000 AXNT20 KNHC 212353 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT TUE OCT 21 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. ...TROPICAL WAVES... A TROPICAL WAVE IS ALONG 22W S OF 15N MOVING W NEAR 10 KT. THIS WAVE HAS WEAKENED SINCE YESTERDAY AND NOW MOST OF THE CONVECTIVE ACTIVITY IS CONFINED TO THE ITCZ. THIS FEATURE STILL SHOWS UP ON THE TOTAL PRECIPITABLE WATER AND 850 MB RELATIVE VORTICITY PRODUCTS FROM CIMSS. A TROPICAL WAVE IS ALONG 50W S OF 22N MOVING W 10-15 KT. THE SSMI-TPW PRODUCT FROM CIMSS INDICATES A NORTHWARD SURGE OF MOISTURE ALONG THE WAVE AXIS. THE WAVE IS INTERACTING WITH A SHARP UPPER-LEVEL TROUGH WITH AXIS ALONG 50W/51W. UPPER DIFFLUENCE AHEAD OF THIS TROUGH IS ENHANCING CONVECTION NEAR THE NORTHERN END OF THE WAVE AXIS. SATELLITE IMAGERY REVEALS A LARGE AREA OF MODERATE TO ISOLATED STRONG CONVECTION EXTENDING NWD FROM 18N-25N BETWEEN 47W-50W. A TROPICAL WAVE IS ALONG 75W S OF 15N MOVING W 10-15 KT. THE WAVE IS LOCATED WITHIN STRONG EASTERLY SURFACE FLOW ACROSS THE CARIBBEAN AND THIS EVENING IS ENHANCING CONVECTION OVER NORTHERN COLOMBIA WHERE A CLUSTER OF MODERATE TO ISOLATED CONVECTION IS SEEN. LATEST VIS IMAGERY FOR THE DAY SHOWED A SWIRL OF LOW CLOUDS JUST AHEAD OF THE WAVE AXIS NEAR 12N76W. ...THE ITCZ... ITCZ AXIS IS CENTERED ALONG 9N13W 8N20W 7N30W 10N48W 9N61W. SCATTERED MODERATE CONVECTION IS FROM 5N-10N BETWEEN 41W-50W. SIMILAR CONVECTION IS NEAR 5N18W. ...DISCUSSION... GULF OF MEXICO... A BROAD UPPER-LEVEL HIGH CENTERED IN THE CENTRAL CARIBBEAN SEA EXTENDS WEAK RIDGING ACROSS THE ENTIRE GULF PRODUCING A W TO SW UPPER LEVEL FLOW. MODERATE TO STRONG SUBSIDENCE/DRY AIR IS NOTED OVER MUCH OF THE GULF. AT THE SURFACE...A SFC TROUGH HAS DEVELOPED OVER THE WESTERN GULF ALONG 93W FROM 21N-26N. WEAK CYCLONIC TURNING IS OBSERVED ALONG THE TROUGH AXIS NEAR 22N. ISOLATED SHOWERS ARE ASSOCIATED WITH THIS FEATURE. A 1025 MB HIGH PRESSURE CENTERED OVER NORTHERN ALABAMA EXTENDS A RIDGE ACROSS THE NRN GULF WATERS N OF 25N. THIS RIDGE IS FORECAST TO MOVE EWD AS A COLD FRONT MOVES OFF THE TEXAS COAST LATE WED. MODERATE TO STRONG NLY WINDS ARE EXPECTED IN THE WAKE OF THE FRONT. WINDS ARE ALSO EXPECTED TO INCREASE ACROSS THE NE CORNER OF THE GULF BY THU DUE TO A TIGHT PRES GRADIENT BETWEEN A STRONG SURFACE HIGH ALONG THE EASTERN SEABOARD AND A LOW PRES OVER THE CENTRAL GULF. CARIBBEAN SEA... A LARGE AREA OF DISTURBED WEATHER REMAINS OVER THE NORTHWESTERN CARIBBEAN SEA. A SFC TROUGH IS ANALYZED ON THE 1800 UTC SFC MAP ALONG 86W SOUTH OF 21N. PRESSURES HAVE RISEN IN THIS AREA AND THE SYSTEM REMAINS DISORGANIZED. SIGNIFICANT DEVELOPMENT APPEARS UNLIKELY. THE GFS COMPUTER MODEL MOVES THIS AREA OF LOW PRES NORTH AHEAD OF THE COLD FRONT FORECAST TO ENTER THE GULF OF MEXICO LATE WED. LOCALLY HEAVY RAINS ARE STILL POSSIBLE OVER PORTIONS OF HONDURAS...GUATEMALA...BELIZE...AND THE YUCATAN PENINSULA. SCATTERED MODERATE CONVECTION IS MAINLY EAST OF THE TROUGH AXIS FROM 13N-21N BETWEEN 80W-86W. SIMILAR CONVECTION IS NOTED OVER PARTS OF HONDURAS AND NICARAGUA. UPPER-LEVEL DIFFLUENCE ASSOCIATED WITH AN UPPER-LEVEL HIGH LOCATED SOUTH OF HISPANIOLA NEAR 15N72W WHICH DOMINATES THE ENTIRE CARIBBEAN SEA IS HELPING TO INDUCE THE CONVECTIVE ACTIVITY OVER THE WESTERN CARIBBEAN AND CENTRAL AMERICA. ANOTHER SURFACE TROUGH EXTENDS ACROSS CENTRAL CUBA INTO THE BAHAMAS THEN CONTINUES NE AS A FRONTAL BOUNDARY OVER THE ATLANTIC OCEAN. MODERATE TRADE WINDS OF 15 TO 20 KT ARE BLOWING ACROSS THE BASIN. A FEW SHOWERS ARE MOVING ACROSS THE SRN WINDWARD ISLANDS AND THE FAR SE CARIBBEAN. THIS ACTIVITY APPEARS TO BE ASSOCIATED WITH THE TAIL END OF AN UPPER-LEVEL TROUGH LOCATED OVER THE CENTRAL ATLC ALONG 50W/51W. LOW-TOPPED SHOWERS ARE MOVING WWD ACROSS THE E AND CENTRAL CARIBBEAN UNDER AN ELY WIND FLOW. SCATTERED SHOWERS AND TSTMS ARE AFFECTING COSTA RICA AND PARTS OF PANAMA LIKELY ASSOCIATED WITH THE CLOSE PROXIMITY OF THE ITCZ. ATLANTIC OCEAN... A DEEP LAYERED TROUGH IS OVER THE W ATLC. THE ATTENDANT COLD FRONT ENTERS THE AREA NEAR 31N55W...TURNING STATIONARY NEAR 22N66W...AND EXTENDS ACROSS THE SE BAHAMAS INTO CENTRAL CUBA. A BAND OF MULTILAYERED CLOUDS WITH ISOLATED SHOWERS IS RELATED TO THIS FRONT OVER THE ATLC. SCATTERED SHOWERS ARE OVER THE CENTRAL BAHAMAS AND WESTERN CUBA NEAR THE FRONTAL BOUNDARY/SFC TROUGH. MODERATE TO STRONG SUBSIDENCE IS IN PLACE ACROSS THE W ATLC N OF 26N AND W OF THE COLD FRONT. A BAND OF TRANSVERSE HIGH CLOUDS ASSOCIATED WITH STRONG UPPER-LEVEL WLY WINDS EXTENDS FROM THE NE PORTION OF THE YUCATAN PENINSULA ACROSS WESTERN CUBA AND THE CENTRAL BAHAMAS INTO THE ATLANTIC OCEAN. PATCHES OF LOW-LEVEL CLOUDS AND MODERATE TRADE WINDS ARE SEEN OVER THE EASTERN ATLC THANKS TO A 1024 MB SFC HIGH LOCATED NORTH OF AREA NEAR 34N36W. A SHARP UPPER-LEVEL TROUGH WITH AXIS ALONG 50W/51W AND AN AMPLIFIED UPPER-LEVEL RIDGE WITH AXIS ALONG 40W CONTINUES TO FUNNEL DEEP-LAYERED TROPICAL MOISTURE NORTHWARD INTO THE CENTRAL ATLC. ANOTHER UPPER-LEVEL TROUGH HAS ITS AXIS JUST WEST OF THE THE CANARY AND CAPE VERDE ISLANDS. THE BASE OF THIS TROUGH REACHES 10N32W. $$ GR