[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 260534
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT SUN AUG 26 2007

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHERN
SECTIONS OF SOUTH AMERICA...AND THE 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.

...TROPICAL WAVES...

TROPICAL WAVE IS ALONG 27W/28W S OF 19N MOVING W 10-15 KT.
THIS WAVE REMAINS POORLY ORGANIZED WITH ISOLATED SHOWERS AND
TSTMS CONFINED NEAR THE INTERSECTION OF THE ITCZ FROM 9N-13N
WITHIN 120 NM OF THE WAVE AXIS. ALTHOUGH THE SATELLITE
PRESENTATION IS UNIMPRESSIVE THE UW-CIMSS TPW ANIMATION DEPICTS
A PRONOUNCED AREA OF HIGHER MOISTURE ASSOCIATED WITH THIS
FEATURE. THIS ANIMATION ALSO SHOWS THE MOISTURE SURGE FLATTENING
IN STRUCTURE OVER TIME POSSIBLY DUE TO A SAHARAN DUST SURGE.

TROPICAL WAVE IS ALONG 52W S OF 15N MOVING W 10 KT. THIS SYSTEM
HAS GENERALLY CHANGED LITTLE SINCE YESTERDAY WITH LOW LEVEL
TURNING CLEARLY APPARENT ON NIGHT CHANNEL VIS IMAGES...THOUGH
STILL WELL EMBEDDED IN THE ITCZ. AN EARLIER QSCAT PASS DID
INDICATE SLIGHT CYCLONIC TURNING ABOUT THE WAVE AXIS THOUGH NOT
AS DEFINED AS IN THE LOW-LEVEL CLOUD DRIFT WINDS...SUGGESTING
MUCH OF THE PRESENCE IS JUST ABOVE THE SFC. WHILE LOW-LEVEL
TURNING HAS BEEN PERSISTING SHOWER ACTIVITY IS VERY LIMITED NEAR
THIS WEAK WAVE.

TROPICAL WAVE IS IN THE W CARIBBEAN AND OVER CENTRAL AMERICA
ALONG 84W S OF 20N MOVING W 10-15 KT OVER THE PAST 24 HRS. THIS
WAVE IS DIFFICULT TO LOCATE WITH THE POSITION BASED ON FORWARD
EXTRAPOLATION WHICH MATCHES UP WITH A BIT OF CURVATURE EVIDENT
IN SFC OBS AND ISOLATED SHOWER ACTIVITY WITHIN 60 NM OF THE AXIS.

THE NRN PORTION OF A HIGH AMPLITUDE TROPICAL WAVE EXTENDS INTO
THE BAY OF CAMPECHE FROM 25N93W THRU 19N96W MOVING W 10-15 KT.
AN ASSOCIATED AREA OF LOW PRES...ANALYZED 1008 MB NEAR
21N95W...FORMED EARLIER TODAY. THIS LOW HAS GENERALLY BECOME
LESS DEFINED WITH ONLY A SMALL CLUSTER OF CONVECTION NEAR IT. NO
FURTHER DEVELOPMENT IS EXPECTED. THE WAVE STILL SHOWS UP FAIRLY
WELL IN BUOY DATA AND THE INTERACTION WITH AN UPPER LOW IS
PRODUCING SCATTERED SHOWERS AND TSTMS ACROSS A PORTION OF THE S
GULF...SEE DISCUSSION BELOW FOR MORE DETAILS.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 11N15W 8N33W 11N49W 9N62W. BESIDES
FOR THE CONVECTION DISCUSSED IN THE TROPICAL WAVES SECTION
...SCATTERED MODERATE IS WITHIN 60 NM OF THE AXIS BETWEEN
41W-44W. SIMILAR ACTIVITY IS FROM 11N-14N E OF 18W LIKELY
ASSOCIATED WITH THE NEXT TROPICAL WAVE.

DISCUSSION...

GULF OF MEXICO...
A CONSIDERABLE AMOUNT OF MOISTURE REMAINS IN THE GULF THIS EARLY
MORNING. THERE ARE SEVERAL FEATURES CONTRIBUTING TO THIS
MOISTENED ENVIRONMENT. STARTING IN THE MID AND UPPER LEVELS...A
WELL DEFINED SLOW MOVING UPPER LOW IS CENTERED ACROSS THE MID
GULF NEAR 27N90W. UPPER RIDGING LOCATED BOTH E AND W OF THIS
UPPER LOW IS PRODUCING AN OVERALL DIFFLUENT PATTERN WHICH HAS
GENERALLY PRODUCED WIDESPREAD HIGH LEVEL CLOUDINESS ACROSS THE
AREA. DEEP MOISTURE IS CONFINED TO THE S GULF WHERE UPPER
DIFFLUENCE IS A BIT MORE CONCENTRATED AND THE AIR IS LIFTED BY A
TROPICAL WAVE AND WEAK AREA OF LOW PRES. DISORGANIZED SCATTERED
SHOWERS AND TSTMS ARE S OF 25N BETWEEN 86W AND 96W. SCATTERED
STRONG CONVECTION IS OVER S MEXICO ASSOCIATED WITH A HIGHLY
PERTURBED ITCZ WHICH APPEARS TO BE INLAND ACROSS THAT AREA. THE
REMAINDER OF THE SFC PATTERN IS VERY TRANQUIL DUE TO A WEAK AREA
OF HIGH PRES CENTERED OVER THE NE GULF. THIS IS KEEPING WINDS
VERY LIGHT ACROSS THE E AND CENTRAL GULF.

LITTLE CHANGE IN THE WEAK SFC PATTERN IS EXPECTED OVER THE NEXT
COUPLE OF DAYS SO WINDS ARE ANTICIPATED TO REMAIN MOSTLY LIGHT.
ALSO A DRIER AIRMASS WILL LIKELY PUSH ACROSS THE AREA FROM E TO
W AS A MID-LEVEL RIDGE BUILDS OVERHEAD.

CARIBBEAN SEA...
THERE ARE A FEW SCATTERED PATCHES OF CONVECTION ACROSS THIS
BASIN...BUT NONE OF THESE SHOW ANY ORGANIZATION. THE MOST
PERSISTENT ACTIVITY IS ASSOCIATED WITH THE ITCZ ACROSS COLOMBIA
AND THE SW CARIB S OF 13N W OF 72W. ELSEWHERE MUCH OF THE
SENSIBLE WEATHER/MOISTURE APPEARS RELATED TO FEATURES ALOFT. THE
MAIN FEATURE IS AN INVERTED MID TO UPPER LEVEL TROUGH WHICH
EXTENDS FROM N COLOMBIA TOWARD HISPANIOLA. STRONG NLY FLOW
BETWEEN THIS TROUGH AND RIDGING FURTHER W HAS BLOWN OFF LAST
EVENING'S TSTM ACTIVITY OVER CUBA AND SPREAD DEBRIS CLOUDINESS
ACROSS MUCH OF THE NW CARIB. NEARLY ALL OF THE LEFTOVER SHOWERS
ARE DIMINISHING EXCEPT FOR THE AREA OVER HAITI WHICH ACTUALLY
LOOKS LIKE IT'S EXPANDING AS IT ROUNDS THE INVERTED TROUGH. MUCH
OF THE REMAINDER OF THE AREA IS RELATIVELY QUIET THOUGH ISOLATED
TO SCATTERED TRADE WIND SHOWERS CAN OCCUR JUST ABOUT ANYWHERE AS
INDICATED BY SAN JUAN'S 88-D. THE TRADE WIND FLOW IS FAIRLY
RELAXED...AN EARLIER QSCAT PASS ONLY SHOWED A SMALL AREA NEAR 20
KT.

ATLANTIC OCEAN...
THE SFC PATTERN ACROSS THE ATLC DISCUSSION AREA REMAINS WEAK
THIS MORNING. THIS WEAK PATTERN IS MAINLY DUE TO AN UNUSUAL (FOR
AUGUST) FRONT DEEP INTO THE SUBTROPICS ENTERING THE AREA NEAR
32N38W TO A 1012 MB LOW NEAR 27N52W THEN DISSIPATING ALONG
24N57W 29N69W. CURRENT SATELLITE IMAGERY SHOWS THE FRONT AND
WEAK LOW BECOMING INCREASING DIFFUSE WITH ONLY ISOLATED SHOWERS
WITHIN 60 NM OF THE BOUNDARY. QSCAT STILL DEPICTS A PRONOUNCED
WIND SHIFT...THOUGH SPEEDS HAVE DECREASED SINCE YESTERDAY. THE
LARGER SCALE EFFECT OF THIS FRONT IS THE DISRUPTION IN THE
TYPICAL SUBTROPICAL RIDGING WHICH HAS ALLOWED WINDS TO BE
FAIRLY LIGHT ACROSS THE BULK OF THE AREA.

IN THE MID AND UPPER LEVELS...A RIDGE IS OVER THE W ATLC
COVERING THE AREA W OF 62W. A DIFFLUENT PATTERN LIES AT THE W
EDGE OF THE RIDGE ASSOCIATED WITH SOME TROUGHING OVER THE
BAHAMAS AND IN THE GULF OF MEX. THIS DIFFLUENCE IS PRODUCING A
FAIR AMOUNT OF CLOUDINESS ACROSS THE AREA W OF 78W. A LARGER
SCALE TROUGH...THE SUPPORT FOR THE FRONT DISCUSSED ABOVE...IS
OVER THE CENTRAL ATLC EXTENDING FROM A LARGE FALL-TYPE LOW NEAR
42N44W INTO THE AREA ALONG 32N50W TO AN UPPER LOW NEAR 24N57W
CONTINUING TOWARD THE NRN LEEWARD ISLANDS. A DOMINATING WELL
DEFINED RIDGE TAKES OVER IN THE E ATLC WITH THE MAIN ANTICYCLONE
CENTERED NEAR 22N41W. OUTSIDE OF THE SMALL AREAS OUTLINED...DRY
AIR ALOFT IS WIDESPREAD ON WATER VAPOR IMAGERY SUPPRESSING
SIGNIFICANT SHOWER ACTIVITY.

$$
CANGIALOSI


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