000 AXNT20 KNHC 311745 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 105 PM EST SAT DEC 31 2011 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 1715 UTC. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 05N03W TO 04N15W. THE INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM 04N15W TO 01N35W TO 02N44W TO 01N50W. ISOLATED MODERATE CONVECTION IS FROM 02N-06N BETWEEN 09W-15W...AND FROM 03N-06N BETWEEN 22W-31W. ...DISCUSSION... GULF OF MEXICO... WATER VAPOR IMAGERY INDICATES MOSTLY WEST-SOUTHWESTERLY UPPER LEVEL FLOW OVER THE GULF THIS AFTERNOON AS AN UPPER LEVEL SHORTWAVE TROUGH CONTINUES MOVING E-NE OF THE REGION OVER NORTHERN FLORIDA INTO THE SW NORTH ATLC. AT THE SURFACE...A RIDGE ANCHORED BY A PAIR OF 1022 MB HIGHS CENTERED NEAR 27N81W AND 27N89W IS FOR THE TIME BEING KEEPING A FRONTAL BOUNDARY ANALYZED FROM THE SE CONUS TO THE LOUISIANA AND TEXAS COASTAL PLAIN AT BAY WITH MOSTLY S TO SW WINDS OVER THE NW AND NORTH-CENTRAL GULF. ELSEWHERE...A SURFACE TROUGH IS ANALYZED OVER THE SW GULF FROM 22N91W. WITH VERY LITTLE LOW TO MIDDLE LEVEL MOISTURE TO WORK WITH...ISOLATED SHOWERS REMAIN POSSIBLE E OF 92W ON THE MOIST SOUTHERLY RETURN FLOW. THE NEXT COLD FRONT IS FORECAST TO ENTER THE NW GULF WATERS EARLY SUNDAY INTRODUCING STRONG NORTH-NORTHEASTERLY WINDS BASIN-WIDE INTO EARLY NEXT WEEK. THEREAFTER A STRONG RIDGE WILL REMAIN IN PLACE OVER THE SE CONUS AND NORTHERN GULF THROUGH THE REMAINDER OF THE UPCOMING WEEK AHEAD. CARIBBEAN SEA... BROAD UPPER LEVEL RIDGING IS ACROSS THE CARIBBEAN WITH WATER VAPOR IMAGERY INDICATING DRY AIR AND SUBSIDENCE EXTENDING BETWEEN THE TROPICAL NORTH ATLC ALONG 45W TO CENTRAL AMERICA AND SOUTHERN MEXICO ALONG 90W. WITH A STABLE ATMOSPHERE ALOFT...THE BASIN REMAINS TRANQUIL CONVECTIVELY...HOWEVER...AT THE SURFACE...A MODEST PRESSURE GRADIENT BETWEEN A SURFACE RIDGE OVER THE WESTERN AND CENTRAL ATLC AND LOWER PRESSURE OVER NORTHERN SOUTH AMERICA IS PRODUCING STRONG E-NE TRADES IN THE RANGE OF 20 TO 30 KT. THESE CONDITIONS ARE EXPECTED TO PERSIST THROUGH EARLY MONDAY OF NEXT WEEK AS A COLD FRONT AND FRONTAL TROUGH ENTER THE SW NORTH ATLC AND NW CARIBBEAN RELAXING THE PRESSURE GRADIENT AND DIMINISHING THE TRADES. WEST OF THE ANTICIPATED COLD FRONT...STRONG N-NE WINDS ARE EXPECTED. ATLANTIC OCEAN... WATER VAPOR IMAGERY SHOWS AN UPPER LEVEL SHORTWAVE TROUGH PROGRESSING OVER THE NW PORTION OF THE SW NORTH ATLC WITH AXIS FROM 35N77W TO 30N80W THAT SUPPORTS A WEAK SURFACE TROUGH ANALYZED FROM THE NW BAHAMAS NEAR 27N77W TO 32N77W. ISOLATED SHOWERS ARE NOTED ON SATELLITE IMAGERY EAST OF THE AXIS FROM 28N-32N BETWEEN 74W-78W. TO THE SE...THE SURFACE WEAKNESS WITHIN THE SUBTROPICAL RIDGE CONTINUES AS ANOTHER SURFACE TROUGH EXTENDS FROM 20N73W TO 25N71W. ISOLATED SHOWERS ARE OCCURRING WITHIN 90 NM EITHER SIDE OF THE BOUNDARY. EAST OF 68W TO THE AFRICAN COAST...ACROSS THE REMAINDER OF THE CENTRAL AND EASTERN ATLC...AN EXPANSIVE AND RELATIVELY STRONG 1039 MB HIGH IS CENTERED SE OF THE AZORES NEAR 35N22W. THE INFLUENCE OF THE RIDGE EXPANDS SOUTHWARD TO 10N AND EXHIBITS AN AXIS EXTENDING FROM THE HIGH W-SW ALONG 32N45W TO 28N67W. WITH SUCH A STRONG HIGH PRESSURE SYSTEM IN PLACE...A STRONG PRESSURE GRADIENT EXISTS WITH GENERALLY MODERATE TO STRONG E-NE TRADES. EARLY MORNING ASCAT PASSES FROM 31/1028 UTC AND 31/1208 UTC INDICATED THESE STRONG TRADES WITH POSSIBLE INTERMEDIATE GALE FORCE NE WINDS IN THE AREA FROM 13N-23N E OF 30W...WHICH INCLUDES THE WATERS SURROUNDING THE CAPE VERDE ISLANDS. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ HUFFMAN