000 AXNT20 KNHC 210550 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 205 AM EDT MON SEP 21 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 0415 UTC. ...TROPICAL WAVES... TROPICAL WAVE EXTENDS FROM 21N40W TO 15N42W MOVING W NEAR 15 KT. THE WAVE COINCIDES WITH A DEEP LAYER MOISTURE MAXIMUM OBSERVED IN TOTAL PRECIPITABLE WATER IMAGERY. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 16N-21N BETWEEN 38W-42W. ...ITCZ... THE ITCZ AXIS IS CENTERED ALONG 11N12W 5N24W 4N36W 6N50W 6N60W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 50 NM BOTH SIDES OF THE AXIS BETWEEN 18W-24W. ...DISCUSSION... GULF OF MEXICO... AS OF 0300 UTC...A SURFACE TROUGH EXTENDS ACROSS THE ERN GULF FROM 28N87W TO 25N86W. SURFACE CONVERGENCE NEAR THE TROUGH IS SUPPORTING SCATTERED SHOWERS/THUNDERSTORMS FROM 26N-28N BETWEEN 84W-87W. ISOLATED SHOWERS/THUNDERSTORMS ARE ALSO ACROSS THE SRN GULF SE OF A LINE FROM 29N83W TO 21N100W. THIS ACTIVITY IS ENHANCED BY UPPER LEVEL DIFFLUENT FLOW BETWEEN AN UPPER LEVEL RIDGE OVER THE WRN GULF CENTERED OVER MEXICO NEAR 21N103W...A SHORTWAVE UPPER LEVEL TROUGH OVER THE NE GULF AND N FLORIDA...AND A SECOND UPPER LEVEL RIDGE OVER THE SE GULF CENTERED OVER WRN CUBA NEAR 23N81W. THE REMAINDER OF THE GULF IS RELATIVELY CALM TONIGHT AS A RIDGE BEGINS TO BUILD ACROSS THE N GULF. EXPECT THE E TO W RIDGE TO CONTINUE BUILDING ACROSS THE N GULF DURING THE NEXT 24 HRS. CARIBBEAN SEA... ISOLATED SHOWERS/THUNDERSTORMS ARE ACROSS THE NW CARIBBEAN N OF 17N W OF 82W. THIS ACTIVITY IS ENHANCED BY UPPER LEVEL DIFFLUENCE BETWEEN AN UPPER LEVEL RIDGE THAT COVERS THE NW CARIBBEAN CENTERED OVER WRN CUBA NEAR 23N81W AND AN UPPER LEVEL INVERTED TROUGH OVER CENTRAL AMERICA. SCATTERED SHOWERS/THUNDERSTORMS ARE S OF CUBA FROM 19N-21N BETWEEN 76W-81W. THIS ACTIVITY IS ALSO ENHANCED BY DIFFLUENT FLOW BETWEEN THE UPPER LEVEL RIDGE OVER THE NW CARIBBEAN AND AN UPPER LEVEL TROUGH DIGGING INTO THE CENTRAL AND ERN CARIBBEAN FROM AN UPPER LEVEL LOW N OF THE WINDWARD ISLANDS NEAR 24N60W. THE UPPER LEVEL TROUGH IS ALSO SUPPORTING ISOLATED SHOWERS/THUNDERSTORMS ACROSS PORTIONS OF HISPANIOLA AND PUERTO RICO FROM 16N-19N BETWEEN 66W-74W. MODERATE TO FRESH TRADE WINDS ARE ACROSS MUCH OF THE BASIN WITH THE STRONGEST WINDS IN THE S CENTRAL CARIBBEAN. ATLANTIC OCEAN... A FEW ISOLATED SHOWERS STILL REMAIN ACROSS THE FAR W ATLC TONIGHT W OF 78W SUPPORTED BY UPPER LEVEL DIFFLUENCE BETWEEN A SHORTWAVE UPPER LEVEL TROUGH OVER THE NE GULF AND NRN FLORIDA AND AN UPPER LEVEL RIDGE COVERING THE REMAINDER OF THE WRN ATLC CENTERED OVER WRN CUBA NEAR 23N81W. A 1016 MB SURFACE LOW IS CENTERED NEAR 30N72W WITH A SURFACE TROUGH EXTENDING THROUGH IT FROM 31N73W TO 28N72W. SCATTERED SHOWERS/ISOLATED THUNDERSTORMS ARE MAINLY E OF THE TROUGH AXIS FROM 28N-31N BETWEEN 69W-73W. AN UPPER LEVEL LOW N OF THE WINDWARD ISLANDS NEAR 24N60W IS SUPPORTING ISOLATED SHOWERS/POSSIBLE THUNDERSTORMS FROM 19N-23N BETWEEN 61W-65W...AND SCATTERED SHOWERS/POSSIBLE THUNDERSTORMS FROM 17N-22N BETWEEN 53W-58W. A 1012 MB SURFACE LOW IS CENTERED NEAR 15N47W. SURFACE CONVERGENCE NEAR THE LOW IS SUPPORTING ISOLATED SHOWERS WITHIN 120 NM E OF THE CENTER FROM 14N-16N. THE REMAINDER OF THE ATLC REMAINS FAIRLY CALM UNDER THE INFLUENCE OF A BROAD SURFACE RIDGE ANCHORED BY A 1025 MB HIGH NEAR 34N41W. IN THE UPPER LEVELS...AN UPPER LEVEL RIDGE IS BETWEEN 35W-45W...E OF THE AFOREMENTIONED UPPER LOW N OF THE WINDWARD ISLANDS. ANOTHER UPPER LEVEL LOW DOMINATES THE FAR E ATLC CENTERED NEAR 30N27W. AN UPPER LEVEL RIDGE DOMINATES THE TROPICAL ATLC E OF 50W SUPPORTING CONVECTION NEAR THE TROPICAL WAVE IN THE CENTRAL ATLC...SEE ABOVE. $$ WALTON