[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 271803
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT FRI JUL 27 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1715 UTC.

...TROPICAL WAVES...
TROPICAL WAVE IS ALONG 31W/32W S OF 17N MOVING SLOWLY W. THIS
WAVE HAS BECOME INCREASINGLY DIFFICULT TO LOCATE OVER THE PAST
SEVERAL HOURS AS IT IS EMBEDDED IN A LARGER SCALE MONSOON
TROUGH. THERE IS A SMALL CLUSTER OF MODERATE TO STRONG
CONVECTION WITHIN 30NM EITHER SIDE OF THE AXIS FROM 13N-15N.
THERE ARE SOME HINTS OF AN INVERTED V SIGNATURE IN THE
STRATOCUMULUS FIELD A LITTLE FURTHER W FROM 14N-18N BETWEEN
33W-37W...WHICH MATCHES UP WELL WITH A POSITIVE MAXIMUM IN
UW-CIMSS SATELLITE DERIVED 850 MB VORTICITY. THUS...THE WAVE MAY
NEED TO BE NUDGED TO THE W A BIT ON THE 1800 UTC MAP.

TROPICAL WAVE IS TILTED ALONG 16N45W 11N45W 6N47W MOVING W 5-10
KT. A 1012 MB LOW IS ATTACHED TO THE WAVE NEAR 12N. ISOLATED
CLUSTERS OF MODERATE CONVECTION ARE WITHIN 250 NM EITHER SIDE OF
THE AXIS MAINLY FROM 9N-15N. THIS WAVE REMAINS IDENTIFIABLE IN
SSMI DERIVED TPW IN ADDITION TO CONVENTIONAL SATELLITE DATA.

TROPICAL WAVE IS MOVING INTO THE WRN CARIBBEAN ALONG 78W S OF
19N MOVING W NEAR 20 KT. ISOLATED SHOWERS AND TSTMS ARE WITHIN
60NM W/120NM E OF THE AXIS FROM 15N-19N. THIS WAVE ALSO SHOWS UP
WELL AS A POLEWARD INFLECTION OF HIGH MOISTURE IN SSMI DERIVED
TPW.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 11N15W 10N20W 13N28W 11N38W 10N50W
9N63W. THE E ATLC PORTION OF THE AXIS IS RATHER ACTIVE THIS
AFTERNOON WITH NUMEROUS MODERATE CONVECTION WITHIN 250NM S OF
THE AXIS E OF 29W. LOW LEVEL FLOW IS ALSO HIGHLY SW TO W IN THIS
VICINITY. METSAT-9 HOVMOLLER DIAGRAMS SUGGEST THE NEXT TROPICAL
WAVE IS NEAR THE COAST OF AFRICA. THE RAOB FROM BAMAKO MALI ALSO
SHOWED THE WAVE PASSAGE WELL YESTERDAY. SCATTERED MODERATE ALSO
NOTED WITHIN 120 NM EITHER SIDE OF THE AXIS BETWEEN 36W-41W.

...DISCUSSION...
GULF OF MEXICO...
THE MAIN FOCUS CONTINUES TO BE THE MESSY WEATHER OFF THE COAST
OF TEXAS AND LOUISIANA. AS OF 27/1500 UTC A 1012 MB LOW WAS OFF
THE UPPER TEXAS COAST NEAR 29N95W. A TROUGH EXTENDS SSW FROM THE
LOW TO NEAR BROWNSVILLE. RADAR...SATELLITE...AND LIGHTNING DATA
DEPICT NUMEROUS SHOWERS AND TSTMS N OF 25N BETWEEN 88W-97W. THE
LOW IS EXPECTED TO MOVE INLAND OVER THE NEXT DAY OR SO AND
SIGNIFICANT DEVELOPMENT IS NOT EXPECTED.  HOWEVER THE SYSTEM WILL
PRODUCE LOCALLY HEAVY RAINFALL OVER PORTIONS OF SOUTHEASTERN
TEXAS AND SOUTHERN LOUISIANA.  SEE STATEMENTS FROM LOCAL
NATIONAL WEATHER SERVICE FORECAST OFFICES FOR ADDITIONAL
INFORMATION. THIS ACTIVITY IS ALSO BEING LARGELY SUPPORTED BY
THE UPPER LOW OVER CENTRAL TEXAS AND UPPER RIDGING EXTENDING E
THROUGH THE CENTRAL GULF FROM MEXICO. ELSEWHERE AT THE SFC...A
1019 MB HIGH IS NEAR THE FLORIDA PANHANDLE. WEAK HIGH PRES
EXPECTED TO REMAIN QUASI-STATIONARY OVER THE NE GULF THROUGH
SAT.

CARIBBEAN SEA...
SCATTERED SHOWERS AND TSTMS ARE AGAIN OVER THE FAR SW CARIBBEAN
IN RESPONSE TO LOW LEVEL SPEED CONVERGENCE DOWNSTREAM FROM THE
MODERATE TO FRESH TRADES NEAR THE COLOMBIAN COAST. ASIDE FROM
THIS AND THE FEW TSTMS WITH THE TROPICAL WAVE...THE CARIBBEAN IS
PRETTY QUIET. UPPER NE FLOW AROUND RIDGING DOMINATES THE NW
PORTION...AHEAD OF THE INVERTED UPPER TROUGHING EXTENDING NE
FROM COSTA RICA TO NEAR HAITI. A WEAK UPPER HIGH NOTED NEAR THE
ABC ISLANDS WHILE TROUGHING AND DRY UPPER AIR DOMINATES THE NE
CARIB. MODERATE TRADES PERSIST THROUGH THE WEEKEND...STRONGEST
IN THE CENTRAL PORTION.

ATLANTIC OCEAN...
SCATTERED SHOWERS AND TSTMS ARE CURRENTLY OVER THE EAST COAST OF
SOUTH FLORIDA...BAHAMAS...AND WRN ATLC W OF 76W. THIS REGION IS
UNDER STRONG UPPER DIFFLUENCE BETWEEN LARGE SCALE TROUGHING OVER
THE EAST COAST AND RIDGING EXTENDING E FROM THE GULF ALONG 26N
OUT TO NEAR 70W. A SFC TROUGH ALSO ENTERS THE W ATLC NEAR 30N72W
AND CONTINUES S TO 24N73W. LOW CLOUD MOTIONS SHOW CLEAR CYCLONIC
TURNING IN THE VICINITY...WITH ASSOCIATED SCATTERED
SHOWERS/ISOLATED TSTMS FROM 23N-27N BETWEEN 68W-75W. AN UPPER
LOW HAS REMAINED QUASI STATIONARY NEAR 28N60W. A SFC TROUGH IS
ALSO ANALYZED IN THIS VICINITY ALONG 31N55W 26N60W. LIGHTNING
DATA SUGGESTS MOST OF THE ASSOCIATED TSTMS ARE CONFINED TO THE
REGION FROM 23N-27N BETWEEN 57W-62W. LARGE SCALE UPPER RIDGING
AND ABUNDANT DRY/STABLE AIR DOMINATES MUCH OF THE E ATLC. A SFC
RIDGE ANCHORED BY A 1023 MB HIGH NEAR 33N40W ALSO DOMINATES THE
E ATLC. THE COMBINATION OF THESE FEATURES HAVE LED TO WIDESPREAD
FAIR WEATHER AND LIGHT TO MODERATE TRADES N OF 15N W OF 50W.

$$
WILLIS


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