000 AXNT20 KNHC 290000 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT THU OCT 28 2010 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 2345 UTC. ...SPECIAL FEATURES... A 1009 MB SURFACE LOW IS OVER THE WESTERN ATLC CENTERED NEAR 25N61W. THIS LOW IS EMBEDDED IN A LARGE SCALE UPPER LEVEL CYCLONIC CIRCULATION CENTERED NEAR 23N69W. SCATTERED MODERATE AND ISOLATED MODERATE CONVECTION CONTINUES TO BE SHEARED NORTH OF THE LOW LEVEL CIRCULATION FROM 26N TO 30N BETWEEN 58W AND 64W. ENVIRONMENTAL CONDITIONS ARE FORECAST TO REMAIN SOMEWHAT CONDUCIVE FOR THE DEVELOPMENT OF A TROPICAL OR SUBTROPICAL DEPRESSION THROUGH FRIDAY...HOWEVER UPPER-LEVEL WINDS ARE EXPECTED TO BECOME LESS FAVORABLE AFTER THAT. THERE IS A HIGH CHANCE OF THIS SYSTEM BECOMING A SUBTROPICAL OR TROPICAL CYCLONE BEFORE IT MERGES WITH A COLD FRONT ON SATURDAY. A 1010 MB SURFACE LOW IS IN THE CENTRAL ATLC CENTERED NEAR 26N41W. THE ASSOCIATED CONVECTION IS FOUND TO THE EAST OF THE CENTER FROM 25N TO 29N BETWEEN 35W AND 41W. ALTHOUGH SHOWER AND THUNDERSTORM ACTIVITY ASSOCIATED WITH THE LOW HAS INCREASED DURING THE PAST FEW HOURS...UPPER-LEVEL WINDS ARE EXPECTED TO BECOME LESS FAVORABLE FOR DEVELOPMENT ON FRIDAY. THERE IS A MEDIUM CHANCE OF THIS SYSTEM BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS AS IT MOVES SLOWLY WESTWARD. A VIGOROUS TROPICAL WAVE EXTENDS FROM 14N49W TO A SFC LOW NEAR 8N51W TO 3N52W MOVING W AT 10-15 KT. THE WAVE REMAINS AS A BROAD CYCLONIC PERTURBATION WITHIN THE ITCZ REGION...AS WELL AS EMBEDDED IN A SURGE OF DEEP MOISTURE ON TOTAL PRECIPITABLE WATER IMAGERY. SATELLITE DERIVED WINDS INDICATE BROAD CYCLONIC TURNING ALONG THE WAVE AXIS. SCATTERED MODERATE AND ISOLATED STRONG CONVECTION IS OCCURRING FROM 4N-15N BETWEEN 45W-56W. ENHANCEMENT OF THE STRONGER ONGOING CONVECTION IS DUE TO UPPER LEVEL DIFFLUENCE PROVIDED BY A BROAD UPPER LEVEL ANTICYCLONE CENTERED NEAR 10N50W. THIS SYSTEM CONTINUES TO SHOW SIGNS OF ORGANIZATION ...AND ENVIRONMENTAL CONDITIONS APPEAR TO BE FAVORABLE FOR GRADUAL DEVELOPMENT OF THIS DISTURBANCE DURING THE NEXT COUPLE OF DAYS. THERE IS A MEDIUM CHANCE OF THIS SYSTEM BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS. REGARDLESS OF DEVELOPMENT...THIS SYSTEM IS EXPECTED TO BRING LOCALLY HEAVY RAINFALL AND STRONG GUSTY WINDS TO THE WINDWARD ISLANDS... VENEZUELA...AND NORTHERN PORTIONS OF GUYANA DURING THE NEXT COUPLE OF DAYS. ...ITCZ... THE ITCZ AXIS IS ANALYZED FROM THE COAST OF GUINEA NEAR 10N14W WESTWARD ALONG 6N20W 7N30W 6N40W 8N50W. SCATTERED MODERATE TO ISOLATED STRONG CONVECTION IS WITHIN 120 NM ON EITHER SIDE OF THE AXIS E OF 28W. ...DISCUSSION... GULF OF MEXICO... A COLD FRONT EXTENDS ACROSS THE GULF FROM THE FLORIDA PANHANDLE NEAR 30N84W TO THE COAST OF MEXICO ALONG 28N87W 26N93W 23N97W. NORTHERLY WINDS RANGING FROM 10 TO 25 KT ARE OBSERVED BEHIND THE FRONT. IN 24 HOURS THIS FRONT IS EXPECTED TO MOVE ACROSS THE GULF RATHER QUICK EXTENDING FROM THE CENTRAL FLORIDA PENINSULA TO THE BAY OF CAMPECHE PRODUCING GALE FORCE WINDS S OF 22N W OF 95W. A PRE-FRONTAL TROUGH EXTENDS FROM THE COLD FRONT NEAR 25N93W SOUTHWARD TO THE NEAR THE CITY OF COATZACOALCOS MEXICO. SCATTERED SHOWERS AND TSTMS ARE WITHIN 60 NM ON EITHER SIDE OF THE COLD FRONT. SIMILAR CONVECTION IS WITHIN 70 NM ON EITHER SIDE OF THE TROUGH. FAIR CONDITIONS ARE ELSEWHERE ACROSS THE AREA OF DISCUSSION UNDER LIGHT EASTERLY SURFACE WINDS AND A DRY AND SUBSIDENT AIR ALOFT. CARIBBEAN SEA... BROAD SCALE UPPER LEVEL CYCLONIC FLOW COVERS THE CARIBBEAN BASIN AND IS MOVING A DRY AND STABLE AIRMASS ALOFT ACROSS THE AREA OF DISCUSSION. HOWEVER...A STREAM OF MID-LEVEL MOISTURE IS NOTED OVER THE NE BASIN FROM N OF 15N W OF 71W. THIS MOISTURE ALONG WITH MARGINAL LOW-LEVEL SPEED CONVERGENCE IS GENERATING WIDELY SCATTERED SHOWERS AND ISOLATED TSTMS IN THIS AREA. OTHER ISOLATED SHOWERS ARE NOTED ON SATELLITE IMAGERY ELSEWHERE ACROSS THE BASIN. ISOLATED TSTMS ARE OCCURRING OVER THE SW CARIBBEAN S OF 11N W OF 76W DUE TO CONVERGENT LOW-LEVEL FLOW AND CLOSE PROXIMITY OF THE E PACIFIC ITCZ AXIS. IN THE NEXT 24 HOURS...A TROPICAL WAVE WILL START TO AFFECT THE LESSER ANTILLES WITH CONVECTION. ATLANTIC OCEAN... ASIDE FROM THE AREAS OF CONCERN NOTED ABOVE IN THE SPECIAL FEATURES SECTION...DRY AND STABLE AIR ALOFT IS NOTED ELSEWHERE ON WATER VAPOR IMAGERY. BROAD UPPER LEVEL RIDGING EXTENDS ACROSS MOST OF THE ATLC ANCHORED BY A SET OF 1026 MB HIGHS NEAR 36N51W AND 38N42W. THE FAR EASTERN ATLC IS UNDER THE INFLUENCE OF ANOTHER SURFACE RIDGE ANCHORED BY A 1024 MB HIGH CENTERED NEAR THE CANARY ISLANDS. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ GARCIA