[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 211053
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT TUE APR 21 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY
THROUGH 1015 UTC.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 5N9W 3N17W CROSSING THE EQUATOR NEAR
22W TO 3S31W TO NE BRAZIL NEAR 2S45W. SCATTERED MODERATE
CONVECTION IS WITHIN 60 NM N OF THE ITCZ AXIS BETWEEN 14W-20W.
SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS S OF 2N BETWEEN
21W-25W.

...DISCUSSION...

THE GULF OF MEXICO...
A DEEP LAYER TROUGH OVER THE E CONUS CONTINUES TO DIG INTO THE
REGION...WITH AN ASSOCIATED COLD FRONT EXTENDING FROM S
FLORIDA TO THE YUCATAN PENINSULA AND A FASTER MOVING SECONDARY
COLD FRONT EXTENDING FROM N FLORIDA TO AROUND 90 NM S OF MOBILE
ALABAMA. LOW LEVEL CONVERGENCE NEAR THESE BOUNDARIES COUPLED
WITH DEEP ATMOSPHERIC LIFT IN MOIST SOUTHWESTERLY FLOW ALOFT ARE
SUPPORTING SCATTERED SHOWERS AND TSTMS OVER THE SE GULF
INCLUDING S FLORIDA. THIS ACTIVITY IS BEING FURTHER ENHANCED BY
A PREFRONTAL TROUGH THAT EXTENDS FROM THE FLORIDA KEYS TO W
CUBA. THE COLD FRONTS ARE FORECAST TO HAVE CLEARED THE REGION
LATER TODAY...WITH SURFACE HIGH PRESSURE TRANSLATING FROM W TO E
ACROSS THE AREA THROUGH MID-WEEK. ATMOSPHERIC SUBSIDENCE NEAR
THIS HIGH IS BEING SUPPORTED BY DRY NORTHWESTERLY FLOW
ALOFT...AND WILL RESULT IN GENERALLY FAIR WEATHER CONDITIONS
ACROSS THE ENTIRE GULF BY THIS AFTERNOON WITH RELATIVELY LIGHT
SURFACE WINDS. THE SURFACE HIGH WILL MOVE E OF THE GULF BY LATE
WEEK...WITH SE RETURN FLOW INCREASING.

THE CARIBBEAN SEA...
A LARGE AREA OF CONVECTIVE ACTIVITY IS INLAND OVER COLOMBIA
TRIGGERED BY A SWLY UPPER JET AND ENHANCED BY LOCAL FLOWS AND
USUAL SFC LOW PRES. EARLIER QUIKSCAT PASS REVEALED 20-25 KT NE/E
WINDS BETWEEN THE COAST OF COLOMBIA AND HISPANIOLA WITH 15-20 KT
TRADES ELSEWHERE E OF 80W. WINDS ARE LIGHT AND VARIABLE OVER THE
W PORTION DUE TO THE PRESENCE OF A WEAK PREFRONTAL TROUGH ALONG
83W/84W. SOME MOISTURE...LIKELY CONTAINING ONLY ISOLATED SHOWERS
AND TSTMS...HAS MOVED INTO THE NW CARIBBEAN AHEAD OF A COLD
FRONT OVER THE E GULF. THIS FRONT IS EXPECTED TO MOVE INTO A
PORTION OF THE AREA BUT SHOULD HAVE LITTLE SIGNIFICANT WEATHER
IMPACTS.

THE ATLANTIC OCEAN...
SCATTERED SHOWERS AND TSTMS ARE WITHIN 300 NM E OF THE FLORIDA
AND GEORGIA COASTS TRIGGERED BY UPPER DIFFLUENT FLOW AND A COLD
FRONT EXTENDING FROM 32N77W TO S FLORIDA. SEE GULF OF MEXICO
SECTION FOR MORE DETAILS. SLY WINDS HAVE INCREASED TO 20-30 KT
NEAR THE N BORDER W OF 72W DUE TO THE TIGHT PRESSURE GRADIENT
BETWEEN THE FRONT AND STRONG HIGH PRES E OF BERMUDA. OVER THE
CENTRAL ATLC...DEEP LAYER TROUGHING REMAINS WELL DEFINED
PROVIDING LIMITED SUPPORT FOR A STATIONARY FRONT FROM 32N46W TO
27N54W. A WEAK SMALL SCALE LOW LIES AT THE BASE OF THE FRONT BUT
IS PRODUCING LITTLE SIGNIFICANT WEATHER. A MORE AMPLIFIED
TROUGH...SUPPORTING ANOTHER FRONT...IS EXPECTED TO SWEEP SE AND
ABSORB OR MERGE WITH THE WEAK LOW/FRONT OVER THE NEXT COUPLE OF
DAYS. A NARROW SWATH OF SCATTERED SHOWERS AND TSTMS ARE LOCATED
IN THE UPPER DIFFLUENT ZONE N OF 22N BETWEEN 35W-41W. AN UPPER
JET EXTENDING NE FROM THE WINDWARD ISLANDS TO 20N40W IS LIKELY
PRODUCING SCATTERED SHOWERS AND TSTMS WITHIN 300 NM E OF THE JET
AXIS. OTHERWISE...THE E ATLC IS DOMINATED BY A STRONG AZORES
HIGH.

$$
CANGIALOSI/COHEN



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