[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 290541
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT WED APR 29 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.

...THE ITCZ...
THE ITCZ AXIS IS CENTERED ALONG 05N10W TO THE EQUATOR AT 16W TO
01S20W THEN NW TO THE EQUATOR AGAIN NEAR 27N THEN TO 05S35W.
SCATTERED MODERATE CONVECTION IS OBSERVED WITHIN 90 NM OF
02N13W.

...DISCUSSION...

GULF OF MEXICO...
MAIN WEATHER MAKER REMAINS AN UPPER TROUGH EXTENDING FROM THE
FLORIDA BIG BEND AREA SW TO THE SOUTH CENTRAL BAY OF CAMPECHE.
THIS FEATURE IS SPONSORING A WELL DEFINED SURFACE TROUGH THAT
EXTENDS FROM THE YUCATAN PENINSULA NE TO NEAR THE SW FLORIDA
COAST. A TIGHT GRADIENT BETWEEN THE SURFACE TROUGH AND SURFACE
RIDGING OVER THE NW GULF IS ENHANCING NE FLOW OFF THE NORTHERN
AND WESTERN COASTS OF THE YUCATAN PENINSULA. SCATTERED SHOWERS
ARE WEST OF THE TROUGH OVER THE EASTERN BAY OF CAMPECHE NEAR THE
YUCATAN COAST ARE DIMINISHING. SCATTEROMETER AND CMAN SITE SHOW
EAST WINDS REACHING 25 KT THROUGH THE STRAITS OF FLORIDA AND
ALONG THE NW CUBAN COAST TO THE YUCATAN CHANNEL. ELSEWHERE
GENERALLY LIGHT TO MODERATE E TO SE FLOW PERSISTS. THE UPPER
TROUGH WILL DAMPEN OUT INTO THU WEAKENING THE SURFACE REFLECTION
AND ALLOWING SURFACE RIDGING FROM THE WESTERN ATLC TO DOMINATE
ACROSS THE GULF...AND ALLOWING SOUTHERLY RETURN FLOW TO INCREASE
ALONG TEXAS COAST.

CARIBBEAN SEA...
HIGH PRESSURE LOCATED N OF AREA MAINTAINS FRESH TO STRONG
SURFACE WIND ACROSS MUCH OF THE BASIN WITH THE STRONGEST WINDS
IN THE TYPICAL AREA NEAR THE COAST OF COLOMBIA. THIS WEATHER
PATTERN IS FORECAST TO PERSIST DURING THE NEXT 24 HOURS. THE
HIGH IS FORECAST TO GRADUALLY WEAKEN TUE THROUGH FRI AND AS A
RESULT... THE TRADE WINDS ARE EXPECTED TO DIMINISH DURING THIS
TIME FRAME AS WELL. DIFFLUENCE ALOFT ON THE SE SIDE OF UPPER
TROUGH FROM THE BAHAMAS TO THE WESTERN GULF OF MEXICO IS
ENHANCING SHOWER ACTIVITY IN THE TRADE WIND FLOW...MAINLY OVER
THE NE CARIBBEAN. SOME EMBEDDED THUNDERSTORMS ARE POSSIBLE WITH
THIS ACTIVITY AS THE UPPER TROUGH OVER THE WESTERN GULF SHIFTS
SE THROUGH THU.

ATLANTIC OCEAN...
W OF 60W...AN UPPER LEVEL LOW REMAINS CENTERED NEAR 29N72W OVER
A 1029 MB SURFACE HIGH CENTERED OFF THE CAROLINA COAST NEAR
34N68W. 15 TO 20 KT TRADES ARE EVIDENT ON THE SOUTHERN FRINGE OF
THE HIGH PRES S OF 25N. DIFFLUENCE ALOFT ON THE SE SIDE OF THE
UPPER LOW IS ENHANCING SCATTERED SHOWERS IN THE TRADE WIND FLOW
NORTH OF PUERTO RICO AND HISPANIOLA. THESE SHOWERS WILL PERSIST
INTO THU AS A TRAILING UPPER TROUGH FOLLOWS THE UPPER LOW AS IT
SHIFTS EAST. DRY SUBSIDENT AIR DOMINATES MAINLY N OF 25N.
E OF 60W...A HIGH PRES RIDGE EXTENDS FROM A 1027 MB HIGH PRES
CELL IN PLACE NEAR THE AZORES...TO ANOTHER 1027 MB HIGH PRES
CENTER NEAR 20N45W. SCATTEROMETER DATA SHOW 20 TO 25 KT NE FLOW
BETWEEN OFF THE NW AFRICAN COAST BETWEEN THE HIGH PRES AND LOW
PRES OVER WEST AFRICA...BRINGING THE DRY AND DUSTY SAHARAN AIR
LAYER AS FAR WEST AS 40W. 15 TO 20 KT TRADES ARE NOTED MAINLY S
OF 20N W OF 30W. ALOFT...A BLOCKING UPPER RIDGE N OF 32N ALONG
55W STARTS TO BREAK DOWN TONIGHT AHEAD OF DEEP LAYER TROUGH
DIGGING INTO THE N CENTRAL ATLC. AN ASSOCIATED SURFACE FRONT
APPROACHES THE AREA S OF 32N E OF 55W BY THU NIGHT...BUT STALLS
AND DISSIPATES THROUGH FRI AS UPPER ENERGY LIFTS OUT TO THE
NE...LEAVING HIGH PRES IN PLACE.

$$
CHRISTENSEN



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