[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 201051
TWDAT

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

...ITCZ...
THE ITCZ IS CENTERED ALONG 5N9W...CROSSING THE EQUATOR NEAR 19W
AND CONTINUES ALONG 2S25W 4S30W AND INTO NE BRAZIL NEAR 5S36W.
NO SIGNIFICANT CONVECTION IS NOTED IN THE DISCUSSION AREA.
OTHERWISE ISOLATED MODERATE CONVECTION ASSOCIATED WITH THE ITCZ
IS SOUTH OF THE EQUATOR.

...DISCUSSION...

GULF OF MEXICO...
AN UPPER LEVEL TROUGH IS ACROSS THE ERN CONUS AND AS OF 0900 UTC
SUPPORTS A COLD FRONT THAT ENTERS THE GULF NEAR PANAMA CITY
FLORIDA AND EXTENDS SW ALONG 26N90W 23N95W TO THE ERN MEXICO
COAST NEAR TAMPICO. LOW-LEVEL CONVERGENCE COUPLED WITH MOIST AND
UNSTABLE MIDDLE TO UPPER LEVEL SOUTHWEST FLOW ALOFT IS PRODUCING
SCATTERED SHOWERS AND ISOLATED TSTMS WITHIN 120 NM E OF THE
FRONT S OF 27N AND THE WRN BAY OF CAMPECHE W OF 92W. THE COLD
FRONT IS FORECAST TO CONTINUE PUSHING EWD AND BE POSITIONED SE
OF THE REGION BY LATE TUESDAY. A HIGH PRESSURE RIDGE WILL BUILD
IN BEHIND THIS FRONT POSSESSING NLY WINDS UP TO 20 KTS WITH A
RELATIVELY COOLER AND DRIER AIRMASS IN PLACE.

CARIBBEAN SEA...
A SURFACE RIDGE LOCATED OVER THE W ATLC IS MAINTAINING FRESH ELY
TRADE WINDS ACROSS THE CARIBBEAN SEA. THE STRONGEST OF THESE
WINDS...UP TO 25 KTS...ARE ACROSS THE CENTRAL CARIBBEAN AND
ALONG THE NRN COAST OF COLOMBIA WHERE SURFACE WIND CONVERGENCE
IS PRODUCING ISOLATED SHALLOW SHOWERS OVER THE SW CARIBBEAN S OF
15N BETWEEN 69W-81W. ELSEWHERE...MAINLY FAIR WEATHER IS
PRESENT...WHERE DEEP LAYER DRY AIR AND SUBSIDENCE IS RESULTING
FROM ZONAL WESTERLY FLOW ALOFT. HOWEVER...AN UPPER LEVEL TROUGH
ACROSS THE W AND CENTRAL ATLC DIPS OVER THE NE CARIBBEAN AND
SUPPORTS LINGERING ISOLATED SHOWERS IN THE VICINITY OF PUERTO
RICO AND THE US/UK VIRGIN ISLANDS. MOIST SW UPPER FLOW ACROSS
THE SE CARIBBEAN COUPLED WITH MID-LEVEL INSTABILITY IS
GENERATING ELEVATED SCATTERED SHOWERS OVER THE WINDWARD ISLANDS
TO OVER THE TROPICAL ATLC EXTENDING TO 50W.

ATLANTIC OCEAN...
A FRONTAL SYSTEM IS LOCATED IN THE CENTRAL ATLC WITH A WEAK 1018
MB LOW NEAR 32N49W AND A COLD FRONT EXTENDING SW FROM THE LOW
ALONG 27N53W TO 23N58W WHERE THE FRONT CONTINUES AS STATIONARY
TO 21N61W. SCATTERED SHOWERS E OF THE FRONT ARE N OF 23N BETWEEN
45W-52W. W OF THE COLD FRONT...A WEAK 1016 MB LOW IS NEAR 28N55W
WITH A SURFACE TROUGH EXTENDING SW TO 26N57W. THIS FEATURE WILL
CONTINUE TO DISSIPATE AS THE UPPER LEVEL SUPPORT MOVE OFF
TOWARDS THE NE. SUBSIDENCE IN UPPER W TO NW FLOW ALOFT ACROSS
THE REMAINDER OF THE W ATLC WEST OF THE COLD FRONT IS ASSOCIATED
WITH A LARGE SCALE TROUGH AND AN UPSTREAM RIDGE LOCATED OVER THE
ERN U.S. SEABOARD. AT THE SURFACE...A 1022 MB HIGH IS CENTERED
NEAR 31N66W AND IS REMAINING STATIONARY. GENERALLY FAIR WEATHER
CONDITIONS ARE PRESENT WEST OF THE FRONT EXCEPT FOR A FEW
ISOLATED SHOWERS IN E TO SE FLOW ON THE SWRN PERIPHERY OF THE
SURFACE HIGH S OF 26N W OF 66W. ACROSS THE E ATLC...SUBSIDENCE
ASSOCIATED WITH A SURFACE RIDGE IS RESULTING IN GENERALLY FAIR
WEATHER CONDITIONS. THIS SURFACE RIDGE IS ANCHORED BY A 1031 MB
SURFACE HIGH NEAR 34N27W. ACROSS THE TROPICAL ATLC...AN UPPER
LEVEL HIGH IS CENTERED NEAR 5N45W WITH UPPER LEVEL DIVERGENCE
ENHANCING CONVECTION ALONG THE ITCZ MAINLY SOUTH OF THE EQUATOR.

$$
HUFFMAN



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