000 AXNT20 KNHC 200906 CCA TWDAT TROPICAL WEATHER DISCUSSION...CORRECTED NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 105 AM EST SAT DEC 20 2008 ...CORRECTED PHRASING OF THE LAST SENTENCE IN GULF OF MEXICO SECTION... 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...METEOROLOGICAL ANALYSIS...WEATHER OBSERVATIONS...AND RADAR. BASED ON 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0445 UTC. ...THE ITCZ... ITCZ IS CENTERED ALONG 9N14W 7N21W 6N34W 4N42W TO THE EQUATOR AT 49W. SCATTERED MODERATE CONVECTION IS FROM 4N-8N BETWEEN 15W-25W. NUMEROUS MODERATE/ISOLATED STRONG CONVECTION IS FROM 1N-10N BETWEEN 27W-38W. ...DISCUSSION... GULF OF MEXICO... A 1023 MB SURFACE HIGH IS OVER THE W ATLC NEAR 28N73W...WITH SURFACE ANTICYCLONIC FLOW OF 10 TO 20 KT AROUND THIS HIGH ACROSS MUCH OF THE GULF REGION. SUBSIDENCE ASSOCIATED WITH THIS HIGH IS RESULTING IN ATMOSPHERIC STABILITY AND FAIR WEATHER CONDITIONS ACROSS MUCH OF THE GULF REGION. THIS STABILITY IS BEING ENHANCED IN THE VICINITY OF A BROAD UPPER LEVEL RIDGE EXTENDING WESTWARD ACROSS THE GULF REGION FROM AN UPPER HIGH CENTERED N OF CUBA NEAR 24N78W. THIS UPPER RIDGE IS ASSOCIATED WITH RELATIVELY LIGHT AND BROAD ANTICYCLONIC FLOW ALOFT...AND DEEP LAYER DRY AIR...ACROSS MUCH OF THE GULF REGION. FARTHER TO THE N...A DEEP LONGWAVE TROUGH AND ASSOCIATED STRONG UPPER LEVEL JET STREAM OVER THE CENTRAL CONUS IS SUPPORTING A SURFACE FRONT EXTENDING FROM THE MID-ATLANTIC STATES ACROSS THE SOUTHERN PLAINS AND INTO THE SOUTHERN ROCKY MOUNTAIN REGION OF THE CONUS. THIS TROUGH IS FORECAST TO MOVE EAST-SOUTHEASTWARD...WITH THE FRONT MOVING SOUTHWARD ACROSS THE GULF ON SUNDAY AND MONDAY AS A COLD FRONT. INCREASED NE TO E SURFACE WINDS ARE FORECAST IN THE WAKE OF THE FRONT...WITH GALE FORCE WINDS EXPECTED SUNDAY AFTERNOON AND EVENING FOR PORTIONS OF THE NW GULF. CARIBBEAN SEA... CONFLUENCE IN WESTERLY FLOW ALOFT IS GENERATING SUBSIDENCE AND ATMOSPHERIC STABILITY ACROSS THE CARIBBEAN REGION...WHERE GENERALLY DEEP LAYER DRY AIR IS PRESENT. THESE FACTORS ARE RESULTING IN FAIR WEATHER CONDITIONS ACROSS MUCH THE CARIBBEAN REGION. THE SOUTHERN PERIPHERY OF THE ANTICYCLONIC FLOW AROUND THE AFOREMENTIONED 1023 MB SURFACE HIGH OVER THE W ATLC NEAR 28N73W IS BRINGING NE SURFACE WINDS OF 15 TO 20 KT TO THE CARIBBEAN REGION...EXCEPT UP TO 25 KT NEAR THE COAST OF COLOMBIA. UPPER LEVEL MOISTURE IS STREAMING NORTHWARD FROM SOUTH AMERICA INTO THE S CARIBBEAN...WITH ISOLATED SHOWERS ACROSS THE S CARIBBEAN S OF 15N E OF 76W. ALSO...A SURFACE TROUGH EXTENDS FROM THE W ATLC NEAR 24N60W TO 20N64W TO THE NE CARIBBEAN NEAR 17N65W...WITH SATELLITE IMAGERY DEPICTING CYCLONIC MOTION OF CLOUDS IN THE VICINITY OF THIS SURFACE TROUGH. LOW LEVEL CONVERGENCE IS RESULTING IN ISOLATED SHOWERS WITHIN 60 NM EITHER SIDE OF THIS SURFACE TROUGH. ATLANTIC OCEAN... ACROSS THE W ATLC...A 1023 MB SURFACE HIGH IS CENTERED NEAR 28N73W...WHICH IS BRINGING SUBSIDENCE AND FAIR WEATHER CONDITIONS TO MUCH OF THE W ATLC. THIS SUBSIDENCE IS BEING ENHANCED IN THE VICINITY OF THE UPPER HIGH N OF CUBA NEAR 24N78W. NORTHERLY UPPER LEVEL FLOW TO THE E OF THIS UPPER HIGH IS ADVECTING UPPER LEVEL MOISTURE ACROSS PORTIONS OF THE W ATLC. FARTHER TO THE E...A SURFACE TROUGH OVER THE CENTRAL ATLC EXTENDS FROM 30N45W TO 26N49W TO 23N47W. LOW LEVEL CONVERGENCE ASSOCIATED WITH THIS SURFACE TROUGH IS RESULTING IN NUMEROUS SHOWERS FROM 23N-30N BETWEEN 40W-47W. THIS ACTIVITY IS BEING ENHANCED BY ATMOSPHERIC INSTABILITY IN THE VICINITY OF AN UPPER TROUGH WITH AN AXIS EXTENDING FROM 19N59W TO 27N51W TO 32N48W TO N OF THE DISCUSSION AREA. ALSO...UPPER LEVEL DIVERGENCE IN THE NE QUADRANT OF AN 80-90-KT UPPER LEVEL JET MAXIMUM E OF THIS UPPER TROUGH AXIS IS SUPPORTING THIS ACTIVITY...ALONG WITH LOW LEVEL CONVERGENCE ASSOCIATED WITH A SURFACE STATIONARY FRONT EXTENDING FROM NW OF THE DISCUSSION AREA TO 32N59W TO 31N56W AND A SURFACE COLD FRONT EXTENDING FROM 31N56W TO 32N59W TO NE OF THE DISCUSSION AREA. ACROSS THE E ATLC...SUBSIDENCE ASSOCIATED WITH A SURFACE RIDGE EXTENDING SOUTHWESTWARD FROM A 1036 MB SURFACE HIGH NEAR 45N10W IS GENERALLY INHIBITING DEEP CONVECTION N OF 18N E OF 34W. HOWEVER...ATMOSPHERIC INSTABILITY ASSOCIATED WITH AN UPPER LOW NEAR 31N18W IS RESULTING IN SCATTERED SHOWERS N OF 27N BETWEEN 16W-25W. FARTHER TO THE S...A SURFACE TROUGH EXTENDS FROM 24N60W TO 20N64W TO THE NE CARIBBEAN NEAR 17N65W...WITH SATELLITE IMAGERY DEPICTING CYCLONIC MOTION OF CLOUDS IN THE VICINITY OF THIS SURFACE TROUGH. LOW LEVEL CONVERGENCE IS RESULTING IN ISOLATED SHOWERS WITHIN 60 NM EITHER SIDE OF THIS SURFACE TROUGH. ALSO...AN UPPER RIDGE IS S OF 12N BETWEEN 16W-51W. UPPER LEVEL DIFFLUENCE ASSOCIATED WITH THIS UPPER RIDGE IS ENHANCING THE CONVECTION ASSOCIATED WITH THE ITCZ. THIS UPPER LEVEL DIFFLUENCE IS ALSO SUPPORTING SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS FROM 7N-11N BETWEEN 46W-56W. $$ COHEN