[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 301038
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT THU APR 30 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...

THE ITCZ AXIS EXTENDS FROM W AFRICA AT 07N11W TO THE EQUATOR AT
24W THEN CONTINUES S OF THE EQUATOR TO NE BRAZIL NEAR 05S37W.
SCATTERED MODERATE CONVECTION IS OBSERVED WITHIN 120 NM OF AXIS
W OF 20W.

...DISCUSSION...

GULF OF MEXICO...
A SURFACE RIDGE EXTENDS FROM HIGH PRES NEAR BERMUDA THROUGH
NORTH FLORIDA AND ACROSS THE NORTHERN GULF WATERS. THIS SURFACE
RIDGE BECAME THE DOMINANT FEATURE OVER THE GULF YESTERDAY AS AN
UPPER TROUGH EXITED TO THE SE OVER FLORIDA AND CUBA...WEAKENING
AN ASSOCIATED SURFACE TROUGH THROUGH THE YUCATAN PENINSULA.
BUOYS AND SCATTEROMETER SHOW SE RETURN FLOW OVER THE NW GULF
REACHING 15 TO 20 KT...BETWEEN THE HIGH PRES RIDGE AND
DEVELOPING LOW PRES OVER THE SOUTHERN PLAINS AND NORTHERN
MEXICAN PLATEAU. STRONG CONVECTION IS FLARING OVER WEST AND
CENTRAL TEXAS...BUT THIS WILL NOT IMPACT GULF WATERS. CMAN SITES
IN THE FLORIDA KEYS ALSO HINT AT 20 KT EASTERLY FLOW PERSISTING
THROUGH THE STRAITS OF FLORIDA AND INTO THE SE GULF WATERS N OF
THE WESTERN CUBAN COAST. A 00Z SCATTEROMETER PASS ALSO SHOWED 20
KT FLOW OFF THE NORTHERN AND WESTERN COASTS OF THE YUCATAN
PENINSULA. LOOKING AHEAD FOR THE NEXT COUPLE OF DAYS...THE
SURFACE RIDGE HOLDS AND LITTLE CHANGE IS EXPECTED.

CARIBBEAN SEA...
SURFACE HIGH PRES NEAR BERMUDA IS MAINTAINING GENERALLY 15 KT
TRADE WIND FLOW ACROSS THE NORTHERN CARIBBEAN WITH SLIGHTLY
HIGHER 15 TO 20 KT EAST FLOW S OF 15N. SCATTERED MODERATE
SHOWERS IN THE TRADE WIND FLOW PERSIST...MAINLY OVER THE NE
CARIBBEAN...BUT THIS ACTIVITY SEEMS A LITTLE DIMINISHED FROM THE
PAST COUPLE OF DAYS. LITTLE CHANGE IS EXPECTED OVER THE NEXT
COUPLE OF DAYS.

ATLANTIC OCEAN...
W OF 50W...AN UPPER TROUGH IS PUSHING THROUGH THE BAHAMAS AND
COMING IN PHASE WITH AN UPPER LOW SLIDING EAST ACROSS
BERMUDA...AHEAD OF A SHORT WAVE TROUGH DIGGING THROUGH THE
CAROLINAS. FOR THE SURFACE...1027 MB HIGH PRES NEAR BERMUDA IS
SHIFTING EAST...AHEAD OF A WEAK COLD FRONT STALLING N OF THE
AREA ASSOCIATED WITH THE SHORT WAVE TROUGH. THIS IN TURN MEANS
THAT THE TRADE WIND FLOW FROM N OF THE LEEWARDS THROUGH THE
SOUTHERN BAHAMAS IS WEAKENING SLIGHTLY. BUOY REPORTS ONLY
SHOWING AROUND 15 KT IN THIS AREA...ALTHOUGH A 03Z ASCAT PASS
HINTED OF PATCH OF 20 KT FLOW AS WELL. WESTWARD MOVING SHOWERS
PERSIST IN THE TRADE WIND FLOW...BUT SOMEWHAT DIMINISHED FROM
EARLIER WITH THE WEAKER FLOW. QUIKSCAT...ASCAT AND A SHIP
OBSERVATION ALL SHOW WEAK CYCLONIC TURNING INDICATIVE OF A
INVERTED SURFACE TROUGH NE OF THE LEEWARDS...ON THE FAVORABLE SE
SIDE OF THE UPPER TROUGH. E OF 50W...SURFACE RIDGE EXTENDS FROM
A 1030 MB HIGH PRES CELL NEAR 31N29W TO A 1027 MB HIGH NEAR
30N45W. 20 TO 25 KT NE FLOW IS NOTED ON SCATTEROMETER OFF THE NW
AFRICAN COAST BETWEEN THE HIGH PRES AND LOW PRES OVER WEST
AFRICA. THIS FLOW WILL DIMINISH SLIGHTLY INTO THU AS AN UPPER
TROUGH AMPLIFIES OVER THE CENTRAL ATLC...INDUCING THE SURFACE
HIGH PRES TO WEAKEN AND SHIFT NE.

$$
CHRISTENSEN





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