000 AXNT20 KNHC 200524 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 205 AM EDT SUN SEP 20 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0430 UTC. ...SPECIAL FEATURES... A 1012 MB LOW IS CENTERED E OF THE WINDWARD ISLANDS NEAR 15N45W MOVING TO THE WNW NEAR 9 KT. ISOLATED MODERATE CONVECTION IS FROM 11N-20N BETWEEN 40W-43W...AND FROM 15N-17N BETWEEN 43W-48W. WHILE THE SYSTEM REMAINS POORLY ORGANIZED...IT HAS A MEDIUM CHANCE...30 TO 50 PERCENT...OF BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HRS. ...TROPICAL WAVES... TROPICAL WAVE IS ALONG 31W S OF 18N MOVING W NEAR 10 KT. THE WAVE COINCIDES WITH A DEEP LAYER MOISTURE MAXIMUM OBSERVED IN TOTAL PRECIPITABLE WATER IMAGERY AS WELL AS A MAXIMUM IN 850 MB RELATIVE VORTICITY SEEN IN THE CIMSS WAVETRAK MODEL GUIDANCE. SCATTERED MODERATE CONVECTION IS FROM 16N-18N BETWEEN 29W-34W. TROPICAL WAVE IS ALONG 96W S OF 20N MOVING W NEAR 12 KT. THE WAVE COINCIDES WITH A DEEP LAYER MOISTURE MAXIMUM IN THE E PACIFIC BASIN WHERE MOST OF THE WAVE AXIS LIES. ISOLATED MODERATE CONVECTION IS IN THE FAR SW GULF FROM 18N-21N BETWEEN 94W-96W. ...ITCZ... THE ITCZ AXIS IS CENTERED ALONG 7N12W 6N20W 11N29W 15N40W 11N53W 10N63W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 8N-12N BETWEEN 15W-18W. ...DISCUSSION... GULF OF MEXICO... AS OF 0300 UTC...A SURFACE TROUGH EXTENDS ACROSS THE FAR NW GULF FROM SW LOUISIANA NEAR 30N93W TO 27N97W. NO SHOWERS ARE CURRENTLY ASSOCIATED WITH THE TROUGH. ANOTHER SURFACE TROUGH EXTENDS FROM THE SE GULF NEAR 26N83W TO THE YUCATAN PENINSULA NEAR 20N89W. ISOLATED SHOWERS/THUNDERSTORMS ARE WITHIN 150 NM EITHER SIDE OF THE TROUGH AXIS. THIS ACTIVITY IS ALSO ENHANCED BY UPPER LEVEL DIFFLUENCE BETWEEN A SHORTWAVE UPPER LEVEL TROUGH OVER THE CENTRAL GULF WITH AXIS ALONG 88W AND AN UPPER LEVEL RIDGE OVER THE SE GULF CENTERED OVER THE STRAIGHTS OF FLORIDA NEAR 24N81W. ISOLATED SHOWERS/THUNDERSTORMS ARE ALSO ACROSS THE SW GULF S OF 23S W OF 89W IN ASSOCIATION WITH UPPER LEVEL DIFFLUENCE BETWEEN THE SHORTWAVE UPPER TROUGH OVER THE CENTRAL GULF AND ANOTHER UPPER LEVEL RIDGE OVER THE WRN GULF CENTERED OVER MEXICO NEAR 20N103W. SOME OF THE SHOWERS MAY ALSO BE ENHANCED BY SURFACE CONVERGENCE NEAR THE TROPICAL WAVE ALONG 96W. EXPECT THE TROUGH IN THE NW GULF TO LIFT N AND DISSIPATE AS A SURFACE RIDGE BUILDS IN FROM THE E. CARIBBEAN SEA... SCATTERED SHOWERS/THUNDERSTORMS ARE ACROSS THE NW CARIBBEAN FROM 13N-23N BETWEEN 76W-83W WITH ISOLATED SHOWERS/THUNDERSTORMS W OF 83W TO THE YUCATAN PENINSULA. THE ACTIVITY IS ENHANCED BY UPPER LEVEL DIFFLUENCE BETWEEN AN UPPER LEVEL RIDGE OVER THE SE GULF AND THE BAHAMAS CENTERED OVER THE STRAIGHTS OF FLORIDA NEAR 24N81W AND AN UPPER LEVEL INVERTED TROUGH OVER CENTRAL AMERICA. THE REMAINDER OF THE CENTRAL AND E CARIBBEAN REMAINS FAIRLY CALM UNDER THE INFLUENCE OF DRY AIR ALOFT. HOWEVER...A FEW ISOLATED SHOWERS/THUNDERSTORMS ARE ACROSS WRN HISPANIOLA FROM 18N-19N BETWEEN 71W-74W DUE TO UPPER LEVEL DIFFLUENT FLOW BETWEEN THE UPPER LEVEL RIDGE OVER THE BAHAMAS AND AN UPPER LEVEL LOW N OF THE WINDWARD ISLANDS NEAR 23N62W. FRESH TRADE WINDS ARE ACROSS THE SRN CARIBBEAN WITH THE STRONGEST NEAR THE COAST OF COLOMBIA. EXPECT SHOWERS/THUNDERSTORMS TO PERSIST OVER THE WRN CARIBBEAN AS THE UPPER LEVEL TROUGH OVER THE SW CARIBBEAN SLOWLY MOVES W. ATLANTIC OCEAN... A FEW ISOLATED SHOWERS REMAIN ACROSS THE WRN ATLC N OF 27N W OF 73W DUE TO UPPER LEVEL DIFFLUENT FLOW BETWEEN AN UPPER LEVEL RIDGE OVER THE BAHAMAS CENTERED OVER THE STRAITS OF FLORIDA NEAR 24N81W AND AN UPPER LEVEL TROUGH ACROSS THE NW ATLC. A 1014 MB SURFACE LOW IS NEAR 28N70W WITH A SURFACE TROUGH EXTENDING THROUGH IT FROM 31N70W TO 24N70W. SURFACE CONVERGENCE NEAR THE LOW AND TROUGH AXIS IS SUPPORTING ISOLATED SHOWERS FROM 25N-27N BETWEEN 70W-72W...AND SCATTERED SHOWERS/THUNDERSTORMS FROM 29N-31N BETWEEN 67W-70W. SCATTERED SHOWERS/THUNDERSTORMS ARE ALSO N OF THE WINDWARD ISLANDS FROM 18N-23N BETWEEN 61W-68W IN ASSOCIATION WITH AN UPPER LEVEL LOW NEAR 23N62W. ELSEWHERE ACROSS THE ATLC...A BROAD SURFACE RIDGE DOMINATES ANCHORED BY A 1026 MB HIGH NEAR 33N42W. IN THE UPPER LEVELS...AN UPPER LEVEL RIDGE IS N OF 25N BETWEEN 35W-50W. AN UPPER LEVEL TROUGH DOMINATES THE E ATLC WITH AXIS ALONG 33N24W TO 23N34W. A BROAD UPPER LEVEL RIDGE COVERS THE TROPICAL ATLC ENHANCING CONVECTION NEAR THE LOW CENTERED AT 15N45W. $$ WALTON