[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 202347
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
705 PM EST TUE JAN 20 2009

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...METEOROLOGICAL ANALYSIS...WEATHER
OBSERVATIONS...AND RADAR.

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2315 UTC.

...THE ITCZ...
THE ITCZ AXIS IS CENTERED ALONG 6N10W 2N20W CROSSING THE EQUATOR
NEAR 23W EXTENDING TO 2S40W AND INTO NE BRAZIL NEAR 3S44W.
SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 120 NM
SOUTH OF AXIS BETWEEN 14W-21W. SIMILAR CONVECTION IS FOUND NEAR
1S33W AND FROM EQUATOR TO 4N BETWEEN 40W-50W. CONVECTION HAS
ALSO FLARED UP OVER N BRAZIL AND THE GUYANAS.

...DISCUSSION...

GULF OF MEXICO...
A DEEP LAYERED TROUGH OVER THE E CONUS DIGS INTO THE NE CORNER
OF THE GULF PRODUCING STRONG WESTERLY AND NORTHWESTERLY FLOW
ALOFT OVER MUCH OF THE GULF REGION. THIS LONG WAVE TROUGH
SUPPORTS A COLD FRONT WHICH CURRENTLY EXTENDS ACROSS THE YUCATAN
CHANNEL AND THE NORTHERN YUCATAN PENINSULA. COLD AIR
STRATOCUMULUS CLOUDS DUE TO THE COLD ADVECTION OVER RELATIVELY
WARM WATERS ARE NOTED BEHIND THE FRONT OVER THE EASTERN HALF OF
THE GULF WHILE CLEARING IS OCCURRING OVER THE WESTERN HALF OF
THE AREA THANKS TO A 1027 MB SURFACE HIGH LOCATED OVER NE
MEXICO. NW TO N WINDS OF 15 TO 25 KT ARE BLOWING BEHIND THE
FRONT USHERING IN THE COLDEST TEMPERATURES OF THE SEASON SO FAR.
VERY STRONG LOW-LEVEL COLD ADVECTION WILL CONTINUE THROUGH THE
NIGHT ACROSS THE FLORIDA PENINSULA. AS A RESULT...A FREEZE
WARNING IS IN EFFECT FOR N AND CENTRAL FLORIDA INCLUDING THE
LAKE OCKEECHOBEE AREA. ALSO A WIND CHILL ADVISORY IS IN EFFECT
FOR ALL BUT FAR SOUTH MIAMI-DADE COUNTY. IN ADDITION...STRONG N
SURFACE WINDS ARE FORECAST TO BLOW THROUGH THE ISTHMUS OF
TEHUANTEPEC RESULTING IN A GAP WIND EVENT IN THE E PACIFIC
REGION WITH GALE FORCE WINDS BEGINNING AT 21/0600 UTC.

CARIBBEAN SEA...
AT 2100 UTC...A STRONG COLD FRONT FROM THE W ATLC STRETCHES
ACROSS THE NW BAHAMAS AND WESTERN CUBA THEN CONTINUES SW
CROSSING THE YUCATAN CHANNEL AND THE NORTHERN YUCATAN PENINSULA.
NLY WINDS...FALLING TEMPERATURES AND PATCHES OF RAIN ARE
ASSOCIATED WITH THE FRONT OVER WESTERN CUBA. THE ABOVE MENTIONED
DEEP-LAYERED TROUGH SUPPORTS THIS FRONT. FURTHER EAST...A
SURFACE TROUGH...REMNANTS OF A FRONTAL BOUNDARY IS ANALYZED FROM
CENTRAL CUBA THROUGH THE CAYMAN ISLANDS TO N HONDURAS. A NARROW
BAND OF CLOUDS WITH EMBEDDED SHOWERS IS STILL ASSOCIATED WITH
THE TROUGH. A SECOND SFC TROUGH IS BETWEEN JAMAICA AND HAITI
GENERATING A PATCH OF LOW/MID CLOUDS WITH MAINLY LIGHT RAIN. THE
SFC RIDGE THAT COVERS MOST OF THE E AND CENTRAL ATLC CLIPS THE
NE CARIBBEAN MAINTAINING A MODERATE TO FRESH EAST SOUTHEAST
TRADE WIND FLOW ACROSS THE REGION. ALOFT...A BROAD MID/UPPER-
LEVEL RIDGE REMAINS IN CONTROL OF THE WEATHER PATTERN ACROSS THE
AREA PRODUCING DRY AIR AND STABLE ATMOSPHERIC CONDITIONS
ESPECIALLY OVER THE EASTERN CARIBBEAN WHERE THE UPPER-LEVEL HIGH
IS CENTERED. LOOKING AHEAD...THE STRONG COLD FRONT IS FORECAST
TO MERGE WITH THE REMNANTS OF A WEAK COLD FRONT ANALYZED AS A
SFC TROUGH ON THE 2100 UTC INTERMEDIATE MAP. THE MERGED FRONT
WILL EXTEND FROM HISPANIOLA TO THE SW CARIBBEAN BY LATE WED THEN
DISSIPATE ON THU.

ATLANTIC OCEAN...
A JET-STREAM BRANCH WITH CORE WINDS OF 110-130 KT IS OVER
CENTRAL FLORIDA AND THE W ATLC AHEAD OF THE DEEP-LAYERED TROUGH
LOCATED OVER THE EASTERN CONUS. THE STRONG SOUTHWESTERLY WINDS
ALOFT ARE REACHING CUBA AND THE CAYMAN ISLANDS. THE DEEP TROUGH
IS ASSOCIATED WITH A SURFACE COLD FRONT THAT ENTERS THE FORECAST
31N73W THEN CONTINUES SW ACROSS THE NW BAHAMAS AND WESTERN CUBA.
GALE FORCE WINDS ARE BLOWING EITHER SIDE OF THE FRONT N OF 27N
WITH THE STRONGEST WINDS UP TO 40 KT WITHIN 240 NM AHEAD OF THE
FRONTAL SYSTEM. LOW LEVEL CONVERGENCE IS SUPPORTING SCATTERED
SHOWERS  WITHIN 60 NM EITHER SIDE OF THIS COLD FRONT. FURTHER
EAST...A DECAYING FRONT ENTERS THE AREA NEAR 31N68W THEN
CONTINUES SW TO CENTRAL CUBA. ANOTHER BAND OF CLOUDS IS TO THE
EAST...AND A SFC TROUGH IS ANALYZED THERE. THIS TROUGH GOES FROM
30N64W TO THE TURKS AND CAICOS ISLANDS. A SFC RIDGE ANCHORED BY
A 1033 MB HIGH LOCATED NEAR 33N28W DOMINATES MUCH OF THE EAST
AND CENTRAL ATLC RESULTING IN MOSTLY FAIR WEATHER AND MODERATE
TO STRONG TRADE WINDS ACROSS THE REGION. THIS HIGH PRES CENTER
IS FORECAST TO MOVE SOUTH IN ABOUT 24 HOURS. ANOTHER WEAKENING
COLD FRONT IS JUST SOUTH OF THE CANARY ISLANDS AND EXTENDS
MAINLY NEWD OVER NW AFRICA. AN UPPER-LEVEL LOW IS SPINNING NEAR
16N48W. ATMOSPHERIC INSTABILITY ASSOCIATED WITH THIS UPPER
FEATURE IS RESULTING IN ISOLATED SHOWERS FROM 10N-20N BETWEEN
40W-46W. ACROSS THE TROPICAL ATLC...WESTERLY FLOW ALOFT IS
PRESENT...WITH UPPER LEVEL DIVERGENCE ENHANCING THE CONVECTION
ASSOCIATED WITH THE ITCZ.

$$
COHEN





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