000 AXNT20 KNHC 212357 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT MON JUN 21 2010 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... ...SPECIAL FEATURES... A STRONG TROPICAL WAVE IS MOVING THROUGH THE ERN CARIBBEAN EXTENDING FROM 22N68W ACROSS ERN HISPANIOLA TO 10N69W MOVING W 10-15 KT. THE WAVE IS ACCOMPANIED BY A LARGE AREA OF DEEP LAYER MOISTURE THAT COVERS THE ENTIRE ERN HALF OF THE CARIBBEAN EVIDENT IN TOTAL PRECIPITABLE WATER IMAGERY. BROAD LOW TO MID-LEVEL CYCLONIC FLOW IS ABOUT THE WAVE. IT APPEARS THAT A SURFACE CIRCULATION IS TRYING TO FORM W OF THE WAVE AXIS NEAR 14N72W SEEN IN THE LAST VISIBLE SATELLITE IMAGERY OF THE DAY. THIS MAY BE ASSOCIATED WITH A PREVIOUSLY ANALYZED SURFACE TROUGH THAT WAS MOVING AHEAD OF THE WAVE AXIS. UPPER LEVEL CONDITIONS REMAIN FAVORABLE AND DEVELOPMENT INTO A TROPICAL CYCLONE IS POSSIBLE OVER THE NEXT COUPLE OF DAYS. SCATTERED MODERATE/ISOLATED STRONG CONVECTION COVERS MUCH OF THE ERN CARIBBEAN FROM 12N-21N BETWEEN 63W-69W...AND FROM 13N-19N BETWEEN 69W-75W AFFECTIONS PORTIONS OF HISPANIOLA...PUERTO RICO...AND THE VIRGIN ISLANDS. ...TROPICAL WAVES... TROPICAL WAVE EXTENDS FROM 16N26W TO 6N28W MOVING W 15-20 KT. A DRY LOW-LEVEL VORTICITY CENTER IS AHEAD OF THE WAVE ANALYZED AS A SURFACE TROUGH EXTENDING FROM 14N33W TO 11N31W. CYCLONIC CURVATURE IS NEAR THIS TROUGH AXIS. TOTAL PRECIPITABLE WATER IMAGERY ALSO INDICATES A DRY CIRCULATION ABOUT THE TROUGH WITH A PEAK IN DEEP LAYER MOISTURE TO THE E ALONG THE WAVE AXIS. VISIBLE SATELLITE IMAGERY ALSO INDICATES A LARGE AREA OF SAHARAN DUST FLOWING AROUND THE WAVE AXIS EXTENDING OUT TO 44W S OF 23N. SCATTERED MODERATE/STRONG CONVECTION IS E OF THE WAVE AXIS FROM 4N-8N BETWEEN 20W-27W. TROPICAL WAVE EXTENDS FROM 14N55W TO 5N56W MOVING W NEAR 15 KT. THE WAVE COINCIDES WITH A DEEP LAYER MOISTURE MAXIMUM OBSERVED IN TOTAL PRECIPITABLE WATER IMAGERY. BROAD CYCLONIC FLOW IS ALSO EVIDENT ABOUT THE WAVE AXIS IN THE LAST VISIBLE SATELLITE IMAGES OF THE DAY. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 8N-13N BETWEEN 56W-62W. TROPICAL WAVE EXTENDS ALONG 21N81W MOVING W NEAR 15 KT. THE NRN EXTEND OF THIS WAVE HAS NOW FRACTURED OFF AND IS BEING CARRIED AS A SURFACE TROUGH ALONG 84W FROM 23N-26N AS OF 2100 UTC. BOTH THE WAVE AND THE FRACTURED PORTION COINCIDE WITH AREAS OF ENHANCED MOISTURE EVIDENT IN TOTAL PRECIPITABLE WATER IMAGERY. VISIBLE SATELLITE IMAGERY INDICATES A CLEAR CYCLONIC WIND SHIFT ABOUT THE WAVE AXIS. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 19N-24N BETWEEN 81W-86W. SIMILAR ACTIVITY IS ALSO OVER ERN CUBA FROM 19N-22N BETWEEN 75W-79W. THIS ACTIVITY MAY BE MORE ASSOCIATED WITH DAYTIME HEATING AND SEABREEZE CONVERGENCE THAN CONVERGENCE NEAR THE WAVE. ...ITCZ... ITCZ AXIS IS CENTERED ALONG 10N11W 8N20W 9N27W 5N38W 10N55W. ISOLATED MODERATE/STRONG CONVECTION IS WITHIN 120 NM EITHER SIDE OF THE AXIS BETWEEN 32W-41W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 120 NM N OF THE AXIS BETWEEN 41W-47W. AN EMBEDDED SURFACE TROUGH EXTENDS ALONG 49W S OF 12N ENHANCING SCATTERED MODERATE/ISOLATED STRONG CONVECTION FROM 6N-12N BETWEEN 47W-53W. ...DISCUSSION... GULF OF MEXICO... A SHORTWAVE UPPER LEVEL TROUGH EXTENDING FROM GEORGIA INTO THE NE GULF SUPPORTS A 1015 MB LOW OVER THE WRN FLORIDA PANHANDLE NEAR 31N86W...AS OF 2100 UTC. A SURFACE TROUGH EXTENDS FROM THE LOW CENTER TO NEAR 29N89W. RADAR IMAGERY INDICATES CLUSTERS OF SHOWERS/THUNDERSTORMS ACROSS THE NRN GULF NEAR THE TROUGH/LOW N OF 25N E OF 96W. MORE WIDESPREAD ACTIVITY IS ACROSS THE FLORIDA PENINSULA DUE TO DAYTIME HEATING AND SEABREEZE CONVERGENCE. A SURFACE TROUGH...FRACTURE OF A TROPICAL WAVE...MAY BE FURTHER ENHANCING SOME OF THIS CONVECTION ALONG THE SW SIDE OF FLORIDA. THE TROUGH EXTENDS ALONG 84W FROM 23N-26N. ELSEWHERE...A WEAK PRESSURE GRADIENT IS ACROSS THE BASIN MAINTAINING LIGHT E-SE WINDS. ALOFT...AN UPPER LEVEL RIDGE CENTERED OVER SRN TEXAS IS PROVIDING MAINLY NE FLOW WITH DRY AIR ALOFT OVER THE NW GULF KEEPING CONDITIONS FAIR. CARIBBEAN SEA... A TROPICAL WAVE S OF CUBA IS ENHANCING SHOWERS/THUNDERSTORMS ACROSS MUCH OF THE ISLAND. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 19N-24N BETWEEN 81W-86W. SIMILAR ACTIVITY IS ALSO OVER ERN CUBA FROM 19N-22N BETWEEN 75W-79W. THIS ACTIVITY MAY BE MORE ASSOCIATED WITH DAYTIME HEATING AND SEABREEZE CONVERGENCE THAN CONVERGENCE NEAR THE WAVE. AN UPPER LEVEL TROUGH EXTENDING FROM THE CENTRAL BAHAMAS TO THE YUCATAN PENINSULA MAY ALSO BE PROVIDING SUPPORT TO THE SHOWER ACTIVITY. ISOLATED SHOWERS/THUNDERSTORMS ARE ALSO ACROSS CENTRAL AMERICA. A SECOND STRONG TROPICAL WAVE EXTENDS ACROSS ERN HISPANIOLA FROM 22N68W TO 10N69W SUPPORTING A LARGE AREA OF SHOWERS/THUNDERSTORMS ACROSS THE NRN CARIBBEAN IMPACTING HISPANIOLA...PUERTO RICO...THE VIRGIN ISLANDS. SEE SPECIAL FEATURES ABOVE ABOVE FOR MORE DETAILS. THE ACTIVITY ACROSS THE ERN HALF OF THE BASIN DUE TO THE TROPICAL WAVE IS FURTHER ENHANCED BY A DIFFLUENT ZONE ALOFT BETWEEN THE UPPER LEVEL TROUGH COVERING THE WRN HALF OF THE AREA...AND AN UPPER LEVEL RIDGE COVERING THE ERN PORTION CENTERED OVER THE SRN LESSER ANTILLES NEAR 14N61W. EXPECT CONTINUED SHOWER ACTIVITY ACROSS MUCH OF THE BASIN AS THE TROPICAL WAVES MOVE WWD. ATLANTIC OCEAN... A FEW ISOLATED SHOWERS/THUNDERSTORMS ARE OFF THE ERN COAST OF FLORIDA AND THE NW BAHAMAS ENHANCED BY DAYTIME HEATING AND SEABREEZE CONVERGENCE. THE REMAINDER OF THE W ATLC IS INFLUENCED BY DRY AIR ALOFT AROUND AN UPPER LEVEL TROUGH EXTENDING FROM THE CENTRAL BAHAMAS TO THE YUCATAN PENINSULA...AND WEAK SURFACE RIDGING EXTENDING FROM THE NE KEEPING CONDITIONS FAIR. AN ACTIVE CARIBBEAN TROPICAL WAVE ALONG 67W-68W IS ENHANCING SCATTERED MODERATE/ISOLATED STRONG CONVECTION S OF 21N BETWEEN 67W-73W. THIS ACTIVITY IS ENHANCED BY DIFFLUENT FLOW ALOFT BETWEEN THE AFOREMENTIONED UPPER LEVEL TROUGH AND AN UPPER LEVEL RIDGE CENTERED OVER THE SRN LESSER ANTILLES NEAR 14N61W. FARTHER E...SURFACE RIDGING DOMINATES ANCHORED BY A 1029 MB HIGH NEAR 33N34W PROVIDING GENERALLY FAIR WEATHER ACROSS THE ERN ATLC. A DRY SAHARAN AIR LAYER WRAPS AROUND THE ERN ATLC TROPICAL WAVE ACCOMPANIED BY AFRICAN DUST EXTENDING TO 44W S OF 23N EVIDENT IN THE LAST VISIBLE SATELLITE IMAGES OF THE DAY. ALOFT...AN UPPER LEVEL TROUGH EXTENDS FROM NEAR 32N30W TO 12N45W EMBEDDED BETWEEN TWO UPPER LEVEL RIDGES. ONE OF THESE RIDGES IS THE PREVIOUSLY MENTIONED ONE OVER THE SRN LESSER ANTILLES. THE SECOND IS CENTERED NEAR 15N30W. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ WALTON