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Atlantic Tropical Weather Discussion



000
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 
WWW.HURRICANES.GOV/MARINE

$$ 
PAW


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