Tropical Weather Discussion
Issued by NWS

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000
AXNT20 KNHC 211817 CCA
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT MON APR 20 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
1715 UTC.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS ACROSS AFRICA INTO THE TROPICAL
ATLANTIC NEAR 07N12W TO 04N15W WHERE THE ITCZ BEGINS AND
CONTINUES S OF THE EQUATOR NEAR 26W TO THE N COAST OF BRAZIL
NEAR 03S40W. SCATTERED MODERATE CONVECTION IS FROM 05S TO 05N
BETWEEN 07W AND 45W.

...DISCUSSION...

GULF OF MEXICO...

ZONAL FLOW IN THE UPPER LEVELS RESIDES OVER THE GULF WITH AN MID
TO UPPER LEVEL SHORTWAVE TROUGH OVER THE MID ATLC STATES. THIS
TROUGH SUPPORTS A COLD FRONT THAT EXTENDS JUST OFFSHORE THE
EASTERN SEABOARD...OVER CENTRAL FL...AND THE GULF NEAR THE TAMPA
BAY AREA AT 28N83W TO 26N91W WHERE IT TRANSITIONS TO A
STATIONARY FRONT TO THE NORTHERN MEXICO COAST NEAR 25N98W. A PRE-
FRONTAL TROUGH EXTENDS ACROSS THE BAHAMAS AND S FLORIDA...AND
EMERGES OVER THE GULF NEAR 26N82W TO 24N88W. SCATTERED SHOWERS
AND THUNDERSTORMS ARE WITHIN 100 NM OF EITHER SIDE OF THE
STATIONARY FRONT. SCATTERED MODERATE CONVECTION AND SHOWERS ARE
BETWEEN THE COLD FRONT AND THE PRE-FRONTAL TROUGH...AND ALSO
WITHIN 50 NM S OF THE TROUGH AXIS. ANOTHER SURFACE TROUGH IS
LOCATED OVER THE SW GULF FROM 23N91W TO 19N92W. THIS TROUGH IS
VOID OF ANY CONVECTION. SURFACE WINDS VARY FROM ONE QUADRANT OF
THE GULF TO THE NEXT...WITH NE WINDS OF 10 TO 15 KT OVER THE NW
BASIN...NW WINDS OF 10 TO 15 KT OVER THE NE AND SW BASIN...AND
SOUTHERLY FLOW OVER THE SE BASIN S OF THE PRE-FRONTAL TROUGH.
WINDS BECOME VARIABLE IN THE VICINITY OF THE FRONTAL BOUNDARY
AND SURFACE TROUGHS. OVER THE NEXT 24 HOURS THE ENTIRE FRONTAL
SYSTEM WILL BECOME STATIONARY. THE WESTERN PORTION OF THE
STATIONARY FRONT WILL DISSIPATE. THIS WILL LEAVE THE STATIONARY
FRONT DRAPED OVER THE EASTERN GULF AND CENTRAL/SOUTH FL
PENINSULA ON WEDNESDAY. CONVECTION WILL CONTINUE TO BE LIKELY
ESPECIALLY WITHIN 100 NM OF THE FRONTAL BOUNDARY TONIGHT THROUGH
WEDNESDAY.

CARIBBEAN SEA...

GENERALLY DRY AND STABLE CONDITIONS IN THE MIDDLE TO UPPER
LEVELS CONTINUE TO DOMINATE THE CARIBBEAN. THIS IS INHIBITING
ANY DEEP CONVECTION ACROSS THE BASIN. AT THE SURFACE...ATLC
RIDGING EXTENDS ACROSS THE NORTHERN CARIBBEAN WITH LOW PRESSURE
OVER NORTHERN COLOMBIA. MODERATE TO FRESH TRADE WINDS BETWEEN
THE RIDGE AND LOW COVER THE MAJORITY OF THE BASIN. OTHER THAN
ISOLATED SHOWERS IN THE LOW LEVEL TRADE WIND MOISTURE...FAIR
WEATHER IS BEING OBSERVED ACROSS THE BASIN.

HISPANIOLA...

MAINLY DAYTIME ISOLATED SHOWER AND THUNDERSTORM ACTIVITY IS
EXPECTED OVER THE ISLAND OVER THE NEXT TWO DAYS.
OTHERWISE...FAIR WEATHER IS EXPECTED.

 ATLANTIC OCEAN...

A MID TO UPPER LEVEL TROUGH OVER THE MID ATLC STATES SUPPORTS A
COLD FRONT THAT IS JUST OFFSHORE THE EASTERN SEABOARD AND
EXTENDS INTO OUR AREA OF DISCUSSION NEAR 31N80W TO NORTH-
CENTRAL FL NEAR 29N81W. A PRE-FRONTAL SURFACE TROUGH EXTENDS
FROM 31N73W TO 27N77W TO THE MIAMI AREA NEAR 26N80W. SCATTERED
MODERATE CONVECTION IS BETWEEN THE COLD FRONT AND SURFACE
TROUGH...AND ALSO WITHIN 50 NM SE OF THE TROUGH AXIS. A NEARLY
STATIONARY STORM SYSTEM OVER THE N CENTRAL ATLC SUPPORTS ANOTHER
COLD FRONT THAT ENTERS OUR AREA NEAR 32N36W TO 27N46W WHERE IT
TRANSITIONS TO A STATIONARY FRONT THAT EXTENDS TO 29N61W.
SHOWERS ARE POSSIBLE WITHIN 75 NM OF EITHER SIDE OF THE FRONT.
CENTRAL ATLC HIGH PRESSURE OF 1021 MB IS CENTERED JUST SOUTH OF
THE FRONTAL SYSTEM NEAR 24N50W. GENERALLY FAIR WEATHER DOMINATES
THE EASTERN ATLC FROM 05N TO 32N. OVER THE NEXT 24 HOURS THE
COLD FRONT OFF THE SE US COAST WILL MOVE SE AND BY WEDNESDAY IS
FORECAST TO EXTEND ACROSS THE NORTHERN BAHAMAS EASTWARD TO 70W.
CONVECTION WITH THUNDERSTORMS WILL BE LIKELY TONIGHT THROUGH
WEDNESDAY ALONG AND WITHIN 150 NM SE OF THE COLD FRONT.

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

$$

LATTO



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