000 AXNT20 KNHC 181744 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT THU OCT 18 2012 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...WEATHER OBSERVATIONS...RADAR...AND METEOROLOGICAL ANALYSIS. BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1615 UTC. ...TROPICAL WAVES... WEAK TROPICAL WAVE IS ALONG 15N45W TO 8N45W MOVING WEST NEAR 15 KT. DUE TO A LARGE UPPER TROUGH JUST WEST OF THE WAVE...IT IS HARD TO DISCERN WHETHER CONVECTION NEAR THE AXIS IS ASSOCIATED WITH THE WAVE OR THE UPPER TROUGH. IT IS MOST LIKELY TIED TO THE UPPER TROUGH DUE TO THE FACT THAT THE WAVE HAS BEEN WEAK. EITHER WAY...SCATTERED MODERATE CONVECTION IS FROM 8N-11N BETWEEN 45W-47W...AND FROM 11N-15N BETWEEN 47W-52W. ...THE ITCZ/THE MONSOON TROUGH... THE MONSOON TROUGH EXTENDS ACROSS WEST AFRICA TO THE COAST OF SENEGAL AT 13N17W CONTINUING ALONG 9N24W 8N29W. THE ITCZ BEGINS AT 8N29W AND ENDS NEAR 10N39W. ISOLATED MODERATE CONVECTION IS WITHIN 150 NM N OF THE AXIS BETWEEN 20W-30W. ...DISCUSSION... GULF OF MEXICO... AN UPPER LEVEL TROUGH COVERING THE EASTERN CONUS SUPPORTS A COLD FRONT THAT IS JUST BEGINNING TO MOVE INTO THE GULF OF MEXICO. AS OF 1500 UTC...IT EXTENDS FROM THE FLORIDA/ALABAMA BORDER AT 31N88W ACROSS SE LOUISIANA TO 28N93W TO THE TEXAS COAST AT 27N97W. A LINE OF SHOWERS/POSSIBLE THUNDERSTORMS IS ALONG THE AXIS AND EXTEND UP TO 100 NM AHEAD OF THE FRONT EAST OF 90W. BESIDES MOISTURE IMMEDIATELY ALONG THE FRONT...THE REMAINDER OF THE BASIN IS UNDER THE INFLUENCE OF MOSTLY DRY AIR ALOFT AROUND AN UPPER LEVEL RIDGE CENTERED OVER CENTRAL MEXICO. THE DRY AIR IS HELPING MAINTAIN CLEAR SKIES EXCEPT FOR A FEW SHOWERS/THUNDERSTORMS IN THE SE GULF NEAR A WEAK SURFACE TROUGH ALONG 27N83W TO 23N85W. THE FRONT IS EXPECTED TO CONTINUE MOVING SE...AND SHOULD EXTEND FROM NE FLORIDA TO NE MEXICO IN 24 HOURS...AND SHOULD MOVE OUT OF THE BASIN BY THE END OF THE WEEKEND. SURFACE RIDGING WILL BUILD IN BEHIND THE FRONT. CARIBBEAN SEA... MOSTLY DRY AIR ALOFT COVERS THE NW CARIBBEAN AROUND AN UPPER LEVEL RIDGE EXTENDING FROM MEXICO ACROSS THE YUCATAN AND INTO THE AREA PROVIDING FAIR CONDITIONS N OF 16N WEST OF 74W. THE REMAINDER OF THE BASIN IS COVERED BY A SECOND BROAD AND ELONGATED UPPER LEVEL RIDGE THAT EXTENDS FROM THE SW CARIBBEAN TO THE NE CARIBBEAN. MODERATE MOISTURE ACCOMPANIES THE UPPER RIDGE AND IS HELPING PRODUCE ISOLATED SHOWERS ACROSS MUCH OF THE SW AND EASTERN CARIBBEAN. THE ACTIVITY IN THE SW CARIBBEAN IS ALSO ENHANCED BY THE PRESENCE OF THE MONSOON TROUGH THAT EXTENDS FROM SOUTHERN NICARAGUA TO NORTHERN COLOMBIA ALONG 11N. A WEAK SURFACE TROUGH IS ALSO IN THE EASTERN CARIBBEAN ALONG 15N63W TO 11N63W HELPING PRODUCE MORE SCATTERED SHOWER ACTIVITY IN ITS VICINITY. EXPECT LITTLE CHANGE OVER THE NEXT 24 HOURS. ATLANTIC OCEAN... AN UPPER LEVEL TROUGH IS MOVING INTO THE WEST ATLC WITH AXIS ALONG 80W. A SHORTWAVE TROUGH EXTENDS OFF THE MAIN LONGWAVE HELPING PRODUCE SHOWERS/THUNDERSTORMS FROM 25N-27N BETWEEN 75W-77W...AND FROM 25N-28N BETWEEN 71W-74W. A FEW ISOLATED PATCHES OF SHOWERS/THUNDERSTORMS ARE ALSO OFF THE FLORIDA COAST FROM 24N-29N. FARTHER EAST...AN UPPER LEVEL RIDGE EXTENDS FROM THE NE CARIBBEAN INTO THE CENTRAL ATLC ALONG 58W DRAWING UP AN AREA OF MOISTURE. AT THE SURFACE...A SURFACE TROUGH EXTENDS FROM NEAR 31N56W TO 22N64W...WHICH IS AN EXTENSION OF A COLD FRONT IN THE NORTHERN ATLC. SCATTERED SHOWERS ARE EAST OF THE SURFACE TROUGH AXIS WITHIN 200 NM. THE REMAINDER OF THE BASIN IS COVERED BY A BROAD SURFACE RIDGE ANCHORED BY A 1026 MB HIGH NEAR 36N36W. THE SURFACE RIDGE IS SUPPORTED BY AN UPPER LEVEL RIDGE COVERING THE EASTERN TROPICAL ATLC WITH AXIS ALONG 22N32W. A BROAD UPPER LEVEL LOW IS CENTERED TO THE WEST NEAR 18N50W...WHICH IS PROVIDING DIFFLUENCE ALOFT NEAR A TROPICAL WAVE TO THE SOUTH. IT IS ALSO HELPING PRODUCE AN AREA OF SHOWERS/POSSIBLE THUNDERSTORMS FROM 15N-18N BETWEEN 36W-38W. IN THE FAR NE CORNER OF THE DISCUSSION AREA...A COLD FRONT EXTENDS FROM SPAIN INTO THE AREA ALONG 32N11W TO 29N19W. SCATTERED SHOWERS ARE UP TO 100 NM AHEAD OF THE FRONT. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ WALTON