000 AXNT20 KNHC 092313 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 705 PM EST SUN DEC 09 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 2230 UTC. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS ACROSS WEST AFRICA TO THE COAST OF GUINEA NEAR 10N15W CONTINUING TO 9N17W WHERE IT TRANSITIONS INTO THE ITCZ ALONG 6N24W 4N34W 7N47W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 4N-7N BETWEEN 23W-36W. SIMILAR ACTIVITY IS FROM 7N-9N BETWEEN 45W-50W. CONVECTION CONTINUES FARTHER WEST...BUT IS ASSOCIATED WITH A SURFACE TROUGH AS WELL AS AN UPPER LEVEL TROUGH. THIS CONVECTION WILL BE DISCUSSED IN THE ATLC SECTION. ...DISCUSSION... THE GULF OF MEXICO... MAINLY SOUTHWEST-WEST FLOW ALOFT COVERS THE GULF OF MEXICO AROUND AN UPPER LEVEL RIDGE WITH AXIS EXTENDING FROM THE NW CARIBBEAN TO JUST EAST OF FLORIDA. WATER VAPOR IMAGERY INDICATES THAT DRY AIR COVERS THE MAJORITY OF THE AREA...WHICH IS HELPING PROVIDE FAIR CONDITIONS AT THE SURFACE. WEAK SURFACE RIDGING ALSO CONTINUES TO SIT OVER THE BASIN PROVIDING LIGHT ANTI-CYCLONIC FLOW OVER THE EASTERN GULF...AND SLIGHTLY STRONGER RETURN FLOW ACROSS THE WESTERN GULF REACHING UP TO 15-20 KT. THE SURFACE RIDGE IS EXPECTED TO WEAKEN FURTHER AND DISSIPATE AS A COLD FRONT ENTERS THE NW GULF EARLY MONDAY ACCOMPANIED BY SHOWERS/THUNDERSTORMS AND STRONG WINDS NEAR THE AXIS. THE CARIBBEAN SEA... AN UPPER LEVEL RIDGE COVERS THE WESTERN TWO-THIRDS OF THE CARIBBEAN WITH AXIS FROM PANAMA TO CENTRAL CUBA. WATER VAPOR IMAGERY INDICATES THAT DRY AIR SPREAD ACROSS THE MAJORITY OF THE BASIN...WHICH IS PROVIDING FAIR CONDITIONS THROUGHOUT. HOWEVER...A SURFACE TROUGH IS ANALYZED IN THE NW CARIBBEAN ALONG 86W FROM 17N-20N SUPPORTING SCATTERED SHOWERS FROM 19N-22N BETWEEN 85W-87W. SHOWERS/THUNDERSTORMS ARE ALSO FARTHER EAST FROM 17N-20N BETWEEN 80W-82W LIKELY DUE TO CONVERGING WIND SPEEDS. SCATTERED SHOWERS/ISOLATED THUNDERSTORMS ARE ALSO IN THE SW CARIBBEAN FROM 10N-13N BETWEEN 79W-83W ASSOCIATED WITH THE MONSOON TROUGH THAT EXTENDS FROM SOUTHERN COSTA RICA TO NORTHERN COLOMBIA. THE ONLY OTHER SHOWER ACTIVITY IS ANOTHER SMALL AREA OF SCATTERED SHOWERS/ISOLATED THUNDERSTORMS NORTH OF VENEZUELA FROM 12N-14N BETWEEN 67W-70W. THIS ACTIVITY MAY BE ENHANCED BY THE TAIL END OF AN UPPER TROUGH EXTENDING FROM THE CENTRAL ATLC. TRADEWIND FLOW OF 20-25 KT IS PRESENT ACROSS THE EASTERN AND CENTRAL CARIBBEAN...AND IS EXPECTED TO PERSIST THROUGHOUT MUCH OF THE WEEK. SHOWERS/THUNDERSTORMS WILL BE MOST LIKELY OVER THE WESTERN CARIBBEAN. THE ATLANTIC OCEAN... A WEAK SURFACE TROUGH IS OVER THE FAR WESTERN ATLC ALONG 33N80W TO 29N81W SUPPORTING SCATTERED SHOWERS UP TO 250 NM TO THE EAST AND ALSO EXTENDING SOUTHWARD. THE REMAINDER OF THE SW NORTH ATLC IS DOMINATED BY SURFACE RIDGING AROUND A 1026 MB HIGH NEAR 32N55W. THE RIDGE IS SUPPORTED BY AN UPPER LEVEL RIDGE EXTENDING FROM THE CARIBBEAN INTO THE W ATLC ALONG 79W. THE SURFACE RIDGE DOMINATES A GOOD PORTION OF THE CENTRAL ATLC AS WELL. FARTHER EAST...AN UPPER LEVEL TROUGH EXTENDS FROM WEST OF THE AZORES ISLANDS TO THE EASTERN CARIBBEAN ALONG 40N33W 23N47W 14N63W. THE UPPER TROUGH SUPPORTS A DISSIPATING STATIONARY FRONT ALONG 30N29W 21N34W WHERE IT TRANSITIONS INTO A SHEAR AXIS TO NEAR 15N52W. ISOLATED SHOWERS ARE WITHIN 60 NM OF THE FRONT...WITH SCATTERED SHOWERS WITHIN 150 NM OF THE SHEAR AXIS. A SURFACE TROUGH IS WEST OF THE FRONT ALONG 32N34W 27N36W 25N45W. POSSIBLE ISOLATED SHOWERS ARE ALONG THE AXIS. FINALLY...THE UPPER TROUGH ALSO SUPPORTS A SURFACE TROUGH NEAR THE ITCZ REGION WITH AXIS ALONG 14N56W 9N59W. SCATTERED SHOWERS/POSSIBLE THUNDERSTORMS ARE FROM 7N-15N BETWEEN 50W-56W. UPPER LEVEL RIDGING COVERS THE REMAINDER OF THE TROPICAL AND EASTERN ATLC. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ WALTON