000 AXNT20 KNHC 160003 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT WED JUL 15 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2345 UTC. ...TROPICAL WAVES... A TROPICAL WAVE IS OVER THE CENTRAL ATLC WITH AXIS APPROXIMATELY ALONG 32W FROM 06N TO 15N MOVING W AT 20-25 KT. TPW IMAGERY INDICATED THE WAVE IS EMBEDDED IN A DEEP MOIST ENVIRONMENT MAINLY E OF THE WAVE AXIS. METEOSAT SAL IMAGERY SHOW SAHARAN DRY AIR AND DUST ENGULFING THE WAVE. SCATTERED MODERATE CONVECTION IS FROM 07N TO 10N BETWEEN 24W AND 31W BEING SUPPORTED BY MIDDLE TO UPPER LEVEL DIVERGENCE. A LARGE AMPLITUDE TROPICAL WAVE IS APPROACHING THE LESSER ANTILLES WITH AXIS APPROXIMATELY ALONG 59W AND S OF 20N...MOVING AT 20 KT. SSMI TPW AND METEOSAT IMAGERY INDICATE DRY AIR ENTRAINMENT IN THE WAVE ENVIRONMENT WHICH IS HINDERING CONVECTION. DUST IS ALSO PRESENT IN THE WAVE ENVIRONMENT AS OBSERVED IN SATELLITE IMAGERY AND IS BEING REPORTED THROUGH THE LESSER ANTILLES. A TROPICAL WAVE IS OVER THE CENTRAL CARIBBEAN WITH AXIS APPROXIMATELY ALONG 78W...MOVING W AT 15-20 KT. SSMI TPW IMAGERY INDICATE THE WAVE IS EMBEDDED IN A MODERATELY MOIST ENVIRONMENT. DIVERGENT FLOW AHEAD OF THE WAVE IN THE MIDDLE LEVELS SUPPORT SCATTERED MODERATE CONVECTION ALONG THE WAVE AXIS FROM 15N TO 16N BETWEEN 76W AND 79W. STRONG DEEP LAYER WIND SHEAR HINDER CONVECTION ELSEWHERE. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH ENTERS THE ATLANTIC OCEAN THROUGH GUINEA BISSAU NEAR 13N17W CONTINUING TO 12N19W. THE ITCZ EXTENDS FROM THAT POINT TO 10N30W THEN RESUMES W OF A TROPICAL WAVE NEAR 10N33W TO 07N45W TO 08N59W. ASIDE FROM THE CONVECTION ASSOCIATED WITH THE TROPICAL WAVES...SCATTERED MODERATE CONVECTION IS OBSERVED FROM 05N TO 11N BETWEEN 35W AND 55W. ...DISCUSSION... GULF OF MEXICO... A BROAD SURFACE RIDGE COVERING LARGE PORTIONS OF THE ATLC BASIN EXTENDS WESTWARD ACROSS SOUTH FLORIDA AND THE STRAITS OF FLORIDA TO THE SOUTH-CENTRAL GULF OF MEXICO. A WEAK SURFACE TROUGH IS OVER THE BAY OF CAMPECHE FROM 24N93W TO 18N95W. ALOFT...AN ELONGATED UPPER LOW IS CENTERED OVER THE ISTHMUS OF TEHUANTEPEC INTO THE BAY OF CAMPECHE PROVIDING SUPPORT FOR THE SURFACE TROUGH NOTED IN THE AREA. A MID-TO UPPER LEVEL ANTICYCLONE OVER E TEXAS WITH RIDGE AXIS EXTENDING ESE ACROSS THE GULF TO CENTRAL FLORIDA. A POCKET OF DEEP LAYERED SUBSIDENCE WAS NOTED OVER THE NW GULF. THE BASE OF A SHARP MID-TO UPPER LEVEL TROUGH ALONG THE EASTERN CONUS IS SLICING ACROSS THE FAR NE GULF. THIS TROUGH IS SUPPORTING A SURFACE TROUGH EXTENDING ACROSS NORTHERN FLORIDA TO 29N85W TO 29N88W. THE CONVECTIVE ACTIVITY ALONG THE TROUGH EARLIER HAS DISSIPATED LEAVING A SWATH OF MULTILAYERED CLOUDS OVER THE NE GULF AND FLORIDA WITH ISOLATED EMBEDDED SHOWERS AND THUNDERSTORMS. LIGHT SE TO S SURFACE WINDS PREVAILED OVER THE GULF S OF 25N...WINDS TURNED MORE TO THE W AND SW OVER THE GULF N OF 25N AND INCREASED TO 15 KT IN THE VICINITY OF THE SURFACE TROUGH. SURFACE RIDGING AND LIGHT FLOW WILL BE THE DOMINANT FEATURE DURING THE NEXT THREE DAYS. CARIBBEAN SEA... A TROPICAL WAVE IS OVER THE CENTRAL CARIBBEAN ALONG 78W IS ASSOCIATED WITH A BROAD MODERATELY MOIST AIRMASS THAT EXTENDS ACROSS THE WESTERN PORTION OF THE BASIN INTO THE GULF OF MEXICO. HOWEVER STRONG DEEP LAYER WIND SHEAR INHIBITS CONVECTION FOR THE MOST PART. OVER THE SW CARIBBEAN...LOWER PRESSURES ASSOCIATED WITH A LOW CENTER OVER N COLOMBIA AND THE EPAC MONSOON TROUGH SUPPORT SCATTERED BUT DIMINISHING MODERATE CONVECTION S OF 12N BETWEEN 74W AND 83W. SAHARAN AIR AND DUST ENGULFING THE NEXT TROPICAL WAVE TO ENTER THE BASIN COVERS THE E CARIBBEAN E OF 70W...THUS INHIBITING CONVECTION. REFER TO THE TROPICAL WAVES SECTION FOR MORE DETAILS. A GENERALLY TIGHT PRESSURE GRADIENT BETWEEN RIDGE OF HIGH PRESSURE OVER THE ATLC EXTENDING ACROSS THE NORTHERN BASIN AND LOWER PRESSURE OVER COLOMBIA SUPPORT TRADE WINDS OF 20-25 KT ACROSS THE CENTRAL CARIBBEAN MAINLY S OF 17N BETWEEN 70W-78W. TRADES OF 15 KT DOMINATE ELSEWHERE. THE NEXT TROPICAL WAVE WILL ENTER THE E CARIBBEAN TONIGHT POSSIBLY ENHANCING SHOWERS OVER THE WINDWARD ISLANDS. HISPANIOLA... RESIDUAL MOISTURE ASSOCIATED WITH THE PASSAGE OF A TROPICAL WAVE WITH AXIS CURRENTLY NEAR 78W IS BEGINNING TO MOVE NW AWAY FROM HISPANIOLA WITH TPW IMAGERY INDICATING A PATCH OF DRIER AIR IN ITS WAKE OVER PUERTO RICO AND THE DOMINICAN REPUBLIC. AT THE UPPER LEVELS...THE AREA IS SITUATED IN A DIFFLUENT ZONE BETWEEN A SMALL UPPER CYCLONE OVER THE CENTRAL BAHAMAS AND AN ANTICYCLONE OVER THE FAR SW CARIBBEAN. A LARGE UPPER LEVEL CYCLONE OVER THE TROPICAL ATLC NEAR 16N59W WITH A BAND OF SUBSIDENCE EXTENDING WWD OVER PUERTO RICO IS FORECAST TO MOVE WEST WITH SUBSIDENCE SWEEPING WESTWARD ACROSS THE ISLAND TOMORROW WHICH WILL LIMIT CONVECTIVE ACTIVITY. ATLANTIC OCEAN... TWO TROPICAL WAVES ARE OVER THE TROPICAL ATLANTIC ALONG 32W AND 59W. PLEASE SEE THE TROPICAL WAVES SECTION ABOVE FOR MORE DETAILS. IN KEEPING WITH THE CLIMATOLOGICAL NORM FOR THIS TIME OF THE YEAR...THE BERMUDA AZORES HIGH EXTENDS A RIDGE ACROSS LARGE PORTIONS OF THE TROPICAL ATLANTIC SUPPORTING MAINLY FAIR WEATHER. OVER THE SW N ATLC...THE BASE OF A MIDDLE LEVEL TROUGH ALONG THE EASTERN CONUS IS GENERATING DIFFLUENT FLOW N OF 27N W OF 75W. THIS WIND FLOW ALOFT ALONG WITH MOISTURE BEING ADVECTED FROM THE CARIBBEAN AND SE CONUS SUPPORT SCATTERED SHOWERS AND TSTMS N OF 29N W OF 77W. FARTHER SOUTH...AN UPPER LOW ANCHORED NEAR ANDROS ISLAND SUPPORTS SIMILAR CONVECTION FROM 21N TO 28N W OF 71W. A VERY LARGE CYCLONIC CIRCULATION CENTERED NEAR 16N59W COVER THE TROPICAL ATLC S OF 25N BETWEEN 45W AND THE CARIBBEAN IS PROVIDING UNUSUALLY STRONG NW FLOW ALOFT OVER THE DEEP TROPICS AND STRONG SUBSIDENCE OVER THE E CARIBBEAN. OTHERWISE...A WEAKENING COLD FRONT EXTENDS OVER THE N-CENTRAL ATLC FROM 31N46W TO 29N55W WITH NO CONVECTION. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ COBB