[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 171124
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
705 AM EST SUN DEC 17 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...
METEOROLOGICAL ANALYSIS...WEATHER OBSERVATIONS...AND RADAR.

BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1115 UTC.

...THE ITCZ...
ITCZ AXIS IS ALONG 8N12W 7N23W 4N40W 2N52W. SCATTERED MODERATE
CONVECTION IS FROM THE EQ TO 9N BETWEEN 29W-37W. ISOLATED
MODERATE IS WITHIN 120 NM N AND 180 NM S OF THE AXIS BETWEEN
17W-24W.

...DISCUSSION...
THE GULF OF MEXICO...
THE MID/UPPER LEVEL SHORTWAVE TROUGH THAT HAS BEEN IN THE GULF
OVER THE PAST FEW DAYS HAS EXITED THE REGION AND IS NOW OFF THE
SE COASTLINE. HOWEVER...THE TAIL END OF IT'S MOISTURE PLUME
STILL COVERS THE EXTREME SE GULF AND THE FLORIDA STRAITS
...NAMELY S OF 25N E OF 83W. DOPPLER RADAR DEPICTS A SHRINKING
SHIELD OF SCATTERED SHOWERS AND ISOLATED TSTMS MOVING ACROSS S
FLORIDA AND THE KEYS WHERE IT HAS BEEN PRETTY GLOOMY OVER THE
PAST 24 HOURS OR SO. THE BULK OF THE DEEP MOISTURE WILL NOT LAST
MUCH LONGER AS DRIER AIR IS ON ITS WAY WITH PLENTY OF IT BEING
ADVECTED INTO NEARLY ALL OF THE GULF. AT THE SFC...THE HIGH PRES
SYSTEM HAS SHIFTED NE AND STRENGTHENED AS PROJECTED BY THE
MODELS ANALYZED AT 1026 MB NEAR THE NC/VA COASTLINE. A WEAK
SMALL SFC TROUGH IS LOCATED ALONG 87W FROM 21N-26N. THIS FEATURE
BROKE OFF FROM THE LARGER TROUGH/FRONTAL BOUNDARY THAT IS
CURRENTLY IN THE WRN ATLC. LOW-LEVEL LIFT E OR DOWNSHEAR OF THIS
SFC BOUNDARY IS ENHANCING SOME ACTIVITY IN THE MOISTURE PLUME
DESCRIBED. OVER THE NEXT COUPLE DAYS...THE UNSETTLED WEATHER IN
THE SE GULF WILL MOVE OUT OF THE AREA AS A WEAK UPPER RIDGE
BUILDS OVERHEAD. THE SFC RIDGE WILL REMAIN NEARLY STATIONARY OFF
THE SE COAST HELPING TO PRODUCE MOSTLY FAIR WEATHER ACROSS THE
REGION.

THE CARIBBEAN SEA...
CONDITIONS IN THE CARIBBEAN ARE QUIET THIS MORNING. THE ONLY
AREA OF ANY MENTIONABLE CLOUDINESS IS ACROSS CUBA AND THE
YUCATAN CHANNEL WHERE THERE IS BROKEN MULTILAYERED CLOUDS AND
ISOLATED SHOWERS. THIS CLOUDINESS IS MAINLY CONTRIBUTED TO A
WEAK SFC TROUGH IN THE YUCATAN CHANNEL/SE GULF AND SWIFT UPPER
LEVEL FLOW ON THE N PERIPHERY OF A STRONG MID/UPPER LEVEL HIGH
CENTERED IN THE CENTRAL CARIBBEAN NEAR 15N74W. THE REMAINDER OF
THE AREA IS VERY STABLE WITH PLENTY OF DRY AIR ALOFT NOTED ON
WATER VAPOR IMAGERY. THE TYPICAL LOW-LEVEL CLOUD
STREAKS...UNDERNEATH THE STRONG MID-LEVEL CAP...EVEN APPEAR
RATHER THIN BASED ON SHORTWAVE IR IMAGES...EXCEPT FOR THE PATCH
OVER PUERTO RICO AND THE LESSER ANTILLES WHERE EMBEDDED
SCATTERED SHOWERS ARE POSSIBLE AS DEPICTED ON SAN JUAN'S 88-D.
TRADE WINDS ARE MOSTLY IN THE 15-20 KT RANGE AND LITTLE CHANGE
OR SOME RELAXING IS EXPECTED OVER THE NEXT FEW DAYS. MOISTURE
MAY INCREASE SLIGHTLY IN THE ERN CARIBBEAN TODAY AND TOMORROW
BUT MUCH OF THIS IS EXPECTED TO BE SHALLOW IN NATURE.

THE ATLANTIC OCEAN...
STARTING IN THE WRN AND CENTRAL ATLC...WIDESPREAD
MOISTURE...PRODUCED BY STRONG UPPER LEVEL WINDS E OF A SHORTWAVE
TROUGH OFF THE SE COASTLINE AND A WEAK FRONTAL BOUNDARY/SFC
TROUGH DRAPED FROM 32N56W TO THE CENTRAL BAHAMAS...IS SPREADING
TO ABOUT 42W MAINLY BETWEEN 24N-32N. THE ATMOSPHERE
CONSIDERABLY DRIES OUT S OF 24N AND E OF 45W AS THE UPPER LEVEL
FLOW DEVELOPS A NLY COMPONENT IN RESPONSE TO A LARGE TROUGH IN
THE E ATLC AND A STRONG RIDGE IN THE CARIBBEAN. THE GFS MODEL
SHOWS THE MOISTURE PLUME SLOWLY THINNING AND PRESSING TO THE S
OVER THE NEXT COUPLE DAYS. THE MODEL ALSO SUGGESTS THAT THE TAIL
END OF THE TROUGH MAY BREAK OFF AND MOVE W WITH THE LOW-LEVEL
FLOW...SIMILAR TO WHAT HAS OCCURRED IN THE GULF...WHICH MAY MAKE
SOME MOISTURE LINGER IN THE BAHAMAS.

IN THE E ATLC...THE MAIN FEATURE IS A LARGE OCCLUDED 1000 MB
LOW LOCATED NEAR 33N32W. OVER THE PAST FEW DAYS...A FEW WEAK
SMALLER SFC LOWS HAVE FORMED TO THE S OF THIS MAIN ONE AND HAVE
BEEN ABSORBED BY THE LARGE CIRCULATION. THE ASSOCIATED COLD
FRONT ENTERS THE AREA NEAR 32N24W AND EXTENDS S-SW ALONG 25N25W
17N32W. MOISTURE IS MOST ORGANIZED WELL N OF THE OCCLUDED
LOW...OUTSIDE OF THE DISCUSSION AREA WITH LIMITED MOISTURE NEAR
THE TRAILING COLD FRONT. THE MOST SIGNIFICANT WEATHER EFFECT
ASSOCIATED WITH THIS LOW PRES SYSTEM CONTINUES TO BE THE STRONG
WINDS AND HIGH SEAS...AS A TIGHTENED PRES GRAD EXISTS BETWEEN
THIS LOW AND A 1021 MB TO IT'S NW NEAR 33N44W PRODUCING GALE
FORCE CONDITIONS N OF THE DISCUSSION AREA. THESE STRONG NLY
WINDS HAVE CREATED SIGNIFICANT SWELL PRODUCING COMBINED SEAS OF
12-15 FT BETWEEN THE LOW AND 40W N OF 28N. A BROAD UPPER LEVEL
RIDGE COVERS THE ERN MOST ATLC AND W AFRICA WITH THE AXIS ALONG
10W. IN THE TROPICAL ATLC...THE PATTERN HAS BECOME MORE
AMPLIFIED WITH EXTENSIVE SWLY FLOW OR TROPICAL JET LOCATED
BETWEEN THE DEEP TROUGH...WHICH IS ASSOCIATED WITH THE LARGE
OCCLUDED LOW MENTIONED...AND A BROAD RIDGE CENTERED NEAR 8N21W.
THIS STRONG SWLY FLOW IS SPREADING HIGH CLOUDINESS AND LIKELY
ISOLATED SHOWERS ACROSS THE E ATLC SE OF A LINE ALONG 8N40W
20N27W 27N19W.

$$
CANGIALOSI



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