[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 201734
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
105 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY
THROUGH 1645 UTC.

...THE ITCZ...
THE ITCZ AXIS IS CENTERED ALONG 7N9W 4N16W 1N21W CROSSING THE
EQUATOR NEAR 23W EXTENDING TO 1S31W AND FURTHER EXTENDING INTO
NE BRAZIL NEAR 3S44W. SCATTERED MODERATE/ISOLATED STRONG
CONVECTION IS S OF 5N BETWEEN 7W-18W. SCATTERED
MODERATE/ISOLATED STRONG CONVECTION IS ALSO S OF 2N BETWEEN
20W-24W. SIMILAR CONVECTION IS S OF 5N BETWEEN 32W-43W.
SCATTERED MODERATE CONVECTION IS FROM 1N-5N BETWEEN 44W-53W.

...DISCUSSION...

GULF OF MEXICO...
A DEEP LAYER TROUGH OVER THE E CONUS AND W ATLC EXTENDS INTO THE
N GULF REGION...WITH STRONG WESTERLY AND NORTHWESTERLY FLOW
ALOFT IN THE BASE OF THIS TROUGH AFFECTING MUCH OF THE GULF
REGION. THIS DEEP TROUGH IS SUPPORTING A SURFACE COLD FRONT IN
THE GULF. THIS COLD FRONT EXTENDS FROM 23N92W TO 24N84W TO THE S
FLORIDA PENINSULA NEAR 26N81W. LOW LEVEL CONVERGENCE IS
SUPPORTING ISOLATED SHOWERS WITHIN 30 NM EITHER SIDE OF THIS
COLD FRONT. TO THE N OF THIS COLD FRONT...DRIER CONDITIONS ARE
PRESENT WITH TEMPERATURES BELOW SEASONAL AVERAGES. SURFACE WINDS
ACROSS THE GULF ARE NW TO N AT 15 TO 25 KT. LOW LEVEL
INSTABILITY IS BEING GENERATED BY THESE WINDS ADVECTING
RELATIVELY COOLER AIR OVER THE WARMER GULF WATERS. THIS IS
RESULTING IN SCATTERED TO BROKEN STRATOCUMULUS CLOUDS TO THE N
OF THE FRONT. HOWEVER...STABLE ATMOSPHERIC CONDITIONS HIGHER IN
THE ATMOSPHERE AND DEEP LAYER DRY AIR ARE GENERALLY INHIBITING
DEEP CONVECTION ACROSS MUCH OF THE GULF REGION. ADDITIONALLY...
STRONG N SURFACE WINDS ARE FORECAST TO BLOW THROUGH THE ISTHMUS
OF TEHUANTEPEC RESULTING IN GALE FORCE WINDS IN THE E PACIFIC
REGION BEGINNING AT 21/0600 UTC.

CARIBBEAN SEA...
THE DEEP LAYER TROUGH OVER THE E CONUS AND W ATLC IS ASSOCIATED
WITH A DISSIPATING SURFACE COLD FRONT IN THE NW CARIBBEAN
REGION. THIS FRONT EXTENDS FROM E OF BELIZE NEAR 16N88W TO
20N83W TO W CUBA NEAR 22N80W. LOW LEVEL CONVERGENCE IS
SUPPORTING ISOLATED SHOWERS WITHIN 30 NM EITHER SIDE OF THIS
FRONT. ALSO...A SURFACE TROUGH EXTENDS FROM W OF HAITI NEAR
19N75W TO 14N79W TO 10N80W. SURFACE OBSERVATIONS INDICATE A
REGION OF CYCLONIC CURVATURE IN THE SURFACE WIND FIELD IN THE
VICINITY OF THIS SURFACE TROUGH...WHERE VISIBLE SATELLITE
IMAGERY DEPICTS CYCLONIC MOTION OF LOW LEVEL CLOUDS. LOW LEVEL
CONVERGENCE IS SUPPORTING SCATTERED SHOWERS WITHIN 60 NM EITHER
SIDE OF THIS SURFACE TROUGH. HOWEVER...DEEP LAYER DRY AIR AND
STABLE ATMOSPHERIC CONDITIONS ARE GENERALLY INHIBITING DEEP
CONVECTION ACROSS MUCH OF THE CARIBBEAN SEA...WITH A BROAD UPPER
LEVEL RIDGE IN PLACE ACROSS THE CARIBBEAN AND AN UPPER HIGH
CENTERED NEAR 14N64W.

ATLANTIC OCEAN...
STRONG SOUTHWESTERLY FLOW ALOFT IS PRESENT ACROSS THE W ATLC...
WITH THE DEEP TROUGH OVER THE E CONUS AND W ATLC. THIS DEEP
TROUGH IS ASSOCIATED WITH A SURFACE COLD FRONT EXTENDING FROM
THE S FLORIDA PENINSULA NEAR 26N81W TO 29N78W TO 32N76W TO N OF
THE DISCUSSION AREA...A SURFACE COLD FRONT EXTENDING FROM W CUBA
NEAR 22N80W TO 29N71W TO 32N67W TO NE OF THE DISCUSSION AREA
THAT IS DISSIPATING W OF 77W...A SURFACE TROUGH EXTENDING FROM
22N70W TO 27N66W TO 31N62W...AND A DISSIPATING SURFACE COLD
FRONT THAT EXTENDS FROM 31N62W TO 32N60W TO NE OF THE DISCUSSION
AREA. LOW LEVEL CONVERGENCE IS SUPPORTING SCATTERED SHOWERS
WITHIN 60 NM EITHER SIDE OF EACH OF THESE SURFACE COLD FRONTS
AND SURFACE TROUGH. THIS ACTIVITY IS BEING ENHANCED BY UPPER
LEVEL DIVERGENCE ASSOCIATED WITH AN UPPER LEVEL JET MAXIMUM
LOCATED NORTH OF THE DISCUSSION AREA. ADDITIONALLY...GALE FORCE
WINDS ARE OCCURRING ACROSS PORTIONS OF THE SW N ATLC N OF 27N.
FARTHER TO THE E...A 1035 MB SURFACE HIGH IS CENTERED NEAR
35N30W. SUBSIDENCE AND STABLE ATMOSPHERIC CONDITIONS ASSOCIATED
WITH THIS SURFACE HIGH ARE RESULTING IN GENERALLY FAIR WEATHER
ACROSS MUCH OF THE CENTRAL AND E ATLC. HOWEVER...AN UPPER LOW IS
CENTERED NEAR 16N48W. ATMOSPHERIC INSTABILITY ASSOCIATED WITH
THIS UPPER LOW IS RESULTING IN ISOLATED SHOWERS FROM 15N-19N
BETWEEN 45W-49W. 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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