000 AXNT20 KNHC 152326 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 705 PM EST SAT DEC 15 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 2015 UTC. ...ITCZ/MONSOON TROUGH... THE INTERTROPICAL CONVERGENCE ZONE EXTENDS FROM THE AFRICAN COAST NEAR 7N12W TO 3N39W TO NORTHERN SOUTH AMERICA NEAR 2N51W. SCATTERED MODERATE TO STRONG CONVECTION LIES N OF THE EQUATOR TO 7N BETWEEN 33W-47W AS WELL AS FROM 3N-6N BETWEEN 24W AND 28W. ...DISCUSSION... GULF OF MEXICO... A BROAD UPPER RIDGE EXTENDS FROM THE EPAC WATERS S OF THE GULF OF TEHAUNTEPEC THROUGH THE BAY OF CAMPECHE AND INTO THE NE GULF OF MEXICO. STRONG WESTERLY FLOW ON THE NORTHERN PERIPHERY OF THE RIDGE IS BRINGING ABUNDANT MID/UPPER LEVEL MOISTURE INTO THE NORTHERN HALF OF THE GULF. A SURFACE RIDGE COVERS THE EASTERN TWO-THIRDS OF THE GULF...ANCHORED BY 1032 MB HIGH PRES LOCATED OVER QUEBEC CANADA AND EXTENDING ALONG THE U.S. EAST COAST THROUGH THE NORTHEAST GULF TO THE YUCATAN PENINSULA. 15 KT SOUTHERLY FLOW LIES OVER THE NW GULF ON THE W SIDE OF THE RIDGE AND AHEAD OF THE NEXT COLD FRONT FORECAST TO ENTER THE GULF WATERS SUN NIGHT. THE COLD FRONT WILL REACH FROM NEAR SE LOUISIANA TO THE SW GULF OF MEXICO MON. SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS WILL ACCOMPANY THE FRONT. THE RETURN FLOW IS FORECAST TO CONTINUE SPREADING EASTWARD THROUGH THE REST OF THE WEEKEND AS THE HIGH OVER THE CONUS SLIDES EAST INTO THE NORTH ATLC. SCATTEROMETER DATA ALONG WITH SURFACE OBSERVATIONS SHOW A GENTLE TO MODERATE E-SE BREEZE IS FOUND ACROSS THE REMAINDER OF THE AREA. CARIBBEAN SEA... AN UPPER TROUGH AXIS BISECTS THE CARIBBEAN ALONG 70W. THE AFOREMENTIONED BROAD UPPER RIDGE STEMMING FROM AN ANTICYCLONE IN THE EPAC DOMINATES THE REGION W OF THE TROUGH AXIS...WITH NW WINDS ALOFT FOUND OVER CUBA AND THE WESTERN CARIBBEAN. WATER VAPOR IMAGERY SHOWS DRY AIR AND IMPLIED SUBSIDENCE HERE. UPPER MOISTURE LIES AHEAD OF THE TROUGH IN THE VICINITY OF PUERTO RICO AND THE VIRGIN ISLANDS SOUTHWESTWARD TOWARD THE NE COAST OF COLOMBIA. UPPER LEVEL DIFFLUENCE IS HELPING TO LIFT MOISTURE THROUGH THE ATMOSPHERE HERE. A SURFACE REFLECTION OF THIS TROUGH WAS EVIDENT ON THE 1714 UTC OSCAT PASS...WITH A TROUGH ANALYZED FROM 17N71W TO 12N74W. WHILE THE SAN JUAN DOPPLER RADAR SHOWS ONLY ISOLATED SHOWERS IN THE LOW LEVELS....LIGHTNING DATA SHOWS THUNDERSTORMS LIE E OF THIS TROUGH TO THE MONA PASSAGE PRIMARILY N OF 14N. A RATHER WEAK PRES GRADIENT WILL PREVAIL ACROSS THE BASIN DURING THE NEXT SEVERAL DAYS PRODUCING GENTLE TO MODERATE TRADEWINDS INTO EARLY NEXT WEEK. ATLANTIC OCEAN... A WEAK SURFACE TROUGH PERSISTS JUST E OF FLORIDA AND EXTENDS ALONG 80W N OF 27N. DOPPLER RADAR REVEALS SOME SHOWER ACTIVITY NEAR THE TROUGH AXIS OFF THE NE FLORIDA COAST THAT EXTENDS NORTHWARD TOWARD THE COASTAL WATERS OFF THE BORDER OF NORTH AND SOUTH CAROLINA. THIS TROUGH IS EXPECTED TO LIFT NORTHWARD ALONG THE U.S. EAST COAST AHEAD OF A COLD FRONT MOVING THROUGH THE OHIO VALLEY SUN AND MON. A SURFACE RIDGE CENTERED PRIMARILY N OF THE AREA ALONG THE U.S. EAST COAST DOMINATES THE FLOW IN THE SW N ATLANTIC. GUSTY NE-E WINDS ON THE SOUTHERN PERIPHERY OF THE RIDGE ARE BRINGING PATCHES OF MOISTURE WITH EMBEDDED SHOWERS TO SOUTH FLORIDA...AFFECTING MAINLY THE E COAST S OF 26N AND THE STRAITS OF FLORIDA ACCORDING TO DOPPLER RADAR. THE UPPER TROUGH PASSING THROUGH THE CARIBBEAN SEA EXTENDS NORTHEASTWARD THROUGH THE DOMINICAN REPUBLIC TO 32N55W. THE NORTHERN PORTION OF THIS TROUGH SUPPORTS A WEAK COLD FRONT THAT EXTENDS FROM 32N53W TO 25N65W WHERE IT WEAKENS AND EXTENDS INTO THE CENTRAL BAHAMAS NEAR 24N75W. A NARROW BAND OF CLOUDS WITH ISOLATED SHOWERS IS ASSOCIATED WITH THE FRONT. THE SOUTHERN PORTION OF THE SUPPORTING UPPER TROUGH IS EXPECTED TO SEPARATE FROM THE NORTHERN STREAM PORTION OVER THE NEXT DAY OR SO...SENDING THE COLD FRONT EASTWARD TOWARD THE WEAKENING SYSTEM OVER THE CENTRAL ATLC. THE UPPER LOW PREVIOUSLY ASSOCIATED WITH THIS SYSTEM IN THE CENTRAL ATLC HAS OPENED UP INTO A TROUGH AS IT FEELS THE INFLUENCE OF THE SOUTHERLY FLOW ON THE EASTERN SIDE OF THE TROUGH SUPPORTING THE COLD FRONT APPROACHING FROM THE WEST. A DISTINCT SURFACE LOW IS STILL IN TACT FOR THE MOMENT...ANALYZED AS A 1010 MB LOW NEAR 20N52W WITH A SURFACE TROUGH THAT EXTENDS FROM 31N46W TO 25N52W THROUGH THE LOW PRES TO 13N57W. TO THE E OF THE SYSTEM...AN UPPER RIDGE IS PROVIDING DIFFLUENCE ALOFT TO SUPPORT SCATTERED SHOWERS AND POSSIBLE ISOLATED THUNDERSTORMS WITHIN 180 NM EITHER SIDE OF A LINE FROM 32N41W TO 21N45W...MORE CONCENTRATED N OF 30N. A SURFACE RIDGE DOMINATES THE E ATLC ANCHORED BY A 1026 MB HIGH NEAR 31N22W. THIS HIGH PRES WILL MOVE NE OF AREA IN ABOUT 24 HOURS. FRESH TRADE WINDS ARE BLOWING ON THE SOUTHERN PERIPHERY OF THE RIDGE. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ SCHAUER/GR