000 AXNT20 KNHC 211754 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT SUN JUN 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. ...SPECIAL FEATURES... A TIGHT PRESSURE GRADIENT BETWEEN HIGH PRESSURE ACROSS THE WESTERN ATLC AND THE GULF OF MEXICO...AND A 1006 MB LOW OVER NORTHERN COLOMBIA SUPPORTS NEAR GALE FORCE WINDS OVER A PORTION OF THE SOUTH-CENTRAL CARIBBEAN TODAY. THE GRADIENT WILL TIGHTEN FURTHER TONIGHT...WHICH WILL RESULT IN GALE FORCE WINDS STARTING AT 0600 UTC TONIGHT FROM 11N TO 14N BETWEEN 72W AND 77W. SEAS OF 10 TO 14 FT ARE EXPECTED. THESE GALE FORCE WINDS ARE FORECAST TO PERSIST UNTIL 1200 UTC MONDAY. PLEASE READ THE HIGH SEAS FORECAST... MIAHSFAT2/FZNT02 KNHC...AND THE OFFSHORE FORECAST...MIAOFFNT3/ FZNT23 KNHC...FOR MORE DETAILS. ...TROPICAL WAVES... A TROPICAL WAVE IS OVER THE EASTERN TROPICAL ATLC WITH AXIS ALONG 20N FROM 16N TO 06N...MOVING W AT AROUND 15 TO 20 KT. SSMI TPW IMAGERY INDICATE THIS WAVE IS EMBEDDED IN A MODERATE MOIST ENVIRONMENT S OF 15N WITH METEOSAT IMAGERY INDICATING SAHARAN DUST AND DRY AIR N OF 15N. SCATTERED MODERATE CONVECTION IS FROM 07N TO 12N BETWEEN THE AFRICAN COAST AND 21W. A TROPICAL WAVE IS OVER THE CENTRAL TROPICAL ATLC WITH AXIS ALONG 40W/41W FROM 12N TO 04N...MOVING W AT 20 KT OVER THE PAST 24 HOURS. SSMI TPW IMAGERY SHOWS THE WAVE IS EMBEDDED IN A MODERATE MOIST ENVIRONMENT S OF 12N...EXCEPT IN THE NORTHERN REGION WHERE METEOSAT SATELLITE IMAGERY INDICATES SAHARAN DRY AIR AND DUST. NO DEEP CONVECTION IS NOTED WITH THE WAVE AT THIS TIME. A TROPICAL WAVE IS IN THE WESTERN TROPICAL ATLC EXTENDING FROM 16N54W TO S AMERICA NEAR 05N57W...MOVING W AT 15 KT OVER THE PAST 24 HOURS. SSMI TPW IMAGERY INDICATES THAT THIS WAVE IS EMBEDDED IN A DEEP MOIST AIRMASS. STRONG WESTERLY SHEAR IS CURRENTLY IMPACTING THIS WAVE. CLUSTERS OF MODERATE CONVECTION ARE FROM 08N TO 15N BETWEEN 51W AND 63W. A TROPICAL WAVE IS IN THE SW CARIBBEAN BASIN WITH AN AXIS ALONG 82W FROM 17N TO PANAMA TO THE EASTERN PACIFIC...MOVING W NEAR 10 KT OVER THE PAST 24 HOURS. SSMI TPW IMAGERY INDICATES THAT THERE IS ABUNDANT MOISTURE S OF 12N ALONG THE WAVE...WITH DRY AIR N OF 12N. SCATTERED MODERATE TO STRONG CONVECTION ARE FROM 09N TO 11N BETWEEN 81W AND 85W. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS ACROSS AFRICA TO 17N16W...THEN RESUMES W OF A TROPICAL WAVE NEAR 08N21W AND CONTINUES TO 06N33W. THE ITCZ BEGINS NEAR 06N43W AND CONTINUES TO E OF A TROPICAL WAVE NEAR 05N55W. BESIDES THE CONVECTION ASSOCIATED WITH THE TROPICAL WAVES...ISOLATED MODERATE CONVECTION IS WITHIN 100 NM OF EITHER SIDE OF THE MONSOON TROUGH BETWEEN 21W AND 30W. ...DISCUSSION... THE GULF OF MEXICO... AN ELONGATED UPPER TROUGH EXTENDS FROM CENTRAL FL SOUTHWESTWARD TO THE YUCATAN PENINSULA. AN UPPER RIDGE IS OVER CENTRAL MEXICO. AREAS OF WEAK UPPER LEVEL DIFFLUENCE OVER THE SW...SE...AND NE GULF SUPPORTS SCATTERED MODERATE CONVECTION WITHIN 50 NM OF THE MEXICO COAST FROM 26N TO 20N...SCATTERED THUNDERSTORMS FROM 22N TO 25N BETWEEN 81W AND 86W...AND FROM 29N TO THE GULF COAST BETWEEN 84W AND 89W. SURFACE RIDGING EXTENDS FROM THE WESTERN ATLC TO THE NORTHERN GULF AND IS ANCHORED BY A 1020 MB HIGH CENTERED OVER THE NE GULF NEAR 27N86W. ANTICYCLONIC FLOW GENERALLY UNDER 10 KT IS OVER THE EASTERN GULF...WHILE SOUTHEASTERLY WINDS AROUND 15 KT ARE OVER THE WESTERN GULF. A SURFACE TROUGH EXTENDS FROM 24N91W TO 18N93W. NO CONVECTION IS ASSOCIATED WITH THIS TROUGH. OVER THE NEXT 24 HOURS EXPECT CONVECTION TO CONTINUE TO BE POSSIBLE OVER THE SW GULF. THE CARIBBEAN SEA... A TROPICAL WAVE IS OVER THE SW CARIBBEAN. PLEASE SEE THE SPECIAL FEATURES SECTION FOR MORE DETAILS. A TIGHT PRESSURE GRADIENT BETWEEN HIGH PRESSURE OVER THE WESTERN ATLC AND GULF OF MEXICO AND LOW PRESSURE OVER N COLOMBIA SUPPORTS NEAR GALE-FORCE WINDS OVER A PORTION OF THE SOUTH-CENTRAL CARIBBEAN. PLEASE SEE THE SPECIAL FEATURES SECTION FOR MORE DETAILS. MODERATE MOISTURE IS CONFINED ALONG THE GREATER ANTILLES WITH RELATIVELY DRY AIR OVER THE CARIBBEAN BETWEEN 12N AND 17N. OTHER THAN CONVECTION ASSOCIATED WITH THE WAVE OVER THE SW BASIN...SCATTERED THUNDERSTORMS ARE FROM 21N TO 22N BETWEEN 82W AND 85W...AND OVER THE SOUTHERN LESSER ANTILLES WELL IN ADVANCE OF A TROPICAL WAVE OVER THE WESTERN ATLC. OVER THE NEXT 24 HOURS CONVECTION WILL SPREAD ACROSS THE LESSER ANTILLES AS A WESTWARD MOVING TROPICAL WAVE CROSSES OVER THE ISLANDS AND INTO THE EASTERN CARIBBEAN. ...HISPANIOLA... ISOLATED THUNDERSTORMS ARE OVER HISPANIOLA THIS AFTERNOON...MAINLY DUE TO DAYTIME HEATING. THESE STORMS ARE EXPECTED TO WEAKEN AROUND SUNSET...REDEVELOPING MONDAY AFTERNOON. ADDITIONAL CONVECTION IS EXPECTED TO SPREAD ACROSS THE ISLAND MONDAY NIGHT...ASSOCIATED WITH A WESTWARD MOVING TROPICAL WAVE. THE ATLANTIC OCEAN... BROAD SURFACE RIDGING COVERS THE ATLC BEING ANCHORED BY A 1027 MB HIGH NEAR 29N37W. METEOSAT SATELLITE IMAGERY INDICATES SAHARAN DRY AIR AND DUST COVERING MOST OF THE TROPICS S OF 20N. THE ONLY NOTABLE CONVECTION OVER THE SUBTROPICAL ATLC S OF 31N IS SCATTERED THUNDERSTORMS FROM 27N TO 29N BETWEEN 78W AND THE FL EAST COAST. FOR INFORMATION ON TROPICAL WAVES SEE THE TROPICAL WAVES SECTION ABOVE. SURFACE RIDGING WILL REMAIN DOMINANT ACROSS THE ATLC THROUGH TUESDAY. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ LATTO