000 AXNT20 KNHC 291130 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 705 AM EST SAT NOV 29 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 9N12W 5N22W 4N33W 6N45W 7N59W. SCATTERED MODERATE CONVECTION IS FROM 3N-6N BETWEEN 7W-13W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 2N-8N BETWEEN 19W-35W. ...DISCUSSION... GULF OF MEXICO... A BROAD 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 AND W GULF...WHILE DEEP LAYER DRY AIR IS PRESENT OVER THE SE 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 IN THE VICINITY OF A SURFACE RIDGE ACROSS THE E GULF THAT ORIGINATES FROM A 1018 MB SURFACE HIGH IN THE W ATLC NEAR 28N66W. FARTHER N...A VIGOROUS AND DEEP TROUGH OVER THE PLAINS OF THE CONUS IS SUPPORTING A SURFACE STATIONARY FRONT THAT EXTENDS FROM THE SE CONUS ACROSS THE SE TEXAS COAST...FURTHER EXTENDING INTO NE MEXICO...WITH A SURFACE LOW ALONG THE FRONT OVER SW LOUISIANA NEAR 31N93W. UPPER LEVEL DIVERGENCE IN THE SW QUADRANT OF A 130-140 KT UPPER LEVEL JET MAXIMUM OVER THE S PLAINS AND SE CONUS IS INTERACTING WITH LOW LEVEL CONVERGENCE NEAR THE SURFACE LOWS AND FRONT TO RESULT IN SCATTERED SHOWERS AND THUNDERSTORMS OVER PORTIONS OF SE TEXAS...SW LOUISIANA...AND THE NW GULF N OF 28N W OF 92W. AS SOUTHERLY RETURN FLOW AROUND THE 1018 MB SURFACE HIGH IN THE W ATLC DRAWS INCREASED MOISTURE AND INSTABILITY OVER THE GULF REGION...THE THREAT FOR STRONG THUNDERSTORMS WILL EXIST ACROSS THE GULF REGION ALONG AND AHEAD OF THE FRONT AS IT MOVES SOUTHWARD AS A SURFACE COLD FRONT THIS WEEKEND...ESPECIALLY GIVEN THE PRESENCE OF STRONG VERTICAL WIND SHEAR. IN THE WAKE OF THE COLD FRONT...RELATIVELY COOLER AND DRIER CONDITIONS ARE EXPECTED. CARIBBEAN SEA... IN THE SW CARIBBEAN...A 1010 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 10N W OF 76W...INCLUDING PORTIONS OF PANAMA. 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 10N73W TO 16N87W TO SE MEXICO NEAR 18N92W 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 RANGING FROM THE MIDDLE 50S TO LOWER 60S ACROSS CUBA. THIS DRIER AIR IS A RESULT OF E AND NE SURFACE WINDS ADVECTING A STRONGLY MODIFIED CONTINENTAL POLAR AIRMASS ACROSS THE N CARIBBEAN REGION. THIS AIRMASS ORIGINATES FROM THE 1018 MB SURFACE HIGH OVER THE W ATLC NEAR 28N66W. ATLANTIC OCEAN... STRONG WESTERLY FLOW ALOFT COVERS MUCH OF THE W AND CENTRAL ATLC. A SURFACE RIDGE EXTENDS ACROSS THE W ATLC FROM A 1018 MB SURFACE HIGH NEAR 28N66W...WITH SUBSIDENCE AND FAIR WEATHER IN THE VICINITY OF THE SURFACE HIGH AND RIDGE. TO THE E...A SURFACE TROUGH EXTENDS FROM 30N50W TO 28N53W TO 26N57W...WITH LOW LEVEL CONVERGENCE RESULTING IN SCATTERED SHOWERS WITHIN 60 NM EITHER SIDE OF THIS FEATURE N OF 28N. THIS ACTIVITY IS BEING ENHANCED BY ATMOSPHERIC LIFT IN MOIST SOUTHWESTERLY FLOW ALOFT E OF AN UPPER TROUGH AXIS EXTENDING FROM 25N52W TO 32N52W TO N OF THE DISCUSSION AREA. FARTHER TO THE E...A SURFACE TROUGH EXTENDS FROM 27N28W TO 30N29W TO 32N32W TO NW OF THE DISCUSSION AREA...WITH LOW LEVEL CONFLUENCE SUPPORTING SCATTERED SHOWERS AND THUNDERSTORMS N OF 29N BETWEEN 29W-33W. ALSO...UPPER LEVEL DIVERGENCE ASSOCIATED WITH A 90-100 KT UPPER LEVEL JET MAXIMUM OVER THE E ATLC IS SUPPORTING SCATTERED SHOWERS WITHIN 90 NM EITHER SIDE OF A LINE FROM 30N19W TO 23N29W. FARTHER TO THE S...A SURFACE TROUGH EXTENDS FROM 22N34W TO 15N46W TO 9N59W...WITH LOW LEVEL CONFLUENCE SUPPORTING SCATTERED SHOWERS AND THUNDERSTORMS WITHIN 60 NM EITHER SIDE OF THIS SURFACE TROUGH. ADDITIONALLY...AN UPPER RIDGE IS PRESENT S OF 13N BETWEEN 19W-51W...WITH STRONG UPPER LEVEL DIFFLUENCE ASSOCIATED WITH THIS RIDGE ENHANCING THE CONVECTION IN THE VICINITY OF THE ITCZ BETWEEN 19W-35W. BY LATE THIS WEEKEND...A SURFACE COLD FRONT WILL BEGIN TO MOVE ACROSS PORTIONS OF THE W ATLC...WITH SCATTERED SHOWERS AND THUNDERSTORMS ACCOMPANYING THE FRONT. THE THREAT FOR STRONG THUNDERSTORMS WILL EXIST ACROSS THE W ATLC ALONG AND ALONG AND AHEAD OF THE FRONT AS IT MOVES SOUTHEASTWARD LATE THIS WEEKEND AND MONDAY...ESPECIALLY GIVEN THE PRESENCE OF STRONG VERTICAL WIND SHEAR. ADDITIONALLY...STRONG WINDS ARE EXPECTED WITH THE FRONT...WITH GALE CONDITIONS EXPECTED LATE SUNDAY INTO MONDAY FOR THE SW N ATLC FROM 29N-31N BETWEEN 71W-77W. IN THE WAKE OF THE COLD FRONT...RELATIVELY COOLER AND DRIER CONDITIONS ARE EXPECTED. $$ COHEN