[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 181804
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
105 PM EST WED NOV 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1745 UTC.

...TROPICAL WAVES...

A TROPICAL WAVE IS WITHIN 450 NM SE OF THE WINDWARD ISLANDS WITH
AXIS NEAR 53W...MOVING W AT APPROXIMATELY 15 TO 20 KT WITHIN THE
LAST 24 HOURS. CIRA LAYER PRECIPITABLE WATER IMAGERY FROM
SURFACE TO 850 MB AND THE METEOSAT SAHARAN AIR LAYER PRODUCT
SHOW DRY AIR IN THE NORTHERN WAVE ENVIRONMENT THAT ALONG WITH
STRONG DEEP LAYER WIND SHEAR HINDER DEEP CONVECTION. ISOLATED
SHOWERS AND TSTMS ARE WITHIN 100 NM W OF THE WAVE AXIS S OF 10N
AND FROM 9N TO 11N BETWEEN 46W AND 50W. MODEL GUIDANCE INDICATE
THE WAVE WILL WEAKEN INTO A SURFACE TROUGH AND DISSIPATE EARLY
THU PRIOR TO REACHING THE CARIBBEAN.

A TROPICAL WAVE IS IN THE EASTERN CARIBBEAN WITH AXIS ALONG
67W...MOVING W AT APPROXIMATELY 15 TO 20 KT WITHIN THE LAST 24
HOURS. CIRA LAYER PRECIPITABLE WATER IMAGERY FROM SURFACE TO 850
MB SHOW THE WAVE IS EMBEDDED IN A MODERATE MOIST ENVIRONMENT.
THE WAVE ITSELF IS ALSO EMBEDDED IN A STRONG DEEP LAYER WIND
SHEAR ENVIRONMENT. HOWEVER, THE BASE OF AN UPPER LEVEL TROUGH
EXTENDING FROM THE ATLC AND WEAK RIDGING N OF S AMERICA IS
GENERATING DIFFLUENCE ALOFT THAT SUPPORT SCATTERED MODERATE
CONVECTION AND ISOLATED TSTMS AHEAD OF THE WAVE...OVER THE
CENTRAL CARIBBEAN...INCLUDING HISPANIOLA. SCATTERED SHOWERS AND
TSTMS ARE OVER THE MONA PASSAGE AND MOVING INTO WESTERN PUERTO
RICO AS THE TROUGH ALOFT MOVES E THROUGH THU. THE WAVE IS
FORECAST TO WEAKEN INTO A SURFACE TROUGH AND DISSIPATE LATE
TODAY.

...ITCZ/MONSOON TROUGH...

THE ITCZ EXTENDS FROM 08N13W AND CONTINUE TO 04N30W TO 06N46W TO
05N52W. ISOLATED SHOWERS ARE WITHIN 30 NM EITHER SIDE OF THE
AXIS BETWEEN 20W AND 30W.

...DISCUSSION...

...THE GULF OF MEXICO...

A MIDDLE TO UPPER LEVEL TROUGH OVER THE CENTRAL UNITED STATES
EXTENDS INTO THE WESTERN GULF OF MEXICO AND SUPPORTS A FRONTAL
SYSTEM ANALYZED AS A COLD FRONT FROM SW ALABAMA NEAR 30N87W TO
25N92W TO A 1008 MB LOW OVER THE W BAY OF CAMPECHE NEAR 20N96W.
AN UPPER LEVEL ANTICYCLONE ANCHORED OVER S MEXICO EXTENDS A
RIDGE AXIS NE ALONG THE FLORIDA PENINSULA AND THE E CONUS. THIS
IS GENERATING A DIFFLUENT ENVIRONMENT THAT ALONG WITH MOISTURE
ADVECTION FROM THE CARIBBEAN SUPPORT SCATTERED MODERATE
CONVECTION AND TSTMS WITHIN 230 NM E OF THE FRONT N OF 23N.
SCATTERED SHOWERS ARE WITHIN 200 NM W OF THE FRONT. E OF FRONT
TO 85W SE TO S WINDS OF 20 TO 25 KT ARE N OF 26N WITH SEAS TO 8
FT. W OF FRONT...FROM 25N TO 26.5N...WINDS ARE FROM THE N-NW OF
20 TO 25 KT WITH SEAS REACHING UP TO 9 FT. BY THU NIGHT...THE
COLD FRONT WILL EXTEND FROM JACKSONVILLE FLORIDA SW TO THE
CENTRAL GULF NEAR 25N90W. A PORTION OF THE FRONT WILL START TO
WEAKEN AND STALL BY FRIDAY...THUS ACTING TO DIMINISH THE WINDS
AND SEAS. SHOWERS ARE EXPECTED TO CONTINUE IN THE N-NE BASIN
THROUGH THIS PERIOD.

...CARIBBEAN SEA...

A TROPICAL WAVE IS IN THE EASTERN CARIBBEAN WITH AXIS ALONG 67W.
THE WAVE IS EMBEDDED IN A MODERATE MOIST ENVIRONMENT AS WELL AS
IN A STRONG DEEP LAYER WIND SHEAR ENVIRONMENT. SCATTERED
MODERATE CONVECTION IS AHEAD OF THE OF THE WAVE OVER THE CENTRAL
CARIBBEAN...INCLUDING HISPANIOLA. THIS CONVECTION IS BEING
SUPPORTED BY AN UPPER LEVEL TROUGH EXTENDING FROM THE ATLC TO A
BASE NE OF COSTA RICA AND DIFFLUENCE GENERATED BY A WEAK RIDGE N
OF S AMERICA. SHOWERS AND TSTMS EXTEND TO THE MONA PASSAGE AND
MOVE INTO WESTERN PUERTO RICO AS THE TROUGH ALOFT MOVES E
THROUGH THU. THE WAVE IS FORECAST TO WEAKEN INTO A SURFACE
TROUGH AND DISSIPATE LATE TODAY. TROUGHING ALOFT ALSO SUPPORTS A
1008 MB LOW OVER THE SW BASIN NEAR 11N81W WITH SURFACE TROUGH
EXTENDING FROM 16N83W TO THE LOW TO 9N81W. THE LOW IS FORECAST
TO STAY NEARLY STATIONARY DURING THE NEXT 24 HOURS...ASSOCIATED
CONVECTION WILL PERSIST THROUGH THIS PERIOD. STRONG PRESSURE
GRADIENT BETWEEN A RIDGE OVER THE W ATLC EXTENDING ACROSS THE
NORTHERN CARIBBEAN AND THE LOW IN THE SW BASIN SUPPORT E WINDS
OF 20 TO 25 KT FROM 13N TO 16N BETWEEN 72W AND 77W WITH SEAS TO
9 FT. WINDS AND SEAS ARE FORECAST TO DIMINISH BY FRIDAY MORNING.

...HISPANIOLA...

SCATTERED MODERATE CONVECTION AND ISOLATED TSTMS ARE OVER THE
CENTRAL CARIBBEAN...INCLUDING HISPANIOLA. THIS CONVECTION IS
BEING SUPPORTED BY AN UPPER LEVEL TROUGH EXTENDING FROM THE ATLC
TO A BASE NE OF COSTA RICA AND DIFFLUENCE GENERATED BY A WEAK
RIDGE N OF S AMERICA. SHOWERS AND TSTMS EXTEND TO THE MONA
PASSAGE. SHOWERS ACROSS THE ISLAND ARE FORECAST TO DIMINISH THU
MORNING AS THE TROUGH ALOFT MOVES EAST WITHIN THIS PERIOD.

...ATLANTIC OCEAN...

AN UPPER TROUGH EXTENDS FROM THE N CENTRAL ATLC SW TO A BASE IN
THE CARIBBEAN...NE OF COSTA RICA. THIS TROUGH CONTINUE TO
SUPPORT A FRONTAL SYSTEM THAT INVOLVES A DISSIPATING COLD FRONT
FROM 32N48W TO 25N60W TO 25N70W AND A REINFORCING COLD FRONT
FROM 32N48W TO 29N61W TO 30N70W. SCATTERED MODERATE CONVECTION
AND ISOLATED TSTMS ARE WITHIN 300 NM S-SE OF THE DISSIPATING
COLD FRONT. OVER THE SW N ATLC...A WARM FRONT EXTENDS FROM THE
NORTHERN BAHAMAS NW TO A FRONTAL TRIPLE POINT OVER NW GEORGIA.
OTHERWISE...RIDGING DOMINATES ELSEWHERE.

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

$$
NR
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