[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 272339
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT FRI OCT 27 2006

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHEASTERN
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...WEATHER OBSERVATIONS...RADAR...
AND METEOROLOGICAL ANALYSIS.

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY
THROUGH 2315 UTC.

...TROPICAL WAVES...

TROPICAL WAVE IS ALONG 40W S OF 13N MOVING W 10 TO 15 KT. THIS
WAVE REMAINS RATHER LOW AMPLITUDE AND HAS BECOME LESS DEFINED
THAN IT WAS YESTERDAY WITH LITTLE CURVATURE NOTED IN SAT IMAGES
AND AVAILABLE SFC DATA. FOR THESE REASONS...THE AXIS IS
CHALLENGING TO LOCATE AND BASED MOSTLY ON CONTINUITY. ASSOCIATED
ISOLATED MODERATE CONVECTION IS WITHIN 300 NM EITHER SIDE OF THE
AXIS.

A TROPICAL WAVE IS ALONG 57W/58W S OF 21N MOVING W 10 TO 15 KT.
A 1009 MB LOW IS ALONG THE WAVE NEAR 14N. THIS LOW PRES SYSTEM
REMAINS FAIRLY WELL DEFINED. IN ADDITION...SHOWERS AND TSTMS
HAVE INCREASED IN INTENSITY AND BECOME MORE ORGANIZED OVER THE
PAST SEVERAL HOURS. SCATTERED MODERATE CONVECTION EXISTS FROM
11N-16N BETWEEN 53W-61W. THE WRN EDGE OF THIS CONVECTION IS
MOVING ACROSS THE ERN CARIB ISLANDS...POSSIBLY PRODUCING SOME
GUSTY WINDS. THE UPPER LEVEL ENVIRONMENT IS FORECAST TO BECOME
SOMEWHAT MORE FAVORABLE NEAR THE SYSTEM FOR SOME ADDITIONAL
DEVELOPMENT DURING THE NEXT DAY OR TWO.

A WEAK TROPICAL WAVE IS ALONG 72W S OF 18N MOVING W 10 TO 15 KT.
CYCLONIC WIND SHIFTS ARE NO LONGER EVIDENT IN THE LOW-LEVELS
BASED UPON THE AVAILABLE DATA. THE WAVE IS EMBEDDED IN A SLIGHT
MOISTENING ENVIRONMENT JUST S OF THE ATLC FRONTAL
BOUNDARY/TROUGH...PRODUCING ONLY ISOLATED SHOWERS.

 ...THE ITCZ...
ITCZ AXIS IS ALONG 10N14W 7N29W 6N47W 10N55W. BESIDES FOR THE
CONVECTION ASSOCIATED WITH THE TROPICAL WAVES...SCATTERED
MODERATE IS WITHIN 180 NM N AND 90 NM S OF THE AXIS BETWEEN
23W-35W. SIMILAR ACTIVITY IS WITHIN 120 NM EITHER SIDE BETWEEN
48W-53W.

...DISCUSSION...
THE GULF OF MEXICO...
A STRONG COLD FRONT...ASSOCIATED WITH A SHARP UPPER TROUGH
CENTERED OVER THE CENTRAL US...CONTINUES TO MOVE QUICKLY
SOUTHEASTWARD IN THE GULF. AS OF 2100 UTC...THE FRONT WAS
ANALYZED FROM SRN ALABAMA TO 25N91W SURGING SWD TO MEXICO NEAR
20N97W THEN NWD ALONG THE E SLOPES OF THE SIERRA MADRE MOUNTAINS
NEAR 22N99W. SCATTERED SHOWERS AND TSTMS ARE WITHIN 120 NM AHEAD
OF THE COLD FRONT...BUT MORE CONVECTIVE WEATHER LIES FURTHER E
IN THE WARM SECTOR ACROSS THE ERN FL PANHANDLE AND SWWARD INTO
THE GULF FOR 200 NM. THIS SQUALL LINE IS QUICKLY MOVING EWARD.
CLUSTERS OF MODERATE CONVECTION HAS ALSO BLOSSOMED NEAR THE BASE
OF THE FRONT OVER MEXICO AND THE SW GULF FROM 18N-21N BETWEEN
96-100W. THIS FRONTAL BOUNDARY MARKS A CLEAR AIRMASS CHANGE FROM
WARM AND HUMID TEMPS IN THE 80'S AND DEWPOINTS IN THE 70'S S  E
OF THE FRONT TO TEMPS FALLING THRU THE 60'S AND DEWPOINTS
PLUMMETING INTO THE 40'S BEHIND THE BOUNDARY. STRONG NLY WINDS
BETWEEN 20 AND 30 KT ARE COMMON BEHIND THE FRONT AND SIMILAR
MAGNITUDE SWLY WINDS AHEAD OF THE FRONT AS STRONG SFC HIGH PRES
BUILD IN. FOR MORE DETAILS IN WINDS AND WAVES REFER TO MIAOFFNT4
AND MIAHSFAT2. THIS FAST MOVING FRONT WILL LIKELY CLEAR THE
ENTIRE AREA LATE TOMORROW.

THE CARIBBEAN SEA...
THE TAIL END OF AN ATLC FRONTAL BOUNDARY/TROUGH IS GRADUALLY
FALLING APART IN THE NRN CARIBBEAN. THIS FEATURE IS ANALYZED AS
A SFC TROUGH FROM HISPANIOLA TO THE YUCATAN CHANNEL. THERE IS
ONLY SLIGHT WIND SHIFT AND SPEED GRADIENT ALONG THE BOUNDARY. A
BROKEN LINE OF SCATTERED SHOWERS AND TSTMS ARE WITHIN 90 NM
EITHER SIDE OF THE TROUGH. THIS ACTIVITY IS BEING ENHANCED BY
UPPER DIFFLUENT FLOW BETWEEN A SPRAWLING UPPER HIGH CENTERED
OVER CENTRAL CUBA AND A SMALL UPPER LOW NEAR 16N80W. THE SRN
CARIB IS FAIRLY QUIET WITH MODERATE DRY AIR ALOFT IN PLACE
...HOWEVER DEBRIS MOISTURE...DRIVEN BY NLY UPPER LEVEL FLOW
ACROSS THE OLD FRONTAL BOUNDARY...IS SPILLING INTO THE AREA
SPARKING ISOLATED SHOWERS. THE MOST ACTIVE WEATHER IS IN THE ERN
CARIB WHERE THE WRN EDGE OF MODERATE CONVECTION ASSOCIATED WITH
A TROPICAL WAVE AND 1009 MB LOW IS NOW MOVING ACROSS THE
WINDWARD ISLANDS. LOCALLY HEAVY RAINS AND GUSTY WINDS ARE
POSSIBLE AS THE SYSTEM CONTINUES TO MOVE W ACROSS THE LESSER
ANTILLES TONIGHT AND TOMORROW. FOR MORE INFORMATION ON THIS
SYSTEM REFER TO THE TROPICAL WAVES SECTION.

THE ATLANTIC OCEAN...
A HIGHLY AMPLIFIED PATTERN REMAINS ESTABLISHED ACROSS THE ATLC.
HIGH PRES RIDGING EXISTS ACROSS MUCH OF THE CARIBBEAN AND WRN
ATLC W OF 62W. A LARGE SLOWLY WEAKENING TROUGH LIES TO THE E OF
THE RIDGE AND COVERS MUCH OF THE CENTRAL ATLC BETWEEN 40W AND 62W
N OF 20N. AN ASSOCIATED COLD FRONT CONTINUES TO SLOWLY BECOME
LESS DEFINED ALONG 32N42W 24N56W THEN ANALYZED A TROUGH/SHEAR
AXIS TO THE DOMINICAN REPUBLIC AND ACROSS THE NRN CARIBBEAN.
SCATTERED SHOWERS AND TSTMS ARE WITHIN 180 NM E OF THE FRONT.
BEHIND THE FRONT...A MODIFIED DRIER AND COOLER AIRMASS EXISTS.
A LARGE STRONG MID/UPPER LEVEL RIDGE IS LOCATED E OF THE TROUGH
CENTERED IN THE SUBTROPICS NEAR 29N29W. THIS RIDGE COVERS THE
REMAINDER OF THE ATLC E OF 40W N OF 20N WITH DRY STABLE AIR
ALOFT WIDESPREAD IN THE REGION. SFC HIGH PRES IS ALSO ANALYZED
UNDERNEATH THE MID/UPPER RIDGE WITH A 1023 MB HIGH NEAR 32N27W.
IN THE DEEP TROPICS...AN UPPER HIGH IS CENTERED NEAR 13N53W. THE
TROPICAL WAVE AND AREA OF LOW PRES APPROACHING THE ERN CARIBBEAN
LIES ON THE WRN EDGE OF THIS ANTICYCLONE. AN UPPER LOW LIES TO
THE E OF TH ANTICYCLONE CENTERED NEAR 17N38W... ERODING THE SWRN
EDGE OF THE AMPLIFIED RIDGE IN THE SUBTROPICS. THIS LOW IS
PROVIDING AN UNFAVORABLE ENVIRONMENT FOR THE TROPICAL WAVE NEAR
40W. UPPER DIFFLUENCE ON THE SE SIDE OF THE LOW IS ENHANCING
CONVECTION IN THE ITCZ BETWEEN 25W-40W.

$$
CANGIALOSI




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