000 AXNT20 KNHC 041748 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 105 PM EST THU DEC 04 2008 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1715 UTC. ...THE ITCZ... THE ITCZ AXIS IS ANALYZED ALONG 8N12W 6N21W 3N32W 5N43W 6N57W. SCATTERED MODERATE CONVECTION IS FROM 2N-5N BETWEEN 8W-14W. SCATTERED MODERATE CONVECTION IS ALSO S OF 6N BETWEEN 22W-34W. ...DISCUSSION... GULF OF MEXICO... STRONG SOUTHWESTERLY FLOW ALOFT COVERS THE GULF REGION...AS A DEEP LAYER TROUGH MOVES EASTWARD OVER THE E CONUS. AN ASSOCIATED SURFACE COLD FRONT IS MOVING SOUTHEASTWARD ACROSS THE NW GULF...EXTENDING FROM A 1018 MB SURFACE LOW IN S MISSISSIPPI NEAR 31N91W TO 27N94W TO NE MEXICO NEAR 24N100W AND EXTENDS FARTHER NORTHWESTWARD ACROSS N MEXICO. LOW LEVEL CONVERGENCE IN THE VICINITY OF THIS COLD FRONT... COMBINED WITH ATMOSPHERIC LIFT IN MOIST SOUTHWESTERLY FLOW ALOFT... IS SUPPORTING SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS ALONG AND WITHIN 60 NM AHEAD OF THE COLD FRONT. INCREASED N TO NE SURFACE WINDS ARE USHERING IN A RELATIVELY COOLER AND DRIER AIRMASS ACROSS THE S CONUS AND NW GULF IN THE WAKE OF THE COLD FRONT. THIS AIRMASS IS BEING SUPPORTED BY A STRONG SURFACE HIGH PRESSURE RIDGE EXTENDING FROM THE PLAINS OF THE CONUS NORTHWESTWARD ACROSS THE NORTHERN ROCKY MOUNTAINS. OVER THE W GULF...A SURFACE TROUGH INTERSECTS THE COLD FRONT NEAR 25N97W AND EXTENDS FARTHER SOUTHWARD FROM 25N97W TO 21N96W TO 19N94W. LOW LEVEL CONFLUENCE NEAR THIS SURFACE TROUGH IS ENHANCING THE SHOWER AND THUNDERSTORM ACTIVITY ASSOCIATED WITH THE COLD FRONT N OF 24N. DEEP LAYER DRY AIR IS INHIBITING DEEP CONVECTION OVER THE SE GULF...WHERE GENERALLY FAIR WEATHER PREVAILS. OVER THE NEXT DAY...THE COLD FRONT IS FORECAST TO CONTINUE MOVING SOUTHEASTWARD OVER THE GULF...BUT IS EXPECTED TO SLOW ITS PROGRESS AS THE STRONGEST UPPER LEVEL ENERGY LIFTS NORTHEAST OF THE GULF REGION. ADDITIONALLY...STRONG N SURFACE WINDS ARE FORECAST TO BLOW THROUGH THE ISTHMUS OF TEHUANTEPEC RESULTING IN GALE FORCE WINDS IN THE EAST PACIFIC REGION BEGINNING AT 05/0600 UTC. CARIBBEAN SEA... AN UPPER HIGH IS CENTERED S OF THE DOMINICAN REPUBLIC NEAR 16N70W...WITH AN UPPER RIDGE AXIS EXTENDING FROM THE UPPER HIGH TO THE NE CARIBBEAN NEAR 18N63W INTO THE W ATLC. UPPER LEVEL DIFFLUENCE SW OF THE UPPER HIGH IS COMBINING WITH DEEP MOISTURE OVER THE SW CARIBBEAN TO RESULT IN NUMEROUS SHOWERS AND SCATTERED THUNDERSTORMS S OF 14N W OF 78W. THIS ACTIVITY IS BEING ENHANCED BY LOW LEVEL CONVERGENCE IN THE VICINITY OF A SURFACE TROUGH EXTENDING FROM 13N79W TO 11N80W TO N OF PANAMA NEAR 9N80W. FARTHER TO THE E...A SECOND SURFACE TROUGH EXTENDS FROM 16N76W TO 13N76W TO N OF COLOMBIA NEAR 10N76W...WITH SCATTERED SHOWERS WITHIN 60 NM EITHER SIDE OF THIS SURFACE TROUGH. ALSO...A SURFACE STATIONARY FRONT OVER THE NW CARIBBEAN EXTENDS FROM E OF THE YUCATAN PENINSULA NEAR 20N86W TO CENTRAL CUBA NEAR 22N79W TO THE W ATLC...WITH SCATTERED SHOWERS WITHIN 60 NM EITHER SIDE OF THIS STATIONARY FRONT. NEAR AND E OF THE AFOREMENTIONED UPPER HIGH NEAR 16N70W...FAIR WEATHER CONDITIONS PERSIST OVER THE E CARIBBEAN WHERE DEEP LAYER SUBSIDENCE IS ENHANCING STABLE ATMOSPHERIC CONDITIONS IN THE PRESENCE OF DEEP LAYER DRY AIR. ATLANTIC OCEAN... SOUTHWESTERLY FLOW ALOFT CONTINUES TO INCREASE OVER THE W ATLC AS THE DEEP TROUGH OVER THE E CONUS PROGRESSES EASTWARD. A SURFACE TROUGH E OF THE FLORIDA PENINSULA EXTENDS FROM 31N81W TO 28N80W TO 26N79W. HOWEVER...THE PRESENCE OF DEEP LAYER DRY AIR ACROSS THE W ATLC IS INHIBITING DEEP CONVECTION NEAR THE SURFACE TROUGH. FARTHER TO THE E...A SURFACE STATIONARY FRONT EXTENDS FROM CENTRAL CUBA NEAR 22N79W TO THE BAHAMAS NEAR 23N74W TO 25N68W...WITH A SURFACE COLD FRONT EXTENDING FROM 25N68W TO 29N62W TO 32N57W TO NE OF THE DISCUSSION AREA. LOW LEVEL CONVERGENCE IS SUPPORTING ISOLATED SHOWERS WITHIN 60 NM EITHER SIDE OF THE SURFACE STATIONARY FRONT AND COLD FRONT. E OF THESE FRONTS...THE FLOW ALOFT IS MORE AMPLIFIED... WITH AN UPPER RIDGE AXIS EXTENDING FROM THE NE CARIBBEAN NEAR 18N63W TO 25N56W TO 32N49W TO NE OF THE DISCUSSION AREA AND A SHARP UPPER LEVEL TROUGH N OF 14N BETWEEN 37W-46W. THIS UPPER TROUGH IS ASSOCIATED WITH AN UPPER LOW NEAR 32N40W...AS WELL AS A SURFACE TROUGH EXTENDING FROM A 1011 MB SURFACE LOW NEAR 29N48W TO 29N45W TO A 1012 MB SURFACE LOW NEAR 25N44W TO 20N48W. LOW LEVEL CONVERGENCE NEAR THESE SURFACE LOWS AND TROUGHS IS SUPPORTING SCATTERED SHOWERS N OF 21N BETWEEN 41W-48W. E OF THE UPPER TROUGH AXIS...NUMEROUS SHOWERS AND ISOLATED THUNDERSTORMS N OF 22N BETWEEN 32W-38W ARE BEING SUPPORTED BY STRONG ATMOSPHERIC LIFT ASSOCIATED WITH A 90-100 KT JET MAXIMUM...ALONG WITH THE PRESENCE OF INCREASED DEEP MOISTURE. OVER THE E ATLC... SUBSIDENCE AND FAIR WEATHER PREVAIL IN THE VICINITY OF A SURFACE RIDGE EXTENDING FROM A 1029 MB SURFACE HIGH NEAR 34N21W TO 26N22W TO 19N25W. FARTHER TO THE S...AN UPPER RIDGE IS S OF 19N BETWEEN THE AFRICAN COAST AND 35W...WITH AN UPPER HIGH NEAR 9N29W. UPPER LEVEL DIVERGENCE ASSOCIATED WITH THE UPPER HIGH AND UPPER RIDGE IS SUPPORTING SCATTERED SHOWERS FROM 13N-16N BETWEEN 23W-31W...AS WELL AS THE CONVECTION ASSOCIATED WITH THE ITCZ. $$ COHEN