000 AXNT20 KNHC 180550 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 205 AM EDT WED OCT 18 2006 TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHEASTERN SECTIONS OF SOUTH AMERICA...AND THE ATLANTIC OCEAN TO THE AFRICAN COAST FROM THE EQUATOR TO 32N. THE FOLLOWING INFORMATION IS BASED ON SATELLITE IMAGERY...WEATHER OBSERVATIONS...RADAR... AND METEOROLOGICAL ANALYSIS. BASED ON 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0515 UTC. ...TROPICAL WAVES... AN ATLANTIC OCEAN TROPICAL WAVE IS ALONG 38W SOUTH OF 18N MOVING WEST NEAR 10 KT. THE WAVE SHOWS A WELL DEFINED INVERTED-V SHAPE. CONVECTION IS BEING DISPLACED TO THE NE BY UPPER SW LEVEL FLOW. SCATTERED MODERATE CONVECTION FROM 12N-18N BETWEEN 36W-39W. THE TROPICAL WAVE THAT WAS PREVIOUSLY ANALYZED ALONG 66W/67W ON THE 1800 UTC MAP IS NO LONGER IDENTIFIABLE BASED ON LATEST SATELLITE IMAGERY AND EARLIER QUIKSCAT PASS. ONLY A SURFACE TROUGH REMAINS OVER THIS AREA ASSOCIATED WITH THE NEARLY STATIONARY AREA OF LOW PRESSURE THAT HAS BEEN MEANDERING JUST NORTH OF PUERTO RICO. THIS IS ALSO A REGION OF UPPER DIFFLUENCE WHICH IS HELPING SUPPORT THE CONVECTION. ...THE ITCZ... ITCZ AXIS IS CENTERED ALONG 10N14W 10N25W 12N34W 9N40W 5N52W. CLUSTERS OF MODERATE TO STRONG CONVECTION ARE FOUND OFF THE COAST OF GUINEA AND GUINEA BISSAU IN AFRICA AND FROM 11N-15N BETWEEN 27W-31W. SIMILAR CONVECTION IS ALONG THE ITCZ AXIS BETWEEN 31W-35W. ...DISCUSSION... GULF OF MEXICO... MAIN FEATURE IN THE GULF TONIGHT IS THE SQUALL LINE EXTENDING NE THROUGH THE NE GULF AND THE FLORIDA PANHANDLE INTO SOUTHERN GEORGIA. THIS IS ASSOCIATED WITH A COMPLEX SURFACE PRESSURE PATTERN OVER THE SE STATES. THE REMAINDER OF THE GULF REMAINS DOMINATED BY 10-20 KT SLY FLOW AT THE SURFACE BETWEEN HIGH PRESSURE WELL NE OF THE AREA AND LOWER PRESSURE OVER MEXICO. IN THE UPPER LEVELS...THE GULF IS DOMINATED BY A LARGE UPPER HIGH CENTERED NEAR 24N90W. UPPER LEVEL MOISTURE COVERS THE GULF E OF 92W AND THE FLORIDA PENINSULA WHILE DRY AIR IS FOUND WEST OF 92W. A NEW COLD FRONT WILL ENTER THE NW GULF WATERS ON THU AND EXTEND FROM BIG BEND FLORIDA TO NEAR TAMPICO ON FRIDAY. CARIBBEAN SEA... THE LARGE UPPER UPPER HIGH ANCHORED IN THE GULF OF MEXICO EXTENDS A RIDGE EWD ACROSS MOST OF THE CARIBBEAN SEA AND CENTRAL AMERICA GIVING THE REGION UPPER NE FLOW AND MOSTLY DRY AIR. A VERY ELONGATED UPPER TROUGH FROM THE ATLC EXTENDS S OVER THE FAR EAST CARIBBEAN. A 1007 MB AREA OF LOW PRESSURE REMAINS JUST NORTH OF PUERTO RICO. THIS FEATURE IS PRODUCING DISORGANIZED SHOWERS AND TSTMS AND UPPER-LEVEL WINDS REMAIN UNFAVORABLE FOR TROPICAL CYCLONE DEVELOPMENT. A SURFACE TROUGH EXTENDS S FROM THIS LOW TO THE ABC ISLANDS...WHERE IS GENERATING SCATTERED SHOWERS AND TSTMS. THE ARE OF LOW PRESSURE IS FORECAST TO MOVE SLOWLY NE AND AWAY FROM PUERTO RICO DURING THE NEXT FEW DAYS. SCATTERED SHOWERS AND ISOLATED TSTMS ARE ALSO OVER THE SW CARIBBEAN DUE TO THE PRESENCE OF THE ITCZ AXIS. TRADE WINDS ARE LIGHT DUE TO A WEAK PRESSURE PATTERN. ATLANTIC OCEAN... THE LARGE UPPER RIDGE SITUATED IN THE GULF OF MEXICO ALSO EXTENDS ACROSS THE W ATLC TO 65W DRYING OUT THE AREA. A SURFACE HIGH OVER THE W ATLC NORTH OF THE AREA EXTENDS A RIDGE ACROSS THE BAHAMAS AND CUBA. DEEP LAYERED TROUGH EXTENDS INTO THE W-CENTRAL ATLC ALONG 60W/61W TO THE FAR E CARIBBEAN. THE ATTENDANT COLD FRONT ENTERS THE REGION NEAR 32N50W THEN CONTINUES SW TO 25N57W. A SURFACE TROUGH RUNS FROM THIS POINT TO THE LOW PRESSURE THAT REMAINS NORTH OF PUERTO RICO. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS AFFECTING THE VIRGIN/LEEWARD ISLANDS. CLUSTERS OF SIMILAR CONVECTION ARE SEEN FROM 18N-20N BETWEEN 60W-64W. ANOTHER DEEP LAYERED TROUGH EXTENDS FROM THE E ATLC THROUGH 32N20W SW TO A WEAKENING UPPER LOW CENTERED NEAR 21N45W. ISOLATED SHOWERS ARE RELATED TO THIS LOW. A STATIONARY FRONT IS JUST NORTH OF THE CANARY ISLANDS. A 1019 MB SURFACE HIGH IS NEAR 30N39W AND DOMINATES THE ATLC BETWEEN 20W-50W. $$ GR