[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 221752
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
105 PM EST THU NOV 22 2012

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.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS ACROSS W AFRICA INTO THE E TROPICAL
ATLC NEAR 9N13W TO 7N17W WHERE THE ITCZ BEGINS AND CONTINUES
ALONG 5N27W TO 7N48W. A SURFACE TROUGH IS DISRUPTING THE ITCZ
FROM 11N49W ALONG 7N51W TO 5N50W. CLUSTERS OF SCATTERED MODERATE
CONVECTION ARE FROM 6N-10N BETWEEN 48W-55W. SCATTERED MODERATE/
ISOLATED STRONG CONVECTION IS FROM 2N-4N BETWEEN 13W-16W.
CLUSTERS OF SCATTERED MODERATE TO ISOLATED STRONG CONVECTION ARE
WITHIN 200 NM S OF THE ITCZ BETWEEN 20W-33W AND WITHIN 225 NM N
OF THE ITCZ BETWEEN 21W-48W.

...DISCUSSION...

GULF OF MEXICO...
A SHORTWAVE UPPER TROUGH IN THE W ATLC EXTENDS W OVER THE
FLORIDA PENINSULA DRAWING DRY CONTINENTAL AIR OVER THE E GULF OF
MEXICO AND ESPECIALLY THE FLORIDA. NEAR ZONAL WESTERLY FLOW
ALOFT COVERS THE REMAINDER OF THE GULF. A SURFACE TROUGH IS IN
THE SW GULF EXTENDING ALONG THE COAST OF MEXICO FROM NEAR
TAMPICO TO COATZACOALCOS. SCATTERED SHOWERS ARE WITHIN 60 NM
EITHER SIDE OF THE TROUGH. OTHERWISE A SURFACE RIDGE DOMINATES
THE GULF ANCHORED BY A SERIES OF HIGHS STRETCHING FROM NEW
ENGLAND TO A 1025 MB HIGH OVER MISSISSIPPI. THIS IS GIVING MOST
OF THE GULF CLEAR SKIES THIS AFTERNOON. THE SURFACE RIDGE WILL
WEAKEN THROUGH FRI. COLD FRONT WILL MOVE INTO FAR NW GULF LATE
FRI REACHING FROM TAMPA FLORIDA TO S TEXAS SAT THEN FROM STRAITS
OF FLORIDA TO S TEXAS EARLY SUN WHERE IT STALL AND DISSIPATE.
HIGH PRESSURE WILL REBUILD E ACROSS REGION BEHIND FRONT.

CARIBBEAN SEA...
A BROAD UPPER RIDGE DOMINATES MOST OF THE CARIBBEAN ANCHORED
OVER S VENEZUELA AND EXTENDING A RIDGE AXIS NNE ACROSS THE
LEEWARD/VIRGIN ISLANDS INTO THE CENTRAL ATLC. A SURFACE TROUGH
EXTENDS FROM THE MONA PASSAGE ALONG 15N71W TO THE COAST OF
COLOMBIA NEAR 12N73W. MOIST SW FLOW ALOFT COVERS THE SW
CARIBBEAN AND COUPLED WITH THE RESULTING NE SURFACE FLOW ARE
GENERATING SCATTERED SHOWERS AND POSSIBLE ISOLATED THUNDERSTORMS
S OF 13N W OF 75W TO INLAND OVER PANAMA AND COSTA RICA. THE
MONSOON TROUGH EXTENDS INLAND OVER PANAMA AND COSTA RICA FURTHER
ENHANCING THE ACTIVITY DESCRIBED ABOVE. NORTHERLY SURFACE FLOW W
OF THE SURFACE TROUGH ARE GENERATING ISOLATED SHOWERS AND
POSSIBLE ISOLATED THUNDERSTORMS WITHIN 225 NM W OF THE SURFACE
TROUGH. SURFACE RIDGE OVER THE GULF OF MEXICO EXTENDS TO OVER
THE W CARIBBEAN. GENTLE TO MODERATE E TRADE WINDS PREVAIL OVER E
AND CENTRAL CARIBBEAN THROUGH FRI. SURFACE RIDGE WILL REMAIN
THROUGH SAT MAINTAINING TIGHT PRESSURE GRADIENT AND FRESH N
WINDS OVER W CARIBBEAN. TRADE WINDS WILL INCREASE OVER CENTRAL
CARIBBEAN BY SAT AND SUN BUT WEAKEN SOME W CARIBBEAN AS ATLC
SURFACE RIDGE STRENGTHENS.

ATLANTIC OCEAN...
A NARROW SHORTWAVE UPPER TROUGH EXTENDS OVER THE FAR W ATLC
COVERING THE AREA W OF 68W TO OVER THE FLORIDA PENINSULA
SUPPORTING A NEWLY DEVELOPED COLD FRONT THAT EXTENDS FROM A 1004
MB LOW NEAR 33N68W ALONG 30N68W ACROSS THE TURKS AND CAICOS TO
THE NE TIP OF CUBA. A WEAK 1008 MB SURFACE LOW IS W OF THE FRONT
NEAR 28N76W WITH A SURFACE TROUGH EXTENDING S TO THE CENTRAL
BAHAMAS NEAR 25N77W. THE AREA IS DOMINATED BY A SWATH OF DRY
STABLE AIR ALOFT THAT EXTENDS FROM OVER FLORIDA AND W CUBA TO
OVER THE CENTRAL ATLC. HOWEVER...ISOLATED LOW LEVEL SHOWERS ARE
POSSIBLE N OF 24N W OF 73W. A BROAD UPPER TROUGH IS IN THE
E/CENTRAL ATLC N OF 24N BETWEEN 26W-42W SUPPORTING A COLD FRONT
THAT EXTENDS THROUGH 32N34W TO 27N41W. SCATTERED SHOWERS AND
POSSIBLE ISOLATED THUNDERSTORMS ARE WITHIN 180 NM E OF THE
FRONT. A REMNANT SURFACE TROUGH IS TO THE SW EXTENDING FROM
26N50W ALONG 23N58W TO 20N64W WITH SCATTERED SHOWERS WITHIN 60
NM EITHER SIDE OF THE TROUGH. A SURFACE RIDGE DOMINATES THE FAR
E ATLC E OF 30W. ANOTHER  COLD FRONT WILL ENTER NW WATERS FRI
NIGHT INTO SAT REACHING FROM 32N63W TO STRAITS OF FLORIDA EARLY
SUN AND WEAKEN THEN STALL WHILE DISSIPATING FROM 32N58W TO
CENTRAL CUBA EARLY MON. HIGH PRESSURE WILL REBUILD ACROSS AREA
IN WAKE OF FRONT.

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

$$
PAW





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