000 AXNT20 KNHC 161748 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT THU JUL 16 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 05N41W TO 15N36W MOVING W AT 20-25 KT. THE WAVE COINCIDES WITH A GLOBAL MODEL INDICATED 700 MB SHORTWAVE TROUGH EMBEDDED SLIGHTLY WITHIN THE MONSOON TROUGH ALONG 10N. TO THE N-NW OF THE DEPICTED WAVE AXIS...A BROADER 700 MB TROUGH IS NOTED BETWEEN 40W-50W. MAXIMUM LOW-LEVEL...850 MB...RELATIVE VORTICITY FIELDS ARE INDICATED ALONG THE WAVE AXIS NEAR 10N. SCATTERED MODERATE CONVECTION IS FROM 06N-12N BETWEEN 32W-42W. TROPICAL WAVE EXTENDS FROM 06N69W TO 17N67W MOVING W AT 20 KT. THE WAVE COINCIDES WITH BROAD GLOBAL MODEL INDICATED 700 MB TROUGHING ACROSS THE EASTERN CARIBBEAN SEA WITH MOST RELATIVE VORTICITY AT 850 MB REMAINING S OF 12N OVER PORTIONS OF NW VENEZUELA. ISOLATED MODERATE CONVECTION IS ACROSS CENTRAL VENEZUELA WITH ISOLATED SHOWERS OCCURRING ACROSS THE CARIBBEAN WATERS FROM 12N-18N BETWEEN 60W-71W. TROPICAL WAVE EXTENDS FROM 04N84W TO 15N84W MOVING W AT 15 KT. WHILE MOST OF THE ENERGY ASSOCIATED WITH THE WAVE CONTINUES TO MOVE INTO THE EASTERN PACIFIC REGION...SUBTLE LOW-LEVEL TROUGHING IS NOTED OVER CENTRAL AMERICA IN THE VICINITY OF THE WAVE. THESE DYNAMICS ARE PROVIDING FOR ISOLATED MODERATE CONVECTION FROM 11N-17N BETWEEN 81W-87W. THIS CONVECTION REMAINS ENHANCED DUE TO UPPER LEVEL DIFFLUENCE ON THE WESTERN PERIPHERY OF AN UPPER LEVEL RIDGE CENTERED OVER THE SW CARIBBEAN SEA. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 12N16W TO 10N35W TO 09N39W. THE INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM 08N41W TO 06N48W TO 07N58W. ASIDE FROM CONVECTION ASSOCIATED WITH THE TROPICAL WAVE ALONG 39W...WIDELY SCATTERED MODERATE CONVECTION IS FROM 05N-09N BETWEEN 11W-24W. ...DISCUSSION... GULF OF MEXICO... UPPER LEVEL NORTHEAST TO EASTERLY FLOW IS OCCURRING OVER MUCH OF THE GULF BETWEEN A MIDDLE TO UPPER LEVEL RIDGE ANCHORED OVER NORTH TEXAS NEAR 31N97W AND A MIDDLE TO UPPER LEVEL LOW CENTERED OVER SOUTHERN MEXICO NEAR 18N97W. DEBRIS MOISTURE AND CLOUDINESS CONTINUES TO SPREAD SOUTHWESTWARD FROM ACTIVE CONVECTION OCCURRING ACROSS THE NE GULF. A WEAKNESS WITHIN THE SURFACE RIDGE...AND ASSOCIATED FRONTAL TROUGHING SAGGING SOUTHWARD ACROSS THE SE CONUS IS GENERATING SCATTERED SHOWERS AND TSTMS FROM 26N-30N BETWEEN 82W-88W. OTHERWISE...THE REMAINDER OF THE BASIN IS UNDER THE INFLUENCE OF SURFACE RIDGING ANCHORED BY A 1017 MB HIGH CENTERED ALONG THE LOUISIANA COAST NEAR 29N91W AND A RIDGE AXIS EXTENDING FROM THE SW NORTH ATLC ALONG 24N. PRIMARILY LIGHT TO GENTLE ANTICYCLONIC WINDS PREVAIL IN THE VICINITY OF THE RIDGING WITH GENTLE TO OCCASIONAL MODERATE SE WINDS OCCURRING ACROSS PORTIONS OF THE WESTERN GULF. THE RIDGE IS FORECAST TO REMAIN NEARLY STATIONARY THROUGH SATURDAY. CARIBBEAN SEA... GENERALLY NORTHWESTERLY FLOW ALOFT IS NOTED ON WATER VAPOR IMAGERY W OF 64W BETWEEN AN UPPER LEVEL RIDGE CENTERED OVER THE SW CARIBBEAN NEAR 11N78W AND A BROAD MIDDLE TO UPPER LEVEL LOW CENTERED NE OF THE LEEWARD ISLANDS NEAR 18N60W. THE NW FLOW IS NOT ONLY PROVIDING STABILITY WITH RELATIVELY DRY AIR ALOFT...BUT IT PROVIDING AMPLE DEEP LAYER WIND SHEAR TO INHIBIT ANY SIGNIFICANT DEEP CONVECTION THIS AFTERNOON. A TROPICAL WAVE IS ALONG 68W MOVING WEST...AND IS GENERATING ISOLATED SHOWERS AND TSTMS FROM 13N-18N BETWEEN 60W-71W. FARTHER WEST...ANOTHER TROPICAL WAVE ALONG 84W IS ENTERING INTO THE EAST PACIFIC REGION...YET CONTINUES TO MOVE ACROSS PORTIONS OF COSTA RICA AND NICARAGUA PRODUCING SCATTERED SHOWERS AND TSTMS FROM 09N-18N BETWEEN 81W-90W...WITH THE NORTHERN EXTENT OF THIS CONVECTION LARGELY INFLUENCED BY MIDDLE TO UPPER LEVEL DIFFLUENCE ON THE WESTERN PERIPHERY OF THE RIDGE CENTERED OVER THE SW CARIBBEAN. FINALLY...TRADES REMAIN ENHANCED ACROSS CENTRAL PORTIONS DUE TO A STRENGTHEN PRESSURE GRADIENT. FRESH TO OCCASIONAL STRONG E-NE WINDS ARE EXPECTED TO PERSIST THROUGH THE UPCOMING WEEKEND. ...HISPANIOLA... CURRENTLY...FAIR WEATHER CONDITIONS PREVAIL ACROSS THE ISLAND. THE APPROACH OF A TROPICAL WAVE SE OF THE ISLAND ALONG 68W IS INCREASING CLOUDINESS AND WIDELY SCATTERED SHOWERS AND ISOLATED TSTMS IN THE ADJACENT SOUTHERN COASTAL WATERS. GIVEN PEAK DAYTIME HEATING AND INSTABILITY...ISOLATED SHOWERS AND TSTMS ARE EXPECTED THROUGH THE LATE AFTERNOON AND EARLY EVENING HOURS ACROSS THE ISLAND...WITH ACTIVITY DIMINISHING THROUGH THE OVERNIGHT HOURS INTO EARLY FRIDAY. ATLANTIC OCEAN... AN UPPER LEVEL TROUGH HAS MOVED EAST OF THE DELMARVA REGION WITH THE AXIS NOW EXTENDING FROM 38N74W TO 29N76W. THIS SHORTWAVE TROUGHING SUPPORTS A 1008 MB LOW CENTERED NEAR 38N68W WITH COLD FRONT EXTENDING SW TO 33N75W BECOMING STATIONARY TO THE WEST TO THE SOUTHERN SOUTH CAROLINA COAST NEAR 33N80W. TO THE SOUTH OF THE FRONT...LOW-LEVEL MOISTURE CONVERGENCE COUPLED WITH MAXIMUM MIDDLE TO UPPER LEVEL DIFFLUENCE IS GENERATING SCATTERED SHOWERS AND ISOLATED TSTMS ACROSS MUCH OF THE SW NORTH ATLC FROM 21N-33N BETWEEN 70W-80W. FARTHER EAST...THE REMAINDER OF THE CENTRAL AND EASTERN ATLC IS UNDER THE INFLUENCE OF A SURFACE RIDGE ANCHORED BY A 1025 MB HIGH CENTERED NEAR 30N58W AND A 1023 MB HIGH CENTERED NEAR 31N35W. A WEAKNESS BETWEEN THESE TWO HIGHS IS ANALYZED AS A SURFACE TROUGH FROM 32N44W TO 27N52W. POSSIBLE ISOLATED SHOWERS ARE OCCURRING WITHIN 60 NM EITHER SIDE OF THE BOUNDARY. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ HUFFMAN