000 AXNT20 KNHC 272338 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 705 PM EST THU NOV 27 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2315 UTC. ...THE ITCZ... THE ITCZ AXIS IS ANALYZED ALONG 7N12W 6N22W 6N33W 8N44W 6N58W. A SURFACE TROUGH...EXTENDING FROM 12N47W TO 10N48W TO 8N48W...IS EMBEDDED WITHIN THE ITCZ. SCATTERED MODERATE CONVECTION IS OCCURRING WITHIN 150 NM EITHER SIDE OF THIS SURFACE TROUGH. ELSEWHERE...SCATTERED MODERATE CONVECTION IS FROM 4N-6N BETWEEN 24W-33W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 5N-10N BETWEEN 33W-41W. ...DISCUSSION... GULF OF MEXICO... AN UPPER LEVEL RIDGE COVERS THE GULF REGION...WITH A 100-110 KT UPPER LEVEL JET ACROSS THE NORTHERN PERIPHERY OF THE RIDGE OVER THE SE CONUS AND NE GULF. UPPER LEVEL MOISTURE CONTINUES STREAMING ACROSS THE N GULF...WHILE DEEP LAYER DRY AIR IS PRESENT OVER THE S GULF. DEEP LAYER SUBSIDENCE AND STABLE ATMOSPHERIC CONDITIONS ARE RESULTING IN FAIR WEATHER CONDITIONS ACROSS MUCH OF THE GULF REGION. THIS DEEP LAYER SUBSIDENCE IS BEING ENHANCED ACROSS E PORTIONS OF THE GULF REGION...WHERE UPPER LEVEL CONVERGENCE IN THE SW QUADRANT OF THE UPPER JET IS SUPPORTING A 1022 MB SURFACE HIGH OVER THE NE GULF NEAR 28N84W. FARTHER NW...A DEEP TROUGH OVER THE GREAT BASIN OF THE W CONUS IS SUPPORTING A SURFACE FRONT THAT EXTENDS FROM THE UPPER MIDWEST TO THE SOUTHERN PLAINS AND EXTENDS ACROSS THE CENTRAL ROCKIES OF THE CONUS. AS THE DEEP TROUGH MOVES EASTWARD...THE SURFACE FRONT WILL MOVE SOUTHWARD ACROSS THE N GULF THIS WEEKEND...WITH SOUTHERLY FLOW INCREASING AHEAD OF THE COLD FRONT. THE FRONT WILL ALSO BE ACCOMPANIED BY A CHANCE OF SHOWERS AND THUNDERSTORMS ALONG THE TEXAS AND LOUISIANA COASTS. IN THE WAKE OF THE COLD FRONT...INCREASED NORTHERLY AND NORTHWESTERLY SURFACE WINDS ARE EXPECTED...ALONG WITH RELATIVELY COOLER AND DRIER CONDITIONS. CARIBBEAN SEA... IN THE SW CARIBBEAN...A 1011 MB SURFACE LOW IS CENTERED N OF PANAMA NEAR 10N79W. LOW LEVEL CONVERGENCE NEAR THIS SURFACE LOW IS SUPPORTING SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS S OF 11N W OF 76W...INCLUDING PANAMA AND S COSTA RICA. THIS ACTIVITY IS BEING ENHANCED BY UPPER LEVEL DIFFLUENCE IN THE VICINITY OF AN UPPER RIDGE PRESENT OVER THE W CARIBBEAN...WITH THE AXIS OF THIS UPPER RIDGE EXTENDING FROM N COLOMBIA NEAR 10N75W TO 16N87W TO SE MEXICO NEAR 18N92W INTO THE W GULF REGION. OVER THE N CARIBBEAN...DEEP LAYER DRY AIR AND SUBSIDENCE ARE IN PLACE RESULTING IN FAIR WEATHER CONDITIONS...WHERE STRONG WESTERLY FLOW IS PRESENT ALOFT. SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS OVER N COLOMBIA AND N VENEZUELA ARE AFFECTING THE NEARBY COASTAL WATERS. THIS ACTIVITY IS BEING SUPPORTED BY GREATER DEEP MOISTURE AND GREATER INSTABILITY OVER THE HIGHER TERRAIN OF N PORTIONS OF COLOMBIA AND VENEZUELA. OUTSIDE OF SHOWERS AND THUNDERSTORM ACTIVITY...FRESH TRADEWINDS PREVAIL ACROSS THE CARIBBEAN. ATLANTIC OCEAN... STRONG WESTERLY FLOW ALOFT COVERS MUCH OF THE W AND CENTRAL ATLC. A SURFACE RIDGE EXTENDS INTO THE W ATLC FROM A 1022 MB SURFACE HIGH OVER THE NE GULF NEAR 28N84W...WITH SUBSIDENCE AND FAIR WEATHER IN THE VICINITY OF THIS RIDGE. E OF THIS RIDGE...A SURFACE TROUGH EXTENDS FROM 24N68W TO 26N66W TO 28N64W...WITH A SURFACE COLD FRONT EXTENDING FARTHER N FROM 28N64W TO 30N61W TO 32N60W TO N OF THE DISCUSSION AREA. LOW LEVEL CONVERGENCE IS RESULTING IN SCATTERED SHOWERS WITHIN 60 NM EITHER SIDE OF THE SURFACE TROUGH AND COLD FRONT...THOUGH DEEP LAYER SUBSIDENCE IS LIMITING THE COVERAGE AND INTENSITY OF THIS ACTIVITY. FARTHER TO THE E...UPPER LEVEL DIVERGENCE IN THE NE QUADRANT OF A 90-100 KT UPPER LEVEL JET IS SUPPORTING A 1003 MB SURFACE LOW IN THE CENTRAL ATLC NEAR 28N43W...WITH AN ASSOCIATED SURFACE TROUGH EXTENDING FROM 32N43W TO 32N34W TO 22N36W TO 9N60W. LOW LEVEL CONVERGENCE NEAR THESE FEATURES IS SUPPORTING SCATTERED SHOWERS AND THUNDERSTORMS N OF 18N BETWEEN 28W-36W AND WITHIN 60 NM EITHER SIDE OF THE SURFACE TROUGH S OF 16N...WITH SCATTERED SHOWERS N OF 27N BETWEEN 38W-46W. AN UPPER TROUGH AXIS IS TILTED FROM 28N33W TO 32N37W TO AN UPPER LOW NEAR 36N44W...WITH UPPER DIFFLUENCE E OF THE UPPER TROUGH AXIS ENHANCING THE SHOWER AND THUNDERSTORM ACTIVITY N OF 25N BETWEEN 38W-46W. ACROSS THE E ATLC...A SURFACE RIDGE IS N OF 20N E OF 22W...WHERE SUBSIDENCE IS RESULTING IN FAIR WEATHER CONDITIONS. OVER THE TROPICAL ATLC...AN UPPER RIDGE IS PRESENT S OF 10N W OF 29W...WITH UPPER LEVEL DIFFLUENCE IN THE VICINITY OF THIS RIDGE ENHANCING THE CONVECTION IN THE VICINITY OF THE ITCZ. ALSO...A SURFACE TROUGH...EXTENDING FROM 12N47W TO 10N48W TO 8N48W...IS EMBEDDED WITHIN THE ITCZ...WITH SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS WITHIN 150 NM EITHER SIDE OF THIS SURFACE TROUGH. $$ COHEN