[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 251751
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT FRI JUL 25 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1715 UTC.

...TROPICAL WAVES...

A STRONG TROPICAL WAVE IS ALONG 40W/41W S OF 23N. SHOWER
ACTIVITY HAS INCREASED SINCE YESTERDAY JUST NORTH THE 1012 SFC
LOW THAT REMAINS ASSOCIATED WITH THE WAVE NEAR 17N. ALTHOUGH
UPPER-LEVEL WINDS ARE CURRENTLY NOT FAVORABLE FOR DEVELOPMENT...
THE WAVE MAY MOVE INTO AN ENVIRONMENT MORE CONDUCIVE FOR
ORGANIZATION IN A COUPLE OF DAYS. THE SYSTEM IS EXPECTED TO MOVE
TO THE WEST-NORTHWEST OR NORTHWEST AT 15 TO 20 MPH DURING THE
NEXT DAY OR TWO. 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 CLUSTER OF MODERATE TO
ISOLATED STRONG CONVECTION IS WITHIN 120 NM NW OF THE LOW CENTER.

A TROPICAL WAVE IS MOVING WWW NEAR 15 KT ACROSS THE E CARIBBEAN
SEA. ITS AXIS IS ALONG 64W AND EXTENDS FROM THE N LEEWARD
ISLANDS TO NE VENEZUELA. THE WAVE IS BENEATH STRONG TO MODERATE
SUBSIDENCE/DRY AIR ALOFT WITH SCATTERED MODERATE CONVECTION
ACROSS NWRN GUYANA AND NERN VENEZUELA. MAINLY LOW TOPPED SHOWERS
ARE RELATED TO THE WAVE THAT SHOWS A WEAK INVERTED-V LOW LEVEL
SIGNATURE.

A TROPICAL WAVE IS OVER CENTRAL AMERICA ALONG 89W S OF 17N
MOVING W NEAR 10 KT. THIS SYSTEM IS GENERATING SOME SHOWER
ACTIVITY OVER BELIZE AND NORTHERN GUATEMALA.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 12N17W 9N24W 12N35W 10N45W 7N58W.
CLUSTERS OF MODERATE/ISOLATED STRONG CONVECTION ARE BETWEEN
11N-15N E OF 20W TO THE AFRICAN COAST. THIS CONVECTIVE ACTIVITY
SEEMS TO BE ASSOCIATED WITH A TROPICAL WAVE CURRENTLY EMERGING
FROM WEST AFRICA. LATEST OBSERVATIONS FROM DAKAR WITH SOUTH
WINDS SUGGEST THAT THE WAVE HAS JUST CROSSED THE AREA. THIS WAVE
WILL BE ADDED TO THE 18Z SFC MAP. IN ADDITION...THE HOVMOLLER
DIAGRAM HAS DEPICTED THE WESTWARD MOVEMENT OF THESE SHOWER/TSTM
ACTIVITY  OVER THE PAST COUPLE OF DAYS. SCATTERED SHOWERS ARE
WHERE THE TROPICAL WAVE ALONG 41W MEETS THE ITCZ. SCATTRED
MODERATE CONVECTION IS ALONG THE COAST AND N PORTION OF GUYANA.
I

...DISCUSSION...

GULF OF MEXICO...
TROPICAL DEPRESSION DOLLY IS STILL GENERATING LOCALLY HEAVY RAIN
OVER PORTIONS OF SOUTH TEXAS AND NE MEXICO. AT 24/1500 UTC...IT
WAS LOCATED NEAR THE TEXAS/MEXICO BORDER...JUST TO THE SOUTH OF
THE TEXAS BIG BEND NEAR LATITUDE 29.2 NORTH...LONGITUDE 104.4
WEST. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1003 MB. MAXIMUM
SUSTAINED WINDS ARE 25 KT WITH GUSTS TO 35 KT. THE DEPRESSION IS
MOVING WEST-NORTHWEST AT 12 MPH AND IS FORECAST TO DEGENERATE
INTO A SURFACE TROUGH LATER TODAY. SO FAR...THE STORM TOTAL
RAINFALL AMOUNTS ARE BETWEEN 6 AND 12 INCHES. THE GULF IN UNDER
THE INFLUENCE OF A SURFACE RIDGE WITH A 1020 MB HIGH LOCATED
OVER THE NE CORNER OF THE ARE NEAR 28N86W. MODERATE TO FRESH SE
WINDS ARE NOW BLOWING ACROSS THE WRN GULF BUT WILL DIMINISH
TONIGHT AS HIGH PRES BUILDS W ACROSS NRN GULF WATERS. MAINLY
LIGHT AND VARIABLE WINDS DOMINATES THE EASTERN GULF. ALOFT...AN
UPPER ANTICYCLONE ANCHORED OVER E TEXAS IS PRODUCING NE TO E
WINDS OVER THE N GULF WATERS. THIS IS AIDING IN GENERATING
SCATTERED SHOWERS WITH EMBEDDED TSTMS ACROSS THE NE PORTION OF
THE GULF. AN UPPER-LEVEL LOW CURRENTLY SPINNING OVER SOUTH
FLORIDA IS GENERATING SCATTRED SHOWERS AND TSTMS. THIS ACTIVITY
IS ALSO AFFECTING THE STRAITS OF FLORIDA AND THE KEYS.

CARIBBEAN SEA...
AN UPPER-LEVEL TROUGH EXTENDS FROM SOUTH FLORIDA ACROSS W CUBA
AND THE YUCATAN PENINSULA. AN UPPER LOW IS EMBEDDED IN THIS
TROUGH  GENERATING SCATTERED SHOWERS AND TSTMS OVER SOUTH
FLORIDA...THE NW BAHAMAS AND WESTERN CUBA. AN UPPER-LEVEL HIGH
SITUATED JUST SOUTH OF HAITI DOMINATES THE REMAINDER OF THE
BASIN WITH MODERATE TO STRONG SUBSIDENCE AND IMPLIED DRY AIR
MASS. S-SW FLOW BETWEEN THE ABOVE MENTIONED UPPER LEVEL FEATURES
IS DRAWING SUFFICIENT UPPER LEVEL MOISTURE FROM THE E PACIFIC
REGION INTO THE W CARIBBEAN SEA ACROSS E-CENTRAL CUBA AND THE
BAHAMA ISLANDS. A TROPICAL WAVE IS MOVING WESTWARD ACROSS THE E
CARIBBEAN. SEE TROPICAL WAVE SECTION. MODERATE TO STRONG TRADE
WINDS OF 20 TO 30 KT ARE NOTED ACROSS THE SOUTH-CENTRAL
CARIBBEAN. AN EARLIER QSCAT PASS CONFIRMED THESE WINDS.

ATLANTIC OCEAN...
A 1029 MB HIGH LOCATED NEAR 38N57W 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. AS PREVIOUSLY MENTIONED...AN UPPER-LEVEL LOW
IS OVER SOUTH FLORIDA WITH A TROUGH EXTENDING SW INTO THE NE
CARIBBEAN AND THE YUCATAN PENINSULA. A SECOND UPPER-LEVEL LOW IS
NEAR 25N62W PRODUCING ISOLATED SHOWERS AND TSTMS FROM 21N-28N
BETWEEN 59W-63W. A THIRD UPPER-LEVEL LOW IS NEAR 24N42W ANS HAS
A TROUGH EXTENDING S OVER THE DEEP TROPICS. SWLY WINDS AHEAD OF
THIS TROUGH ARE PRODUCING MODERATE SHEAR OVER THE TROPICAL
WAVE/LOW IN THE ATLC ALONG 41W. STRONG SUBSIDENCE AND A DRY
STABLE ATMOSPHERE ARE IN PLACE OVER THE CENTRAL ATLC...MAINLY
BETWEEN 45W-60W WITH AN UPPER ANTICYCLONE LOCATED NEAR 19N52W.

$$
GR


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