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AXNT20 KNHC 182324
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT SAT APR 18 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 2315 UTC.


...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS ACROSS AFRICA INTO THE TROPICAL ATLC NEAR 7N12W TO 4N13W WHERE THE ITCZ BEGINS AND CONTINUES ALONG 1N20W THEN S OF THE EQUATOR NEAR 32W. CLUSTERS OF SCATTERED MODERATE TO ISOLATED STRONG CONVECTION ARE FROM 5N TO S OF THE EQUATOR BETWEEN 25W-36W.


...DISCUSSION...

GULF OF MEXICO... A BROAD UPPER RIDGE ANCHORED IN THE E PACIFIC EXTENDS ACROSS THE YUCATAN PENINSULA TO OVER FLORIDA THEN ALONG THE EASTERN SEABOARD. THIS IS ADVECTING UPPER MOISTURE ACROSS THE NW AND N/CENTRAL GULF WATERS. A STRONG UPPER LOW OVER THE CENTRAL PLAINS EXTENDS AN UPPER TROUGH OVER TEXAS PUSHING INTO THE FAR NW GULF. AN AREA OF DIFFLUENCE OVER THE NW GULF BETWEEN THE UPPER TROUGH/RIDGE COMBINED WITH THE UPPER MOISTURE IS GENERATING SCATTERED TO NUMEROUS SHOWERS WITH EMBEDDED CLUSTERS OF NUMEROUS THUNDERSTORMS WITHIN 120 NM OF LINE FROM PANAMA CITY FLORIDA ALONG 28N89W TO 24N93W. A SHORTWAVE UPPER TROUGH IN THE W ATLC IS SUPPORTING A FRONTAL BOUNDARY THAT EXTENDS ACROSS FLORIDA AND INLAND ALONG THE N GULF COAST STATES TO TEXAS AND NE MEXICO. THIS IS FURTHER ENHANCING THE SHOWERS/THUNDERSTORM ACTIVITY. A SURFACE TROUGH IS IN THE W GULF SE OF THE ABOVE ACTIVITY AND ALONG 27N91W 24N94W TO 21N96W. THIS IS LEAVING THE S GULF WITH MOSTLY CLEAR SKIES THIS EVENING. THE FRONT OVER THE NE GULF WILL EXIT TONIGHT. THE UPPER LEVEL FEATURES WILL MAINTAIN THE POTENTIAL FOR THUNDERSTORMS ACROSS THE NW AND N/CENTRAL GULF TONIGHT. A WEAK COLD FRONT WILL PASS E ACROSS THE N/CENTRAL AND NE GULF ON MON AND MON NIGHT WITH WEAK HIGH PRESSURE REBUILDING IN THE WAKE OF THE FRONT. A SURFACE TROUGH WILL DEVELOP AND SHIFT W OFF THE YUCATAN PENINSULA EACH NIGHT MOVING NW ACROSS THE SW WATERS DURING THE EARLY MORNING HOURS AND DISSIPATE BY THE EARLY AFTERNOON.

CARIBBEAN SEA... A BROAD UPPER TROUGH EXTENDS FROM THE CENTRAL ATLC ACROSS HISPANIOLA TO 14N78W WHILE ONE UPPER RIDGE COVERS THE FAR NW CARIBBEAN WITH THE AXIS OVER THE YUCATAN PENINSULA AND A SECOND UPPER RIDGE ANCHORED IN THE TROPICS EXTENDING ACROSS SOUTH AMERICA COVERING THE FAR E CARIBBEAN. SATELLITE WATER VAPOR IMAGERY SHOWS STRONG SUBSIDENCE AND DRY STABLE AIR ACROSS THE CARIBBEAN BETWEEN THE TWO UPPER RIDGES. TROPICAL MOISTURE IS BEING ADVECTED ACROSS THE FAR E CARIBBEAN DUE TO THE PROXIMITY OF AN UPPER RIDGE INLAND OVER VENEZUELA AND COMBINED WITH THE EASTERLY TRADE WINDS ARE GENERATING ISOLATED SHOWERS SE OF LINE FROM 17N62W IN THE LEEWARD ISLANDS AND THE GUAJIRA PENINSULA OF COLOMBIA. HEAVY AFTERNOON SHOWERS/SCATTERED THUNDERSTORMS COVER CUBA BETWEEN 78W-82W. ISOLATED SHOWERS/THUNDERSTORMS COVER PUERTO RICO...HISPANIOLA...AND JAMAICA. THIS IS LEAVING THE REMAINDER OF THE CARIBBEAN UNDER CLEAR SKIES THIS EVENING. FRESH TO STRONG TRADE WINDS WILL DEVELOP EACH NIGHT OFFSHORE OF THE GULF OF HONDURAS. FRESH TO STRONG TRADE WINDS WILL DEVELOP ALONG THE COAST OF COLOMBIA EACH NIGHT THROUGH TUE.

HISPANIOLA... ISOLATED AFTERNOON SHOWERS/ISOLATED THUNDERSTORMS ARE STARTING TO DEVELOP ACROSS THE ISLAND THIS EVENING. AN UPPER TROUGH EXTENDS FROM THE CENTRAL ATLC ACROSS THE ISLAND INTO THE CARIBBEAN AND WILL PERSIST THROUGH LATE SUN BEFORE BECOMING A WESTERLY FLOW ALOFT. LOW LEVEL MOISTURE COUPLED WITH THE EASTERLY TRADE WINDS WILL CONTINUE THE PATTERN OF ISOLATED AFTERNOON SHOWERS WITH POSSIBLE THUNDERSTORMS THROUGH TUE.

ATLANTIC OCEAN... SCATTERED SHOWERS/ISOLATED THUNDERSTORMS THAT HAVE DEVELOPED INLAND OVER NE FLORIDA AND SE GEORGIA ARE MOVING INTO THE COASTAL WATERS FROM 29N-32N. A SHORTWAVE UPPER TROUGH IN THE W ATLC IS SUPPORTING A WEAK 1014 MB LOW NEAR 32N74W WITH A COLD FRONT EXTENDING ALONG 30N74W TO 29N77W WHERE IT BECOMES STATIONARY TO INLAND OVER FLORIDA NEAR SAINT AUGUSTINE. SCATTERED SHOWERS/ISOLATED THUNDERSTORMS ARE WITHIN 120 NM S OF THE FRONT BETWEEN 74W-78W. A BROAD UPPER TROUGH OVER THE NE ATLC IS SUPPORTING A COLD FRONT THAT ENTERS THE E ATLC NEAR 32N26W ALONG 26N35W TO 25N44W WHERE IT BECOMES STATIONARY TO 27N53W THEN BECOMES A WARM FRONT TO BEYOND 32N58W. AN UPPER TROUGH EXTENDS FROM THE CENTRAL ATLC NEAR 25N65W ACROSS HISPANIOLA INTO THE CARIBBEAN. A BROAD SURFACE RIDGE COVERS THE ATLC BRIDGING THE FRONT ACROSS THE CENTRAL ATLC AND ANCHORED BY 1029 MB HIGH ABOUT 800 NM W-SW OF THE AZORES AND A WEAKER 1022 MB HIGH NEAR MADEIRA ISLANDS. W ATLC COLD FRONT WILL REACH FROM BERMUDA TO THE NW BAHAMAS EARLY TONIGHT THEN STALL E TO W ALONG 26N ON SUN BEFORE DISSIPATING BY MON NIGHT. A SECOND COLD FRONT WILL MOVE OFFSHORE THE UNITED STATES COAST LATE MON NIGHT AND STALL FROM 31N72W TO THE NW BAHAMAS ON TUE NIGHT.

FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE

$$ PAW

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