[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 261034
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1015 UTC.

...TROPICAL WAVES...

TROPICAL WAVE IS ALONG 29W S OF 20N MOVING W 10-15 KT. THIS WAVE
REMAINS POORLY ORGANIZED WITH SCATTERED SHOWERS AND TSTMS
ALIGNED LINEARLY WITHIN THE INTERSECTION OF THE ITCZ FROM
10N-13N BETWEEN 24W-32W. 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 16N MOVING W 10 KT. THIS SYSTEM
HAS GENERALLY CHANGED LITTLE SINCE YESTERDAY WITH LOW LEVEL
TURNING AND A LOW LATITUDE INVERTED V-SHAPE CLEARLY APPARENT ON
NIGHT CHANNEL VIS IMAGES...THOUGH STILL PARTIALLY EMBEDDED IN
THE ITCZ. ASCAT PASSED DIRECTLY OVER THIS WAVE AROUND 00Z AND
CONFIRMED THAT THIS CYCLONIC TURNING IS AT THE SFC. WHILE THIS
WAVE HAS MAINTAINED FAIR STRUCTURE...SHOWER ACTIVITY IS VERY
LIMITED.

TROPICAL WAVE IS IN THE W CARIBBEAN AND OVER CENTRAL AMERICA
ALONG 84W/85W S OF 21N 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 25N94W THRU 19N97W MOVING W 10-15 KT.
THIS WAVE STILL MAINTAINS FAIR CURVATURE...ESPECIALLY OFF THE
SFC AS BUOY AND METAR DATA DO NOT SHOW THE SAME REFLECTION SEEN
IN EARLIER DATA. THIS SYSTEM IS EXPECTED TO MOVE INLAND OVER
MEXICO WITH NO FURTHER DEVELOPMENT EXPECTED. THE INTERACTION
WITH AN UPPER LOW IS PRODUCING SCATTERED SHOWERS AND TSTMS
ACROSS A FAIRLY LARGE PORTION OF THE S GULF...SEE DISCUSSION
BELOW FOR MORE DETAILS.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 13N16W 7N30W 9N51W 5N55W. BESIDES
FOR THE CONVECTION DISCUSSED IN THE TROPICAL WAVES SECTION
...SCATTERED MODERATE IS WITHIN 90 NM N OF THE AXIS BETWEEN
40W-44W. SIMILAR ACTIVITY IS WITHIN 60 NM EITHER SIDE OF THE
AXIS E OF 20W.

DISCUSSION...

GULF OF MEXICO...
UNSETTLED WEATHER CONTINUES ACROSS THE SRN HALF OF THE GULF OF
MEXICO THIS MORNING. THERE ARE A FEW FEATURES CONTRIBUTING TO
THIS MOIST ENVIRONMENT. STARTING IN THE MID AND UPPER LEVELS...A
WELL DEFINED SLOW MOVING UPPER LOW IS CENTERED ACROSS THE N
CENTRAL GULF NEAR 28N91W. UPPER RIDGING LOCATED BOTH E AND W OF
THIS UPPER LOW IS PRODUCING AN OVERALL DIFFLUENT PATTERN WHICH
HAS GENERATED 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. DISORGANIZED SCATTERED SHOWERS AND TSTMS ARE S OF 25N
BETWEEN 87W AND 97W. SCATTERED MODERATE TO STRONG CONVECTION IS
OVER S MEXICO ASSOCIATED WITH A HIGHLY NWD PERTURBED ITCZ WHICH
APPEARS TO BE VERY NEAR 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 S CARIB FROM 11N-14N BETWEEN 67W-76W. 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 HAS SPREAD IT'S DEBRIS
CLOUDINESS ACROSS MUCH OF THE W HALF OF THE CARIB. MOST OF THE
LEFTOVER SHOWERS ARE WEAK...THOUGH THERE ARE A FEW NEW SMALL
BURSTS NEAR HISPANIOLA WHERE UPPER INSTABILITY IS A LITTLE MORE
PRONOUNCED. 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 RADAR. 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
32N37W TO A 1012 MB LOW NEAR 26N57W THEN CONTINUING W AS A SFC
TROUGH TO 25N65W. CURRENT SATELLITE IMAGERY SHOWS THE FRONT AND
WEAK LOW BECOMING INCREASING DIFFUSE WITH ONLY ISOLATED SHOWERS
WITHIN 60 NM OF THE BOUNDARY/LOW. ISOLATED SHOWERS HAVE ALSO
POPPED UP IN A LOW-LEVEL CONFLUENT ZONE ON THE RETURN SIDE OF
THE RIDGE TO THE N OF THE FRONT N OF 26N BETWEEN 67W-69W. QSCAT
STILL DEPICTS A PRONOUNCED WIND SHIFT NEAR THE BOUNDARY...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 79W. A LARGER
SCALE TROUGH...THE SUPPORT FOR THE FRONT DISCUSSED ABOVE...IS
OVER THE CENTRAL ATLC EXTENDING FROM A LARGE QUASI-STATIONARY
FALL-TYPE LOW NEAR 43N44W. TROUGHING EXTENDS INTO THE AREA ALONG
32N49W TO AN UPPER LOW NEAR 25N57W CONTINUING TOWARD THE NRN
LEEWARD ISLANDS. A DOMINATING WELL DEFINED RIDGE TAKES OVER IN
THE E ATLC WITH THE MAIN ANTICYCLONE CENTERED NEAR 22N42W.
OUTSIDE OF THE SMALL AREAS OUTLINED...DRY AIR ALOFT IS
WIDESPREAD ON WATER VAPOR IMAGERY SUPPRESSING SIGNIFICANT SHOWER
ACTIVITY.

$$
CANGIALOSI




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