000 AXNT20 KNHC 172328 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 705 PM EST SAT NOV 17 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2245 UTC. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS ACROSS WEST AFRICA TO THE COAST OF GUINEA AT 10N14W TO 7N17W. THE ITCZ BEGINS AT 7N17W AND CONTINUES ALONG 6N28W 8N40W THEN RESUMES NEAR 12N45W TO 11N52W 8N59W. SCATTERED MODERATE CONVECTION IS FROM 7N-9N BETWEEN 25W-27W. AN UPPER LEVEL TROUGH OVER THE EASTERN ATLC CONTINUES TO PROVIDE A LARGE AREA OF DIFFLUENCE ALOFT NORTH OF THE ITCZ REGION AND CONCENTRATED NEAR A SURFACE TROUGH ALONG 19N35W TO 13N45W. ISOLATED MODERATE CONVECTION IS FROM 9N-14N BETWEEN 40W-45W. THE REMAINDER OF THE ACTIVITY IS FARTHER NORTH AND WILL BE DESCRIBED IN THE ATLC DISCUSSION SECTION. ...DISCUSSION... GULF OF MEXICO... MAINLY NORTHWESTERLY FLOW ALOFT COVERS THE GULF OF MEXICO BETWEEN AN UPPER LEVEL RIDGE EXTENDING THROUGH MEXICO INTO TEXAS...AND AN UPPER LEVEL LOW CENTERED OVER SOUTH CAROLINA WITH TROUGH AXIS EXTENDING SOUTHWARD ALONG 83W. WATER VAPOR IMAGERY INDICATES MOSTLY DRY AIR IS WRAPPING AROUND THE WEST SIDE OF THE UPPER TROUGH HELPING PROVIDE FAIR CONDITIONS ACROSS THE MAJORITY OF THE GULF. AT THE SURFACE...NORTHEAST TO EAST WINDS OF 10-15 KT SPREAD ACROSS THE BASIN AROUND THE BASE OF A SURFACE RIDGE COVERING THE EASTERN CONUS. SOME STRONGER WINDS UP TO 20 KT ARE PRESENT IN THE CENTRAL GULF AND THROUGH THE FLORIDA STRAITS. ISOLATED SHOWERS ARE PRESENT IN THE FAR SW GULF NEAR A SURFACE TROUGH PARALLEL TO THE MEXICO COAST ALONG 24N97W TO 19N95W. A FEW ISOLATED SHOWERS/POSSIBLE THUNDERSTORMS ARE ALSO ACROSS FLORIDA AND THE FAR SE GULF NORTH OF CUBA. SURFACE RIDGING IT EXPECTED TO REMAIN ACROSS THE EASTERN CONUS AND GULF OF MEXICO FOR THE NEXT COUPLE OF DAYS. ISOLATED SHOWERS WILL REMAIN OVER THE FAR SW AND SE GULF. CARIBBEAN SEA... THE UPPER LEVEL TROUGH OVER THE SE CONUS AND EASTERN GULF CONTINUES SOUTH INTO THE NW CARIBBEAN ACCOMPANIED BY DRY AIR ALOFT...WHICH IS PROVIDING FAIR CONDITIONS ACROSS THIS PORTION OF THE BASIN. HOWEVER...DIFFLUENCE ALOFT BETWEEN THE UPPER TROUGH AND AN UPPER LEVEL RIDGE OVER THE EASTERN CARIBBEAN ALONG 63W IS GENERATING SHOWERS AND ISOLATED THUNDERSTORMS FROM THE SW CARIBBEAN TO HISPANIOLA AND COVERING MUCH OF THE CENTRAL CARIBBEAN. THIS ACTIVITY IS ALSO BEING GENERATED BY SURFACE CONVERGENCE BETWEEN TRADEWIND FLOW COMING FROM THE EAST AND NORTHERLY FLOW PRESENT OVER THE WESTERN CARIBBEAN. THIS CONVERGENCE BECOMES CONCENTRATED AROUND A WEAK 1010 MB SURFACE LOW IN THE FAR SW GULF NEAR 11N77W AT THE END OF THE MONSOON TROUGH AXIS WHICH EXTENDS ACROSS NORTHERN PANAMA TO THE LOW CENTER. OVER THE EASTERN CARIBBEAN...FAIR CONDITIONS ARE PRESENT AS DRY AIR ALOFT IS PRESENT NEAR THE UPPER RIDGE AXIS. LITTLE CHANGE IS EXPECTED OVER THE NEXT COUPLE OF DAYS. ATLANTIC OCEAN... AN UPPER LEVEL LOW OVER SOUTH CAROLINA CONTINUES TO SUPPORT A STATIONARY FRONT ALONG 32N76W 30N78W 26N80W. SCATTERED SHOWERS AND THUNDERSTORMS ARE NEAR THE NORTHERN PORTIONS OF THE FRONT N OF 29N BETWEEN 76W-81W. HOWEVER...MOIST SOUTHWESTERLY FLOW ALOFT BETWEEN THE UPPER LOW/TROUGH AND AN UPPER LEVEL RIDGE EXTENDING FROM THE EASTERN CARIBBEAN INTO THE ATLC TO NEAR 35N55W IS HELPING SUPPORT A LARGE AREA OF OVERCAST SKIES BETWEEN 60W-75W WITH SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS FROM 21N-28N BETWEEN 65W-71W WITH ISOLATED ACTIVITY ELSEWHERE. MORE SCATTERED ACTIVITY IS ALSO NEAR A SURFACE TROUGH IN THE MIDDLE ALONG 32N63W TO 25N66W. THE UPPER LEVEL RIDGE IN THE CENTRAL ATLC FEEDS INTO A BROAD UPPER RIDGE OVER THE NE ATLC SUPPORTING A BROAD SURFACE RIDGE ANCHORED BY A 1028 MB HIGH NEAR 34N34W...WHICH CONTINUES INTO THE TROPICAL ATLC. HOWEVER...AN UPPER LEVEL TROUGH SOUTH OF THE RIDGE ALONG 28N33W TO 9N50W IS SUPPORTING A SURFACE TROUGH ALONG 19N35W TO 13N44W. SURFACE CONVERGENCE ALONG WITH DIFFLUENCE ALOFT IS GENERATING SCATTERED SHOWERS/POSSIBLE THUNDERSTORMS FROM 14N-23N BETWEEN 28W-41W. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ WALTON