[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 282339
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
705 PM EST TUE 28 DEC 2004

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHEASTERN SECTIONS
OF SOUTH AMERICA...AND 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.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 10N10W 6N20W 4N36W 5N45W 3N55W.
SCATTERED MODERATE CONVECTION WITHIN 60 NM OF THE AXIS BETWEEN
24W-32W AND 200 NM N OF THE AXIS BETWEEN 32W-38W. ISOLATED
SHOWERS/TSTMS WITHIN 150 NM OF THE AXIS BETWEEN 40W-50W.
SCATTERED MODERATE WITHIN 200 NM OF THE AXIS BETWEEN 51W-63W
OVER FRENCH GUIANA...SURINAME...AND S GUYANA.

...DISCUSSION...

GULF OF MEXICO...
HIGH PRES CONTINUES TO SLIDE TO THE E OVER EASTERN NORTH
CAROLINA AND THIS HAS NOW PLACED THE GULF JUST ABOUT ON THE WRN
NOSE OF THE ASSOCIATED SFC RIDGE. BROKEN LOW/MID LEVEL CLOUDS
HAVE BEEN STREAMING QUICKLY WWD ACROSS FLORIDA AND THE GULF
WATERS BUT RETURN FLOW IS BECOMING RE-ESTABLISHED OVER THE W
GULF AND TEXAS COAST AND THIS IS BRINGING SOME OF THE CLOUDS
EVER CLOSER TO SHORE. WHILE RIDGING DOMINATES AT LEAST THE LOWER
HALF OF THE ATMOSPHERE...AN UPPER LEVEL SHORTWAVE TROF IS
STRAGGLING ACROSS S FLORIDA TO THE YUCATAN PENINSULA AND IS
PRODUCING STRONG SUBSIDENCE OVER THE SE GULF AND FLORIDA
STRAITS. AS SUCH...A BROKEN STRATOCU FIELD ORIGINATING OVER THE
W ATLC IS BEING ADVECTED OVER S FLORIDA AND HAS NOT ATTAINED
VERTICAL DEPTH HIGHER THAN ABOUT 800 MB NEAR THE TOP OF THE
INVERSION. THE RIDGE WILL STAY IN PLACE THROUGH MOST OF THE WEEK
AND LIMIT THE THREAT OF SHOWERS OVER THE AREA UNTIL LATE FRI/SAT
WHEN MOISTURE RETURNS ON THE W SIDE OF THE MID-LEVEL HIGH.

CARIBBEAN...
A FRONTAL BOUNDARY HAS STALLED OVER THE W/CNTRL CARIBBEAN WATERS
FROM HAITI SWWD TO COSTA RICA AND THE DEEPEST CONVECTION IS
LOCATED TO THE NW. SCATTERED WEAK/MODERATE CONVECTION EXTENDS
OVER AN AREA FROM 10N-18N BETWEEN 78W-84W W OF THE FRONT WITH A
FEW OF THE STORMS MOVING INLAND OVER COSTA RICA...NICARAGUA...
AND FAR E HONDURAS. A STATIONARY UPPER LEVEL TROF IS POSITIONED
ALONG THE EAST COAST OF CNTRL AMERICA BUT THE FLOW IS ALIGNED
PARALLEL TO THE FRONTAL BOUNDARY SO THERE IS LITTLE UPPER
DIFFLUENCE TO SUPPORT WIDESPREAD CONVECTION. DRY SW/W FLOW
EXTENDS ACROSS THE REST OF THE CNTRL/E CARIBBEAN WITH A COUPLE
OF SHOWERS MOVING SW ACROSS THE LEEWARD ISLANDS AND OVER THE ABC
ISLANDS AND VENEZUELAN COAST.

WEST ATLANTIC...
STRONG COLD FRONT HAS JUST ABOUT PUSHED ACROSS THE W ATLC WATERS
AND NOW STRETCHES ALONG 32N52W 24N60W TO THE N COAST OF THE
DOMINICAN REPUBLIC. WIDELY SCATTERED SHOWERS EXTENDS UP TO 160
NM BEHIND THE FRONT AND THEN ARE REPLACED BY A MOSTLY BROKEN
DECK OF STRATOCU THAT MOVE S OVER THE W ATLC WATERS AND THEN
CURVE TO THE W TOWARDS FLORIDA. THE UPPER LEVEL FLOW IS BECOMING
ZONAL OVER THE AREA AS THE STRONGER TROF DYNAMICS LIFT OUT OVER
THE N ATLC...AND THIS IS PRODUCING STRONG SUBSIDENCE WITHIN A
CONFLUENCE ZONE WHICH EXTENDS TO THE E OF THE BAHAMAS.

REMAINDER OF ATLANTIC...
A DEEP-LAYERED 1006 MB LOW IS CENTERED SE OF THE W ATLC COLD
FRONT NEAR 22N51W...OR ABOUT 690 NM ENE OF THE NORTHERN LEEWARD
ISLANDS. THE LOW IS TILTED STRONGLY TO THE E WITH HEIGHT WITH
THE UPPER LEVEL SIGNATURE CENTERED IN THE VICINITY OF 22N44W.
THE MOST ACTIVE WEATHER IS ASSOCIATED WITHIN THE DIFFLUENT ZONE
E OF THE UPPER LOW WITH SCATTERED MODERATE CONVECTION FROM
18N-24N BETWEEN 39W-43W. THE LOW IS EMBEDDED WITHIN A LARGER
TROF WHICH EXTENDS TO ABOUT 10N ALONG 43W/44W...AND A BROADER
DIFFLUENT ZONE IS PRODUCING A LARGE AREA OF HIGH CLOUDS WITH
POSSIBLE SHOWERS S OF 30N BETWEEN 26W-40W. JUST TO THE S...THE
UPPER FLOW HAS A WELL-DEFINED NLY CROSS-EQUATORIAL COMPONENT S
OF 7N AND IS PRODUCING FAVORABLE DIVERGENCE OVER THE ITCZ WITH
SCATTERED MODERATE CONVECTION DEVELOPING NEAR THE AXIS BETWEEN
25W-38W. A WEAK UPPER RIDGE EXTENDS E OF THIS REGION ALONG THE
COAST OF AFRICA FROM LIBERIA TO GHANA...AND BROAD ZONAL FLOW
STRETCHES WELL TO THE N TO NEAR 25N. N OF THAT...A NARROW
CYCLONIC SHEAR AXIS/TROF IS DRAPED FROM CNTRL ALGERIA TO THE
CANARY ISLANDS...WITH A STRONG CAP BEING PLACED OVER BRISK
EASTERLY SFC WINDS RIDING W OUT OF AFRICA.

$$
BERG



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