000 AXNT20 KNHC 171143 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 705 PM EST SAT DEC 17 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1115 UTC. ...ITCZ/MONSOON TROUGH... THE INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM 06N11W TO 06N29W TO 05N39W TO 06N54W. WIDELY SCATTERED MODERATE CONVECTION IS FROM 04N-08N BETWEEN 23W-43W. ...DISCUSSION... GULF OF MEXICO... AN UPPER LEVEL RIDGE REMAINS ANCHORED IN THE WESTERN CARIBBEAN SEA AND EXTENDS NORTHWARD CONTINUING TO IMPACT MUCH OF THE EASTERN GULF AND FLORIDA PENINSULA THIS MORNING. HOWEVER...A WEAK MIDDLE TO UPPER LEVEL SHORTWAVE MOVING ACROSS THE CREST OF THE RIDGE OVER THE SE CONUS SUPPORTS A COLD FRONT ANALYZED INTO THE GULF NEAR 30N87W THEN SW TO 28N93W BECOMING STATIONARY ALONG 26N95W TO 22N96W AND INLAND OVER EAST-CENTRAL MEXICO. A FEW ISOLATED SHOWERS ARE NOTED ON MOSAIC DOPPLER RADAR IMAGERY WITHIN 60 NM EITHER SIDE OF THE FRONT...HOWEVER THE MAIN IMPACT WITH THE FRONT IS INCREASED NORTHERLY WINDS IN THE RANGE OF 15 TO 20 KT AND MOSTLY OVERCAST SKIES. THE FRONT IS FORECAST TO REMAIN STATIONARY TODAY AND DISSIPATE FURTHER OVER THE DURATION OF THE WEEKEND. AS THE FRONT DISSIPATES...SURFACE HIGH PRESSURE WILL BUILD ACROSS THE GULF THROUGH THE REMAINDER OF THE WEEKEND WITH NORTHEASTERLY WINDS PERSISTING THROUGH SUNDAY NIGHT. BY MONDAY...SOUTHERLY RETURN FLOW IS EXPECTED TO RE-ESTABLISH OVER PORTIONS OF THE WESTERN GULF AS A AREA OF LOW PRESSURE DEVELOPS OVER NORTH TEXAS AND OKLAHOMA. CARIBBEAN SEA... AN UPPER LEVEL ANTICYCLONIC CIRCULATION INFLUENCES MUCH OF THE WESTERN CARIBBEAN CENTERED NEAR 16N80W WITH AXIS EXTENDING NORTHWARD ALONG 80W. ON THE SOUTHERN PERIPHERY OF THE RIDGE... S-SE DIFFLUENT FLOW ALOFT CONTINUES TO ENHANCE SCATTERED SHOWERS AND TSTMS S OF 16N BETWEEN 76W-83W. MOST OF THIS CONVECTIVE ACTIVITY IS FOCUSED NORTH OF THE MONSOON TROUGH AXIS EXTENDING FROM THE E PACIFIC ALONG 09N TO NORTHERN COLOMBIA. OTHERWISE THE REMAINDER OF THE WESTERN CARIBBEAN W OF 70W IS UNDER STRONG NE TRADES DUE TO AN INCREASED PRESSURE GRADIENT FROM A 1023 MB HIGH CENTERED OVER THE SW NORTH ATLC. FARTHER EAST...A VERY DRY AND STABLE ATMOSPHERE IS NOTED UNDER NW FLOW ALOFT ON THE SOUTHWESTERN PERIPHERY OF AN UPPER LEVEL LOW CENTERED NEAR 27N50W AND ASSOCIATED TROUGHING E OF 70W. HOWEVER...A SHEAR LINE EXTENDS ACROSS THE SE CARIBBEAN FROM 12N60W TO 12N72W WITH WIDELY SCATTERED LOW-TOPPED SHOWERS OCCURRING WITHIN 90 NM EITHER SIDE OF THE BOUNDARY AS IT CONTINUES TO BECOME MORE DIFFUSE. EARLIER ASCAT PASSES AROUND 17/0110 UTC AND 17/0252 UTC INDICATED STRONG NE WINDS WERE OCCURRING IN WAKE OF THE SHEAR LINE AXIS ACROSS MUCH OF THE EASTERN AND CENTRAL CARIBBEAN BETWEEN 62W-77W IN THE RANGE OF 20 TO 25 KT. A SECONDARY AREA OF LOW-LEVEL MOISTURE CONVERGENCE EMBEDDED WITHIN THE STRONGER NE TRADES IS GENERATING ISOLATED SHOWERS N OF 15N E OF 70W... INCLUDING PUERTO RICO...THE US/UK VIRGIN ISLANDS...AND LEEWARD ISLANDS. HIGH PRESSURE IS FORECAST TO REMAIN ANCHORED NE OF THE BAHAMAS THROUGH THE REMAINDER OF THE WEEKEND MAINTAINING THE AREA OF INCREASED E-NE TRADES. ATLANTIC OCEAN... AN UPPER LEVEL RIDGE ANCHORED IN THE WESTERN CARIBBEAN SEA CONTINUES TO INFLUENCE THE SW NORTH ATLC W OF 60W. A MOSTLY DRY AND STABLE AIRMASS IS ASSOCIATED WITH THIS UPPER LEVEL FEATURE AND CONTINUES TO SUPPORT A 1023 MB SURFACE HIGH CENTERED NEAR 29N71W. WINDS HAVE GENERALLY BECOME LIGHT NEAR THE HIGH CENTER AND TO THE E OF 62W. A FEW FAST-MOVING ISOLATED SHOWERS ARE STILL POSSIBLE WITHIN THE SCATTERED TO BROKEN STRATOCUMULUS CLOUDS THIS MORNING GENERALLY S OF 30N W OF 56W. FARTHER EAST... AN UPPER LEVEL LOW CENTERED NEAR 27N50W SUPPORTS A COMPLEX AREA OF LOW PRESSURE ACROSS THE CENTRAL ATLC FOCUSED ON A NEARLY STATIONARY 1007 MB LOW NEAR 26N50W. A PAIR OF COLD FRONTS STEM FROM THE LOW...WITH THE PRIMARY FRONT SLOWLY DISSIPATING FROM 29N48W TO 24N46W TO 16N50W TO 14N55W WHERE IT TRANSITIONS TO A SHEAR LINE TO 12N62W. A SECONDARY COLD FRONT IS ANALYZED FROM THE LOW SW TO 18N56W. A PRE-FRONTAL TROUGH IS LOCATED EAST OF THE PRIMARY FRONT ALONG 10N52W TO 18N48W. LOW-LEVEL CONVERGENCE EAST OF THE SURFACE TROUGH AND FRONT ALONG WITH STRONG MIDDLE TO UPPER LEVEL DIFFLUENCE IS GENERATING A BROAD AREA OF SCATTERED SHOWERS AND ISOLATED TSTMS FROM 10N-32N BETWEEN 40W-48W. A FEW ISOLATED SHOWERS ARE ALSO OCCURRING IN THE VICINITY OF THE LOW CENTER FROM 24N-29N BETWEEN 48W-54W IN ASSOCIATION WITH THE MIDDLE TO UPPER LEVEL LOW. THE REMAINDER OF THE EASTERN ATLC IS UNDER THE INFLUENCE OF A SURFACE RIDGE ANCHORED BY A 1033 MB HIGH CENTERED SE OF THE AZORES NEAR 36N23W. THE RIDGE AXIS EXTENDS SW FROM THE HIGH TO 20N40W. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ HUFFMAN