[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 201758
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
105 PM 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1715 UTC.

...SPECIAL FEATURE...

TROPICAL DEPRESSION GAMMA IS CENTERED NEAR 16.9N 85.3W JUST NE
OF THE BAY ISLANDS AT 20/1500 UTC AND NEARLY STATIONARY.
ESTIMATED MINIMUM CENTRAL PRESSURE IS 1007 MB. MAXIMUM SUSTAINED
WIND SPEEDS ARE 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 PRODUCING LIMITED CONVECTION AND COULD
BECOME A REMNANT LOW OR DISSIPATE BY THIS EVENING.   GAMMA WILL
EVENTUALLY BE ABSORBED BY A COLD FRONT EXPECTED TO MOVE INTO THE
NW CARIBBEAN BY MON NIGHT.  WIDELY SCATTERED SHOWERS AND PERHAPS
A TSTM IS WITHIN 60 NM OF THE CENTER WITH OTHER TERRAIN-ENHANCED
RAINS OVER NRN HONDURAS.

...ITCZ...

ITCZ IS CENTERED ALONG 7N13W 5N30W 4.5N51W.  SCATTERED MODERATE
FROM 4N-8N BETWEEN 16W-33W.  WIDELY SCATTERED MODERATE
CONVECTION IS FROM 3N-8N BETWEEN 35W-49W.

...DISCUSSION...

GULF OF MEXICO...
COMPLEX PATTERN DEVELOPING WITH ONE LOW OVER THE E-CENTRAL GULF
NEAR 26.5N87W...1013 MB... AND A 1016 MB LOW ALONG A COLD FRONT
NEAR 28N95W WITH THE FRONT EXTENDING SW TO TO 22N98W IN E MEXICO
INTO THE HIGH ELEVATIONS OF THE SIERRA MADRES.  OVERCAST LOW
CLOUDS ARE BEHIND THE FRONT AND OVER THE NE GULF N AND E OF THE
LOW.  A FEW TSTMS ARE WITHIN 90 NM OF 27N93.5W ALONG THE FRONT
AND WITHIN 90 NM OF THE LOW IN THE NE QUADRANT.  IT IS A LITTLE
NEBULOUS ON WHETHER THE COLD FRONT IN THE WESTERN GULF WILL BE
THE MAIN FEATURE TRACKING ACROSS THE AREA OR IF THE FRONT WILL
BE MORE ASSOCIATED WITH THE E-CENTRAL GULF LOW.  IN ANY EVENT A
LOW WILL BE CONSOLIDATING OVER GEORGIA TOMORROW ... SENDING A
COLD FRONT SURGING ACROSS THE GULF LEAVING LATE TOMORROW.  THE
COOLEST AIR OF THE SEASON IS BEHIND THE FRONT WITH GALES
POSSIBLE IN THE EXTREME SW GULF.  ALL OF THIS IS BEING FORCED BY
A STRONG UPPER TROUGH... FROM MISSOURI INTO CENTRAL MEXICO...
WHICH IS PROVIDING LIFT/DYNAMICS FOR THE LOWS IN THE GULF.  THE
EVENTUAL MOVEMENT/FORMATION OF THE LOW PRESSURE SYSTEM IN THE SE
UNITED STATES IS DUE TO THIS STRONG TROUGH... EVENTUALLY LEAD TO
AN E COAST "NOR'EASTER" TYPE EVENT THOUGH WITHOUT MUCH SNOW.
WITH THE STRONG TROUGH IN PLACE... SHOWERS/TSTMS ARE A GOOD BET
AS THE FRONT CROSSES FLORIDA TOMORROW.

CARIBBEAN...
A LARGE AND SUBSIDENT MID/UPPER LEVEL HIGH IS CENTERED OVER THE
CNTRL CARIBBEAN JUST S OF HAITI 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.D. GAMMA THEN NE ACROSS CUBA
WITH INCREASING SHEAR OVER GAMMA. A SMALL CLUSTER OF DEEP
CONVECTION IS ASSOCIATED WITH GAMMA BUT OTHERWISE THE REST OF
THE AREA IS ONLY BEING AFFECTED BY ISOLATED SHOWERS JUST W OF
THE WINDWARD ISLANDS AND A LITTLE W OF THE ABC ISLANDS. A COLD
FRONT IS EXPECTED TO MOVE INTO THE NW CARIBBEAN MON NIGHT AND
WILL PUSH T.D. 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...
LARGE UPPER HIGH OVER CARIBBEAN RIDGES UP INTO THE SW ATLC TO
PRODUCE WLY FLOW ALOFT... WITH CORRESPONDING SURFACE RIDGING
PERSISTING W OF 60W.  ILL-DEFINED WARM FRONT EXTENDS ACROSS
CENTRAL FLORIDA NEAR ORLANDO TO 28N77W WITH OVERCAST LOW CLOUDS
AND ISOLATED SHOWERS  N OF THE FRONT W OF 75W.  PATCHY CUMULUS
ARE BEHIND A COLD FRONT...ADVANCING ACROSS THE CENTRAL ATLC FROM
NEAR 32N50W TO 26N60W WITH ONLY ISOLATED SHOWERS NEAR THE
FRONT.  FARTHER E...A STRENGTHENING 1008 MB LOW IS NEAR 28N44W
MOVING SLOWLY NE.  A NEARBY UPPER TROUGH SHOULD ALLOW A
CONTINUED DEEPENING OF THE LOW WITH UPPER DYNAMICS/LIFT ALREADY
PRODUCING ISOLATED TSTMS WITHIN 90 NM OF THE TROUGH AND MORE
WIDELY SCATTERED ACTIVITY FROM 17N-29N BETWEEN 44W-50W NEAR AN
ASSOCIATED SURFACE TROUGH.  THIS LOW WILL HAVE TO BE WATCHED IN
THE COMING DAYS FOR A POSSIBLE TRANSITION TO A SUBTROPICAL STORM
AS UPPER HEIGHTS RISE IN THE MID-LATITUDE CENTRAL ATLC...
BLOCKING ANY DEPARTURE OF THE LOW FOR AT LEAST THE NEXT 3-5 DAYS
AND PERHAPS ALLOWING FOR UPPER RIDGING TO FORM NEAR THE SYSTEM.
HIGH-AMPLITUDE UPPER RIDGING IS ALONG 6N37W TO 22N28W THEN
32N33W WITH BROKEN CIRRUS WITHIN 300 NM OF THE RIDGE AXIS.
DIFFLUENT FLOW NEAR THE RIDGE AXIS IS ENHANCING ITCZ CONVECTION
TODAY.  FINALLY A LARGE DEEP-LAYERED LOW IS NEAR 38N17W WITH AN
UPPER TROUGH SOUTHWARD TO WESTERN MAURITANIA.  ASSOCIATED COLD
FRONT IS SWINGING THRU THE CANARY ISLANDS WITH ISOLATED
SHOWERS.  THE TRADES IN THE ATLC ARE MUCH WEAKER THAN NORMAL
WITH THE ABSENCE OF THE SUBTROPICAL RIDGE DUE TO ALL OF THE
UPPER TROUGHINESS IN THE SUBTROPICAL/MID-LATITUDE ATLC.

$$
BLAKE

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