[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 210012
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
705 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2315 UTC.

...SPECIAL FEATURE...

TROPICAL DEPRESSION GAMMA IS CENTERED NEAR 17.0N 85.5W JUST NE
OF THE BAY ISLANDS AT 20/2100 UTC MOVING NORTH AT 2 KT.
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 TONIGHT.  THE
REMNANTS OF 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
CONVECTION IS FROM 5N-8N BETWEEN 18W-22W...AND FROM 4N-9N
BETWEEN 23W-29W.

...DISCUSSION...

GULF OF MEXICO...
1013 MB LOW IS OVER THE CENTRAL GULF OF MEXICO NEAR 27N87W.  A
SURFACE TROUGH EXTENDS S FROM THE LOW TO THE YUCATAN PENINSULA
NEAR 22N87W.  A WARM FRONT EXTENDS E FROM THE SAME LOW TO
CENTRAL FLORIDA NEAR 29N81W.  SCATTERED MODERATE CONVECTION IS
OFF THE FLORIDA COAST FROM 28N-30N BETWEEN 84W-86W.  A COLD
FRONT HAS SWEPT THROUGH TEXAS AND IS OVER THE W GULF AND IS IN
THE PROCESS OF MERGING WITH THE CENTRAL GULF LOW.  THE COLD
FRONT IS ALONG 27N87W 27N92W 20N97W 21N100W.  15-20 KT N WIND
AND OVERCAST LOW CLOUD ARE BEHIND THE COLD FRONT TO THE FOOT OF
THE SIERRA MADRE MOUNTAINS AND TO THE TEXAS COAST.  IN THE UPPER
LEVELS...SW FLOW DOMINATES THE ENTIRE GULF DUE TO CONVERGENCE
BETWEEN A TROUGH OVER THE CENTRAL UNITED STATES AND AN
ANTICYCLONIC CIRCULATION OVER THE NORTH CENTRAL CARIBBEAN.
MOISTURE IS OVER THE NE GULF WITH SUBSIDENCE ELSEWHERE.  EXPECT
THE COLD FRONT TO EXTEND FROM N FLORIDA TO W CUBA TO THE GULF OF
HONDURAS AT 1800 UTC MONDAY WITH STRONG NW WIND AND COOLER
TEMPERATURES OVER THE ENTIRE GULF OF MEXICO.

CARIBBEAN...
T.D. GAMMA HAS WEAKENED SINCE YESTERDAY AND HAS LOST ITS DEEP
CONVECTION.  THE CENTER IS STILL VISIBLE BUT UPPER LEVEL SHEAR
HAS TAKEN A TOLL ON THE SYSTEM.  A REMNANT LOW IS EXPECTED BY
1800 UTC MONDAY.  NO SIGNIFICANT CONVECTION IS NOTED ELSEWHERE
IN THE CARIBBEAN SEA.  IN THE UPPER LEVELS...AN ANTICYCLONIC
CIRCULATION IS OVER HISPANIOLA NEAR 18N70W.  ANTICYCLONIC FLOW
COVERS THE ENTIRE SEA.  STRONG SUBSIDENCE IS E OF 80W.  EXPECT
THE COLD FRONT TO EXTEND OVER THE NW CARIBBEAN WITH SOME
CONVECTION.

ATLANTIC...
LARGE ANTICYCLONIC CIRCULATION OVER HISPANIOLA 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 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 32N47W TO 27N54W 23N64W WITH ONLY ISOLATED SHOWERS NEAR THE
FRONT.  FARTHER E...A STRENGTHENING 1003 MB LOW IS NEAR 28N43W
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.

$$
FORMOSA


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