[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 170540
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
105 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0515 UTC.

...THE ITCZ...
ITCZ AXIS IS ALONG 7N13W 4N25W 3N40W 2N50W. SMALL CLUSTERS OF
ISOLATED MODERATE CONVECTION ARE WITHIN 360 NM N AND 240 NM S OF
THE AXIS BETWEEN 29W-37W. SCATTERED MODERATE IS WITHIN 60 NM
EITHER SIDE OF THE AXIS BETWEEN 19W-21W.

...DISCUSSION...
THE GULF OF MEXICO...
THE MID/UPPER LEVEL SHORTWAVE TROUGH THAT HAS BEEN IN THE GULF
OVER THE PAST FEW DAYS HAS NOW MOVED JUST E OF THE AREA OFF THE
SE COASTLINE. HOWEVER...CONSIDERABLE MOISTURE IS STILL COVERING
THE EXTREME SE GULF AND S FLORIDA...NAMELY S OF 26N E OF 85W.
DOPPLER RADAR FROM MIAMI AND KEY WEST DEPICT A LARGE SHIELD OF
SCATTERED SHOWERS AND POSSIBLY ISOLATED TSTMS MOVING ACROSS S
FLORIDA WHERE IT WAS A PRETTY GLOOMY DAY YESTERDAY. STRONG WLY
UPPER LEVEL WINDS AND ISENTROPIC LIFT IS LIKELY THE CULPRIT IN
PRODUCING THIS ACTIVITY. THE BULK OF THE DEEP MOISTURE WILL
LIKELY NOT LAST MUCH LONGER AS DRIER AIR IS ON ITS WAY WITH
PLENTY OF IT BEING ADVECTED INTO THE REMAINDER OF THE GULF.
AT THE SFC...THE HIGH PRES SYSTEM HAS SHIFTED NE AND
STRENGTHENED AS PROJECTED BY THE MODELS ANALYZED AT 1024 MB NEAR
VIRGINIA BEACH. A WEAK SMALL SFC TROUGH IS LOCATED ALONG 86W
FROM 22N-26N. THIS FEATURE LIKELY BROKE OFF FROM THE LARGER
WELL-DEFINED TROUGH/FRONTAL BOUNDARY THAT IS CURRENTLY IN THE
WRN ATLC. LOW-LEVEL LIFT NEAR THE SFC BOUNDARY IS ENHANCING SOME
ACTIVITY E OF THE AXIS. 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 ARE BROKEN MULTILAYERED CLOUDS AND
ISOLATED SHOWERS. THIS CLOUDINESS IS MAINLY CONTRIBUTED TO A
WEAK SFC TROUGH IN THE SE GULF AND STRONG UPPER LEVEL WINDS ON
THE N PERIPHERY OF A STRONG MID/UPPER LEVEL HIGH CENTERED IN THE
SRN 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 THE LESSER
ANTILLES WHERE BRIEF SHALLOW ISOLATED SHOWERS ARE POSSIBLE.
TRADE WINDS ARE MOSTLY IN THE 15-20 KT RANGE AND LITTLE CHANGE
OR SOME RELAXING IS EXPECTED OVER THE NEXT FEW DAYS. LOW-LEVEL
MOISTURE MAY INCREASE SLIGHTLY IN THE ERN CARIBBEAN LATER TODAY
AND TONIGHT BUT OVERALL MAINLY DRY CONDITIONS ARE EXPECTED TO
PREVAIL.

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 32N60W TO THE CENTRAL BAHAMAS...IS SPREADING
TO ABOUT 45W 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. HOWEVER...THE MODEL DOES SHOW THE TAIL END OF
THE TROUGH BREAKING OFF AND MOVING W...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 SFC
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 32N23W AND EXTENDS S-SW ALONG 25N24W
15N33W. 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 SOME RIDGING TO IT'S NW PRODUCING GALE FORCE
CONDITIONS N OF THE DISCUSSION AREA. THESE STRONG NLY WINDS HAVE
CREATED SIGNIFICANT SWELL PRODUCING COMBINED SEAS OF 12-16 FT
BETWEEN THE LOW AND 40W N OF 26N. A BROAD UPPER LEVEL RIDGE
COVERS THE ERN MOST ATLC AND W AFRICA WITH THE AXIS ALONG 11W.
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 7N24W. THIS STRONG
SWLY FLOW IS SPREADING HIGH CLOUDINESS AND LIKELY ISOLATED
SHOWERS ACROSS THE E ATLC SE OF A LINE ALONG 9N40W 19N27W 24N19W.

$$
CANGIALOSI




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