Tropical Weather Discussion
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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
HTTP://WWW.HURRICANES.GOV/MARINE

$$
PAW


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