[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 201146
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
705 AM EST SUN NOV 20 2005

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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1115 UTC.

...SPECIAL FEATURE...

TROPICAL DEPRESSION GAMMA IS CENTERED NEAR 16.7N 85.1W...OR 65
NM NNE OF LIMON HONDURAS...AT 20/1200 UTC AND NEARLY STATIONARY.
ESTIMATED MINIMUM CENTRAL PRESSURE IS 1006 MB. MAXIMUM SUSTAINED
WIND SPEED HAS DECREASED TO 30 KT WITH GUSTS TO 40 KT. SEE
LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT2/
WTNT22 KNHC AND THE PUBLIC ADVISORY UNDER HEADERS MIATCPAT2/
WTNT32 KNHC FOR MORE DETAILS. GAMMA IS ON A QUICK WEAKENING
TREND NOW THAT THE LOW-LEVEL CENTER HAS BECOME EXPOSED FROM THE
SMALL CLUSTER OF DEEP CONVECTION 120 NM TO ITS NNE. A MID/UPPER
HIGH OVER THE CNTRL CARIBBEAN AND A TROUGH OVER THE GULF OF
MEXICO ARE PRODUCING MODERATE/STRONG SOUTHERLY SHEAR OVER THE
SYSTEM AND KEEPING ITS LOW AND UPPER LEVEL CIRCULATIONS
DECOUPLED. SCATTERED MODERATE CONVECTION IS FROM 18N-21N BETWEEN
82W-85W...OR UP TO 220 NM W OF GRAND CAYMAN. GAMMA WILL CONTINUE
TO WEAKEN AND EVENTUALLY BE ABSORBED BY A COLD FRONT EXPECTED TO
MOVE INTO THE NW CARIBBEAN BY MON NIGHT.

...ITCZ...

ITCZ IS CENTERED ALONG 11N14W 3N33W 4N42W EQ51W...AND STRETCHING
ACROSS PANAMA AND COSTA RICA. NUMEROUS MODERATE/ISOLATED STRONG
CONVECTION WITHIN 120 NM OF THE AXIS BETWEEN 17W-30W. SCATTERED
MODERATE/ISOLATED STRONG FROM 1N-9N BETWEEN 30W-45W. ISOLATED
SHOWERS/TSTMS OVER PANAMA AND COSTA RICA.

...DISCUSSION...

GULF OF MEXICO...
A NEGATIVELY-TILTED UPPER TROUGH IS LOCATED OVER THE EASTERN
TWO-THIRDS OF THE CONTINENTAL U.S. AND NRN MEXICO WITH A STRONG
90 KT JET EXTENDING FROM THE WRN GULF TO THE ATLC COASTS OF
GEORGIA AND THE CAROLINAS. THE JET IS PULLING SOME HIGH LEVEL
MOISTURE FROM THE NW CARIBBEAN TOWARDS THE STRAITS OF FLORIDA
AND S FLORIDA BUT THIS AREA IS SLOWLY SHIFTING E AND THINNING
OUT AS GAMMA WEAKENS IN THE CARIBBEAN. A DISSIPATING WARM FRONT
EXTENDS FROM NEAR LAKE OKEECHOBEE SWWD TO 26N87W AND WIDELY
SCATTERED SHOWERS/TSTMS HAVE BEEN DEVELOPING TO THE N FROM
26N-30N BETWEEN 84W-88W. OVERCAST LOW CLOUDS ARE STILL BANKED
AGAINST THE SIERRA MADRE ORIENTALS OF MEXICO...EXTENDING UP TO
150 NM OFFSHORE. A STRONG SHORTWAVE TROUGH IS SLIPPING S ACROSS
W TEXAS AND A COLD FRONT IS NOW MOVING OFF THE COAST. A COASTAL
TROUGH HAS SET UP AHEAD OF THE FRONT FROM 29N95W 21N97W WITH A
1018 MB LOW NEAR 28N96W...AND THIS FEATURE IS TRIGGERING WIDELY
SCATTERED SHOWERS/TSTMS FROM 26N-30N BETWEEN 93W-96W. COOLER AND
DRIER AUTUMNAL AIR BEHIND THE FRONT WILL SPREAD SE ACROSS THE
ENTIRE GULF BY MON NIGHT...WITH A GOOD CHANCE FOR SCATTERED
SHOWERS/TSTMS ACROSS FLORIDA ON MON.

CARIBBEAN...
A LARGE AND SUBSIDENT MID/UPPER LEVEL HIGH IS CENTERED OVER THE
CNTRL CARIBBEAN JUST SW OF HISPANIOLA NEAR 16N75W WITH EXTREMELY
DRY AIR LOCATED E OF 80W. A THINNING PLUME OF TROPICAL MOISTURE
IS SURGING N ON THE WRN PERIPHERY OF THE HIGH...EXTENDING FROM
SRN PORTIONS OF CNTRL AMERICA ACROSS T.S. GAMMA THEN NE ACROSS
CUBA. A SMALL CLUSTER OF DEEP CONVECTION IS ASSOCIATED WITH
GAMMA BUT OTHERWISE THE REST OF THE AREA IS ONLY BEING AFFECTED
BY ISOLATED SHOWERS NEAR THE WINDWARD ISLANDS AND THE ABC
ISLANDS. A COLD FRONT IS EXPECTED TO MOVE INTO THE NW CARIBBEAN
MON NIGHT AND WILL PUSH T.S. GAMMA AND THE DEEPEST TROPICAL
MOISTURE S AND E OVER THE SW/CNTRL CARIBBEAN...WITH DRIER AIR
FILTERING ACROSS W CUBA...THE CAYMAN ISLANDS...AND THE YUCATAN
PENINSULA THROUGH THE UPCOMING WEEK.

ATLANTIC...
THE FRONTAL BOUNDARY WHICH HAS BEEN LOCATED ACROSS THE BAHAMAS
AND THE STRAITS OF FLORIDA HAS LIFTED NWD AS A WARM FRONT
OVERNIGHT AND EXTENDS FROM 27N80W 26N68W THEN CONTINUES AS A
COLD FRONT TO 28N60W 32N53W. ISOLATED SHOWERS LIE UP TO 150 NM N
OF THE FRONT ESPECIALLY W OF 73W TO THE FLORIDA COAST. THE UPPER
FLOW OVER THE W ATLC IS PRIMARILY WESTERLY DUE TO AN UPPER HIGH
OVER THE CARIBBEAN...AND PATCHY HIGH LEVEL CLOUDS ARE BEING
ADVECTED NEWD OVER THE AREA FROM CUBA. FARTHER E...A
STRENGTHENING UPPER LOW IS LOCATED OVER THE CNTRL ATLC NEAR
28N44W WITH A TROUGH EXTENDING SW TO 13N56W. UPPER DIVERGENCE E
OF THE LOW ALONG AN UPPER RIDGE NEAR 38W HAS INDUCED THE
DEVELOPMENT OF A 1008 MB LOW NEAR 28N46W WITH SCATTERED MODERATE
CONVECTION FROM 18N-32N BETWEEN 36W-44W. A DEEP UPPER TROUGH IS
OVER THE E ATLC E OF 30W WITH THE ASSOCIATED JET AS FAR S AS 16N
AND A DISSIPATING COLD FRONT IS DRAPED ACROSS THE CANARY ISLANDS
FROM 32N12W 28N20W 28N26W. AN OLD FRONTAL BOUNDARY ALSO LIES TO
THE SE ALONG 30N13W 25N17W 22N24W. BROKEN STRATOCUMULUS EXTENDS
NW OF THE FRONT BUT SHOWER ACTIVITY MOSTLY N OF 32N.

$$
BERG



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