[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 171754
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
105 PM EST THU DEC 17 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
1715 UTC.

...SPECIAL FEATURES...

A COLD FRONT EXTENDS FROM THE FLORIDA/ALABAMA BORDER THROUGH
26N92W TO 20N97W NEAR POZA RICA MEXICO. A BAND OF SCATTERED
SHOWERS AND ISOLATED TSTMS ARE ACCOMPANYING THE FRONT. A PRE-
FRONTAL TROUGH IS LOCATED FROM NEAR TALLAHASSEE FLORIDA TO
23N88W WITH SCATTERED SHOWERS AND ISOLATED TSTMS OCCURRING
WITHIN 120 NM AHEAD OF THE TROUGH. FRESH TO STRONG NORTHERLY
WINDS ARE ALREADY BEING USHERED IN THE WAKE OF THE FRONT AND
WINDS WILL INCREASE TO GALE FORCE OFFSHORE OF VERACRUZ BY
SUNRISE FRI AND THEN WILL DIMINISH BELOW GALE FORCE JUST AFTER
SUNSET FRI. SEAS WILL BUILD TO UP TO 14 FT DURING THE STRONGEST
WINDS.

...ITCZ/MONSOON TROUGH...

A TROUGH EXTENDS FROM 02N AND THE PRIME MERIDIAN TO 03N03W TO
02N08W. THE INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM
04N11W TO 04N20W TO 03N29W THEN RESUMES FROM 03N32W TO THE
EQUATOR AND 45W. A SURFACE TROUGH IS EMBEDDED IN THE ITCZ FROM
08N29W TO 01N29W. SCATTERED MODERATE CONVECTION IS FROM 01N-06N
BETWEEN 24W-31W AND FROM 06N-13N BETWEEN 26W-32W.

...DISCUSSION...

GULF OF MEXICO...

THE MAIN WEATHER STORY IS THE COLD FRONT MOVING THROUGH THE
WESTERN GULF AS IS DETAILED IN THE SPECIAL FEATURES SECTION
ABOVE. AHEAD OF THE FRONT...MAINLY GENTLE TO MODERATE SE WINDS
AND 1-3 FT SEAS PREVAIL. BROAD AND EXPANSIVE UPPER LEVEL RIDGING
COVERS THE GULF WATERS EXTENDING FROM A PARENT ANTICYCLONE
LOCATED ALONG S CENTRAL GUATEMALA. MEANWHILE A DEEP UPPER LEVEL
TROUGH IS LOCATED TO THE NW OVER THE U.S. CENTRAL PLAINS
SUPPORTING THE COLD FRONT AT THE SURFACE. THE FRONT IS FORECAST
TO REACH FROM 30N85W TO 24N90W TO 18N93W THIS EVENING...THEN
FROM NEAR TAMPA BAY FLORIDA TO 25N87W TO 18N93W FRI MORNING...
THEN PUSHING SE OF THE BASIN FRI EVENING. FRESH TO STRONG
NORTHERLY WINDS WILL COVER THE MAJORITY OF THE BASIN BEHIND THE
FRONT ALONG WITH BUILDING SEAS OF 7-11 FT. WINDS AND SEAS WILL
DIMINISH ACROSS THE NW HALF OF THE BASIN AS HIGH PRESSURE BUILDS
IN THE WAKE OF THE FRONT...WHILE FRESH TO STRONG NE FLOW WILL
PERSIST ACROSS THE SE HALF OF THE BASIN INTO SAT MORNING.
CONDITIONS WILL BE ESPECIALLY HAZARDOUS NEAR THE YUCATAN CHANNEL
AND IN THE STRAITS OF FLORIDA.

CARIBBEAN SEA...

A MIDDLE TO UPPER LEVEL LOW IS LOCATED NE OF THE AREA NEAR
23N67W WITH A TROUGH AXIS EXTENDING FROM THE LOW THROUGH 19N69W
TO 17N74W AND CONTINUING TO THE SW CARIBBEAN NEAR 10N80W. A
SEPARATE TROUGH EXTENDS FROM THE LOW TO THE SE-S THROUGH 16N66W
TO 13N62W. WATER VAPOR SATELLITE IMAGERY SHOWS SCATTERED SHOWERS
AND ISOLATED TSTMS NE OF THE TROUGH WHERE THE GREATEST
INSTABILITY EXISTS. OTHERWISE VERY DRY AND STABLE AIR DOMINATES
THE BASIN. BROAD HIGH PRESSURE RIDGING NE OF THE AREA IN THE
ATLC COMBINED WITH 1006 MB LOW PRESSURE OVER NORTHERN COLOMBIA
NEAR 09.5N75W IS RESULTING IN A TIGHT PRESSURE GRADIENT
ESPECIALLY ACROSS THE CENTRAL CARIBBEAN WHERE TRADES ARE RUNNING
AT FRESH TO STRONG LEVELS. THE PRESSURE GRADIENT WILL CONTINUE
TO TIGHTEN DURING THE NEXT 24-48 HOURS AND THE AREA OF FRESH TO
STRONG TRADES WILL EXPAND WESTWARD TO 81W/82W BY SAT MORNING.
MEANWHILE A STRONG COLD FRONT WILL SLIP SE OF THE YUCATAN
PENINSULA AND CHANNEL FRI EVENING AND NIGHT REACHING A POSITION
FROM WESTERN CUBA NEAR 22N81W TO THE NE YUCATAN PENINSULA NEAR
20N87W BY SAT MORNING. FRESH TO STRONG N-NE WINDS WILL QUICKLY
ARRIVE BEHIND THE FRONT WITH SEAS BUILDING TO UP TO 11 FT NEAR
THE YUCATAN CHANNEL.

...HISPANIOLA...

A MIDDLE TO UPPER LEVEL LOW IS LOCATED NE OF THE AREA NEAR
23N67W WITH A TROUGH AXIS EXTENDING FROM THE LOW THROUGH 19N69W
TO 17N74W. INSTABILITY ALONG WITH UPPER LEVEL DIFFLUENCE IS
HELPING TO SUPPORT SCATTERED SHOWERS AND ISOLATED TSTMS ACROSS
THE MAJORITY OF THE ISLAND. THE ACTIVITY IS BECOMING MORE
ISOLATED ACROSS THE NW PORTION INCLUDING NORTHERN HAITI AS
SOMEWHAT DRIER AIR AND MORE STABLE CONDITIONS ARE BEGINNING TO
MOVE IN THE WAKE OF THE TROUGH. IF THE LOW AND TROUGH CONTINUE
TO MOVE E AS IS FORECAST THAN CONDITIONS SHOULD GRADUALLY
IMPROVE FROM THE W TO THE E THROUGH THE NEXT 24-48 HOURS.

ATLANTIC OCEAN...

A COLD FRONT EXTENDS FROM 32N39W TO 26N56W TO 26N63W THEN
CONTINUES AS A STATIONARY FRONT TO 32N71W. SCATTERED SHOWERS CAN
BE FOUND WITHIN 60 NM EITHER SIDE OF THE FRONT E OF 62W. THE
WESTERN PORTION OF THIS FRONT IS IN THE PROCESS OF DISSIPATING
ACROSS THE NE PORTION OF THE SW N ATLC OFFSHORE WATERS AREA. A
SURFACE TROUGH IS MOVING ACROSS THE TROPICAL N ATLC FROM 21N56W
TO 18N60W WITH SCATTERED SHOWERS IN THE VICINITY. OTHERWISE
BROAD HIGH PRESSURE RIDGING COVERS THE MAJORITY OF THE BASIN W
OF 60W WITH MODERATE TO FRESH ANTICYCLONIC FLOW...EXCEPT UP TO
STRONG N OF HISPANIOLA. A COLD FRONT IS FORECAST TO MOVE INTO
THE NW PORTION BY FRI MORNING EXTENDING FROM 31N74W TO THE
WESTERN BAHAMAS FRI EVENING...THEN FROM 31N67W TO THE SE BAHAMAS
SAT MORNING. FRESH TO STRONG NORTHERLY WINDS WILL FOLLOW THE
FRONT ALONG WITH BUILDING SEAS OF 6-9 FT. ELSEWHERE 1021 MB HIGH
PRESSURE IS LOCATED NEAR 21N38W WITH A RIDGE EXTENDING FROM NE
THROUGH SW. MAINLY FAIR WEATHER CAN BE FOUND E OF 60W OUTSIDE OF
THE MENTIONED COLD FRONT AND TROUGH WHICH IS EMBEDDED IN THE
ITCZ.

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

$$
LEWITSKY
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