[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 272352
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2315 UTC.

...TROPICAL WAVES...
TROPICAL WAVE IS ADJUSTED AHEAD ALONG 34W/35W S OF 17N ON THE
1800 UTC SFC MAP BASED ON SATELLITE IMAGERY AND THE SSMI-DERIVED
TOTAL PRECIPITABLE WATER WHERE SOME TURNING IS NOTED ON THE
NORTHERN END OF THE WAVE. SCATTERED MODERATE CONVECTION IS
WITHIN 200 NM EAST OF THE WAVE AXIS. LOOKING FURTHER EAST...A
WELL DEFINED TROPICAL WAVE IS JUST MOVING OUT OF AFRICA AND WILL
PROBABLY BE INTRODUCED ON THE 0000 UTC SFC MAP. THE RAOB FROM
BAMAKO MALI SHOWED THE WAVE PASSAGE WELL YESTERDAY. CURRENTLY
SATELLITE IMAGERY...SURFACE OBSERVATIONS AND EARLIER QUIKSCAT
PASS SHOW GOOD TURNING ALONG THE WAVE AXIS NEAR 11N.

TROPICAL WAVE IS ALONG 45W/46W MOVING W 5-10 KT. A VORTICITY
MAXIMUM IS SEEN ALONG THE WAVE AXIS NEAR 11N. ISOLATED CLUSTERS
OF MODERATE CONVECTION ARE WITHIN 250 NM EITHER SIDE OF THE AXIS
MAINLY FROM 9N-14N. THIS WAVE IS WELL DEFINED IN SSMI-DERIVED
TOTAL PRECIPITABLE WATER.

TROPICAL WAVE IS MOVING INTO THE WRN CARIBBEAN ALONG 79W/80W S
OF 18N MOVING W NEAR 15 KT. THIS WAVE PAIRED WITH THE ITCZ IS
GENERATING CLUSTERS OF MODERATE TO ISOLATED STRONG CONVECTION
OVER PANAMA AND COSTA RICA. THIS WAVE ALSO SHOWS UP WELL AS A
POLEWARD INFLECTION OF HIGH MOISTURE IN SSMI-DERIVED TOTAL
PRECIPITABLE WATER.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 9N16W 8N22W 10N30W 11N41W 10N50W
9N60W. CLUSTERS OF MODERATE TO ISOLATED STRONG CONVECTION ARE
MOVING JUST OFF THE AFRICAN COAST ASSOCIATED WITH A NEW TROPICAL
WAVE. METSAT-9 HOVMOLLER DIAGRAMS IS SHOWING THE WESTWARD
PROPAGATION OF THE WAVE. SCATTERED MODERATE/ISOLATED STRONG
CONVECTION IS ALSO FOUND WITHIN 120 NM EITHER SIDE OF THE AXIS
BETWEEN 21W AND 31W.

...DISCUSSION...
GULF OF MEXICO...
THE MAIN WEATHER FEATURE ACROSS THE BASIN IS A WEAK AREA OF LOW
PRESSURE NEAR THE UPPER TEXAS COAST THAT HAS ALREADY MOVED
INLAND. THIS SYSTEM AND THE ASSOCIATED SFC TROUGH IS GENERATING
A LARGE AREA OF NUMEROUS SHOWERS WITH EMBEDDED TSTMS OVER
PORTIONS OF SOUTHEASTERN TEXAS AND SOUTHERN LOUISIANA AS WELL AS
OVER THE NORTHERN GULF WATERS N OF 26N WEST OF 88W. AS OF
27/2100 UTC A 1011 MB LOW IS ANALYZED NEAR 29N96W. A TROUGH
EXTENDS SW FROM THE LOW ACROSS THE DEEP SOUTH INTO NE MEXICO
WHERE SHOWERS AND TSTMS ARE ALSO FLARED UP. THIS ACTIVITY IS
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 COUPLE OF WEAK SFC HIGHS OF 1016 MB ARE
NEAR THE FLORIDA PANHANDLE AND SE LOUISIANA. DIFFLUENCE BETWEEN
A DEEP LAYERED TROUGH OVER THE EASTERN SEABOARD AND THE RIDGE
ACROSS THE GULF IS HELPING TO GENERATE SHOWERS AND TSTMS OVER
THE STATE OF FLORIDA AND THE FAR W ATLC. A SFC RIDGE FROM THE
ATLANTIC OCEAN WILL DOMINATE THE GULF DURING THE WEEKEND.

CARIBBEAN SEA...
HIGH PRES NORTH OF THE AREA IS PRODUCING MODERATE TO STRONG
TRADE WINDS IN THE S CENTRAL CARIBBEAN. THIS WEATHER PATTERN IS
FORECAST TO PERSIST THROUGH WED. AS IS USUAL FOR THIS TIME OF
THE YEAR...TROPICAL WAVES CONTINUES TO MOVE WESTWARD ACROSS THE
BASIN ENHANCING THE SHOWER/TSTM ACTIVITY PARTICULARLY DURING THE
AFTERNOON AND EVENING HOURS. ONE OF THIS WAVE IS ALONG 80W. SEE
ABOVE. THERE IS A CLUSTER OF MODERATE TO ISOLATED STRONG
CONVECTION OVER NORTHERN COLOMBIA RELATED TO THE SEMI-PERMANENT
LOW PRES THAT SITS THERE. THE REMAINDER OF 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 IS OVER
NORTHERN COLOMBIA WHILE TROUGHING AND DRY UPPER AIR DOMINATES
THE EASTERN CARIBBEAN E OF 70W. MODERATE TRADES PERSIST THROUGH
THE WEEKEND...STRONGEST IN THE CENTRAL PORTION.

ATLANTIC OCEAN...
DOPPLER RADAR FROM THE SE U.S. IS SHOWING SCATTERED SHOWERS AND
TSTMS OVER SOUTH-CENTRAL FLORIDA AND THE E COASTAL WATERS...
NORTHWESTERN BAHAMAS AND WRN ATLC W OF 77W. 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 31N72W AND
CONTINUES MAINLY S TO THE CENTRAL BAHAMAS NEAR 23N75W. SCATTERED
SHOWERS/ISOLATED TSTMS ARE AHEAD OF THIS TROUGH FROM 23N-27N
BETWEEN 70W-73W. AN UPPER LOW HAS REMAINED QUASI STATIONARY NEAR
29N61W. A SFC TROUGH...REFLECTION OF THIS UPPER FEATURE IS ALSO
ANALYZED ALONG 3058W 25N63W. SCATTERED SHOWERS/ISOLATED TSTMS
ARE WITHIN 180 NM AHEAD OF THE TROUGH AXIS. 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 33N35W ALSO
DOMINATES THE E-CENTRAL ATLC. FAIR WEATHER AND LIGHT TO MODERATE
TRADES ARE FOUND UNDER THE INFLUENCE OF THIS RIDGE.

$$
GR




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