000 AXNT20 KNHC 151156 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 805 AM EDT TUE SEP 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1045 UTC. ...SPECIAL FEATURE... A 1012 MB LOW MIDWAY BETWEEN THE CAPE VERDE ISLANDS AND THE LESSER ANTILLES IS CENTERED NEAR 12N41W ALONG A TROPICAL WAVE THAT EXTENDS FROM 17N41W THROUGH THE LOW TO 8N41W MOVING W 5-10 KT OVER THE PAST 24 HOURS. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 45 NM OF LINE FROM 10N40W TO 8N44W. SCATTERED MODERATE CONVECTION IS WITHIN 45 NM OF LINE FROM 16N38W TO 14N43W. SOME DEVELOPMENT OF THIS LOW IS POSSIBLE DURING THE NEXT COUPLE OF DAYS AFTER WHICH THE UPPER LEVEL WINDS ARE EXPECTED TO BECOME UNFAVORABLE FOR DEVELOPMENT. THERE IS A HIGH CHANCE OF TROPICAL FORMATION OVER THE NEXT 48 HOURS. A 1012 MB LOW S OF THE CAPE VERDE ISLANDS IS CENTERED NEAR 9N22W ALONG A TROPICAL WAVE THAT EXTENDS FROM 15N23W THROUGH THE LOW TO 8N22W MOVING W-SW NEAR 10 KT OVER THE PAST 24 HOURS. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 8N-12N BETWEEN 23W-26W. THE ACTIVITY SHOWS SIGNS OF ORGANIZATION AND ENVIRONMENTAL CONDITIONS ARE EXPECTED TO BE CONDUCIVE FOR FURTHER DEVELOPMENT. THERE IS A MEDIUM CHANCE OF TROPICAL FORMATION OVER THE NEXT 48 HOURS. ...TROPICAL WAVES... TROPICAL WAVE IN THE E CARIBBEAN EXTENDS ALONG 63W FROM 11N-21N MOVING W NEAR 15 KT OVER THE PAST 24 HOURS. SSMI TPW INDICATES THE WAVE IS EMBEDDED WITHIN SURGE OF DEEP MOISTURE. ANY CONVECTION AROUND THIS WAVE IS ASSOCIATED WITH AN UPPER FEATURE AND IS BEING ENHANCED BY THE TROPICAL WAVE. TROPICAL WAVE ANALYZED IN THE W CARIBBEAN EXTENDS ALONG 82W FROM 10N-19N MOVING W 10-15 KT OVER THE PAST 24 HOURS. SSMI TPW INDICATES THE CARIBBEAN IS COVERED IN MODERATE MOISTURE. ANY CONVECTION AROUND THIS WAVE IS ASSOCIATED WITH AN UPPER FEATURE AND IS BEING ENHANCED BY THE TROPICAL WAVE. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS ACROSS AFRICA INTO THE E TROPICAL ATLC NEAR 18N16W THROUGH THE 1012 MB LOW ALONG THE EASTERN MOST TROPICAL WAVE CONTINUING ALONG 12N36W TO JUST E OF THE 1012 MB LOW ALONG THE NEXT TROPICAL NEAR 12N40W. THE ITCZ BEGINS W OF THE SECOND WAVE NEAR 11N43W AND CONTINUES ALONG 9N52W TO SOUTH AMERICA NEAR 9N61W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 75 NM N OF THE ITCZ BETWEEN 51W-54W. THE REMAINDER OF THE CONVECTION IS ASSOCIATED WITH THE TROPICAL WAVES IN THE SPECIAL FEATURES. ...DISCUSSION... GULF OF MEXICO... AN UPPER TROUGH IN THE NW ATLC IS SUPPORTING A COLD FRONT IN THE NW ATLC AND A STATIONARY FRONT THAT EXTENDS INTO THE DISCUSSION AREA AND ENTERS THE GULF OF MEXICO ACROSS CENTRAL FLORIDA JUST N OF WEST PALM BEACH TO NAPLES THEN ALONG 26N86W TO 26N90W WHERE IT DISSIPATES TO 28N95W. AN UPPER RIDGE EXTENDS FROM OVER MEXICO ALONG 20N COVERING THE GULF MEXICO AND THE NW CARIBBEAN AND IS PROVIDING DIFFLUENCE ALOFT. SCATTERED TO NUMEROUS SHOWERS/ ISOLATED THUNDERSTORMS ARE WITHIN 210 NM N OF THE FRONT BETWEEN 86W-93W WITH SCATTERED SHOWERS/ISOLATED THUNDERSTORMS WITHIN 240 NM S OF THE FRONT BETWEEN 91W-95W. A SURFACE TROUGH IS IN THE SW GULF EXTENDING FROM 23N96W TO S MEXICO NEAR 18N93W WITH SCATTERED SHOWERS/ISOLATED THUNDERSTORMS WITHIN 125 NM NE OF THE SURFACE TROUGH AND WITHIN 60 NM SW OF THE SURFACE TROUGH S OF 20N. A 1013 MB LOW IS ALONG THE COAST OF MEXICO NEAR 23N97W GENERATING SCATTERED SHOWERS/ISOLATED THUNDERSTORMS FROM 21N-24N W OF 96W TO THE COAST OF MEXICO. A SURFACE TROUGH...REMNANTS OF GRACE...EXTENDS ALONG THE COAST OF SE FLORIDA THROUGH THE STRAITS OF FLORIDA NEAR 24N80.5W AND TO OVER CUBA NEAR 22N81W GENERATING SCATTERED SHOWERS/ISOLATED THUNDERSTORMS S OF 26N E OF 86W INCLUDING S FLORIDA AND THE FLORIDA KEYS. BOTH THE FRONT AND THE 1013 MB LOW WILL DISSIPATE BY TONIGHT. THE SURFACE TROUGH...REMNANTS OF GRACE...WILL MOVE THROUGH THE STRAITS OF FLORIDA TODAY AND STALL ALONG 88W BY WED NIGHT. CARIBBEAN SEA... AN UPPER RIDGE EXTENDS ALONG 20N FROM OVER MEXICO AND THE GULF OF MEXICO TO 74W COVERING THE W CARIBBEAN. A SECOND UPPER RIDGE EXTENDS FROM THE W ATLC OVER THE E CARIBBEAN. AN UPPER LOW IS IN THE SW CARIBBEAN NEAR 10N78W AND EXTENDS AN UPPER TROUGH NE ALONG 16N73W TO OVER HISPANIOLA. AT THE SURFACE ARE TWO TROPICAL WAVES...PLEASE REFER TO THE SECTION ABOVE FOR DETAILS. THE UPPER RIDGES ARE PROVIDING DIFFLUNCE ALOFT TO GENERATE SCATTERED SHOWERS/ISOLATED THUNDERSTORMS N OF 18N TO CUBA BETWEEN 76W-85W. SIMILAR CONVECTION IS OVER THE E CARIBBEAN FROM 13N-18N BETWEEN 60W-69W INCLUDING THE LESSER ANTILLES AND FROM 18N-20N BETWEEN 60W-63W. W CARIBBEAN TROPICAL WAVE WILL REACH THE YUCATAN PENINSULA BY WED. E CARIBBEAN TROPICAL WAVE WILL MOVE ACROSS THE REMAINDER CENTRAL CARIBBEAN BY WED AND REACH THE W CARIBBEAN THU. ...HISPANIOLA... SKIES REMAIN CLEAR ACROSS THE ISLAND THIS MORNING. THE UPPER TROUGH THAT EXTENDS FROM THE SW CARIBBEAN WILL PERSIST THROUGH THIS MORNING THEN SHIFT W TO OVER HAITI BY WED. MOISTURE WILL INCREASE LATER TODAY AHEAD OF THE E CARIBBEAN TROPICAL WAVE THAT WILL MOVE ACROSS THE ISLAND TONIGHT AND WED. THIS WILL INCREASE THE CHANCE OF SHOWERS/THUNDERSTORMS FOR THIS EVENING THROUGH WED. ATLANTIC OCEAN... A NARROW UPPER TROUGH IN THE NW ATLC IS SUPPORTING A COLD FRONT N OF THE AREA WITH A STATIONARY FRONT EXTENDING ALONG 32N69W 28N76W THEN ACROSS CENTRAL FLORIDA INTO THE GULF OF MEXICO JUST N OF WEST PALM BEACH. SCATTERED SHOWERS/ISOLATED THUNDERSTORMS ARE FROM 27N-30N W OF 74W TO THE COAST OF FLORIDA. A SURFACE TROUGH...REMNANTS OF GRACE...EXTENDS FROM THE COAST OF FLORIDA NEAR 26N80W INTO THE STRAITS OF FLORIDA TO OVER CUBA TO NEAR 22N81W GENERATING SCATTERED SHOWERS/ISOLATED THUNDERSTORMS S OF 25N TO OVER CUBA W OF 77W. A SURFACE TROUGH IS IN THE W/CENTRAL ATLC EXTENDING FROM 29N58W 26N59W TO 24N60W WITH SCATTERED SHOWERS/ISOLATED THUNDERSTORMS FROM 24N-29N BETWEEN 45W-66W AND N OF 29N BETWEEN 53W-60W. THE ABOVE SURFACE TROUGH IS A WEAKNESS IN THE SURFACE RIDGE THAT DOMINATES THE ATLC E OF THE W ATLC FRONT AND ANCHORED BY A 1023 MB HIGH N OF THE AREA NEAR 34N39W. W ATLC FRONT N OF 30N WILL SHIFT E OF THE AREA TONIGHT WHILE THE REMAINDER WILL DISSIPATE TODAY. THE SURFACE TROUGH...REMNANTS OF GRACE...WILL MOVE INTO THE GULF OF MEXICO TODAY. THE E CARIBBEAN TROPICAL WAVE WILL REACH THE WINDWARD PASSAGE WED NIGHT. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ PAW