000 AXNT20 KNHC 181757 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 105 PM EST WED DEC 18 2013 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 INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS ALONG 06N15W TO 06N28W TO THE EQUATOR NEAR 45W. ISOLATED MODERATE CONVECTION IS FROM 03N-09N BETWEEN 11W-34W. A SURFACE TROUGH IS ANALYZED FROM THE ITCZ AXIS NEAR 07N28W TO THE CAPE VERDE ISLANDS NEAR 15N24W IN ASSOCIATION WITH A VIGOROUS MIDDLE TO UPPER LEVEL LOW CENTERED NEAR 18N31W. WITH PLENTY OF MOISTURE ADVECTION OCCURRING WITHIN THE AREA OF MAXIMUM MIDDLE TO UPPER LEVEL DIFFLUENCE...SCATTERED MODERATE CONVECTION IS OCCURRING FROM 09N- 21N BETWEEN 15W-27W. ...DISCUSSION... GULF OF MEXICO... WATER VAPOR IMAGERY INDICATES A VERY BROAD MIDDLE TO UPPER LEVEL LONGWAVE TROUGH MOVING OFFSHORE OF THE NE AND MID-ATLC CONUS WITH A BASE NOTED OVER PORTIONS OF THE SW NORTH ATLC...FLORIDA PENINSULA...AND THE NE GULF. ON THE SOUTHWESTERLY PERIPHERY OF THE TROUGHING...PRIMARILY WEST-NORTHWESTERLY DRY AIR AND STABLE FLOW ALOFT CONTINUES TO INFLUENCE THE GULF THIS AFTERNOON. AT THE SURFACE...RIDGING FURTHER SUPPORTS THE STABILITY ALOFT ANCHORED BY A 1026 MB HIGH CENTERED ACROSS THE NW GULF NEAR 27N95W. NORTHEASTERLY WINDS IN THE RANGE OF 5 TO 15 KT...WITH THE EXCEPTION OF PORTIONS OF THE EASTERN GULF IN THE RANGE OF 10 TO 20 KT...ARE EXPECTED TO GRADUALLY VEER MORE EASTERLY BY EARLY THURSDAY. AS THE HIGH PRESSURE AREA IS SHIFTS EASTWARD OVERNIGHT INTO EARLY THURSDAY...E-SE FLOW WILL RE-ESTABLISH ACROSS THE NORTHWESTERN HALF OF THE BASIN AS AN AREA LOW PRESSURE BEGINS TO DEVELOP ACROSS THE CENTRAL HIGH PLAINS OF COLORADO...WESTERN KANSAS...AND THE TEXAS AND OKLAHOMA PANHANDLES. SOUTHERLY RETURN FLOW IS EXPECTED TO INCREASE BY THE WEEKEND ACROSS THE WESTERN GULF AHEAD OF THE NEXT COLD FRONT EXPECTED TO EMERGE OFF THE TEXAS AND LOUISIANA COASTS EARLY SUNDAY. CARIBBEAN SEA... SOUTH-SOUTHWESTERLY FLOW ALOFT CONTINUES OVER THE WESTERN CARIBBEAN W OF 70W BETWEEN BROAD TROUGHING TO THE NORTH OVER THE FLORIDA PENINSULA AND AN UPPER LEVEL RIDGE OVER THE CENTRAL CARIBBEAN WITH AXIS ALONG 70W. WATER VAPOR IMAGERY INDICATES AMPLE MIDDLE TO UPPER LEVEL MOISTURE ADVECTION IS OCCURRING OVER CENTRAL AMERICA AND THE WESTERN CARIBBEAN THAT CONTINUES TO SUPPORT WIDELY SCATTERED SHOWERS AND ISOLATED TSTMS GENERALLY WEST OF 76W. LOW-LEVEL MOISTURE CONVERGENCE OF THE TRADES...IN TANDEM WITH THE FAVORABLE MIDDLE TO UPPER LEVEL DYNAMICS IS GENERATING THIS ACTIVITY WITH THE MOST INTENSE CONVECTION OCCURRING S OF 12N IN CLOSE PROXIMITY OF THE MONSOON TROUGH AXIS. FARTHER EAST...UPPER LEVEL WEST-NORTHWESTERLY FLOW E OF 70W REMAINS VERY DRY AND STABLE WITH MOSTLY FAIR SKIES AND CONDITIONS NOTED FOR HISPANIOLA...PUERTO RICO...AND THE LESSER ANTILLES. A FEW PASSING ISOLATED SHOWERS ARE HOWEVER POSSIBLE ACROSS THE EASTERN CARIBBEAN AS THESE SHOWERS REMAIN EMBEDDED WITHIN TRADE WINDS RANGING FROM 15 TO 25 KT. ...HISPANIOLA... CURRENTLY RELATIVELY DRY AIR AND STABLE CONDITIONS ALOFT PREVAIL WITH SATELLITE IMAGERY INDICATING ONLY LOWER LEVEL CLOUDINESS AND POSSIBLE ISOLATED SHOWERS OCCURRING ACROSS WESTERN PORTIONS OF THE ISLAND INCLUDING THE ADJACENT COASTAL WATERS BETWEEN 68W- 71W THIS AFTERNOON. THE OVERALL STABILITY WILL LIKELY LIMIT ANY SIGNIFICANT CONVECTION...HOWEVER AN ISOLATED SHOWER CANNOT BE RULED OUT DURING THE LATE AFTERNOON AND EARLY EVENING HOURS WITH PEAK DAYTIME HEATING AND INSTABILITY OCCURRING NEAR THE SURFACE. LOOKING AHEAD...A MOSTLY NORMAL PATTERN OF WINTER TIME TRADES IS EXPECTED TO CONTINUE ACROSS THE ISLAND WITH WINDS INCREASING SLIGHTLY THURSDAY INTO FRIDAY DUE TO A STRENGTHENING PRESSURE GRADIENT ACROSS THE REGION. THE STRONG TRADES WILL PERSIST DURING THE UPCOMING WEEKEND. ATLANTIC OCEAN... A BROAD MIDDLE TO UPPER LEVEL LONGWAVE TROUGH IS NOTED ON WATER VAPOR IMAGERY OFF THE NEW ENGLAND AND MID-ATLC COAST THAT SUPPORTS A STATIONARY FRONT ANALYZED INTO THE DISCUSSION AREA NEAR 32N63W EXTENDING SW TO THE CENTRAL BAHAMAS NEAR 24N76W THEN TO CENTRAL CUBA. ISOLATED SHOWERS AND TSTMS ARE OCCURRING WITHIN 150 NM EAST OF THE FRONT. WHILE THE FRONT IS FORECAST TO GRADUALLY WEAKEN AND BECOME DIFFUSE OVERNIGHT INTO THURSDAY...A COLD FRONT CURRENTLY ANALYZED FROM 33N72W TO 31N76W WILL BECOME THE PRIMARY BOUNDARY WEDNESDAY ACROSS THE SW NORTH ATLC. FARTHER EAST...THE REMAINDER OF THE CENTRAL AND EASTERN ATLC IS UNDER THE INFLUENCE OF A LARGE AREAL SURFACE RIDGE ANCHORED BY A 1033 MB HIGH CENTERED NEAR 33N31W. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ HUFFMAN