000 AXNT20 KNHC 211740 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT WED MAY 21 2008 TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHERN SECTIONS OF SOUTH AMERICA...AND THE 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1715 UTC. ...TROPICAL WAVES... A TROPICAL WAVE IS ALONG 20W/21W S OF 12N MOVING W 10 KT. VISIBLE IMAGES SHOW A WELL DEFINED BUT BROAD AREA OF LOW-LEVEL CYCLONIC TURNING CENTERED NEAR 6N. SCATTERED SHOWERS AND TSTMS ARE MAINLY WITHIN 300 NM E OF THE AXIS S OF 8N. A TROPICAL WAVE IS ALONG 52W S OF 10N MOVING W 10-15 KT. VISIBLE IMAGERY REVEALS MODERATE LOW-LEVEL CYCLONIC TURNING ALONG THE WAVE AXIS. HOWEVER...MOST OF ITS DEEP CLOUDINESS HAS BEEN ABSORBED BY A HIGH AMPLITUDE UPPER TROUGH WHICH IS NOW E OF THE WAVE. TROPICAL WAVE IS ALONG 77W S OF 13N MOVING W 10-15 KT. THIS WAVE IS MAINLY INLAND OVER W COLOMBIA. WHILE ONLY A WEAK SIGNATURE OF THIS WAVE IS APPARENT ON SATELLITE IMAGERY...THE MIMIC TPW ANIMATION DOES SHOW FAIRLY GOOD CONTINUITY OF THIS FEATURE. THIS WAVE MAY BE ENHANCING CONVECTION OVER THE SW CARIBBEAN. SEE CARIBBEAN DISCUSSION FOR MORE DETAILS. ..THE ITCZ... ITCZ AXIS IS CENTERED ALONG 8N13W 5N22W 3N30W 2N37W 4N50W. SCATTERED MODERATE TO STRONG CONVECTION IS WITHIN 30 NM EITHER SIDE OF THE AXIS BETWEEN 29W-31W. ISOLATED MODERATE CONVECTION IS S OF 3N W OF 47W. ...DISCUSSION... GULF OF MEXICO... A STRONG SW TO W UPPER FLOW REGIME CONTINUES OVER THE REGION KEEPING THE MID AND UPPER LEVELS FAIRLY MOIST. HOWEVER...UNLIKE YESTERDAY THERE IS NOT A SYNOPTIC SCALE LOW-LEVEL BOUNDARY TO PROVIDE ENHANCED LIFT. THEREFORE...SHOWER AND TSTM ACTIVITY IS FAIRLY LIMITED. IR IMAGES SHOW THE THICKEST CLOUDINESS OVER THE W GULF FROM 20N-27N BETWEEN 87W-96W. LIGHTNING DATA HAS RECENTLY DETECTED A FEW FLASHES IN THIS CLOUDINESS...SO ISOLATED ACTIVITY SEEMS LIKELY IN THE OUTLINED AREA. OTHERWISE...THE REGION LIES ON THE W PERIPHERY OF A CENTRAL ATLC SFC RIDGE PROVIDING MAINLY 10-15 KT S TO SW FLOW AND WARM/HUMID CONDITIONS. SLY WINDS ARE EXPECTED TO INCREASE OVER THE W WATERS LATER TONIGHT AND THU AS LOW PRES DEEPENS OVER THE ROCKIES. CARIBBEAN SEA... IR IMAGERY AND LIGHTNING DATA INDICATE SCATTERED SHOWERS AND TSTMS OVER THE SW WATERS MAINLY S OF 15N W OF 77W. THIS ACTIVITY IS ASSOCIATED WITH AN UPPER DIFFLUENT PATTERN ON THE SW SIDE OF A BROAD UPPER RIDGE WITH SOME POSSIBLE ENHANCEMENT FROM A NEARBY TROPICAL WAVE. OTHERWISE...A SUBSIDENT ENVIRONMENT IS IN PLACE CAPPING THE TYPICAL STREAMS OF LOW-LEVEL CLOUDS AND ALLOWING MAINLY FAIR WEATHER TO DOMINATE. ELY TRADES ARE STRONGEST...NEAR 20 KT...OVER THE S CENTRAL WATERS WITH MAINLY 10-15 KT SE TO S WINDS OBSERVED ELSEWHERE. ATLANTIC OCEAN... BROAD MID-UPPER RIDGING COVERS THE W ATLC WITH STRONG ZONAL FLOW LYING ON ITS N PERIPHERY OVER THE N PORTION OF THE DISCUSSION ZONE. THIS STRONG UPPER FLOW IS TRANSPORTING HIGH LEVEL CLOUDS N OF 28N W OF 50W AND IS GENERATING ISOLATED TSTMS OVER THE NW BAHAMAS...AS NOTED IN LIGHTING DATA. ELSEWHERE...LIKE THE CARIBBEAN...DRY STABLE AIR IS EMBEDDED IN THE CORE OF THE RIDGE PROVIDING MAINLY FAIR WEATHER W OF 50W. A HIGH AMPLITUDE LONGWAVE TROUGH LIES TO THE E OF THE RIDGE ANCHORED BY AN UPPER LOW NEAR 27N33W AND EXTENDS SW ALONG 18N34W 6N48W. UPPER DIFFLUENCE AND STRONG SW FLOW ALOFT E OF THE TROUGH AXIS ARE GENERATING A SWATH OF CLOUDINESS...WITH EMBEDDED SCATTERED SHOWERS AND TSTMS...WITHIN 180 NM E OF THE TROUGH AXIS S OF 18N. A LARGE SCALE MID-UPPER RIDGE IS SITUATED OVER W AFRICA AND IS LIKELY ENHANCING CONVECTION WITHIN THE ITCZ. AT THE SFC...A 1024 MB HIGH CENTERED NEAR 29N44W IS PROVIDING MODERATE NE/E TRADES ACROSS THE TROPICS AND MAINLY LIGHT WINDS ACROSS THE SUBTROPICS. HOWEVER...THE EXCEPTION TO THIS IS OVER THE W ATLC N OF 26N W OF 62W WHERE STRONG SW WINDS EXIST IN RESPONSE TO A LOW PRES SYSTEM OVER THE N ATLC. $$ CANGIALOSI/BELL