[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 010558
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT FRI MAY 01 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 06N10W TO THE EQUATOR AT
29W TO NE BRAZIL NEAR 02S44W. SCATTERED MODERATE CONVECTION IS
NOTED WITHIN 90 NM N OF AXIS BETWEEN 25W AND 30W.

...DISCUSSION...

GULF OF MEXICO...
A RIDGE OF HIGH PRES EXTENDS ACROSS THE NORTHERN GULF FROM THE
WESTERN ATLC. LOW PRES REMAINS IN PLACE OVER THE MEXICAN
PLATEAU. THE RESULTING PRESSURE GRADIENT BETWEEN THESE FEATURES
IS SUPPORTING 15 TO 20 KT E TO SE FLOW FROM THE STRAITS OF
FLORIDA TO THE TEXAS COAST. CMAN SITES IN THE FLORIDA KEYS SHOW
WINDS HAVE DIMINISHED SLIGHTLY FROM YESTERDAY...ALTHOUGH A 00Z
QUIKSCAT PASS FROM 00Z SHOWED PERSISTENT 25 KT FLOW OFF THE NW
CUBAN COAST. FLOW ALOFT REMAINS GENERALLY ZONAL BETWEEN AN UPPER
SHORT WAVE TROUGH OVER THE MISSISSIPPI VALLEY AND AN UPPER RIDGE
TO THE SOUTH. LITTLE CHANGE IS EXPECTED THROUGH SATURDAY.

CARIBBEAN SEA...
A 1030 MB SURFACE HIGH CENTERED WELL NORTH OF THE AREA OVER THE
NW ATLC IS MAINTAINING GENERALLY MODERATE MAINLY NE TRADES WINDS
ACROSS THE CARIBBEAN...ALTHOUGH SOMEWHAT HIGHER ALONG THE SOUTH
AMERICAN COAST ESPECIALLY OFF COLOMBIA. SCATTERED SHOWERS ARE
EMBEDDED IN THE NE TRADE WIND FLOW MAINLY OVER THE NE
CARIBBEAN...BUT OTHERWISE NO SIGNIFICANT CONVECTION IS NOTED.

ATLANTIC OCEAN...
W OF 50W...UPPER TROUGH AXIS EXTENDS FROM 32N55W TO THE SOUTHERN
BAHAMAS. DIFLUENT FLOW ALOFT ON THE SE SIDE OF THE UPPER TROUGH
IS SPONSORING AN ELONGATED SURFACE TROUGH FROM ROUGHLY 30N55W TO
THE LEEWARD ISLANDS. SATELLITE IMAGERY SHOWS COPIOUS CLOUD COVER
AND LIKELY WIDESPREAD SHOWER ACTIVITY WITHIN 180 NM EITHER SIDE
OF THE SURFACE TROUGH. PROGRESSIVE UPPER PATTERN IS LIMITING THE
SOUTHWARD PUSH OF A COLD FRONT ORIENTED EAST TO WEST ALONG
32N...AND THIS FEATURE WILL STALL AND DISSIPATE W OF BERMUDA
TODAY. 1030 MB SURFACE HIGH IS CENTERED WELL N OF BERMUDA BEHIND
THE FRONT. BUOYS AND SCATTEROMETER DATA SHOW A BAND OF NE TRADES
AROUND 15 TO 20 KT S OF 25N BETWEEN THE HIGH PRES AND THE
SURFACE TROUGH. SCATTERED SHOWERS EMBEDDED IN THIS FLOW DIMINISH
AS THE MOVE WEST AWAY FROM THE MOIST TROUGH AND INTO DRIER AND
MORE STABLE AIR NEAR THE BAHAMAS.
E OF 50W...A SURFACE RIDGE EXTENDS FROM A 1030 MB HIGH PRES CELL
OFF THE SPANISH COAST THROUGH THE AZORES TO A 1028 MB HIGH NEAR
30N44W. THIS RIDGE HAS BEEN WEAKENING AND SHIFTING EAST AHEAD OF
A BROAD UPPER TROUGH DIGGING THROUGH THE CENTRAL ATLC.
SCATTEROMETER DATA SHOW PERSISTENT 20 TO 25 NE WINDS OFF THE NW
AFRICAN COAST THROUGH THE CANARY ISLANDS BETWEEN THE SURFACE
RIDGE AND LOW PRES OVER W AFRICA. GENERALLY 15 TO 20 KT TRADES
PERSIST ELSEWHERE S OF 25N ON THE SOUTHERN PERIPHERY OF THE
RIDGE.

$$
CHRISTENSEN




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