[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 200531
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
105 AM EST THU 20 JAN 2005

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHEASTERN
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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0445 UTC.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 6N8W 4N18W 5N31W 3N45W 4N54W.
SCATTERED MODERATE/STRONG CONVECTION IS WITHIN 175/200 NM OF
LINE FROM 7N27W TO 6N42W.

...DISCUSSION...

GULF OF MEXICO INTO THE CENTRAL ATLANTIC...
SPLIT FLOW CONTINUES OVER THE GULF OF MEXICO WITH THE N BRANCH
OF THE JET STREAM CONFINED WELL N OF THE AREA WHILE THE INACTIVE
S STREAM EXTENDS FROM SE TEXAS E OVER THE STRAITS OF FLORIDA.
MID/UPPER LEVEL PACIFIC MOISTURE IS BEING ADVECTED INTO W MEXICO
BUT THIS PLUME DRIES OUT AS IT RIDES UP AND OVER A RIDGE OVER
INTERIOR MEXICO. AS A RESULT...ONLY STREAKS OF HIGH CLOUDS
EXTEND ACROSS THE SW GULF. AT THE LOWER LEVELS...POST-FRONTAL
NORTHERLY FLOW AND ASSOCIATED COLD AIR STRATOCUMULUS CLOUDS
PREVAIL OVER ALL BUT THE EXTREME W GULF WHERE RETURN FLOW IS
GENERATING CLOUDINESS AND ISOLATED SHOWERS ALONG A COASTAL
TROUGH FROM SE TEXAS TO VERACRUZ MEXICO. THIS ACTIVITY SHOULD
PERSIST THRU TONIGHT AND DRY OUT LATER TODAY. VERY BROAD
MID/UPPER LEVEL TROUGH DOMINATES THE E UNITED STATES INTO THE
CENTRAL ATLC W OF 50W WHICH BY FAR IS THE MOST SIGNIFICANT
FEATURE IN THE ENTIRE AREA. A SHORTWAVE TROUGH AND ASSOCIATED
COLD FRONT MOVING E TOWARD BERMUDA IS ROTATING THROUGH THIS
PATTERN AND PRODUCING SCATTERED MODERATE CONVECTION ALONG A
SURFACE COLD FRONT FROM 32N51W TO OVER THE VIRGIN ISLANDS. THIS
ACTIVITY IS PRIMARILY FOCUSED N OF 30N IN LINE WITH THE
STRONGEST DYNAMICS/LIFT WHICH IS QUICKLY MOVING OUT OF THE AREA.
W OF THE FRONT...STRONG POST-FRONTAL NORTHERLY FLOW...COLD AIR
ADVECTION...AND A FIELD OF BROKEN STRATOCUMULUS CLOUDS PREVAIL.

CARIBBEAN AND TROPICAL ATLANTIC...
THE MAIN FEATURE OF NOTE IN THIS AREA IS A NEAR STATIONARY
MID/UPPER LEVEL RIDGE EXTENDING FROM CENTRAL AMERICA ACROSS THE
TROPICAL ATLC TO JUST W OF THE CAPE VERDE ISLANDS. THE MID/UPPER
LEVEL TROUGH OVER THE GULF AND W ATLC MERGES WITH THE RIDGE OVER
THE E CARIBBEAN BUT WITH MID/UPPER LEVEL DRY/STABLE AIR
DOMINATING THE CARIBBEAN AND W TROPICAL ATLC ONLY LOW LEVEL
CLOUDS CAN FORM. THE COLD FRONT THAT ENTERS THE NE CARIBBEAN
OVER THE VIRGIN ISLANDS EXTENDS TO 17N67W WHERE IT CONTINUES AS
A DISSIPATING STATIONARY FRONT ALONG THE COAST OF CENTRAL
PANAMA. OVERCAST LOW CLOUDS WITH ISOLATED SHOWERS ARE INLAND AND
WITHIN 90 NM OF THE COAST OF PANAMA ALONG COSTA RICA TO S
NICARAGUA. SE OF THE FRONT...A WEAK LOW LEVEL TROUGH ALONG
59W/60W IS GENERATING SCATTERED SHOWERS AND A FEW ISOLATED
THUNDERSTORMS OVER THE WINDWARD ISLANDS WITH ISOLATED SHOWERS
OVER THE LEEWARD ISLANDS.

EASTERN ATLANTIC...
LARGE DEEP LAYERED LOW NEAR 30N37W WITH A SURFACE 1008 MB LOW
CENTERED TO THE S NEAR 29N37W. THIS SYSTEM IS LOSING ITS PUNCH
NOW THAT THE CENTERS ARE NO LONGER AS VERTICALLY STACKED AS OVER
THE PAST FEW DAYS. THIS SYSTEM CONTINUES TO DOMINATE THE
WEATHER WITH A LARGE AREA OF SCATTERED MODERATE CONVECTION FROM
23N-35N BETWEEN 23W-32W. THE SYSTEM SHOULD CONTINUE TO WEAKEN AS
IT MOVES N OUT OF THE AREA. OVER THE FAR E TROPICAL ATLC...UPPER
LEVEL DIFFLUENT FLOW ON THE SOUTH SIDE OF THE AFOREMENTIONED
DEEP LAYERED LOW IS PRODUCING ENHANCED ITCZ CONVECTION AND
OVERCAST SKIES WITH SCATTERED SHOWERS WITHIN 250 NM OF LINE FROM
10N29W OVER W AFRICA NEAR 19N16W INCLUDING THE CAPE VERDE
ISLANDS.

$$
WALLACE


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