000 AXNT20 KNHC 172353 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 705 PM EST MON DEC 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 2315 UTC. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 08N13W TO 08N16W. THE INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM 08N16W TO 04N30W TO 02N45W. WIDELY SCATTERED MODERATE CONVECTION IS FROM 02N-06N BETWEEN 05W-18W. SCATTERED MODERATE CONVECTION IS FROM THE EQUATOR TO 07N BETWEEN 20W-44W...AND FROM 06N-10N BETWEEN 44W-49W. ...DISCUSSION... GULF OF MEXICO... A BROAD MIDDLE TO UPPER LEVEL TROUGH IS NOTED ON WATER VAPOR IMAGERY PROGRESSING EASTWARD OVER THE LOWER MISSISSIPPI RIVER VALLEY AND NW GULF WITH AXIS EXTENDING FROM 36N88W TO 24N101W. THIS TROUGHING SUPPORTS A COLD FRONT ANALYZED FROM THE SOUTH- CENTRAL LOUISIANA COAST NEAR 30N91W S-SW TO THE MEXICO COAST NEAR 23N98W. EXAMINING MOSAIC DOPPLER RADAR IMAGERY AND LIGHTNING DATA...IT APPEARS THE FRONT REMAINS MOSTLY DRY WITH THE MAIN IMPACTS OF A SIGNIFICANT WIND SHIFT AND MUCH COOLER AND DRIER AIRMASS FOLLOWING IN WAKE OF THE FRONT. TO THE EAST OF THE FRONT...SURFACE PRESSURE ANALYSIS INDICATES TROUGHING COVERS MUCH OF THE NORTHERN GULF N OF 28N...CENTRAL GULF BETWEEN 90W- 93W...AND SW GULF S OF 24N BETWEEN 90W-96W. A SURFACE TROUGH IS ANALYZED FROM THE FLORIDA PANHANDLE SW TO 26N94W AND IS PROVIDING MOST OF THE FOCUS FOR SCATTERED SHOWERS AND ISOLATED TSTMS OCCURRING WITHIN 120 NM EITHER SIDE OF THE BOUNDARY. ANOTHER SURFACE TROUGH EXTENDS FROM 24N94W TO 19N96W IN THE SW GULF WITH INCREASED CLOUDINESS AND POSSIBLE ISOLATED SHOWERS S OF 23N W OF 94W. THE COLD FRONT IS FORECAST TO SWEEP EAST OF THE BASIN BY LATE TUESDAY WITH HIGH PRESSURE DOMINATING ANCHORED BY A HIGH CENTERED IN THE VICINITY OF THE NE GULF WATERS. CARIBBEAN SEA... CONDITIONS ACROSS THE CARIBBEAN SEA BASIN REMAIN FAIRLY TRANQUIL THIS EVENING AS WATER VAPOR IMAGERY INDICATES VERY DRY AIR AND SUBSIDENCE PREVAILS. AN UPPER LEVEL ANTICYCLONIC CIRCULATION IS CENTERED NEAR 22N76W AND INFLUENCES MUCH OF THE NW CARIBBEAN. OVER THE EASTERN CARIBBEAN...AN UPPER LEVEL TROUGH AXIS EXTENDS FROM THE CENTRAL ATLC FROM 20N54W TO 16N65W TO 14N79W. AT THE SURFACE...A PAIR OF WEAK TROUGHS ARE ANALYZED FROM 14N-18N ALONG 64W...AND FROM 16N80W TO 20N81W. ISOLATED SHOWERS ARE OCCURRING OVER THE NE CARIBBEAN N OF 16N BETWEEN 61W-65W...AND FROM 16N-20N BETWEEN 79W-83W. OTHERWISE...TRADE WINDS PREVAIL IN THE RANGE OF 10 TO 20 KT WITH LITTLE CHANGE EXPECTED THROUGH MIDWEEK. ATLANTIC OCEAN... WITH A BROAD MIDDLE TO UPPER LEVEL TROUGH CURRENTLY LOCATED OVER THE SE CONUS AND APPROACHING FROM THE WEST...AN UPPER LEVEL ANTICYCLONIC CIRCULATION IS CENTERED OVER THE SW NORTH ATLC NEAR 22N76W AND EXTENDS A RIDGE AXIS N-NE TO BEYOND 32N70W. AT THE SURFACE HOWEVER...A SURFACE RIDGE ANCHORED BY A 1020 MB HIGH CENTERED NEAR 24N55W IS EXPECTED TO SHIFT EAST WITH INCREASED SOUTHWESTERLY WINDS N OF 29N W OF 60W TO IMPACT THE SW NORTH ATLC WATERS. CURRENTLY...SCATTERED SHOWERS AND ISOLATED TSTMS ARE BEGINNING TO SHIFT OFFSHORE AND REMAIN WEST OF A LINE FROM 29N81W TO 32N76W. FARTHER EAST...A WEAKENING SURFACE TROUGH IS ANALYZED ON THE SOUTHEASTERN PERIPHERY OF THE PREVIOUSLY MENTIONED SURFACE RIDGE FROM 30N46W TO 26N52W TO 24N61W. ISOLATED SHOWERS ARE OCCURRING WITHIN 90 NM EITHER SIDE OF THE BOUNDARY. FINALLY...AN UPPER LEVEL TROUGH AXIS EXTENDS FROM 32N43W TO 16N61W AND SUPPORTS A SURFACE TROUGH ANALYZED FROM 32N36W TO 22N46W. THE TROUGHING REPRESENTS A WEAKNESS IN THE SUBTROPICAL RIDGING ACROSS THE CENTRAL AND EASTERN ATLC WITH WIDELY SCATTERED SHOWERS AND ISOLATED TSTMS OCCURRING WITHIN 240 NM EITHER SIDE OF A LINE FROM 32N35W TO 20N41W TO 10N58W. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ HUFFMAN