Tropical Weather Discussion
Issued by NWS

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000
AXNT20 KNHC 212345
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT TUE APR 21 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 5N17W WHERE THE ITCZ BEGINS AND CONTINUES ALONG
2N23W THEN S OF THE EQUATOR NEAR 28W. SCATTERED STRONG
CONVECTION IS WITHIN 60 NM ALONG THE COAST OF LIBERIA BETWEEN 8W-
10W. CLUSTERS OF SCATTERED MODERATE TO ISOLATED STRONG
CONVECTION ARE FROM 3N TO S OF THE EQUATOR BETWEEN 5W-9W AND
WITHIN 90/120 NM S OF ITCZ BETWEEN 17W-23W. ISOLATED MODERATE
CONVECTION IS FROM 3N-6N BETWEEN 47W-51W.

...DISCUSSION...

GULF OF MEXICO...
A BROAD UPPER RIDGE ANCHORED IN THE E PACIFIC EXTENDS ACROSS S
MEXICO AND THE YUCATAN PENINSULA TO ACROSS CUBA AND INTO THE W
ATLC COVERING THE GULF S OF 24N. A STRONG UPPER TROUGH COVERS
THE N GULF AND ALL OF THE E CONUS WITH THE UPPER LOW OVER THE
GREAT LAKES AND SUPPORTING A COLD FRONT IN THE W ATLC WITH A
STATIONARY FRONT EXTENDING ACROSS FLORIDA BETWEEN VERO BEACH AND
TAMPA BAY THEN ALONG 26N90W WEAKENING TO THE COAST OF MEXICO
NEAR 25N98W. A PRE-FRONTAL SURFACE TROUGH EXTENDS FROM THE W
ATLC ACROSS S FLORIDA NEAR HOMESTEAD ALONG 25N84W TO 25N90W.
SCATTERED TO NUMEROUS SHOWERS WITH EMBEDDED CLUSTERS OF
THUNDERSTORMS ARE FROM 24N TO THE STATIONARY FRONT E OF 89W.
SCATTERED SHOWERS AND POSSIBLE ISOLATED THUNDERSTORMS ARE ACROSS
THE REMAINDER OF THE GULF N OF 23N E OF 93W. FAIR WEATHER COVERS
THE SW GULF WITH A SURFACE TROUGH EXTENDING OFFSHORE OF MEXICO
FROM 24N96W TO 18N94W. FRONT WILL SLOWLY WEAKEN THROUGH WED
NIGHT. ITS REMNANTS WILL LIFT NORTHWARD AS A WARM FRONT THU AND
THU NIGHT AS LOW PRESSURE INTENSIFIES OVER THE CENTRAL PLAINS.
OTHERWISE...WEAK HIGH PRESSURE WILL PREVAIL OVER THE AREA
THROUGH FRI.

CARIBBEAN SEA...
AN UPPER RIDGE AXIS EXTENDS ACROSS THE YUCATAN PENINSULA THEN
OVER CENTRAL CUBA AND INTO THE W ATLC. A SECOND UPPER RIDGE
ANCHORED IN THE TROPICS EXTENDS ACROSS SOUTH AMERICA. THIS IS
INDUCING A WEAK UPPER TROUGH THAT EXTENDS FROM THE VIRGIN
ISLANDS ALONG 15N71W TO NICARAGUA NEAR 14N84W. SATELLITE WATER
VAPOR IMAGERY SHOWS STRONG SUBSIDENCE AND DRY STABLE AIR ACROSS
THE CARIBBEAN N OF THE UPPER TROUGH AXIS TO 20N. AFTERNOON
SHOWERS/ISOLATED THUNDERSTORMS ARE ACROSS PUERTO RICO...
HISPANIOLA AND E CUBA. THE UPPER FLOW OVER THE S CARIBBEAN IS
ADVECTING TROPICAL MOISTURE ACROSS THE AREA TO GENERATE
SCATTERED SHOWERS/ISOLATED THUNDERSTORMS MAINLY S OF 13N BETWEEN
74W-83W. THIS IS LEAVING THE REMAINDER OF THE CARIBBEAN UNDER
CLEAR SKIES THIS EVENING. FRESH TO LOCALLY STRONG TRADE WINDS
WILL DEVELOP EACH NIGHT OFFSHORE OF THE GULF OF HONDURAS AS WELL
AS ALONG THE COAST OF COLOMBIA THROUGH FRI.

HISPANIOLA...
SCATTERED AFTERNOON SHOWERS/ISOLATED THUNDERSTORMS HAVE
DEVELOPED ACROSS THE ISLAND THIS EVENING MAINLY OVER THE HIGHER
ELEVATIONS. EASTERLY TRADE WINDS COUPLED WITH DAYTIME HEATING
WILL CONTINUE THE PATTERN OF ISOLATED AFTERNOON SHOWERS WITH
POSSIBLE THUNDERSTORMS THROUGH FRI.

ATLANTIC OCEAN...
THE BROAD UPPER TROUGH OVER THE E CONUS AND N GULF OF MEXICO IS
MOVING INTO THE NW ATLC SUPPORTING COLD FRONT THAT ENTERS THE
REGION NEAR 32N75W ALONG 28N78W TO THE COAST OF FLORIDA NEAR
VERO BEACH WHERE IT BECOMES STATIONARY AS IT CONTINUES INTO THE
GULF OF MEXICO. A PRE-FRONTAL SURFACE TROUGH EXTENDS FROM 27N77W
ACROSS S FLORIDA INTO THE GULF OF MEXICO NEAR HOMESTEAD. AN
UPPER RIDGE EXTENDS FROM THE CARIBBEAN ACROSS CENTRAL CUBA TO
27N66W AND IS PROVIDING DIFFLUNCE ALOFT TO GENERATE SCATTERED
SHOWERS/ISOLATED THUNDERSTORMS WITHIN 120 NM OF LINE FROM THE
BAHAMAS NEAR 24N77W ALONG 27N71W TO 31N68W. AN UPPER LOW OVER
THE NE ATLC IS SUPPORTING A COLD FRONT EXTENDS INTO THE E ATLC
NEAR 32N33W THEN PASSING THROUGH THE CENTRAL ATLC ALONG 28N38W
TO 27N46W WHERE IT BECOMES STATIONARY ALONG 26N54W TO 28N61W. A
BROAD SURFACE RIDGE COVERS THE ATLC E OF 70W AND IS BRIDGING THE
E/CENTRAL ATLC FRONTAL BOUNDARY. THE RIDGE IS ANCHORED BY 1028
MB HIGH OVER THE CANADIAN MARITIMES AND A WEAKER 1021 MB HIGH
NEAR 24N51W AND A 1020 MB HIGH NEAR 32N20W. W ATLC COLD FRONT
WILL REACH FROM NEAR 31N68W TO 27N75W WHERE IT WILL BECOME
STATIONARY TO WEST PALM BEACH BY LATE TONIGHT THEN FROM NEAR
31N65W TO 27N72W AND A WEAKENING STATIONARY FRONT TO WEST PALM
BEACH BY WED AFTERNOON THEN BECOMING DISSIPATING STATIONARY
FRONT ALONG 27N WED NIGHT AND THU. THE REMNANTS OF THE FRONT
WILL THEN LIFT N AS A WARM FRONT FRI. ANOTHER COLD FRONT WILL
MOVE OFF THE NE FLORIDA COAST THU NIGHT REACHING FROM NEAR
BERMUDA TO THE CENTRAL BAHAMAS FRI AFTERNOON.

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

$$
PAW



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