000 AXNT20 KNHC 271737 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT FRI JUL 27 2012 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...WEATHER OBSERVATIONS...RADAR...AND METEOROLOGICAL ANALYSIS. BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1645 UTC. ...TROPICAL WAVES... TROPICAL WAVE IS MOVING W AT 15-20 KT THROUGH THE CENTRAL TRPCL ATLC ALONG 20N36W TO 10N37W. TOTAL PRECIPITABLE WATER IMAGERY INDICATES THAT THE WAVE LIES WITHIN A SURGE OF DEEP LAYER MOISTURE. THERE IS ALSO A CLEARING IN THE WIDESPREAD SAHARAN AIR LAYER THAT IS PRESENT ACROSS MUCH OF THE TROPICAL ATLC. A RECENT ASCAT SCATTEROMETER PASS ALSO INDICATES THAT THERE IS LOW-LEVEL CYCLONIC FLOW AROUND THE AXIS. DUE TO THE LARGE AROUND OF DUST NEAR THE WAVE...MOST DEEP CONVECTION IS SUPPRESSED EXCEPT FOR AREAS WITHIN THE MONSOON TROUGH WHERE SCATTERED MODERATE CONVECTION IS FROM 7N-10N BETWEEN 36W-45W. TROPICAL WAVE IS APPROACHING THE LESSER ANTILLES MOVING W AT 15-20 KT CURRENTLY ALONG 21N54W TO 11N55W. THE WAVE PREVIOUSLY EXTENDING MORE TOWARDS THE NORTH...BUT IT APPEARS THAT THE NRN PORTION WILL MOVE NW WHILE THE SRN PORTION WILL CONTINUE W. FOR THIS REASON...THE WAVE HAS BEEN SPLIT SO THAT THE NRN PORTION WILL CONTINUE AS A SURFACE TROUGH. THE WAVE LIES ON THE W SIDE OF A SURGE OF DEEP LAYER MOISTURE PRESENT IN TOTAL PRECIPITABLE WATER IMAGERY. DUE TO DUST SURROUNDING THE WAVE...ONLY ISOLATED MODERATE CONVECTION IS NEAR THE ITCZ REGION FROM 7N-11N BETWEEN 53W-57W. TROPICAL WAVE IS MOVING W OFF THE YUCATAN PENINSULA ALONG 22N89W TO 16N91W AT 15 KT. TOTAL PRECIPITABLE WATER IMAGERY INDICATES THAT THE WAVE LIES IN THE MIDDLE OF A SURGE OF DEEP LAYER MOISTURE THAT EXTENDS FROM THE FAR NW CARIBBEAN INTO THE SW GULF OF MEXICO. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS E OF THE WAVE AXIS FROM 16N-21N BETWEEN 87W-90W. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS ACROSS W AFRICA TO THE COAST OF SENEGAL AT 14N17W CONTINUING ACROSS ATLC WATERS ALONG 12N29W 9N40W 11N47W. THE ITCZ BEGINS AT 10N47W AND CONTINUES TO 9N61W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 7N-11N BETWEEN 16W-23W...AND FROM 7N-10N BETWEEN 26N-32N. ...DISCUSSION... GULF OF MEXICO... THE NRN GULF OF MEXICO IS EXPERIENCING SCATTERED SHOWERS/THUNDERSTORMS N OF 28N BETWEEN 84W-92W...DUE TO DIFFLUENCE ALOFT NEAR THE NRN EXTENT OF AN INVERTED UPPER LEVEL TROUGH THAT EXTENDS FROM THE WRN FLORIDA PANHANDLE TO THE YUCATAN PENINSULA. THE REMAINDER OF THE BASIN IS EXPERIENCING MOSTLY FAIR CONDITIONS DUE TO DRY AIR ALOFT AROUND AN UPPER LEVEL RIDGE CENTERED IN THE W ATLC. THE UPPER RIDGE SUPPORTS SURFACE RIDGING ACROSS THE BASIN ALONG 27N. A FEW HEAVY SHOWERS HAVE POPPED UP OVER W CENTRAL FLORIDA. SHOWERS/THUNDERSTORMS ARE ALSO OVER THE YUCATAN PENINSULA ASSOCIATED WITH A TROPICAL WAVE ABOUT TO MOVE INTO THE SW GULF. SEE TROPICAL WAVE SECTION ABOVE FOR MORE DETAILS. LIGHT ANTI-CYCLONIC FLOW IS AROUND THE SURFACE RIDGE. EXPECT THE TROPICAL WAVE TO MOVE ACROSS THE SW GULF WITH POSSIBLE SHOWERS/THUNDERSTORMS ALONG IT. THE REMAINDER OF THE BASIN WILL REMAIN UNDER SURFACE RIDGING WITH SHOWERS/THUNDERSTORMS LIKELY ACROSS THE NRN GULF. CARIBBEAN SEA... THE ENTIRE CARIBBEAN IS MOSTLY DRY TODAY AS IT IS IMPACTED WITH SAHARAN DUST AND DRY AIR ALOFT. AN INVERTED UPPER TROUGH OVER THE YUCATAN PENINSULA HAD FLARED UP SOME STORMS OVER THE NW WATER...WHICH HAVE NOW DISSIPATED. AN UPPER LEVEL RIDGE COVERS THE SW CARIBBEAN...AS WELL AS THE FAR ERN CARIBBEAN. A DRY UPPER LEVEL LOW IS ACROSS THE N CENTRAL CARIBBEAN ACROSS THE WINDWARD PASSAGE. TRADEWIND FLOW OF 15-20 KTS IS ACROSS MUCH OF THE BASIN WITH ONLY A FEW ISOLATED LOW-LEVEL SHOWERS EMBEDDED WITHIN THE FLOW. A FEW ISOLATED SHOWERS/THUNDERSTORMS ARE ALSO OVER PORTIONS OF NICARAGUA AND COSTA RICA. EXPECT LITTLE CHANGE FOR THE NEXT 24 HOURS. A TROPICAL WAVE APPROACHING THE LESSER ANTILLES SHOULD REACH THE ERN CARIBBEAN WITHIN THE NEXT 24-36 HOURS. ATLANTIC OCEAN... A LARGE UPPER LEVEL RIDGE COVERS THE W ATLC CENTERED NEAR 33N68W SUPPORTING A 1020 MB HIGH NEAR 26N70W. MOSTLY FAIR WEATHER IS ACROSS THIS AREA DUE TO AN AREA OF SAHARAN DUST THAT IS ALSO PRESENT ACROSS THE CARIBBEAN. A WEAK 1016 MB LOW IS JUST N OF THE DISCUSSION AREA NEAR 32N61W. A STATIONARY FRONT EXTENDS FROM THE LOW CENTER ALONG 30N60W 28N67W 31N71W. SCATTERED SHOWERS/ISOLATED THUNDERSTORMS ARE WITHIN 120 NM SW OF THE AXIS. FARTHER E...A SURFACE TROUGH IS ALONG 27N48W TO 24N53W. THE TROUGH IS ACTUALLY A SPLIT OFF PORTION OF A TROPICAL WAVE TO THE S. DUE TO THE LARGE AREA OF SAHARAN DUST...NO SHOWERS OR THUNDERSTORMS ARE NEAR THE TROUGH. THE REMAINDER OF THE BASIN IS DOMINATED BY SURFACE RIDGING AROUND A 1026 MB HIGH NEAR 34N40W. THE RIDGE...IN COMBINATION WITH THE SAHARAN AIR LAYER IS MAINTAINING FAIR CONDITIONS BASIN-WIDE. ALOFT...AN UPPER LEVEL LOW IS CENTERED NEAR 24N58W...BUT IS NOT CAUSING ANY WEATHER. A PAIR OF UPPER RIDGES COVER THE TROPICAL ATLC CENTERED NEAR 19N46W AND 18N20W. A BROAD UPPER TROUGH IS BETWEEN THEM ALONG 30W. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ WALTON