUPPORTING GENERALLY FAIR WEATHER W OF 93W. EXPECT LITTLE CHANGE OVER THE NEXT 24 HRS. CARIBBEAN SEA... MOST OF THE CARIBBEAN REMAINS FAIRLY CALM TONIGHT WITH DRY AIR ALOFT ACROSS MUCH OF THE BASIN. ISOLATED SHOWERS/POSSIBLE THUNDERSTORMS ARE ACROSS THE NRN CARIBBEAN N OF 17N BETWEEN 69W-80W INCLUDING PORTIONS OF HISPANIOLA AND JAMAICA. SCATTERED SHOWERS/THUNDERSTORMS ARE ACROSS CUBA N 19N BETWEEN 75W-84W. BOTH OF THESE AREAS OF ACTIVITY ARE ENHANCED BY UPPER LEVEL DIFFLUENCE BETWEEN AN UPPER LEVEL RIDGE CENTERED OVER W CUBA NEAR 23N83W AND AN UPPER LEVEL LOW N OF THE LEEWARD ISLANDS NEAR 20N63W. A FEW ISOLATED SHOWERS ARE S OF 14N BETWEEN 74W-84W DUE TO SURFACE CONVERGENCE NEAR THE E PACIFIC ITCZ. MODERATE TRADE WINDS ARE ACROSS THE BASIN WITH STRONGER WINDS NEAR THE COAST OF COLOMBIA. EXPECT SHOWER ACTIVITY TO INCREASE OVER THE WINDWARD ISLANDS AS A TROPICAL WAVE ALONG 60W/61W MOVES WWD INTO THE E CARIBBEAN. ATLANTIC OCEAN... AS OF 2100 UTC...A 1011 MB LOW IS OFF THE N FLORIDA COAST NEAR 30N79W. A STATIONARY FRONT EXTENDS THROUGH THE LOW FROM 31N75W TO THE FLORIDA COAST NEAR 29N81W CONTINUING ALONG THE NRN GULF OF MEXICO. SURFACE CONVERGENCE AHEAD OF THE FRONT IS SUPPORTING SCATTERED SHOWERS/THUNDERSTORMS N OF 79N W OF 75W AFFECTING THE WRN BAHAMAS...CUBA...AND FLORIDA. ISOLATED SHOWERS/THUNDERSTORMS ARE N OF 25N BETWEEN 62W-75W. THESE AREAS OF ACTIVITY ARE ALSO ENHANCED BY UPPER LEVEL DIFFLUENCE BETWEEN AN UPPER LEVEL RIDGE CENTERED OVER WRN CUBA NEAR 23N83W...AN UPPER LEVEL TROUGH N OF 33N OVER THE NW ATLC...AND AN UPPER LEVEL LOW N OF THE LEEWARD ISLANDS NEAR 20N63W. A WEAK 1017 MB SURFACE HIGH IS CENTERED NEAR 25N60W. TO THE NE OF THE HIGH A WARM FRONT DIPS INTO THE DISCUSSION AREA EXTENDING ALONG 29N54W 32N55W TO A SURFACE LOW WELL N OF THE AREA. ISOLATED SHOWERS/POSSIBLE THUNDERSTORMS ARE E OF THE FRONT N OF 28N BETWEEN 50W-54W. THE ACTIVITY IS ALSO ENHANCED BY UPPER LEVEL DIFFLUENCE BETWEEN AN UPPER LEVEL HIGH NEAR 26N53W AND THE AFOREMENTIONED UPPER LEVEL TROUGH OVER THE NW ATLC. A DYING STATIONARY FRONT CLIPS THE AREA EXTENDING ALONG 32N35W 39N40W 31N44W. NO SHOWERS ARE CURRENTLY ASSOCIATED WITH THE FRONT. ELSEWHERE ACROSS THE ATLC...A 1009 MB LOW...REMNANTS OF FRED...REMAINS THE DOMINANT FEATURE. SEE SPECIAL FEATURES ABOVE. IN THE UPPER LEVELS...AN UPPER LEVEL TROUGH IS ALONG 16N47W TO 28N30W. STRONG SWLY FLOW ALOFT ALONG THE E SIDE OF THIS UPPER TROUGH CONTINUES TO PROVIDE A SHEER ENVIRONMENT FOR THE REMNANTS OF FRED. AN UPPER LEVEL HIGH IS OFF THE COAST OF AFRICA NEAR 20N17W ENHANCING CONVECTION NEAR THE CAPE VERDE ISLANDS. $$ WALTON