[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 111720
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
105 PM EST FRI DEC 11 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...

ATLC GALE WARNING...LOW PRESSURE AT 1004 MB IS ANALYZED NEAR
33N58W. A COLD FRONT EXTENDS FROM THE LOW THROUGH 28N60W TO
25N65W TO THE SOUTHEAST BAHAMAS NEAR 23N76W. A TROUGH IS
WRAPPING IN BEHIND THE LOW EXTENDING FROM THE LOW THROUGH 30N60W
TO 29N67W. RECENT SCATTEROMETER PASSES INDICATE GALE FORCE WINDS
ALREADY OCCURRING TO THE NORTH OF THE DISCUSSION WATERS WHERE A
STORM WARNING IS NOW IN EFFECT. THE SCATTEROMETER DATA ALSO
SHOWED ONLY FRESH WINDS SO FAR WRAPPING AROUND INTO THE
DISCUSSION WATERS...HOWEVER WINDS ARE NOW FORECAST TO INCREASE
TO MINIMAL GALE FORCE BY 00 UTC TONIGHT N OF 29N W OF THE FRONT
TO 56W...AS WELL AS N OF 29N E OF THE FRONT TO 50W. THE GALE
FORCE WINDS WILL CONTINUE UNTIL SUN MORNING. SEAS ARE FORECAST
TO BUILD TO UP TO 15 FT THIS WEEKEND.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH AXIS EXTENDS FROM 02N AND THE PRIME MERIDIAN
TO 04N10W. THE INTERTROPICAL CONVERGENCE ZONE EXTENDS FROM
04N10W TO 05N26W TO 03N35W TO 05N44W. SCATTERED MODERATE
CONVECTION IS FROM 03N-06N BETWEEN 21W-32W. A SURFACE TROUGH
EXTENDS FROM 08N46W TO 01N47W. SCATTERED MODERATE CONVECTION IS
FROM 04N-06N BETWEEN 45W-48W.

...DISCUSSION...

GULF OF MEXICO...

A SHARP MIDDLE TO UPPER LEVEL TROUGH HAS RECENTLY CLEARED THE
BASIN WITH WATER VAPOR SATELLITE IMAGERY INDICATING VERY DRY
AIR AND SUBSIDENCE AS RIDGING BUILDS IN ALOFT. AT THE SURFACE...
1020 MB HIGH PRESSURE IS LOCATED IN THE FAR NE GULF NEAR 29N84W
WITH A SURFACE RIDGE EXTENDING SW-W TO NEAR 24N98W. SURFACE
OBSERVATIONS INDICATE GENTLE TO MODERATE E-SE WINDS ACROSS THE
BASIN E OF 90W...WITH MODERATE TO LOCALLY FRESH RETURN FLOW W OF
90W. SEAS ARE 2 FT OR LESS E OF 90W...AND BUILDING TO 4-6 FT IN
THE NW GULF WHERE THE RETURN FLOW AND FETCH ARE THE GREATEST.
THE HIGH IS FORECAST TO GRADUALLY SHIFT NE TO THE CAROLINAS BY
SAT MORNING...THEN TO WELL OFFSHORE AND E OF THE OUTER BANKS BY
SUN MORNING. MEANWHILE DEEPENING LOW PRESSURE AND AN ATTENDANT
COLD FRONT WILL BE MOVING THROUGH THE CENTRAL U.S. APPROACHING
THE TEXAS COAST SUN MORNING. A VERY TIGHT PRESSURE GRADIENT WILL
RESULT FROM THIS COMBINATION AND POSITIONING OF FEATURES
ALLOWING FOR RETURN FLOW TO INCREASE TO FRESH TO STRONG ACROSS
THE BASIN BY EARLY SUN MORNING. SEAS WILL BUILD TO 7-9 FT AS A
RESULT.

CARIBBEAN SEA...

A WEAKENING AND FLATTENING MIDDLE TO UPPER LEVEL TROUGH EXTENDS
OVER THE EASTERN CARIBBEAN FROM NEAR THE ANEGADA PASSAGE TO NW
VENEZUELA. A SHARP AND DEEP UPPER LEVEL TROUGH IS MOVING THROUGH
THE NW CARIBBEAN EXTENDING FROM CENTRAL CUBA TO THE GULF OF
HONDURAS. UPPER LEVEL DIFFLUENCE IS BETWEEN THESE TWO FEATURES
AND DEEP TROPICAL MOISTURE FROM THE NORTHEAST PACIFIC OCEAN IS
ALSO GETTING ADVECTED ACROSS THE AREA. AS A RESULT...NUMEROUS
SHOWERS AND ISOLATED TO SCATTERED TSTMS ARE OCCURRING N OF 16N
BETWEEN 70W AND 80W. THE REMAINDER OF THE BASIN HAS FAIRLY
TRANQUIL WEATHER OUTSIDE OF A FEW ISOLATED SHOWERS OR
THUNDERSTORMS. SCATTEROMETER DATA AND SURFACE OBSERVATIONS
INDICATE FRESH TO STRONG TRADES IN THE CENTRAL CARIBBEAN MAINLY
S OF 17N BETWEEN 68W AND 78W WHERE A TIGHT PRESSURE GRADIENT
REMAINS BETWEEN 1008 MB LOW PRESSURE POSITIONED OVER NORTHERN
COLOMBIA NEAR 08N75W AND CENTRAL ATLC RIDGING NE OF THE AREA.
MODERATE TO LOCALLY FRESH TRADES DOMINATE THE REMAINDER OF THE
BASIN. LITTLE CHANGE IN THE SENSIBLE WEATHER EXPECTED THROUGH
THE NEXT 24-48 HOURS AS THE SURFACE PATTERN VARIES LITTLE.

...HISPANIOLA...

AS MENTIONED IN THE CARIBBEAN SECTION...A SHARP AND DEEP UPPER
LEVEL TROUGH IS MOVING TOWARD THE AREA WITH DEEP TROPICAL
MOISTURE BEING ADVECTED OUT AHEAD OF IT WHERE UPPER LEVEL
DIFFLUENCE ALSO RESIDES IN A NARROW SWATH. NUMEROUS SHOWERS AND
ISOLATED TO SCATTERED TSTMS ARE IN THE PROCESS OF MOVING ACROSS
THE ISLAND FROM THE SW-W AND THESE CONDITIONS WILL REMAIN LIKELY
THROUGH EARLY SUN OR UNTIL THE UPPER TROUGH CLEARS THE AREA.
EMBEDDED GUSTY WINDS WILL ALSO BE POSSIBLE IN THE EMBEDDED
TSTMS. VERY DRY AND STABLE AIR IS EXPECTED TO ARRIVE BEHIND THE
UPPER TROUGH.

ATLANTIC OCEAN...

AS MENTIONED IN THE SPECIAL FEATURES SECTION...1004 MB LOW
PRESSURE JUST N OF THE AREA NEAR 33N58W EXTENDS A COLD FRONT
THROUGH 28N60W TO 25N65W TO THE SOUTHEAST BAHAMAS NEAR 23N76W
WITH GALE FORCE WINDS LIKELY AROUND THE LOW BY THIS EVENING. A
SURFACE TROUGH EXTENDS FROM NEAR 30N77W TO NEAR BIMINI TO THE
STRAITS OF FLORIDA NEAR 23.5N81.5W. SURFACE HIGH PRESSURE AT
1019 MB IS BETWEEN THESE FEATURES NEAR 30.5N72.5W. A SHARP AND
DEEP UPPER TROUGH CURRENTLY OVER THE FLORIDA PENINSULA IS
APPROACHING THE FAR WESTERN PORTION OF THE BASIN. COPIOUS
MOISTURE IS EVIDENT IN WATER VAPOR AND INFRARED SATELLITE
IMAGERY W OF 65W TO THE SURFACE TROUGH AXIS...WITH ADDITIONAL
SCATTERED MODERATE CONVECTION N OF 25N WITHIN 120 NM AHEAD OF
THE COLD FRONT. VERY HEAVY RAINFALL AND GUSTY WINDS ARE POSSIBLE
ACROSS THE BAHAMAS AND TURKS AND CAICOS ISLANDS...EASTERN CUBA
AND HISPANIOLA FOR THE NEXT 24-48 HOURS. THE COLD FRONT WILL
CONTINUE TO MOVE TO THE E THROUGH THE WEEKEND...HOWEVER...A
SURFACE TROUGH THAT IS CURRENTLY AHEAD OF THE TROUGH ANALYZED
FROM 24N69W TO ACROSS CENTRAL HAITI WILL BE LEFT BEHIND. THIS
TROUGH IS FORECAST TO MOVE W-NW BY SAT MORNING FROM A POSITION
NEAR 26N72W TO THE WINDWARD PASSAGE...THEN APPROACHING THE
FLORIDA PENINSULA FROM THE NW BAHAMAS NEAR 27N77W TO N CENTRAL
CUBA NEAR 23N79.5W. FRESH TO STRONG WINDS AND CONVECTION IN
EASTERLY FLOW IS EXPECTED TO ACCOMPANY THE TROUGH.

ANOTHER COLD FRONT IS TO THE E REACHING FROM 32N32W TO 28.5N41W
TO 32N51W WITH A PRE-FRONTAL TROUGH LOCATED ABOUT 180 NM TO ITS
SE. LIMITED CONVECTION OTHER THAN SOME SCATTERED SHOWERS ARE
FOUND WITH THESE FEATURES. HIGH PRESSURE AT 1023 MB IS S OF THIS
COLD FRONT NEAR 26N46W WITH BROAD SURFACE RIDGING DOMINATING THE
REMAINDER OF THE TROPICAL ATLC WATERS.

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

$$
LEWITSKY
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