000 AXNT20 KNHC 211746 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT TUE JUL 21 2015 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 1715 UTC. ...TROPICAL WAVES... TROPICAL WAVE EXTENDS FROM 09N26W TO 18N23W MOVING W AT 20 KT. THE WAVE COINCIDES WITH A VERY BROAD AND SUBTLE 700 MB TROUGH NOTED IN GLOBAL MODEL GUIDANCE BETWEEN 18W-28W. A NARROW AND WEAK AREA OF 850 MB RELATIVE VORTICITY ALSO EXTENDS ACROSS THE WAVE AXIS FROM 13N23W TO 10N30W INDICATING THE STRETCHED OUT NATURE OF THE ENERGY ASSOCIATED WITH THE WAVE. NO SIGNIFICANT DEEP CONVECTION IS OCCURRING WITH THE WAVE AT THIS TIME DUE TO SAHARAN DUST COVERING MUCH OF THE EASTERN TROPICAL ATLC. TROPICAL WAVE EXTENDS FROM 09N59W TO 18N55W MOVING W AT 20 KT. THE WAVE COINCIDES WITH 700 MB TROUGHING ALOFT BETWEEN 54W-61W ON THE SOUTHWESTERN PERIPHERY OF A MID-LEVEL RIDGE CENTERED OVER THE CENTRAL ATLC NEAR 23N51W. SCATTERED MODERATE CONVECTION IS OCCURRING WITHIN 90 NM EITHER SIDE OF A LINE FROM 07N54W TO 11N64W...INCLUDING TRINIDAD AND TOBAGO...AND COASTAL NE VENEZUELA. TROPICAL WAVE EXTENDS FROM 08N69W TO 18N66W MOVING W AT 20 KT. THE WAVE REMAINS EMBEDDED WITHIN A NARROW MAXIMUM OF TOTAL PRECIPITABLE WATER BETWEEN 64W-69W THAT STRETCHES NORTH- NORTHEASTWARD FOCUSED ALONG A SURFACE TROUGH EXTENDING FROM 19N66W TO 24N61W. THE MOISTURE THEN EXTENDS INTO THE INFLUENCE OF AN UPPER LEVEL TROUGH AXIS EXTENDING OVER THE CENTRAL ATLC. ISOLATED MODERATE CONVECTION IS FROM 05N-10N BETWEEN 64W-71W ACROSS PORTIONS OF CENTRAL AND NW VENEZUELA. ISOLATED SHOWERS ARE OCCURRING ACROSS THE EASTERN CARIBBEAN S OF 16N BETWEEN 65W- 71W. TROPICAL WAVE EXTENDS FROM 07N76W TO 17N74W MOVING W AT 15-20 KT. THE WAVE COINCIDES WITH BROAD 700 MB TROUGHING BETWEEN 72W- 79W AND IS LARGELY INFLUENCED ALOFT BY AN UPPER LEVEL RIDGE CENTERED OVER THE SW CARIBBEAN NEAR 14N82W. ISOLATED MODERATE CONVECTION IS FROM 06N-11N BETWEEN 75W-80W. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH AXIS EXTENDS FROM THE AFRICAN COAST NEAR 14N17W TO 10N22W TO 06N34W. THE INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM 06N34W TO 05N42W TO 07N53W. ...DISCUSSION... GULF OF MEXICO... NORTHEAST TO EASTERLY FLOW ALOFT PREVAILS OVER MUCH OF THE GULF THIS AFTERNOON BETWEEN A MIDDLE TO UPPER LEVEL ANTICYCLONIC CIRCULATION CENTERED OVER CENTRAL TEXAS AND AN UPPER LEVEL LOW CENTERED OVER THE NORTHERN YUCATAN PENINSULA. WHILE A MAJORITY OF THE BASIN IS UNDER THIS RELATIVELY STABLE FLOW...AT THE SURFACE...WEAK TROUGHING AND LOW-LEVEL MOISTURE CONVERGENCE IS PRESENT ACROSS THE NE GULF STEMMING FROM A WEAK STREAM OF 500 MB RELATIVE VORTICITY EXTENDING FROM OVER THE FLORIDA BIG BEND REGION SW TO OVER THE NW GULF NEAR 27N93W. THIS MID-LEVEL VORTICITY IS PROVIDING FOCUS FOR SCATTERED SHOWERS AND TSTMS OCCURRING FROM 25N-29N BETWEEN 83W-90W. OTHERWISE...A SURFACE RIDGE AXIS EXTENDS FROM THE SW NORTH ATLC ALONG 25N TO 90W THEN TO THE EAST-CENTRAL MEXICO COAST NEAR TUXPAN. GENTLE TO OCCASIONAL MODERATE BREEZE ANTICYCLONIC FLOW IS FORECAST ACROSS THE BASIN THROUGH LATE THURSDAY. CARIBBEAN SEA... THE MAIN IMPACT FOR THE CARIBBEAN BASIN THIS AFTERNOON IS THREE TROPICAL WAVE MOVING WESTWARD. WHILE THOSE ARE DETAILED ABOVE...WATER VAPOR IMAGERY INDICATES THAT MOST OF THE MOISTURE IS FOUND E OF 70W AS DRY AIR ALOFT REMAINS IN PLACE OVER THE WESTERN CARIBBEAN IN ASSOCIATION WITH AN UPPER LEVEL RIDGE ANCHORED NEAR 14N81W. FARTHER EAST...MOISTURE AND CLOUDINESS INCREASES WITH LOW-LEVEL MOISTURE CONVERGENCE OCCURRING ALONG A LINE EXTENDING FROM 10N60W SE OF TRINIDAD AND TOBAGO TO THE ABC ISLANDS NEAR 13N70W. WIDELY SCATTERED SHOWERS AND TSTMS ARE OCCURRING WITHIN 90 NM OF THIS AREA...WITH ISOLATED SHOWERS AND TSTMS OCCURRING ELSEWHERE GENERALLY E OF 70W. FINALLY...MODERATE TO FRESH BREEZE CONDITIONS ARE EXPECTED TO PERSIST THROUGH LATE THURSDAY WHEN THEREAFTER THE PRESSURE GRADIENT ACROSS THE SOUTH- CENTRAL PORTION OF THE BASIN WILL STRENGTHEN INCREASING E-NE WINDS S OF 15N BETWEEN 69W-80W FRIDAY INTO THE UPCOMING WEEKEND. ...HISPANIOLA... CURRENTLY...MOSTLY CLEAR SKIES PREVAIL...HOWEVER WITH THE APPROACH OF A TROPICAL WAVE ALONG 68W...HIGHER PROBABILITY OF SCATTERED SHOWERS AND TSTMS IS LIKELY THROUGH LATE THURSDAY INTO FRIDAY. ATLANTIC OCEAN... NORTH-NORTHEASTERLY FLOW ALOFT PREVAILS OVER MUCH OF THE SW NORTH ATLC BETWEEN AN UPPER LEVEL ANTICYCLONE CENTERED NEAR 31N78W AND AN UPPER LEVEL LOW CENTERED NEAR 23N63W. WHILE OVERALL CONDITIONS REMAIN STABLE ACROSS THE SW NORTH ATLC WITHIN A SURFACE RIDGE WITH AXIS ALONG 25N/26N...LOW-LEVEL MOISTURE CONVERGENCE IS MAXIMIZED ALONG A LINE FROM 26N79W TO 31N77W IN WHICH ISOLATED SHOWERS AND TSTMS ARE OCCURRING WITHIN 60 NM EITHER SIDE OF THE LINE. FARTHER EAST...WITHIN THE INFLUENCE OF THE UPPER LEVEL LOW...A SURFACE TROUGH...THE NORTHERN PIECE OF ENERGY FRACTURED AWAY FROM THE TROPICAL WAVE ALONG 68W...IS GENERATING SCATTERED SHOWERS AND TSTMS FROM 20N-24N BETWEEN 62W- 67W...AND WITHIN 90 NM OF THE POINT 26N58W. OTHERWISE...A NEARLY STATIONARY RIDGE ANCHORED BY A 1023 MB HIGH CENTERED NEAR 29N46W INFLUENCES THE REMAINDER OF THE CENTRAL AND EASTERN ATLC. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ HUFFMAN