000 AXNT20 KNHC 211148 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 805 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1045 UTC. ...TROPICAL WAVES... TROPICAL WAVE EXTENDS FROM 21N41W TO 14N42W MOVING W NEAR 15 KT. THE WAVE COINCIDES WITH A DEEP LAYER MOISTURE MAXIMUM OBSERVED IN TOTAL PRECIPITABLE WATER IMAGERY. SATELLITE IMAGERY INDICATES LOW/MID-LEVEL CYCLONIC FLOW IN THE VICINITY OF THE WAVE AXIS. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 17N-22N BETWEEN 39W-43W. ...ITCZ... THE ITCZ AXIS IS CENTERED ALONG 12N15W 5N24W 6N35W 9N45W 7N60W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 100 NM BOTH SIDES OF THE AXIS BETWEEN 19W-26W. ...DISCUSSION... GULF OF MEXICO... A BROAD AND WEAK SURFACE TROUGH EXTENDS ACROSS THE ERN GULF FROM 28N86W TO 22N90W. SURFACE CONVERGENCE NEAR THE TROUGH IS SUPPORTING ISOLATED SHOWERS/POSSIBLE THUNDERSTORMS WITHIN 100 NM SE OF THE TROUGH AXIS. ISOLATED SHOWERS/THUNDERSTORMS ARE ALSO ACROSS THE SRN GULF SE OF A LINE FROM 28N85W TO 21N97W. THIS ACTIVITY IS ENHANCED BY UPPER LEVEL DIFFLUENT FLOW BETWEEN AN UPPER LEVEL RIDGE OVER THE WRN AND CENTRAL GULF CENTERED OVER MEXICO NEAR 21N102W...A SHORTWAVE UPPER LEVEL TROUGH OVER THE NE GULF AND N FLORIDA...AND A SECOND UPPER LEVEL RIDGE OVER THE SE GULF CENTERED OVER THE STRAITS OF FLORIDA NEAR 24N79W. THE REMAINDER OF THE GULF IS RELATIVELY CALM AS A SURFACE RIDGE BUILDS ACROSS THE N GULF. EXPECT THE E TO W RIDGE TO CONTINUE BUILDING ACROSS THE N GULF AND SHIFT NE BY TUE. CARIBBEAN SEA... ISOLATED SHOWERS/THUNDERSTORMS ARE ACROSS THE NW CARIBBEAN N OF 12N W OF 76W. THIS ACTIVITY IS ENHANCED BY SURFACE CONVERGENCE NEAR A SURFACE TROUGH EXTENDING FROM THE BAHAMAS NEAR 24N75W ACROSS CUBA TO 17N79W. THE ACTIVITY IS ALSO SUPPORTED BY UPPER LEVEL DIFFLUENCE BETWEEN AN UPPER LEVEL RIDGE THAT COVERS THE NW CARIBBEAN AND WRN ATLC CENTERED OVER THE STRAITS OF FLORIDA NEAR 24N79W AND AN UPPER LEVEL INVERTED TROUGH OVER CENTRAL AMERICA. SCATTERED SHOWERS/THUNDERSTORMS ARE ACROSS THE SW CARIBBEAN S OF 11N W OF 81W DUE TO SURFACE CONVERGENCE NEAR THE E PACIFIC ITCZ. THE REMAINDER OF THE CARIBBEAN REMAINS CALM EXCEPT FOR A FEW ISOLATED SHOWERS/THUNDERSTORMS ACROSS THE NRN CARIBBEAN N OF 16N BETWEEN 67W-74W. THIS ACTIVITY IS ENHANCED BY DIFFLUENT FLOW BETWEEN THE UPPER LEVEL RIDGE OVER THE NW CARIBBEAN AND WRN ATLC AND AN UPPER LEVEL TROUGH DIGGING INTO THE CENTRAL AND ERN CARIBBEAN FROM AN UPPER LEVEL LOW N OF THE WINDWARD ISLANDS NEAR 24N59W. 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 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 THE STRAITS OF FLORIDA NEAR 24N79W. A 1017 MB SURFACE LOW IS CENTERED NEAR 30N74W WITH A SURFACE TROUGH EXTENDING THROUGH IT FROM 32N72W TO 28N74W. 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 24N59W IS SUPPORTING SCATTERED SHOWERS/THUNDERSTORMS FROM 17N-21N BETWEEN 54W-59W...AND FROM 20N-21N BETWEEN 45W-52W. A 1011 MB SURFACE LOW IS CENTERED NEAR 15N48W. SURFACE CONVERGENCE NEAR THE LOW IS SUPPORTING ISOLATED SHOWERS WITHIN 100 NM E OF THE CENTER FROM 15N-16N. THE REMAINDER OF THE ATLC REMAINS FAIRLY CALM UNDER THE INFLUENCE OF A BROAD SURFACE RIDGE ANCHORED BY A 1024 MB HIGH NEAR 34N42W. 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