[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 210558
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT SAT OCT 21 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY
THROUGH 0530 UTC.

...TROPICAL WAVES...
A TROPICAL WAVE IS ALONG 42W S OF 21N MOVING W 10 TO 15 KT. A
1010 MB LOW IS ALONG THE WAVE NEAR 14N. THIS LOW PRES AREA IS
ONLY A ROTATION OF LOW CLOUDS WELL REMOVED FROM THE ASSOCIATED
ISOLATED MODERATE CONVECTION A FEW HUNDRED NM TO ITS E.
OBVIOUSLY THIS WAVE IS STILL FEELING EFFECTS OF STRONG W-SWLY
SHEAR. ISOLATED MODERATE CONVECTION IS ALSO OCCURRING WITHIN 300
NM EITHER SIDE OF THE WAVE AXIS S OF 9N. THIS FEATURE WILL
REMAIN IN AN UNFAVORABLE ENVIRONMENT OVER THE NEXT COUPLE OF
DAYS.

A WEAK TROPICAL WAVE IS ALONG 55W S OF 16N MOVING W 10 TO 15 KT.
THIS WAVE DOES NOT EXHIBIT ANY SIGNATURE ON SATELLITE IMAGERY OR
IN AVAILABLE SFC DATA...THEREFORE THE PSN IS BASED ON
CONTINUITY. THIS FEATURE WILL LIKELY BECOME ABSORBED INTO THE
BROAD TROUGH IN THE CARIBBEAN.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 9N14W 6N32W 8N40W 9N54W 9N62W. THE
ERN PORTION OF THE AXIS HAS BECOME A LITTLE MORE ACTIVE...
SCATTERED MODERATE CONVECTION IS E OF 18W FROM 6N-12N. SCATTERED
MODERATE IS WITHIN 180 NM S OF THE AXIS BETWEEN 17W-26W.
ISOLATED MODERATE IS FROM 6N-12N BETWEEN 30W-35W. NUMEROUS
MODERATE IS ALONG THE N COAST OF S AMERICA DRIFTING NWD FROM
11N-13N BETWEEN 63W-68W.

...DISCUSSION...
THE GULF OF MEXICO...
A WEAK SHORTWAVE TROUGH ACROSS THE NRN PORTION OF THE AREA HAS
FLATTENED WITH UPPER LEVEL FLOW BECOMING MORE ZONAL ACROSS THE
SRN U.S. AND NRN GULF. THIS HAS MADE THE ASSOCIATED FRONTAL
BOUNDARY NEARLY STATIONARY ACROSS THE GULF. AS OF 03 UTC...THE
FRONT WAS STILL ANALYZED AS A COLD FRONT FROM NEAR ST. AUGUSTINE
TO 27N86W THEN STATIONARY TO A 1008 MB LOW NEAR 25N96W. THE
FRONT THEN CONTINUES SWD TO 19N96W AND THEN NWD ALONG THE E
SLOPES OF THE SIERRA MADRE MOUNTAINS IN MEXICO. THIS SFC
BOUNDARY IS SLOWLY WEAKENING IN THE CENTRAL AND WRN GULF WITH
WINDS VEERING FROM N-NE TO ENE N OF THE BOUNDARY OVER THE PAST
SEVERAL HOURS. ONLY ISOLATED SHOWERS ARE FOUND WITHIN 150 NM N
OF THE BOUNDARY AND NEAR THE LOW. TRANQUIL WEATHER CONTINUES
ACROSS THE SRN PORTION OF THE GULF...THANKS TO DRY STABLE AIR
ALOFT IN PLACE GENERATED BY A HIGHLY NE-SW ELONGATED MID/UPPER
RIDGE. THE SFC FRONT IS EXPECTED TO LIFT NWD AS A WARM FRONT
LATER TODAY BEFORE THE NEXT COLD FRONT...CURRENTLY DRAPED
ACROSS THE CNTRL U.S....PUSHES OFF THE GULF COAST EARLY SUN. GFS
ANTICIPATES THIS SECOND FRONT TO DIG MUCH FURTHER S POSSIBLY
CLEARING THE ENTIRE AREA BY LATE MON.

THE CARIBBEAN SEA...
SOME UNSETTLED WEATHER IS CONTINUING IN THE ERN CARIBBEAN DUE TO
A SLOW MOVING PERSISTENT DEEP LAYER TROUGH. A 1007 MB LOW IS
ANALYZED OVER HISPANIOLA NEAR 19N70W WITH A SFC TROUGH EXTENDING
SOUTHWESTWARD ALONG 16N74W 14N79W. DESPITE THE RATHER LOW SFC
PRESSURES...THE LOW MENTIONED IS VERY BROAD AND POORLY
STRUCTURED WITH ONLY ISOLATED SHOWERS IN ITS VICINITY. MOST OF
THE MORE IMPRESSIVE RAINFALL IS OCCURRING FARTHER E ASSOCIATED
WITH THE MOIST SWLY FLOW ON THE E SIDE OF THE MID/UPPER TROUGH
DRAWING DEEP TROPICAL MOISTURE NWD. SCATTERED SHOWERS AND TSTMS
ARE ACROSS THE WINDWARD...LEEWARD AND VIRGIN ISLANDS. SCATTERED
TO NUMEROUS MODERATE CONVECTION IS MOVING NWD OFF THE NRN S
AMERICA COAST FROM 11N-13N BETWEEN 63W-68W. GFS SHOWS THIS
MOISTURE SLOWLY THINNING OUT AND DRIFTING W OVER THE NEXT FEW
DAYS AS THE UPPER TROUGH MOVES W AND A WEAK UPPER RIDGE BUILDS
OVER THE AREA. THE WRN CARIBBEAN REMAINS QUIET WITH VERY DRY AIR
ALOFT BEING ADVECTED IN THE REGION FROM AN ELONGATED UPPER RIDGE
TO THE N. SFC WINDS ARE LIGHT AND VARIABLE ACROSS THE CARIBBEAN
DUE TO THE PRESENCE OF THE SFC TROUGH. EASTERLY TRADES WILL
LIKELY RESUME LATE SAT/EARLY SUN.

THE ATLANTIC OCEAN...
A FAIRLY COMPLEX MID/UPPER LEVEL PATTERN EXISTS ACROSS THE ATLC.
IN THE WRN ATLC...AN UPPER HIGH IN THE GULF OF MEXICO HAS
RIDGING THAT EXTENDS NE ACROSS THE NRN BAHAMAS. ANOTHER UPPER
HIGH IS CENTERED E OF BERMUDA NEAR 31N58W. VERY DRY STABLE AIR
IS NOTED N OF 25N GENERATED BY THESE ANTICYCLONES. DEEP LAYER
TROUGHING EXISTS BETWEEN THESE UPPER RIDGES WITH THE SFC
BOUNDARY EXTENDING FROM A 1007 MB LOW OVER HISPANIOLA TO 24N67W.
A LARGE AREA OF MOISTURE WITH EMBEDDED AREAS OF DEEP CONVECTION
EXISTS S OF THE LARGE ANTICYCLONE NEAR BERMUDA AND E OF THE DEEP
LAYER TROUGH IN THE CNTRL CARIBBEAN...NAMELY S OF 25N BETWEEN
50W AND 70W. THE DEEPEST BLOB OF CONVECTION IS NE OF PUERTO RICO
FROM 19N TO 23N BETWEEN 61W AND 65W. DEBRIS UPPER LEVEL MOISTURE
IS THEN ADVECTED EASTWARD BY A WLY JET N OF AN UPPER HIGH IN THE
TROPICAL N ATLC...AS WELL AS ANOTHER FARTHER E NEAR 16N46W...AND
S OF AN UPPER LOW NEAR 26N42W. THIS JET HAS CORE WINDS NEAR 80
KT BASED ON UW-CIMSS SATELLITE DERIVED WINDS. THE TROPICAL ERN
ATLC IS DOMINATED BY UPPER RIDGING WITH AN ANTICYCLONE CENTERED
OVER THE CAPE VERDE ISLANDS. THE E ATLC SFC PATTERN IS DOMINATED
BY WEAK E-W RIDGING IN THE SUBTROPICS FROM A 1018 MB NEAR 31N57W
TO A 1020 MB HIGH NEAR 27N32W TO A 1017 MB HIGH OVER MOROCCO.
THIS RIDGE IS BLEMISHED A SFC TROUGH EXTENDING FROM A 1010 MB
ALONG 32N48W 26N54W AND POSSIBLY ANOTHER TROUGH ASSOCIATED WITH
THE UPPER LEVEL LOW NEAR 26N42W.

$$
CANGIALOSI




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