000 AXNT20 KNHC 270007 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT WED AUG 26 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. ...SPECIAL FEATURES... TROPICAL STORM ERIKA IS CENTERED NEAR 16.6N 58.9W AT 26/2100 UTC OR ABOUT 170 NM E OF ANTIGUA...MOVING W AT 15 KT. ESTIMATED CENTRAL PRESSURE IS 1005 MB. MAXIMUM SUSTAINED WIND SPEED IS 40 KT WITH GUSTS TO 50 KT. NUMEROUS MODERATE TO ISOLATED STRONG CONVECTION IS FROM 13N TO 17N BETWEEN 55W AND 59W. SCATTERED MODERATE CONVECTION IS ELSEWHERE FROM 12N TO 19N BETWEEN 54W AND 60W. PLEASE SEE THE LATEST FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT5/WTNT25 KNHC FOR MORE DETAILS. ...TROPICAL WAVES... A TRPCL WAVE CAME OFF THE WEST AFRICAN COAST EARLIER THIS AFTERNOON. ITS AXIS IS APPROXIMATELY ALONG 18W AND IS EXPECTED TO MOVE W AT 10-15 KT WITHIN THE NEXT 48 HOURS. MODERATE MOISTURE IS ASSOCIATED WITH THIS WAVE FROM THE SURFACE TO 850 MB AS INDICATED BY CIRA LAYER PRECIPITABLE WATER IMAGERY. LOW-LEVEL MOISTURE CONVERGENCE SUPPORTS ISOLATED SHOWERS AND TSTMS FROM 07N TO 14N BETWEEN 18W AND 25W. FURTHER CONVECTION IS BEING HINDERED BY THE PRESENCE OF SAHARAN DRY AIR AND DUST IN THE NORTHERN WAVE ENVIRONMENT. A TROPICAL WAVE IS OVER THE CENTRAL ATLANTIC WITH AXIS NEAR 36W...MOVING W AT 15 KT DURING THE PAST 24 HOURS. A BROAD AREA OF MODERATE MOISTURE IS ASSOCIATED WITH THIS WAVE FROM THE SURFACE TO NEARLY 700 MB AS INDICATED BY CIRA LAYER PRECIPITABLE WATER IMAGERY. THIS IMAGERY ALSO SHOWS A TONGUE OF DRY AIR WRAPPING THE WAVE ENVIRONMENT...WHICH COINCIDES WITH THE PRESENCE OF SAHARAN DRY AIR AND DUST ACCORDING TO ENHACEMENTS OF METEOSAT IMAGERY. NO CONVECTION IS OBSERVED AT THIS TIME. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH AXIS EXTENDS W OF A TROPICAL WAVE FROM 10N20W TO 09N32W TO 08N39W. THE ITCZ BEGINS NEAR 08N39W AND CONTINUES TO 08N50W. ASIDE THE CONVECTION ASSOCIATED WITH THE WAVE E OF THE CAPE VERDE ISLANDS...ISOLATED SHOWERS ARE FROM 03N TO 11N BETWEEN 23W AND 37W. ...DISCUSSION... GULF OF MEXICO... A BROAD MIDDLE TO UPPER-LEVEL TROUGH EXTENDS FROM THE OHIO VALLEY S-SW ACROSS THE GULF TO A BASE OVER THE YUCATAN PENINSULA. THIS TROUGH SUPPORTS A FRONTAL SYSTEM ANALYZED AS STATIONARY FROM A 1010 MB LOW OVER SOUTH CAROLINA ACROSS NORTHERN FLORIDA TO 29N82W TO 24N90W TO 24N94W. THE UPPER TROUGH ALSO SUPPORT A PAIR OF SURFACE TROUGHS...ONE AHEAD OF THE FRONT ALONG THE FLORIDA PENINSULA AND A SECOND TROUGH W OF THE FRONT TAIL FROM 24N96W TO 18N94W. MOISTURE ADVECTION FROM THE CARIBBEAN IS CONVERGING WITH MOISTURE ASSOCIATED WITH THE FRONT GENERATING INSTABILITY THAT ALONG WITH A DIVERGENT ENVIRONMENT ALOFT SUPPORT HEAVY SHOWERS AND TSTMS OVER THE SW GULF S OF 25N W OF 91W. SIMILAR CONVECTION ASSOCIATED WITH THE TROUGH ALONG FLORIDA EXTENDS OVER SE GULF WATERS FROM 25N TO 26N E OF 83W. DRY AIR SUBSIDENCE AND STRONG DEEP LAYER WIND SHEAR N OF THE FRONT SUPPORT FAIR WEATHER N OF 26N. NORTHERLY WIND FLOW OF OF LESS THAN 15 KT COVERS THE BASIN. A LOW PRESSURE CENTER IS FORECAST TO DEVELOP OVER THE NE GULF ASSOCIATED WITH THE STATIONARY FRONT THAT IS EXPECTED TO DISSIPATE BY FRIDAY. CARIBBEAN SEA... AN ELONGATED UPPER LOW EXTENDS FROM THE CENTRAL BAHAMAS S-SW TO PANAMA COASTAL WATERS...WHICH ALONG WITH SHALLOW MOISTURE IN THE CENTRAL AND WESTERN GULF SUPPORT SCATTERED MODERATE CONVECTION AND TSTMS ALONG CUBA AND ADJACENT SOUTHERN WATERS...SOUTHERN AND WESTERN JAMAICA AND SW CARIBBEAN S OF 14N W OF 78W. A SURFACE TROUGH...REMNANTS OF DANNY...CONTINUE TO ENHANCE SCATTERED SHOWERS AND TSTMS ALONG HAITI AND NORTHERN COASTAL WATERS AND ISOLATED SHOWERS AND TSTMS OVER CENTRAL AND WESTERN DOMINICAN REPUBLIC. ISOLATED SHOWERS CONTINUE ACROSS THE WINDWARD ISLANDS ASSOCIATED WITH THE PROXIMITY OF TROPICAL STORM ERIKA. SEE SPECIAL FEATURES FOR DETAILS. THE PASSAGE OF ERIKA THROUGH THE NE CARIBBEAN THU WILL SUPPORT HEAVY SHOWERS AND POSSIBLE TSTMS ACROSS THE LEEWARD ISLANDS...PUERTO RICO AND ADJACENT WATERS. ...HISPANIOLA... THE REMNANTS OF DANNY IN THE FORM OF A SURFACE TROUGH CONTINUE TO ENHANCE SCATTERED SHOWERS AND TSTMS ALONG HAITI AND NORTHERN COASTAL WATERS AND ISOLATED SHOWERS AND TSTMS OVER CENTRAL AND WESTERN DOMINICAN REPUBLIC. TROPICAL STORM ERIKA CURRENTLY LOCATED E OF THE LEEWARD ISLANDS WILL MOVE N OF THE ISLAND FRIDAY. SHOWERS ASSOCIATED WITH THE CYCLONE ARE EXPECTED TO START THU AFTERNOON AND CONTINUE THROUGH SATURDAY...HEAVIEST SHOWERS EXPECTED FRIDAY AS THE CENTER OF THE SYSTEM MOVES N OF THE ISLAND OVER SW N ATLC WATERS. ATLANTIC OCEAN... THE MAIN FEATURE IN THE ATLC IS T.S. ERIKA DISCUSSED IN SPECIAL FEATURE. SEE ABOVE. A BROAD MIDDLE TO UPPER-LEVEL TROUGH EXTENDS FROM THE OHIO VALLEY S-SW ACROSS THE GULF TO A BASE OVER THE YUCATAN PENINSULA. THIS TROUGH SUPPORTS A FRONTAL SYSTEM ANALYZED AS STATIONARY FROM A 1010 MB LOW OVER SOUTH CAROLINA ACROSS NORTHERN FLORIDA FROM 30N81W TO 28N82W THE ACROSS THE CENTRAL GULF OF MEXICO. MOISTURE ADVECTION FROM THE SW N ATLC IS CONVERGING WITH MOISTURE ASSOCIATED WITH THE FRONT GENERATING INSTABILITY THAT ALONG WITH A DIVERGENT ENVIRONMENT ALOFT SUPPORT HEAVY SHOWERS AND TSTMS N OF 24N W OF 75W. SIMILAR CONVECTION IS OVER HAITI NORTHERN WATERS. OTHERWISE...SURFACE RIDGING AND FAIR WEATHER DOMINATE ELSEWHERE. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ NR