[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 200546
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0515 UTC.

...ITCZ...
THE ITCZ IS CENTERED ALONG 4N AND THE PRIME MERIDIAN CROSSING
THE EQUATOR NEAR 10W AND CONTINUES ALONG 2S20W AND INTO NE
BRAZIL NEAR 3S40W. SCATTERED MODERATE CONVECTION IS WITHIN 50 NM
OF A LINE FROM 6N13W TO 3N19W. OTHERWISE ISOLATED 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 0300 UTC
SUPPORTS A COLD FRONT THAT ENTERS THE GULF NEAR NEW ORLEANS
LOUISIANA AND EXTENDS SW ALONG 28N90W 25N94W TO THE NE MEXICO
COAST NEAR 24N98W. LOW-LEVEL CONVERGENCE ALONG AND TO THE EAST
OF THE FRONT...ANALYZED AS A SURFACE TROUGH EXTENDING FROM
29N88W TO 24N91W...IS GENERATING SCATTERED SHOWERS AND ISOLATED
TSTMS IN THE WRN BAY OF CAMPECHE W OF 94W AND ACROSS THE NE GULF
N OF 25N. MOIST MIDDLE TO UPPER LEVEL SOUTHWEST FLOW ALOFT IS
PROVIDING ADDITIONAL SUPPORT FOR THIS CONVECTIVE ACTIVITY. THE
COLD FRONT IS FORECAST TO CONTINUE PROGRESSING EWD AND POSITION
ITSELF SE OF THE REGION BY 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 COLOMBIA COAST. GENERALLY FAIR WEATHER IS PRESENT
BASIN WIDE...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 THE TAIL END OF A COLD FRONT N OF PUERTO
RICO. LOW-LEVEL CONVERGENCE E OF THE FRONT IS GENERATING
ISOLATED SHOWERS N OF 18N W OF THE MONA PASSAGE WHILE MOIST SW
UPPER FLOW ACROSS THE ERN CARIBBEAN COUPLED WITH MIDDLE LEVEL
INSTABILITY IS GENERATING ELEVATED SCATTERED SHOWERS OVER THE
LESSER ANTILLES S OF 16N AND TO THE E OVER THE TROPICAL ATLC
EXTENDING TO 55W.

ATLANTIC OCEAN...
A FRONTAL SYSTEM IS LOCATED IN THE CENTRAL ATLC WITH A WARM
FRONT THROUGH 31N52W TO A WEAKENING 1016 MB LOW NEAR 28N54W AND
A COLD FRONT EXTENDING SW FROM THE LOW TO NW PUERTO RICO AND THE
MONA PASSAGE. SCATTERED SHOWERS E OF THE FRONT ARE N OF 24N
BETWEEN 46W-53W. SUBSIDENCE IN UPPER W TO NW FLOW ALOFT ACROSS
THE W ATLC WEST OF THE COLD FRONT IS ASSOCIATED WITH A LARGE
SCALE TROUGH OVER THIS AREA AND AN UPSTREAM RIDGE LOCATED OVER
THE ERN U.S. SEABOARD. AT THE SURFACE...A 1022 MB HIGH IS
CENTERED NEAR 31N65W AND IS REMAINING STATIONARY. GENERALLY FAIR
WEATHER CONDITIONS ARE PRESENT WEST OF THE FRONT EXCEPT FOR SOME
ISOLATED SHOWERS IN E TO SE FLOW ON THE SWRN PERIPHERY OF THE
SURFACE HIGH S OF 26N W OF 67W. ACROSS THE E ATLC...SUBSIDENCE
ASSOCIATED WITH A SURFACE RIDGE IS RESULTING IN GENERALLY FAIR
WEATHER CONDITIONS. THIS SURFACE RIDGE IS ANCHORED BY A 1032 MB
SURFACE HIGH NEAR 34N27W. ACROSS THE TROPICAL ATLC...AN UPPER
LEVEL HIGH IS CENTERED NEAR 4N44W. UPPER LEVEL DIVERGENCE
ASSOCIATED WITH THIS FEATURE IS ENHANCING CONVECTION ALONG THE
ITCZ.

$$
HUFFMAN




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