Tropical Weather Discussion
Issued by NWS

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000
AXNT20 KNHC 202353
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT SAT SEP 20 2014

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
2330 UTC.

...TROPICAL WAVES...

A TROPICAL WAVE IS OVER THE E ATLANTIC AND CAPE VERDE ISLANDS
WITH AXIS EXTENDING FROM 13N23W TO 21N22W MOVING W AT 5 KT. THIS
SLOW MOVING WAVE IS EMBEDDED IN A LARGE AREA OF DEEP MOISTURE
ALONG THE MONSOON TROF S OF 19N. DRY SAHARAN AIR IS LOCATED N OF
19N ALONG THE WAVE. ISOLATED MODERATE CONVECTION IS FROM 12N-19N
BETWEEN 18W AND 26W.

A TROPICAL WAVE IS OVER THE CENTRAL TROPICAL ATLANTIC WITH AXIS
EXTENDING FROM 10N54W TO 21N53W...MOVING W AT 15-20 KT. SSMI TPW
SHOWS A LARGE AREA OF DEEP MOISTURE AHEAD AND BEHIND THE WAVE
FROM 9N-18N BETWEEN 47W AND 60W. SCATTERED MODERATE CONVECTION
IS OCCURRING FROM 12N-19N BETWEEN 49W AND 53W.

A TROPICAL WAVE IS OVER THE CENTRAL CARIBBEAN WITH AXIS
EXTENDING FROM 12N75W TO 22N74W...MOVING W AT 10-15 KT. MODERATE
MOISTURE IS SUPPORTING MAINLY DIURNAL THUNDERSTORMS ACROSS
JAMAICA AND E CUBA. DEEP LAYER SHEAR IS INHIBITING CONVECTION
ELSEWHERE ALONG THE WAVE.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 16N16W TO
09N39W. THE ITCZ AXIS EXTENDS FROM 09N39W TO 09N51W. OTHER THAN
THE CONVECTION MENTIONED IN THE TROPICAL WAVE SECTION...ISOLATED
MODERATE CONVECTION IS FROM 07N-13N BETWEEN 26W-37W.

...DISCUSSION...

GULF OF MEXICO...

NORTHERLY UPPER LEVEL FLOW DOMINATES THE GULF BETWEEN AN UPPER
LEVEL ANTICYCLONE OVER N MEXICO AND AN UPPER TROUGH OVER THE SE
CONUS. LOW PRESSURE THAT DEVELOPED OVER THE ATLANTIC OFFSHORE
WATERS OFF THE SE CONUS HAS HELPED TRANSITION A STATIONARY FRONT
OVER THE GULF INTO A COLD FRONT. THIS COLD FRONT EXTENDS FROM
28N94W TO THE FL W COAST NEAR 27N82W. SCATTERED MODERATE
CONVECTION IS OCCURRING ALONG AND WITHIN 200 MILES SOUTH OF THE
COLD FRONT. OVER THE NEXT 24 HOURS THE COLD FRONT IS EXPECTED TO
STALL OUT ACROSS THE SE GULF AND DIFFLUENT FLOW ALOFT IS
FORECAST TO DEVELOP. THESE FACTORS WILL LIKELY ENHANCE
CONVECTION ACROSS THE SE GULF THROUGH SUNDAY.

CARIBBEAN SEA...

WEAK UPPER LEVEL DIFFLUENCE PERSISTS ACROSS THE W CARIBBEAN
BASIN BETWEEN UPPER LEVEL RIDGES...ONE ACROSS N MEXICO...AND THE
OTHER OVER THE W ATLANTIC CENTERED NEAR 27N72W. THIS DIFFLUENCE
IS INTERACTING WITH MODERATE MOISTURE TO PRODUCE ISOLATED
THUNDERSTORMS FROM 13N-22N BETWEEN 80W AND 85W. SOME OF THE
THUNDERSTORM ACTIVITY IN THE EXTREME NW CORNER OF THE CARIBBEAN
MAY BE ENHANCED DUE TO A SOUTHWARD MOVING COLD FRONT IN THE
GULF. CONVECTION IN THE CENTRAL CARIBBEAN IS ASSOCIATED WITH A
TROPICAL WAVE DISCUSSED IN THE TROPICAL WAVES SECTION. ANOTHER
REGION OF UPPER LEVEL DIFFLUENCE IS LOCATED ACROSS THE WINWARD
AND LEEWARD ISLANDS BETWEEN THE UPPER RIDGE IN THE W ATLANTIC
AND ANOTHER UPPER RIDGE IN THE CENTRAL ATLANTIC NEAR 15N43W.
THIS DIFFLUENCE IS INTERACTING WITH A VERY MOIST AIRMASS TO
PRODUCE SCATTERED SHOWERS AND THUNDERSTORMS ACROSS THE WINDWARD
AND LEEWARD ISLANDS. OVER THE NEXT 24 HOURS THE REGION OF UPPER
LEVEL DIFFLUENCE IN THE W CARIBBEAN IS EXPECTED TO INTERACT WITH
A SURFACE FRONTAL BOUNDARY TO THE NORTH TO ENHANCE CONVECTION
ACROSS THE NW CARIBBEAN. THE REGION OF DIFFLUENCE AND DEEP
MOISTURE ACROSS THE WINDWARD AND LEEWARD ISLANDS IS EXPECTED
TO SHIFT WESTWARD. A TROPICAL WAVE APPROACHING THE E CARIBBEAN
WILL BRING ADDITIONAL CHANCES FOR SHOWERS AND THUNDERSTORMS TO
THE WINWARD AND LEEWARD ISLANDS THROUGH SUNDAY.

...HISPANIOLA...

A TROPICAL WAVE MOVED WEST OF HISPANIOLA TODAY. MODERATE
MOISTURE REMAINS ACROSS THE AREA AND IS SUPPORTING MAINLY
DIURNAL SCATTERED THUNDERSTORMS OVER LAND AREAS. OVER THE NEXT
24 HOURS MODERATE MOISTURE IS EXPECTED TO REMAIN ACROSS
HISPANIOLA WHICH WILL SUPPORT MAINLY DAYTIME SHOWERS AND
THUNDERSTORMS.

ATLANTIC OCEAN...

FOR INFORMATION ABOUT THE TROPICAL WAVES...REFER TO THE TROPICAL
WAVES SECTION ABOVE. AN UPPER LOW IS LOCATED NEAR 25N51W.
SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS ARE OCCURRING UNDER
THIS LOW FROM 25N-30N BETWEEN 47W AND 55W. SURFACE LOW PRESSURE
IS LOCATED NEAR 30N78W MOVING NE. A COLD FRONT EXTENDS SOUTHWEST
FROM THIS LOW AND CROSSES THE FL PENINSULA E COAST NEAR 28N81W.
SCATTERED MODERATE TO ISOLATED STRONG CONVECTION IS FROM 24N-34N
BETWEEN 69W AND 80W. OVER THE NEXT 24 HOURS THE COLD FRONT WILL
STALL OUT ACROSS S FL AND THE BAHAMAS. ENHANCED CONVECTION WILL
LIKELY CONTINUE IN THE VICINITY OF THE FRONTAL BOUNDARY THROUGH
SUNDAY.

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

$$
LATTO



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