000 AXNT20 KNHC 180533 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 105 AM EST TUE NOV 18 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0515 UTC. ...TROPICAL WAVES... A TROPICAL WAVE IS OVER THE E CARIBBEAN ALONG 68W/69W S OF 18N MOVING W 10-15 KT. A MAXIMUM IN DEEP LAYER MOISTURE COINCIDES WITH THE WAVE AXIS BASED ON CIMSS TOTAL PRECIPITABLE WATER PRODUCT. ALSO...CIMSS WAVETRAK PRODUCT INDICATES A MAXIMUM IN LOW LEVEL CYCLONIC CIRCULATION ALONG THE WAVE AXIS. SCATTERED SHOWERS ARE WITHIN 60 NM EITHER SIDE OF WAVE AXIS S OF 16N. ...THE ITCZ... THE ITCZ AXIS IS ANALYZED ALONG 8N13W 7N22W 7N36W 7N44W 6N54W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 3N-12N BETWEEN 19W-28W. SCATTERED MODERATE CONVECTION IS WITHIN 150 NM N OF THE ITCZ AXIS BETWEEN 37W-42W. ...DISCUSSION... GULF OF MEXICO... A BROAD UPPER LEVEL TROUGH OVER THE E CONUS EXTENDS INTO THE GULF...WITH WESTERLY FLOW ALOFT AND DEEP LAYER DRY AIR COVERING MUCH OF THE GULF REGION. ALSO...A MODIFIED CONTINENTAL POLAR AIRMASS PERSISTS ACROSS THE GULF REGION. AS A RESULT... TEMPERATURES ACROSS THE GULF REGION ARE BELOW SEASONAL AVERAGES. THIS RELATIVELY COOLER AND DRIER AIRMASS IS BEING SUPPORTED BY A 1028 MB SURFACE HIGH CENTERED OVER SE TEXAS...WITH AN ASSOCIATED SURFACE RIDGE EXTENDING INTO THE W GULF. AS THE COOLER AIR IS BEING ADVECTED OVER THE RELATIVELY WARMER GULF WATERS...WEAK LOW LEVEL INSTABILITY IS SUPPORTING STRATOCUMULUS CLOUDS S OF 25N ACROSS THE GULF. HOWEVER...SUBSIDENCE AND STABLE ATMOSPHERIC CONDITIONS HIGHER IN THE ATMOSPHERE ARE INHIBITING DEEP CONVECTION ACROSS THE GULF REGION. THE AFOREMENTIONED BROAD UPPER TROUGH IS ALSO SUPPORTING A REINFORCING SURFACE FRONT FURTHER NORTH. THIS FRONT IS CURRENTLY DRAPED FROM THE SE CONUS INTO THE PLAINS OF THE CONUS AND THEN NORTHWARD ACROSS THE NORTHERN ROCKY MOUNTAINS. AS THE ASSOCIATED UPPER LEVEL ENERGY TRANSLATES SOUTHEASTWARD...THE SURFACE FRONT WILL MOVE SOUTHEASTWARD AS A COLD FRONT ACROSS THE CENTRAL AND E GULF OVER THE NEXT DAY. AN EVEN COOLER AND DRIER AIRMASS IS IN THE WAKE OF THIS FRONT...WITH FREEZE WATCHES IN EFFECT ACROSS PORTIONS OF THE SE CONUS ALONG THE GULF COAST FOR TUESDAY NIGHT. ADDITIONALLY...STRONG N TO NE SURFACE WINDS ARE BLOWING THROUGH THE ISTHMUS OF TEHUANTEPEC RESULTING IN GALE FORCE WINDS IN THE E PACIFIC REGION...WHICH ARE FORECAST TO BECOME STORM FORCE AT 19/0000 UTC. CARIBBEAN SEA... ACROSS THE NW CARIBBEAN...A SURFACE STATIONARY FRONT EXTENDS FROM E CUBA NEAR 21N76W TO 17N81W TO CENTRAL NICARAGUA NEAR 12N85W. LOW LEVEL CONVERGENCE NEAR THIS FRONT IS INTERACTING WITH DEEP MOISTURE OVER THE W CARIBBEAN TO GENERATE SCATTERED SHOWERS AND THUNDERSTORMS FROM 11N-18N BETWEEN 78W-84W. THIS ACTIVITY IS BEING ENHANCED BY UPPER LEVEL DIVERGENCE IN THE VICINITY OF AN UPPER RIDGE PRESENT OVER THE W CARIBBEAN...WITH THE AXIS OF THE UPPER RIDGE EXTENDING FROM NW VENEZUELA NEAR 10N71W TO 15N79W TO 20N84W. OVER THE E CARIBBEAN...AN UPPER LEVEL TROUGH IS PRESENT...WITH UPPER LEVEL DIVERGENCE IN MOIST SOUTHWESTERLY FLOW ALOFT SUPPORTING SCATTERED SHOWERS OVER THE E CARIBBEAN S OF 16N E OF 73W. THIS ACTIVITY IS BEING ENHANCED BY THE TROPICAL WAVE ALONG 68W/69W. ATLANTIC OCEAN... A BROAD UPPER TROUGH IS OVER THE E CONUS AND THE W ATLC...WHICH IS SUPPORTING A SURFACE STATIONARY FRONT THAT EXTENDS FROM E CUBA NEAR 21N76W TO 26N69W TO 32N63W TO NE OF THE DISCUSSION AREA. ISOLATED SHOWERS ARE WITHIN 60 NM EITHER SIDE OF THIS STATIONARY FRONT...WITH THE COVERAGE OF THIS ACTIVITY BEING LIMITED AS THE STRONGEST UPPER LEVEL ENERGY REMAINS N OF THE DISCUSSION AREA. TO THE W OF THIS STATIONARY FRONT...A MODIFIED CONTINENTAL POLAR AIRMASS IS IN PLACE...WITH TEMPERATURES BELOW SEASONAL AVERAGES ACROSS THE FLORIDA PENINSULA. FARTHER TO THE E...A 1018 MB SURFACE HIGH IS CENTERED NEAR 29N56W...WHICH IS BEING SUPPORTED BY A SHARP UPPER LEVEL RIDGE WITH AN AXIS EXTENDING FROM 24N57W TO 29N54W TO 32N54W TO NE OF THE DISCUSSION AREA. TO THE E...AN UPPER LOW IS CENTERED NEAR 31N37W THAT IS ACCOMPANIED BY AN UPPER TROUGH N OF 18N BETWEEN 27W-45W. THE UPPER LOW AND UPPER TROUGH ARE ACCOMPANIED BY A SURFACE LOW AND TWO SURFACE TROUGHS. ONE SURFACE TROUGH EXTENDS FROM A 1004 MB SURFACE LOW NEAR 32N40W TO 27N39W TO 23N39W...WITH SCATTERED SHOWERS N OF 26N BETWEEN 36W-42W. THE SECOND SURFACE TROUGH EXTENDS FROM 31N30W TO 26N31W TO 22N34W...WITH SCATTERED SHOWERS AND THUNDERSTORMS WITHIN 90 NM EITHER SIDE OF THIS SECOND SURFACE TROUGH. THE ACTIVITY ASSOCIATED WITH THE SECOND SURFACE TROUGH IS BEING ENHANCED BY UPPER LEVEL DIFFLUENCE IN SOUTHWESTERLY FLOW ALOFT BETWEEN THE ACCOMPANYING UPPER TROUGH...AND AN UPPER RIDGE THAT IS N OF 19N BETWEEN THE AFRICAN COAST AND 27W. OVER THE TROPICAL ATLC...AN UPPER RIDGE IS S OF 10N BETWEEN THE AFRICAN COAST AND 27W...WITH ANOTHER UPPER RIDGE PRESENT S OF 6N BETWEEN 30W-38W. UPPER LEVEL DIVERGENCE IN THE VICINITY OF THESE UPPER RIDGES IS ENHANCING THE CONVECTION ASSOCIATED WITH THE ITCZ. $$ COHEN