000 AXNT20 KNHC 202356 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT TUE OCT 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 19N24W TO 8N28W DRIFTING WESTWARD. WAVE AXIS IS OBSERVED ON THE VISIBLE SATELLITE IMAGERY AND IN THE SATELLITE DERIVED WINDS. THE DEEP LAYER MOISTURE MAXIMUM AS OBSERVED IN TOTAL PRECIPITABLE WATER IMAGERY APPEARS TO BE WEAKENING AND MAY ACCOUNT FOR THE REAL LACK OF MOVEMENT IN THE WAVE AXIS AS WELL AS THE LACK OF ANY DEEP CONVECTION. ISOLATED SHOWERS ARE FROM 12N-18N BETWEEN 23W-28W WHICH INCLUDES ALL OF THE CAPE VERDE ISLANDS. ...ITCZ... ITCZ AXIS IS CENTERED ALONG 10N12W 6N20W 13N37W 9N53W 8N60W. A 1009 MB SURFACE LOW IS EMBEDDED WITHIN THE AXIS CENTERED NEAR 13N38W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 60 NM OF LINE FROM 6N34W TO 8N36W. CLUSTERS OF ISOLATED MODERATE CONVECTION DOT THE AREA FROM 3N-8N BETWEEN 15W-27W. ...DISCUSSION... GULF OF MEXICO... BROAD SURFACE RIDGE DOMINATES THE GULF ANCHORED OVER GEORGIA BY A 1026 MB HIGH. A BROAD UPPER RIDGE ANCHORED OVER SW MEXICO COVERS THE W GULF WHILE A STRONG DEEP LAYERED TROUGH COVERS THE REMAINDER OF THE GULF. THIS UPPER TROUGH IS ASSOCIATED WITH THE FRONTAL BOUNDARY THAT PASSED THROUGH THE GULF OVER THE WEEKEND PROVIDING DRY STABLE AIR OVER THE E GULF. HOWEVER... MOIST TROPICAL AIR IS NOW BEING DRAWN ACROSS THE W GULF BY THE UPPER RIDGE AND WITH EASTERLY SURFACE FLOW IS BANKING LOW LEVEL CLOUDS WITH POSSIBLE ISOLATED SHOWERS OVER THE W GULF AGAINST THE E SLOPES OF THE SIERRA MADRE MOUNTAINS. THE SURFACE RIDGE IS EXPECTED TO SHIFT E AS ANOTHER FRONT MOVES INTO THE GULF ON THU. CARIBBEAN SEA... THE DEEP LAYERED TROUGH OVER THE E GULF OF MEXICO DIPS S OVER THE NW CARIBBEAN WITH THE REMNANT DISSIPATING STATIONARY FRONT EXTENDING ACROSS CENTRAL CUBA NEAR 21N77W S OF THE CAYMAN ISLANDS TO 18N82W. A 1007 MB LOW IS CENTERED NEAR 12N82W MOVING W TO INLAND OVER NICARAGUA AT 2100 UTC WITH A 1011 MB LOW IN THE GULF OF HONDURAS NEAR ROATAN ISLAND DRIFTING NW. A NARROW UPPER RIDGE IS JUST TO THE E EXTENDING FROM COLOMBIA NEAR 10N75W TO 12N78W THEN NE THROUGH THE WINDWARD PASSAGE INTO THE W ATLC PROVIDING DIFFLUENCE ALOFT TO ENHANCE A BROAD AREA OF SCATTERED SHOWERS/ISOLATED THUNDERSTORMS THAT COVERS THE W CARIBBEAN W OF A LINE FROM PANAMA NEAR 9N78W TO JAMAICA THEN NE OVER HAITI. A BROAD UPPER TROUGH COVERS THE E CARIBBEAN EXTENDING FROM AN UPPER LOW IN THE CENTRAL ATLC PROVIDING DRY STABLE AIR E OF 70W. ATLANTIC OCEAN... THE BROAD DEEP LAYERED TROUGH THAT COVERS THE E GULF OF MEXICO EXTENDS OVER THE FLORIDA PENINSULA INTO THE W ATLC WITH THE ASSOCIATED COLD FRONT ENTERING THE REGION NEAR 32N59W SW TO 25N71W WHERE IT BECOMES STATIONARY ACROSS THE BAHAMA ISLANDS TO 22N76W WHERE IT DISSIPATES IN THE W CARIBBEAN WITH ISOLATED SHOWERS WITHIN 60 NM EITHER SIDE OF THE FRONT. A NARROW UPPER RIDGE EXTENDS FROM THE CARIBBEAN THROUGH THE WINDWARD PASSAGE ALONG 25N69W TO 32N58W PROVIDING DIFFLUENCE ALOFT TO ENHANCE SCATTERED SHOWERS AND POSSIBLE ISOLATED THUNDERSTORMS MAINLY S OF 24N BETWEEN 70W-78W. A WEAK SURFACE TROUGH IS TO THE E ALONG 67W FROM 21N-24N. BROAD UPPER LOW IS IN THE CENTRAL ATLC NEAR 24N50W WITH AN UPPER TROUGH EXTENDING SW TO COVER THE E CARIBBEAN AND SUPPORTING A SURFACE TROUGH THAT EXTENDS ALONG 54W FROM 21N-27N. BROAD UPPER RIDGE OVER THE TROPICAL ATLC ANCHORED NEAR 10N38W EXTENDS A RIDGE AXIS N TO 27N30W PROVIDING DIFFLUENCE ALOFT TO ENHANCE SCATTERED SHOWERS/ISOLATED THUNDERSTORMS WITHIN 120/150 NM OF LINE FROM 18N52W TO 29N41W. $$ WALLACE