[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 250001
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT THU JUL 24 2008

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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2315 UTC.

...SPECIAL FEATURES...

T.D. DOLLY IS DUMPING HEAVY RAINS AS IT MOVES FARTHER INLAND
ALONG THE RIO GRANDE RIVER VALLEY. AT 24/2100 UTC...DOLLY WAS
LOCATED NEAR 28.2N 100.6W...ABOUT 35 MILES...55 KM SOUTH OF
EAGLE PASS TEXAS MOVING WEST-NORTHWEST AT 12 KT. ESTIMATED
MINIMUM PRESSURE IS 1000 MB. MAXIMUM SUSTAINED WIND SPEED IS
30 KT WITH HIGHER GUSTS. DISSIPATION OF THE SYSTEM IS EXPECTED
IN A DAY OR SO. PLEASE SEE THE LAST NHC FORECAST/ADVISORY UNDER
AWIPS/WMO HEADERS MIATCMAT4/WTNT24 KNHC AND THE PUBLIC ADVISORY
UNDER MIATCPAT4/WTNT34 KNHC FOR MORE DETAILS. DOPPLER RADAR AND
SURFACE DATA INDICATE THAT DOLLY STILL HAS A LARGE AND BROAD
CIRCULATION ACCOMPANIED BY A FEW REMAINING CONVECTIVE BANDS
MAINLY OVER INLAND SOUTH TEXAS. UPPER LEVEL MOISTURE/CLOUDINESS
AND 10-20 KT SOUTHEASTERLY SURFACE WINDS REMAINS ACROSS THE WRN
GULF THIS EVENING WITH CLEARING EXPECTED AS SURFACE HIGH
PRESSURE REGAINS CONTROL OVER THE GULF OF MEXICO THIS WEEKEND.

...TROPICAL WAVES...

A HIGH AMPLITUDE TROPICAL WAVE IS ALONG 35W/36W S OF 23N MOVING
W NEAR 20 KT. VIS SATELLITE IMAGERY INDICATES A BROAD CYCLONIC
CIRCULATION AND A 1010 MB LOW ALONG THE WAVE AXIS NEAR 14N. THIS
LOW IS FORECAST BY THE COMPUTER MODELS TO MOVE WEST DURING THE
NEXT 24-48 HOURS. SHOWER ACTIVITY REMAINS LIMITED AT THIS TIME
FROM 17N-23N BETWEEN 32W-39W. THE WAVE SHOWS UP VERY WELL ON THE
MIMIC-TPW PRODUCT FROM CIMSS WHERE A LARGE BULGE OF MOISTURE IS
OBSERVED. TIGHT PRESSURE GRADIENT BETWEEN THE LOW AND THE ATLC
SURFACE HIGH WILL PRODUCE AN INCREASE IN WINDS ACROSS THE
CENTRAL ATLC THROUGH THE WEEKEND.

A TROPICAL WAVE IS ALONG 59W/60W S OF 18N MOVING W NEAR 10-15
KT. WEAK INVERTED-V CURVATURE IS OBSERVED ON SATELLITE IMAGERY
AND EXTENDS NORTHWARD TO NEAR SAINT LUCIA. THE WAVE IS BENEATH
STRONG TO MODERATE SUBSIDENCE/DRY AIR ALOFT WITH SCATTERED
MODERATE CONVECTION ACROSS NWRN GUYANA AND NERN VENEZUELA. LOW
TOPPED SHOWERS ARE ALSO ACROSS THE WINDWARD ISLANDS S OF 13N.

A TROPICAL WAVE IS OVER CENTRAL AMERICA AND THE GULF OF HONDURAS
ALONG 86W S OF 17N MOVING W NEAR 10 KT. CLUSTERS OF SCATTERED
MODERATE CONVECTION ARE EAST OF THE WAVE AXIS AFFECTING THE SW
CARIBBEAN AND THE ERN COASTS OF NICARAGUA/COSTA RICA. A
DIFFLUENT PATTERN ALOFT OVER THE AREA IS AIDING IN ENHANCING
THIS CONVECTIVE ACTIVITY.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 11N15W 8N19W 10N27W 10N33W 9N39W
6N54W. SCATTERED MODERATE TO STRONG CONVECTION IS ALONG THE W
AFRICAN COAST FROM 10N-14N BETWEEN 13W-17W AND MAY BE ASSOCIATED
WITH A NEW TROPICAL WAVE PROPAGATING OFF THE COAST. FURTHERMORE
THE HOVMOLLER DIAGRAM HAS DEPICTED THE WESTWARD MOVEMENT OF
THESE SHOWERS AND TSTMS OVER THE PAST COUPLE OF DAYS. SCATTERED
MODERATE CONVECTION IS FROM 6N-11N BETWEEN 20W-26W.

...DISCUSSION...

GULF OF MEXICO...
BROAD UPPER LEVEL ANTICYCLONE ASSOCIATED WITH DOLLY AND CENTERED
OVER THE SOUTHERN GREAT PLAINS EXTENDS A RIDGE ACROSS THE ENTIRE
GULF OF MEXICO AND THE FLORIDA PENINSULA. THIS IS AIDING IN
GENERATING SCATTERED SHOWERS WITH EMBEDDED TSTMS ACROSS SOUTHERN
FLORIDA. MAINLY UPPER LEVEL MOISTURE/CLOUDINESS ARE OBSERVED IN
THE WAKE OF DOLLY OVER THE WESTERN GULF. A FEW SCATTERED
SHOWERS/TSTMS ARE ACROSS SRN MEXICO AND THE FAR ERN BAY OF
CAMPECHE. AT THE SURFACE...THE ATLANTIC RIDGE EXTENDS WESTWARD
AND ENVELOPS THE ERN GULF WITH A WEAK 1020 MB HIGH CENTERED NEAR
28N86W. LIGHT AND VARIABLE WINDS PREVAIL UNDER THE INFLUENCE OF
THIS SYSTEM AND WILL CONTINUE TO BUILD ACROSS THE WRN GULF OVER
THE WEEKEND.

CARIBBEAN SEA...
AN UPPER-LEVEL TROUGH EXTENDS FROM THE WRN ATLC S-SW INTO THE NW
CARIBBEAN AND INTO THE GULF OF HONDURAS. THIS TROUGH IS
GENERATING SCATTERED SHOWERS/TSTMS ACROSS WRN CUBA EXTENDING
INTO ADJACENT NW CARIBBEAN COASTAL WATERS. THE REMAINDER OF THE
BASIN IN UNDER THE INFLUENCE OF AN UPPER-LEVEL RIDGE ANCHORED ON
AN ANTICYCLONE LOCATED OVER PUERTO RICO. S-SW FLOW BETWEEN THE
ABOVE MENTIONED UPPER LEVEL FEATURES IS DRAWING SUFFICIENT UPPER
LEVEL MOISTURE FROM THE E PACIFIC REGION INTO THE CARIBBEAN SEA
ACROSS THE SW CARIBBEAN TO JAMAICA...ERN CUBA AND THE WINDWARD
PASSAGE. THESE DIFFLUENT UPPER WINDS ARE ENHANCING SCATTERED
MODERATE CONVECTION OVER PANAMA AND THE SW CARIBBEAN S OF 11N.
MODERATE TO STRONG SUBSIDENCE DOMINATES THE ERN PORTION OF THE
BASIN. A TROPICAL WAVE IS MOVING WESTWARD ACROSS CENTRAL AMERICA
WITH A SECOND TROPICAL WAVE APPROACHING THE LESSER ANTILLES. SEE
TROPICAL WAVE SECTION FOR DETAILS. MODERATE TO STRONG TRADE
WINDS ARE ACROSS THE AREA WITH THE STRONGEST WINDS JUST OFF THE
COLOMBIAN COAST.

ATLANTIC OCEAN...
A 1030 MB HIGH LOCATED NEAR 37N55W DOMINATES ALMOST THE ENTIRE
FORECAST AREA. THIS SURFACE RIDGE WILL REMAIN IN PLACE DURING
THE NEXT FEW DAYS PRODUCING MODERATE TO STRONG TRADE WINDS
ACROSS THE TROPICS. BROAD AREA OF UPPER TROUGHING COVERS THE WRN
ATLC AND EXTENDS S INTO THE NW CARIBBEAN. A SURFACE TROUGH IS
OVER THE WEST-CENTRAL ATLC AND NOW EXTENDS FROM 23N62W TO
31N61W. SATELLITE IMAGERY INDICATES THAT LOW LEVEL CLOUDS REMAIN
ASSOCIATED WITH THIS TROUGH NEAR 29N. THE REMAINDER OF THE
ATLANTIC OCEAN IS DOMINATED BY BENIGN UPPER LEVEL FEATURES WHERE
STRONG SUBSIDENCE AND A DRY STABLE ATMOSPHERE ARE IN PLACE...
PARTICULARLY BETWEEN 40W-65W. A LARGE AREA OF STRATOCUMULUS
CLOUDS IS WRAPPING AROUND THE SURFACE LOW ASSOCIATED WITH THE
TROPICAL WAVE OVER THE ERN ATLC.

$$
HUFFMAN




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