000 AXNT20 KNHC 051749 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT SUN OCT 05 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... TROPICAL WAVE IS ALONG 25W/26W S OF 18N MOVING W 10-15 KT. BROAD LOW LEVEL CIRCULATION IS DISCERNIBLE ON SATELLITE IMAGERY AROUND WAVE AXIS...WHICH COINCIDES WITH A MAXIMUM IN CIMSS WAVETRACK DERIVED LOW LEVEL COUNTERCLOCKWISE CIRCULATION. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 210 NM W OF WAVE AXIS N OF 10N...WITH ISOLATED MODERATE CONVECTION WITHIN 210 NM W OF WAVE AXIS S OF 7N. TROPICAL WAVE IS ALONG 55W/56W S OF 19N MOVING W NEAR 15 KT. VISIBLE SATELLITE IMAGERY DEPICTS INVERTED-V SIGNATURE IN LOW LEVEL CLOUD COVERAGE...WITH COUNTERCLOCKWISE CURVATURE IN OBSERVED SURFACE WIND FIELD. ISOLATED SHOWERS ARE OCCURRING WITHIN 90 NM EITHER SIDE OF WAVE AXIS N OF 12N. TROPICAL WAVE IS ALONG 66W/67W S OF 19N MOVING W 10-15 KT. WAVE STRUCTURE IS GENERALLY ILL-DEFINED FROM SATELLITE IMAGERY... THOUGH COUNTERCLOCKWISE CURVATURE IS NOTED IN OBSERVED SURFACE WIND FIELD OVER E CARIBBEAN REGION NEAR WAVE AXIS. ISOLATED SHOWERS ARE WITHIN 150 NM E OF WAVE AXIS S OF 13N. ...THE ITCZ... THE ITCZ AXIS IS ANALYZED ALONG 7N12W 8N23W 9N40W 12N54W 12N65W ACROSS THE S CARIBBEAN INTO THE E PACIFIC REGION NEAR 11N86W. ISOLATED MODERATE CONVECTION IS FROM 6N-13N BETWEEN 34W-40W. SCATTERED MODERATE CONVECTION IS FROM 9N-15N BETWEEN 42W-47W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS OVER THE S CARIBBEAN FROM 10N-14N BETWEEN 72W-83W. ...DISCUSSION... GULF OF MEXICO... AN UPPER TROUGH OVER THE E CONUS AND A SECONDARY UPPER TROUGH OVER MEXICO EXTEND INTO THE GULF. AS A RESULT...SOUTHWESTERLY FLOW ALOFT COVERS MUCH OF THE GULF...WITH MOISTURE STREAMING THROUGH THE FLOW OVER THE GULF SE OF A LINE FROM 27N85W TO 20N97W. ALSO TO THE SE OF THIS LINE...A SURFACE TROUGH EXTENDS FROM 23N88W TO A 1012 MB SURFACE LOW OVER THE YUCATAN PENINSULA NEAR 19N89W...AND ANOTHER SURFACE TROUGH EXTENDS FROM NEAR THE FLORIDA KEYS NEAR 25N82W TO THE S FLORIDA PENINSULA NEAR 25N80W. WEAKLY CONVERGENT FLOW INTO THESE FEATURES...COMBINED WITH MOISTURE AND ATMOSPHERIC LIFT IN SW FLOW ALOFT...IS RESULTING IN SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS OVER THE GULF S OF 26N BETWEEN 81W-88W. ISOLATED SHOWERS ARE OCCURRING OVER THE BAY OF CAMPECHE IN RESPONSE TO LOW LEVEL SUPPORT FROM THE SURFACE LOW OVER THE YUCATAN PENINSULA. DRY CONDITIONS COVER MUCH OF THE GULF NW OF A LINE FROM 27N85W TO 20N97W. CARIBBEAN SEA... AN UPPER RIDGE EXTENDS FROM W CUBA TO THE GULF OF HONDURAS... WITH DEEP MOISTURE CIRCULATING AROUND THE RIDGE. ALSO...A 1012 MB SURFACE LOW IS OVER THE YUCATAN PENINSULA NEAR 19N89W...WITH A SURFACE TROUGH EXTENDING FROM THE LOW INTO THE GULF OF MEXICO NEAR 23N88W. THESE FEATURES CONTINUE TO RESULT IN SCATTERED MODERATE CONVECTION OVER THE NW CARIBBEAN N OF 17N AND W OF 82W...AFFECTING THE YUCATAN PENINSULA AND BELIZE. TO THE E...AN UPPER TROUGH EXTENDS NORTHWARD FROM PANAMA TO HAITI. DEEP TROPICAL MOISTURE AND WEAKLY UNSTABLE AIR WITHIN THE TROUGH...COMBINED WITH WEAK LOW LEVEL CONVERGENCE NEAR THE ITCZ AXIS...ARE RESULTING IN SCATTERED MODERATE CONVECTION FROM 9N-14N BETWEEN 72W-81W...AFFECTING THE SW CARIBBEAN. OVER THE E CARIBBEAN...DRIER AIR IS PRESENT UNDER WEAK A WEAK RIDGE ALOFT...WITH ISOLATED SHOWERS S OF 16N AND E OF 69W BEING SUPPORTED BY THE ITCZ. ATLANTIC OCEAN... AN UPPER TROUGH OVER THE E CONUS CONTINUES TO SUPPORT MOIST SOUTHWESTERLY FLOW ALOFT OVER THE SW ATLC...WHERE A WEAKENING STATIONARY SURFACE FRONT EXTENDS FROM 23N71W TO 28N77W AND A SURFACE TROUGH EXTENDS FROM 28N77W TO THE S FLORIDA PENINSULA NEAR 25N80W. THE COMBINATION OF THESE FEATURES CONTINUES RESULTING IN ISOLATED SHOWERS AND THUNDERSTORMS WITHIN 150 NM EITHER SIDE OF THE WEAKENING STATIONARY SURFACE FRONT AND THE SURFACE TROUGH. AN UPPER HIGH NEAR 29N68W AND ITS ASSOCIATED UPPER RIDGE ARE BRINGING DRY AND STABLE CONDITIONS TO THE W ATLC N OF 21N BETWEEN 59W-74W. A DEEP UPPER LOW SPINNING OVER THE CENTRAL ATLC NEAR 22N57W IS SUPPORTING A SURFACE TROUGH THAT EXTENDS FROM 27N55W TO NEAR 21N56W. THIS SURFACE TROUGH CONTINUES TO MOVE WESTWARD ON THE SOUTHERN PERIPHERY OF THE SURFACE RIDGE OVER THE CENTRAL ATLC ANCHORED BY A 1025 MB HIGH NEAR 34N38W. THE SURFACE TROUGH IS SUPPORTING SCATTERED MODERATE CONVECTION WITHIN 180 NM E OF THE TROUGH AXIS S OF 22N AND ISOLATED MODERATE CONVECTION WITHIN 150 NM E OF THE TROUGH AXIS N OF 25N. OVER THE NE ATLC...AN UPPER TROUGH IS N OF 19N BETWEEN THE W AFRICAN COAST AND 32W. UPPER SUPPORT FROM AN UPPER LEVEL WIND SPEED MAXIMUM E OF THE TROUGH AXIS IS GENERATING SCATTERED MODERATE CONVECTION FROM 20N-24N BETWEEN 18W-23W. THE TYPICAL E/W UPPER RIDGE AXIS EXTENDS ACROSS THE TROPICAL ATLC ALONG 12N BETWEEN W AFRICA AND 51W. $$ COHEN