000 AXNT20 KNHC 281125 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 705 AM EST FRI NOV 28 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1045 UTC. ...THE ITCZ... THE ITCZ AXIS IS ANALYZED ALONG 8N12W 4N22W 4N33W 7N45W 6N58W. A SURFACE TROUGH...EXTENDING FROM 11N48W TO 10N49W TO 8N50W...IS EMBEDDED WITHIN THE ITCZ. A RECENT ASCAT PASS DEPICTS CYCLONIC CURVATURE IN THE LOW LEVEL WIND FIELD IN THE VICINITY OF THIS TROUGH. SCATTERED MODERATE CONVECTION IS OCCURRING WITHIN 60 NM EITHER SIDE OF THIS SURFACE TROUGH N OF 10N. ELSEWHERE... SCATTERED MODERATE CONVECTION IS WITHIN 90 NM S OF THE ITCZ AXIS BETWEEN 12W-25W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 3N-10N BETWEEN 29W-38W. ...DISCUSSION... GULF OF MEXICO... AN UPPER LEVEL RIDGE COVERS THE GULF REGION...WITH STRONG UPPER LEVEL WINDS ACROSS THE NORTHERN PERIPHERY OF THE RIDGE OVER THE SE CONUS AND N 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 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 SE QUADRANT OF A 100-110 KT UPPER LEVEL JET MAXIMUM OVER THE ALABAMA AND FLORIDA PANHANDLE COASTS IS SUPPORTING A 1021 MB SURFACE HIGH OVER THE CENTRAL FLORIDA PENINSULA NEAR 28N82W. FARTHER NW...A DEEP TROUGH OVER THE W CONUS IS SUPPORTING A SURFACE FRONT THAT EXTENDS FROM THE GREAT LAKES REGION 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 GULF LATE THIS WEEKEND AS A COLD FRONT...WITH SOUTHERLY FLOW INCREASING AHEAD OF THE FRONT. THE FRONT IS ALSO FORECAST TO BE ACCOMPANIED BY SCATTERED SHOWERS AND THUNDERSTORMS. STRONG WINDS ARE ALSO EXPECTED WITH THE FRONT...WITH GALE CONDITIONS EXPECTED ON SUNDAY FOR THE MIDDLE GULF N OF 25N BETWEEN 85W-90W AND FOR THE E GULF N OF 25N BETWEEN 81W-85W. IN THE WAKE OF THE COLD FRONT...RELATIVELY COOLER AND DRIER CONDITIONS ARE EXPECTED...ALONG N TO NW SURFACE WINDS. CARIBBEAN SEA... IN THE SW CARIBBEAN...A 1011 MB SURFACE LOW IS CENTERED N OF PANAMA NEAR 10N78W. LOW LEVEL CONVERGENCE NEAR THIS SURFACE LOW IS SUPPORTING SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS S OF 10N W OF 77W...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 13N83W TO SE MEXICO NEAR 18N91W TO THE W GULF. OVER THE N CARIBBEAN... DEEP LAYER SUBSIDENCE IS IN PLACE RESULTING IN FAIR WEATHER...WHERE STRONG WESTERLY CONFLUENT FLOW ALOFT IS PRESENT. RELATIVELY DRY CONDITIONS PREVAIL ACROSS PORTIONS OF THE N CARIBBEAN...WITH DEWPOINTS IN THE UPPER 50S AND LOWER 60S ACROSS CUBA. THIS DRIER AIR IS A RESULT OF NE SURFACE WINDS ADVECTING A STRONGLY MODIFIED CONTINENTAL POLAR AIRMASS ACROSS THE N CARIBBEAN REGION. THIS AIRMASS ORIGINATES FROM THE 1021 MB SURFACE HIGH OVER THE CENTRAL FLORIDA PENINSULA NEAR 28N82W AND IS IN THE WAKE OF A COLD FRONT THAT IS E OF THE BAHAMAS. OUTSIDE OF SHOWER AND THUNDERSTORM ACTIVITY...FRESH TRADEWINDS GENERALLY 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 1021 MB SURFACE HIGH OVER THE CENTRAL FLORIDA PENINSULA NEAR 28N82W... WITH SUBSIDENCE AND FAIR WEATHER IN THE VICINITY OF THIS RIDGE. TO THE E OF THE BAHAMAS...A SURFACE COLD FRONT EXTENDS FROM 23N68W TO 27N59W TO 32N54W TO N OF THE DISCUSSION AREA. LOW LEVEL CONVERGENCE IS RESULTING IN SCATTERED SHOWERS WITHIN 90 NM EITHER SIDE OF THIS COLD FRONT. FARTHER TO THE E...UPPER LEVEL DIVERGENCE IN THE NE QUADRANT OF A 90-100 KT UPPER LEVEL JET MAXIMUM IS SUPPORTING A 1000 MB SURFACE LOW IN THE CENTRAL ATLC NEAR 31N40W...WITH THREE ASSOCIATED SURFACE TROUGHS. ONE SURFACE TROUGH EXTENDS FROM 32N40W TO 32N31W...WITH ANOTHER SURFACE TROUGH EXTENDING FROM 32N32W TO 23N31W...AND ANOTHER SURFACE TROUGH EXTENDS FROM 31N50W TO 30N45W. LOW LEVEL CONVERGENCE NEAR THE SURFACE LOW AND THREE SURFACE TROUGHS IS SUPPORTING SCATTERED SHOWERS AND THUNDERSTORMS N OF 28N BETWEEN 25W-35W. AN ASSOCIATED UPPER TROUGH AXIS IS TILTED FROM 28N28W TO 32N42W TO NW OF THE DISCUSSION AREA...WITH UPPER DIFFLUENCE E OF THE UPPER TROUGH AXIS ENHANCING THE SHOWER AND THUNDERSTORM ACTIVITY N OF 26N BETWEEN 26W-35W. ACROSS THE E ATLC...A SURFACE RIDGE IS N OF 18N E OF 26W...WHERE SUBSIDENCE IS RESULTING IN GENERALLY FAIR WEATHER. FARTHER TO THE S...AN UPPER RIDGE IS PRESENT S OF 12N W OF 19W...WITH ASSOCIATED UPPER LEVEL DIFFLUENCE ENHANCING THE CONVECTION IN THE VICINITY OF THE ITCZ. ADDITIONALLY...A SURFACE TROUGH OVER THE TROPICAL N ATLC EXTENDS FROM 15N45W TO 11N51W TO 9N59W. A RECENT ASCAT PASS INDICATES LOW LEVEL CONFLUENCE IN THE VICINITY OF THIS TROUGH...WITH SCATTERED SHOWERS AND THUNDERSTORMS WITHIN 90 NM EITHER SIDE OF THIS FEATURE. ALSO...A SURFACE TROUGH...EXTENDING FROM 11N48W TO 9N48W TO 7N49W...IS EMBEDDED WITHIN THE ITCZ...WITH SCATTERED SHOWERS AND THUNDERSTORMS OCCURRING WITHIN 180 NM EITHER SIDE OF THIS SURFACE TROUGH N OF 10N. BY LATE THIS WEEKEND...A COLD FRONT WILL BEGIN TO MOVE ACROSS PORTIONS OF THE W ATLC...WITH SCATTERED SHOWERS AND THUNDERSTORMS ACCOMPANYING THE FRONT. ADDITIONALLY...STRONG WINDS ARE EXPECTED WITH THE FRONT...WITH GALE CONDITIONS EXPECTED LATE SUNDAY AND MONDAY FOR THE SW N ATLC FROM 27N-31N BETWEEN 65W-70W. IN THE WAKE OF THE COLD FRONT...RELATIVELY COOLER AND DRIER CONDITIONS ARE EXPECTED... ALONG W TO NW SURFACE WINDS. $$ COHEN