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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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