000 AXNT20 KNHC 202338 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 805 PM 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2315 UTC. ...TROPICAL WAVES... TROPICAL WAVE IS TILTED FROM 21N39W TO 14N41W MOVING W NEAR 15 KT. THE WAVE POSITION IS BASED ON THE DEEP LAYERED MOISTURE MAXIMUM AS OBSERVED IN TOTAL PRECIPITABLE WATER IMAGERY AND THE CURVATURE OBSERVED IN THE VISIBLE SATELLITE IMAGERY. DENSE CLOUD COVER WITH CLUSTERS OF SCATTERED MODERATE/ISOLATED STRONG CONVECTION COVER THE AREA FROM 15N-22N BETWEEN 37W-43W. ...ITCZ... THE ITCZ AXIS IS CENTERED ALONG 10N12W 4N28W 6N44W 6N59W. SMALL CLUSTERS OF ISOLATED MODERATE CONVECTION ARE WITHIN 45 NM OF THE ITCZ BETWEEN 18W-24W. ...DISCUSSION... GULF OF MEXICO... A SURFACE TROUGH EXTENDS ACROSS LOUISIANA ENTERING THE GULF JUST W OF VERMILION BAY TO OFF THE TEXAS COAST NEAR 27N97W SUPPORTED BY AN UPPER TROUGH MOVING ACROSS THE MISSISSIPPI VALLEY. A SECOND SURFACE TROUGH IS IN THE SE GULF EXTENDING FROM 26N84W TO THE YUCATAN NEAR 22N88W. AN UPPER RIDGE EXTENDS FROM S/CENTRAL MEXICO INTO THE GULF NEAR TAMPICO NE TO NEAR PANAMA CITY FLORIDA WITH A SECOND UPPER RIDGE OVER THE SE GULF S OF A LINE FROM TAMPA TO THE NE YUCATAN PENINSULA. THIS IS CREATING AN INVERTED UPPER TROUGH BETWEEN THESE TWO UPPER RIDGES. SCATTERED SHOWERS/ ISOLATED THUNDERSTORMS ARE WITHIN 90 NM OF A LINE FROM 23N92W TO NEAR 26N84W WITH SCATTERED/NUMEROUS SHOWERS/THUNDERSTORMS ARE INLAND AND WITHIN 60 NM ALONG THE COAST OF FLORIDA S OF 29N TO JUST N OF THE FLORIDA KEYS. OTHERWISE THE REMAINDER OF THE GULF REMAINS TRANQUIL THIS EVENING. CARIBBEAN SEA... AN UPPER LEVEL RIDGE COVERS THE W CARIBBEAN ANCHORED OVER CENTRAL CUBA COVERING THE AREA N OF 15N W OF 72W WITH AN UPPER TROUGH EXTENDING FROM THE CENTRAL ATLC OVER THE NE CARIBBEAN N OF 16N E OF 71W ACROSS THE LEEWARD ISLANDS. THE S CARIBBEAN IS UNDER WESTERN UPPER FLOW DUE TO AN UPPER RIDGE ANCHORED OVER SOUTH AMERICA. SCATTERED SHOWERS/ISOLATED THUNDERSTORMS COVER THE W CARIBBEAN W OF A LINE FROM E CUBA NEAR 20N75W TO THE HONDURAS/ NICARAGUA BORDER INCLUDING JAMAICA. SIMILAR ACTIVITY IS N OF 17N TO OVER THE GREATER ANTILLES BETWEEN VIRGIN ISLANDS TO HAITI. THE REMAINDER OF THE CARIBBEAN REMAINS TRANQUIL THIS EVENING. ATLANTIC OCEAN... A SURFACE TROUGH IS IN THE W ATLC EXTENDING FROM 31N71W THROUGH A WEAKENING 1016 MB LOW NEAR 29N72W TO 27N72W WITH ISOLATED SHOWERS WITHIN 60 NM OF THE SURFACE TROUGH. AN UPPER RIDGE ANCHORED OVER CENTRAL CUBA COVERS THE SW ATLC S OF 29N W OF 70W ENHANCING SCATTERED SHOWERS/ISOLATED THUNDERSTORMS FROM 24N29N W OF 77W TO OVER THE FLORIDA PENINSULA. AN UPPER LOW IS TO THE E CENTERED NEAR 24N61W COVERING THE AREA FROM 16N-27N BETWEEN 50W-70W WITH A SURFACE TROUGH EXTENDING FROM 29N61W TO 23N63W AND GENERATING SCATTERED SHOWERS/ISOLATED THUNDERSTORMS WITHIN 60 NM OF THE SURFACE TROUGH. SIMILAR ACTIVITY IS ALONG THE S PERIPHERY OF THE UPPER LOW WITHIN 90 NM OF LINE FROM 18N54W TO 21N64W. A LONG UPPER TROUGH EXTENDS FROM THE E ATLC ACROSS TO THE CENTRAL ATLC THROUGH A PAIR OF UPPER LOWS CENTERED NEAR 30N28W AND 28N46W SUPPRESSING THE ITCZ TO THE S. A WEAK SURFACE RIDGE DOMINATES THE ATLC WITH A 1025 MB HIGH NEAR 33N41W. $$ WALLACE