[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 300543
TWDAT

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

...THE ITCZ...

THE ITCZ AXIS EXTENDS FROM W AFRICA AT 07N11W TO THE EQUATOR AT
25W THEN CONTINUES S OF THE EQUATOR TO NE BRAZIL NEAR 03S40W.
SCATTERED MODERATE CONVECTION IS OBSERVED WITHIN 90 NM N OF AXIS
BETWEEN 18W AND 21W...WITHIN 90 NM S OF AXIS BETWEEN 29W AND
33W...AND WITHIN 60 NM OF AXIS W OF 36W.

...DISCUSSION...

GULF OF MEXICO...
A SURFACE RIDGE EXTENDS FROM HIGH PRES NEAR BERMUDA THROUGH
NORTH FLORIDA AND ACROSS THE NORTHERN GULF WATERS. THE SURFACE
RIDGE HAS BECAME DOMINANT OVER THE GULF ON WED 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. THE IS EXCEPT IS THE
COLOMBIAN COAST WHERE 20 TO 25 KT WINDS WERE NOTED ON A 23Z
QUIKSCAT PASS. 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. RECENT BUOY REPORTS ONLY
SHOWING AROUND 15 KT IN THIS AREA...ALTHOUGH A 23Z QUIKSCAT 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 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





This weather bulletin was brought to you by:
www.nashvilleweather.net