[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 201753
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
105 PM EST TUE NOV 20 2007

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHERN
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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1715 UTC.

...TROPICAL WAVES...
TROPICAL WAVE IS ALONG 80W S OF 19N MOVING W 15-20 KT. CLUSTERS
OF MODERATE TO ISOLATED STRONG CONVECTION ARE OVER THE SW
CARIBBEAN SOUTH OF 15N AND JUST W OF THE WAVE AXIS. THIS
ACTIVITY IS AFFECTING THE CARIBBEAN PLAINS OF NICARAGUA. DEEP
LOW LEVEL CONVERGENT FLOW AND UPPER DIFFLUENCE ARE ALSO
ENHANCING THIS CONVECTIVE ACTIVITY.

TROPICAL WAVE IS ALONG 93/94W S OF 21N MOVING W 10-15 KT. THE
WAVE IS MOVING ACROSS THE BAY OF CAMPECHE AND THE ISTHMUS OF
TEHUANTEPEC GENERATING SOME CLOUDINESS WITH MAINLY LIGHT
SHOWERS. THE MIMIC-TPW SHOWS A SMALL SURGE OF MOISTURE OVER THE
BAY OF CAMPECHE INDICATING THE PRESENCE OF THIS FEATURE.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 10N14W 8N30W 9N40W 7N60W. SCATTERED
MODERATE/STRONG CONVECTION ARE WITHIN 140 NM N OF AXIS BETWEEN
32W-37W. THIS ACTIVITY IS ALSO AHEAD OF A SFC TROUGH ANALYZED
ALONG 31W/32W ON THE 1200 UTC SURFACE MAP. UPPER DIFFLUENCE IS
HELPING TO INDUCE THIS SHOWER/TSTM ACTIVITY.

DISCUSSION...

GULF OF MEXICO...
A CUT-OFF CYCLONIC CIRCULATION IS CENTERED OVER THE NW PORTION
OF MEXICO COVERING NORTH-CENTRAL MEXICO AND SOUTHERN TEXAS. A
PLUME OF MID/UPPER LEVEL MOISTURE IS S AND SE OF THE CUT OFF LOW
CROSSING CENTRAL MEXICO INTO THE GULF. THIS PLUME OF MOISTURE IS
ASSOCIATED WITH A JETSTREAM BRANCH. SATELLITE DERIVED WINDS
INDICATED CORE SPEEDS OF AROUND 80 KT. BROAD UPPER RIDGE
DOMINATES THE GULF AND THE SE U.S.. A SURFACE RIDGE REMAINS OVER
THE GULF ANCHORED OVER GEORGIA/THE CAROLINAS BY A 1025 MB HIGH.
PATCHES OF LOW LEVEL CLOUDS WITH ISOLATED SHOWERS DOTS THE
ENTIRE REGION. THE NEXT COLD FRONT IS EXPECTED TO ENTER THE GULF
ON THU BRINGING AN INCREASE IN SHOWER ACTIVITY AND GUSTY WINDS.

CARIBBEAN SEA...
CLUSTERS OF MODERATE TO STRONG CONVECTION ARE CONCENTRATED OVER
THE SW CARIBBEAN DUE TO SEVERAL FACTORS. SEE THE TROPICAL WAVE
SECTION FOR DETAILS. A DISSIPATING FRONTAL TROUGH FROM THE
CENTRAL ATLC ENTERS THE NE CARIBBEAN THROUGH THE LEEWARD ISLANDS
EXTENDING EAST TO WEST JUST SOUTH OF PUERTO RICO AND HISPANIOLA.
PATCHES OF LOW/MID CLOUDS WITH EMBEDDED SHOWERS ARE OVER THOSE
ISLANDS. CURRENTLY...THE SAN JUAN DOPPLER RADAR INDICATES THAT
THE SHOWER ACTIVITY IS MAINLY OVER THE COASTAL WATERS. SAN JUAN
REPORTED 24 HOURS RAINFALL AMOUNT OF 1.02 INCHES THIS MORNING. A
DIFFERENCE IN PRES BETWEEN THE COLOMBIAN LOW AND HIGH PRES N OF
AREA IS PRODUCING BRISK TRADE WINDS OF 20 TO 25 KT OVER MUCH OF
THE BASIN. AN EARLIER QUIKSCAT PASS CONFIRMED THESE WINDS. BROAD
UPPER-LEVEL RIDGE COVERS THE AREA ANCHORED ON AN UPPER HIGH OVER
SOUTH AMERICA. THE ITCZ AXIS EXTENDS ACROSS SOUTH AMERICA AND
PANAMA INTO THE E PACIFIC REGION ENHANCING SCATTERED SHOWERS AND
ISOLATED THUNDERSTORMS PARTICULARLY OVER E PANAMA AND THE
PACIFIC COAST OF COLOMBIA. DEBRIS MOISTURE FROM THIS CONVECTION
EXTENDS EWD ACROSS THE ABC ISLANDS.

ATLANTIC OCEAN...
SATELLITE LOOPS INDICATE THAT A COLD FRONT IS PUSHING SOUTH AND
SE ACROSS THE W ATLC AND THE BAHAMAS. THE FRONT EXTENDS ALONG
32N60W 27N66W 25N75W. AN EARLIER QUIKSCAT PASS AND SURFACE
OBSERVATIONS INDICATED NEAR GALE FORCE WINDS BEHIND THE FRONT. A
BAND OF MULTILAYERED CLOUDS WITH EMBEDDED SHOWERS IS N OF 27N
WITHIN 200 NM AHEAD OF THIS FRONTAL SYSTEM. LIGHTNING DATA ALSO
DEPICTS ISOLATED TSTM IN ASSOCIATION WITH THIS BAND. ANOTHER DRY
COLD FRONT WILL ENTER THE DISCUSSION AREA TONIGHT. AHEAD OF
THESE FRONTAL BOUNDARIES...THERE IS A DISSIPATING FRONTAL TROUGH
EXTENDING OVER THE CENTRAL ATLC AND THE NE CARIBBEAN. FURTHER
EAST...A WEAK 1018 MB HIGH CENTERED N OF THE CAPE VERDE ISLANDS
NEAR 20N25W DOMINATES THE E ATLC. AN ASCAT PASS FROM THIS
MORNING SHOWED VERY WELL THE ANTICYCLONE CIRCULATION. ALOFT...AN
UPPER TROUGH EXTENDS OVER THE W ATLC AND THE CENTRAL BAHAMAS
SUPPORTING THE ABOVE MENTIONED COLD FRONTS. DRY AIR IS ALONG THE
TROUGH AXIS N OF 24N WEST OF 68W...INCLUDING N-CENTRAL FLORIDA.
POCKETS OF LOW/MID CLOUDS WITH SCATTERED SHOWERS AND ISOLATED
TSTMS ARE BETWEEN SOUTH FLORIDA AND WEST-CENTRAL CUBA. BROAD
UPPER RIDGE WITH AXIS EXTENDING NWD ALONG 50W DOMINATES THE
CENTRAL ATLC. BROAD UPPER TROUGH COVERS THE REMAINDER OF THE
ATLC N OF 20N E OF 45W.

$$
GR




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