000 AXNT20 KNHC 211752 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT TUE OCT 21 2008 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1715 UTC. ...TROPICAL WAVES... A TROPICAL WAVE IS ALONG 21W/22W S OF 15N MOVING W NEAR 5-10 KT. AN ELONGATED CYCLONIC CIRCULATION IS OBSERVED ON SATELLITE IMAGERY WITH A WEAKLY SHEARED INVERTED-V CLOUD SIGNATURE. AN AREA OF SCATTERED MODERATE CONVECTION IS FROM 11N-15N BETWEEN 17W-21W. A TROPICAL WAVE IS ALONG 49W S OF 20N MOVING W NEAR 10-15 KT. THE SSMI-TPW PRODUCT FROM CIMSS INDICATES A NORTHWARD SURGE OF MOISTURE ALONG THE WAVE AXIS. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 18N-21N BETWEEN 43W-46W AND FROM 20N-23N BETWEEN 48W-51W. THIS ACTIVITY IS BEING DRAWN NORTHWARD BY A SHARP UPPER-LEVEL TROUGH AXIS ALONG 51W. A TROPICAL WAVE IS ALONG 74W S OF 15N MOVING W NEAR 10 KT. THE WAVE IS LOCATED WITHIN STRONG EASTERLY SURFACE FLOW ACROSS THE CARIBBEAN. NO SHOWERS OR DEEP CONVECTION OBSERVED WITH THE WAVE. ...THE ITCZ... ITCZ AXIS IS CENTERED ALONG 12N15W 10N20W 9N23W 7N34W 9N47W 9N51W 9N62W. IN ADDITION TO CONVECTION ASSOCIATED WITH TROPICAL WAVES...SCATTERED MODERATE CONVECTION IS FROM 5N-8N BETWEEN 17W-21W AND FROM 5N-10N BETWEEN 40W-47W. SIMILAR CONVECTION IS FROM 11N-13N BETWEEN 54W-61W. ...DISCUSSION... GULF OF MEXICO... A BROAD UPPER-LEVEL HIGH CENTERED IN THE CENTRAL CARIBBEAN SEA EXTENDS WEAK RIDGING ACROSS THE ENTIRE GULF. MODERATE TO STRONG SUBSIDENCE/DRY AIR IS NOTED OVER THE GULF. AT THE SURFACE...A 1025 MB HIGH PRESSURE CENTERED OVER CENTRAL ALABAMA EXTENDS A RIDGE ACROSS THE NRN GULF N OF 25N. A SECOND 1021 MB HIGH IS CENTERED JUST SOUTH OF TAMPICO MEXICO NEAR 21N98W. WEAK LOW TO MIDDLE LEVEL CYCLONIC FLOW IS ACROSS THE S/CENTRAL GULF AND YUCATAN PENINSULA WHICH IS GENERATING POSSIBLE SHALLOW SHOWERS FROM 21N-25N BETWEEN 89W-94W. EXPECT THE RIDGE ACROSS THE GULF TO WEAKEN IN ADVANCE OF A WEAK FRONTAL BOUNDARY FORECAST TO MOVE INTO THE FAR NW GULF WATERS BY LATE WED. CARIBBEAN SEA... A SURFACE TROUGH EXTENDS ACROSS CENTRAL CUBA W-SW TO THE GULF OF HONDURAS INTO A 1011 MB SURFACE LOW NEAR 16N87W. THIS LOW IS PRODUCING DISORGANIZED SCATTERED SHOWERS AND TSTMS OVER A LARGE PORTION OF THE WRN CARIBBEAN SEA W OF 77W. SCATTERED MODERATE/ ISOLATED STRONG CONVECTION IS FROM 11N-14N BETWEEN 77W-82W IN THE SW CARIBBEAN AND FROM 14N-21N BETWEEN 80W-87W IN THE NW CARIBBEAN. SUPPORTING THIS CONVECTION IS UPPER-LEVEL DIFFLUENCE ASSOCIATED WITH AN UPPER-LEVEL HIGH LOCATED SOUTH OF HISPANIOLA NEAR 16N71W WHICH DOMINATES THE ENTIRE CARIBBEAN SEA. THE PRESSURE GRADIENT BETWEEN THIS SURFACE LOW AND HIGH PRESSURE OVER THE W ATLC AND GULF OF MEXICO IS PRODUCING MODERATE TO STRONG ELY WINDS ACROSS THE ENTIRE CARIBBEAN BASIN. ELSEWHERE... A FEW SCATTERED SHOWERS ARE NOTED ACROSS THE SRN WINDWARD ISLANDS AND SE CARIBBEAN DUE PRIMARILY TO LOW-MID LEVEL MOISTURE CONVERGENCE AND UPPER-LEVEL DIFFLUENCE. ATLANTIC OCEAN... A DEEP LAYERED TROUGH IS OVER THE W ATLC AND SUPPORTS A COLD FRONT THAT ENTERS THE AREA NEAR 32N54W...TURNING STATIONARY NEAR 23N65W...AND EXTENDS ACROSS THE SRN BAHAMAS TO INLAND ACROSS CENTRAL CUBA. A BAND OF MULTILAYERED CLOUDS WITH EMBEDDED SHOWERS IS WITHIN 150 NM OF THE COLD FRONT N OF 24N. ELSEWHERE ALONG THE FRONTAL BOUNDARY MULTILAYERED CLOUDS ARE OBSERVED WITH POSSIBLE SCATTERED SHOWERS ACROSS THE BAHAMAS...STRAITS OF FLORIDA AND WRN CUBA. SUBSIDENCE/DRY AIR AND A STABLE ATMOSPHERE ARE IN PLACE ACROSS THE W ATLC N OF 26N AND W OF THE COLD FRONT. IN THE E ATLC...A 1025 MB HIGH IS NEAR 32N38W AND EXTENDS A SURFACE RIDGE OVER THE NE ATLC E OF 43W. A SHARP UPPER-LEVEL TROUGH WITH AXIS ALONG 51W AND AN AMPLIFIED UPPER-LEVEL RIDGE WITH AXIS ALONG 40W CONTINUES TO FUNNEL DEEP-LAYERED TROPICAL MOISTURE NORTHWARD INTO THE CENTRAL ATLC. UPPER-LEVEL DIFFLUENCE BETWEEN THIS LOW AND THE UPPER-LEVEL HIGH LOCATED OVER THE CARIBBEAN SEA IS ENHANCING CONVECTION ALONG THE ITCZ EAST OF THE WINDWARD ISLANDS TO 51W. ANOTHER UPPER-LEVEL TROUGH EXTENDS BETWEEN THE CANARY AND CAPE VERDE ISLANDS E OF 28W. $$ HUFFMAN