[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 151802
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT WED APR 15 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1715 UTC.

...THE ITCZ...
THE ITCZ AXIS IS CENTERED ALONG 5N9W...CROSSING THE EQUATOR
ALONG 18W EXTENDING TO 3S30W AND INTO NE BRAZIL NEAR 4S40W. THE
TROPICAL WAVE-LIKE FEATURE THAT WAS ANALYZED AS A SFC TROUGH ON
THE SFC MAP IS NO LONGER IDENTIFIABLE BASED ON LATEST SATELLITE
IMAGERY. CONVECTION HAS DIMINISHED SINCE YESTERDAY IN THAT AREA.
CURRENTLY... SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS
NOTED FROM THE EQUATOR TO THE AFRICAN COAST BETWEEN THE PRIME
MERIDIAN AND 10W. SCATTERED MODERATE CONVECTION IS ALSO FROM THE
EQUATOR TO 4N BETWEEN 10W AND 20W. SIMILAR CONVECTION IS NOTED
WHERE THE ITCZ AXIS MEETS THE COAST OF BRAZIL.

...DISCUSSION...

THE GULF OF MEXICO...
AS OF 1500 UTC...A COLD FRONT EXTENDING OVER SOUTH FLORIDA
BECOMES STATIONARY OVER THE GULF OF MEXICO ALONG 23N83W 25N86W
23N90W. A QSCAT PASS FROM AROUND 1130 UTC SHOWED VERY WELL THE
WIND SHIFT RELATED TO THE FRONT. THE UPPER LEVEL SUPPORT THAT
GENERATED STRONG CONVECTION YESTERDAY IN THE VICINITY OF THIS
FRONT HAS NOW OUTRUN THE FRONT...WITH ISOLATED SHOWERS AND
THUNDERSTORMS OCCURRING ALONG THE FRONTAL BOUNDARY EARLY THIS
AFTERNOON. THE FRONT WILL CONTINUE TO DRIFT SOUTHWARD THIS
AFTERNOON AND EXTEND FROM THE FLORIDA KEYS TO THE YUCATAN
PENINSULA TONIGHT BEFORE WEAKENING ON THU. HIGH PRES WILL BUILD
OVER THE SE U.S. BEHIND THE FRONT THROUGH THE WEEKEND. WINDS
WILL INCREASE ACROSS THE WESTERN GULF ON FRI DUE TO A TIGHT PRES
GRADIENT BETWEEN THE RIDGE OVER THE SE CONUS AND LOWER PRES OVER
MEXICO. THE GFS COMPUTER MODEL INDICATES SE WINDS OF 20 TO 25 KT
IN THAT AREA. A SFC TROUGH PERSISTS OVER THE BAY OF CAMPECHE AND
EXTENDS FROM 22N92W TO 18N93W. ISOLATED SHOWERS ARE ASSOCIATED
WITH THIS TROUGH. IN THE UPPER LEVELS...A RIDGE WITH AXIS ALONG
92W DOMINATES MUCH OF THE GULF REGION. THE NEXT COLD FRONT IS
FORECAST TO MOVE OFF THE SE TEXAS COAST SAT NIGHT AND EXTENDS
FROM SE LOUISIANA TO VERACRUZ SUN AFTERNOON.

THE CARIBBEAN SEA...
FRESH TRADEWINDS ARE BLOWING ACROSS THE EAST AND CENTRAL
CARIBBEAN. WINDS VEER TO THE SE OVER THE WESTERN CARIBBEAN DUE
TO THE PRESENCE OF THE FRONTAL ZONE ACROSS THE GULF OF MEXICO.
SHALLOW MOISTURE EMBEDDED IN THE TRADE WIND FLOW WILL CONTINUE
TO MOVE ACROSS THE BASIN PRODUCING ISOLATED TO SCATTERED PASSING
SHOWERS. SOME OF THEM ARE ALREADY AFFECTING TRINIDAD AND TOBAGO
IN THE WINDWARD ISLANDS AS WELL AS THE UK/US VIRGIN ISLANDS AND
THE EASTERN PORTION OF PUERTO RICO. ALOFT...THE BASE OF AN
UPPER-LEVEL TROUGH OVER THE W ATLC REACHES CUBA WITH WLY WINDS
DOMINATING THE NW CARIBBEAN. THE REMAINDER OF THE AREA IS UNDER
THE INFLUENCE OF A BROAD RIDGE WITH MODERATE TO STRONG
SUBSIDENCE. EXPECT LITTLE CHANGE OVER THE NEXT 24 HOURS.

THE ATLANTIC OCEAN...
A COLD FRONT ENTERS THE AREA NEAR 31N76W THEN CONTINUES SW
ACROSS SOUTH FLORIDA INTO THE GULF OF MEXICO WHERE IT BECOMES
STATIONARY. S TO SW WINDS OF 20 TO 25 KT ARE BLOWING AHEAD OF
THE FRONT N OF 27N TO NEAR 70W. WINDS SHIFT TO THE W AND THEN NW
WITH THE SAME SPEEDS BEHIND THE FRONT. ISOLATED SHOWERS AND
POSSIBLE THUNDERSTORMS ARE NOTED ALONG THE FRONTAL BOUNDARY...
WHICH IS ASSOCIATED WITH AN UPPER LEVEL TROUGH OVER THE W ATLC.
ANOTHER COLD FRONT IS OVER THE CENTRAL ATLC AND ENTERS THE
FORECAST AREA NEAR 31N38W EXTENDING SW TO NEAR 25N51W. VIS
SATELLITE IMAGERY REVEALS A NARROW BAND OF BROKEN CLOUDS WITH
ISOLATED SHOWERS ASSOCIATED WITH THE FRONT. THE REMAINDER OF THE
REGION IS UNDER THE INFLUENCE OF TWO HIGH PRESSURE SYSTEMS...A
1027 MB HIGH TO THE WEST OF THE SECOND FRONT CENTERED NEAR
32N51W AND A 1029 MB HIGH TO THE EAST OF THE FRONTAL SYSTEM
LOCATED NEAR 32N28W. IN THE UPPER LEVELS...A TROUGH/RIDGE/TROUGH
PATTERN IS PRESENT ACROSS MOST OF THE FORECAST REGION WITH THE
FIRST TROUGH OVER THE W ATLANTIC W OF 65W...AND THE SECOND
TROUGH EXTENDING FROM 30N25W TO NEAR 14N45W.

$$
GR


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