[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 132359
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
705 PM EST THU DEC 13 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2315 UTC

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 8N13W 5N25W 3N40W EQUATOR AT 50W.
SCATTERED MODERATE CONVECTION IS WITHIN 140 NM NORTH OF AXIS
BETWEEN 25W-32W...AND WITHIN 100 NM EITHER SIDE OF AXIS BETWEEN
18W-22W.

DISCUSSION...
GULF OF MEXICO...
A SLOW MOVING COLD FRONT TRAILS FROM SE LOUISIANA TO NEAR
TAMPICO MEXICO THEN CONTINUES AS A STATIONARY FRONT ALONG THE E
SLOPES OF THE SIERRA MADRE MOUNTAINS. CONSIDERABLY COOLER AND
DRIER AIR IS FILTERING IN BEHIND THE FRONT. A NARROW LINE OF
SCATTERED SHOWERS MARKS THE LEADING EDGE OF THIS COOLER AIR
MASS. THE COLD FRONT WILL STALL OVER THE CENTRAL GULF WATERS
BRIEFLY TONIGHT THEN MOVE NORTH AS A WARM FRONT FRI IN ADVANCE
OF A STRONGER COLD FRONT THAT IS FORECAST TO MOVE ACROSS THE
GULF ON SATURDAY BRINGING A NOTICEABLE INCREASE IN WINDS AND
SEAS. AS OF 2100 UTC...A 1020 MB HIGH WAS ANALYZED OVER THE NE
CORNER OF THE GULF EXTENDING A RIDGE OVER THE REMAINDER OF TH
GULF INCLUDING THE YUCATAN PENINSULA. MOISTURE ASSOCIATED WITH
THE REMNANTS OF T.D. OLGA IS ALREADY AFFECTING THE SE PORTION OF
THE GULF AND THE FLORIDA KEYS. MOSAIC DOPPLER RADAR FROM THE SE
U.S. SHOWS SCATTERED SHOWERS WITH EMBEDDED TSTMS OVER THIS AREA.
A BAND OF SHOWERS WITH A FEW TSTMS IS ALSO SEEN OVER THE FLORIDA
PANHANDLE AND SE LOUISIANA. ALOFT...A RIDGE IS SLOW MOVING EWD
ACROSS THE EASTERN PORTION OF THE GULF WHILE SWLY WINDS AHEAD OF
A CUT-OFF LOW LOCATED OVER THE SW U.S./NW MEXICO ARE INVADING
THE WESTERN HALF OF THE GULF. THESE WINDS ARE TRANSPORTING
ABUNDANT UPPER LEVEL MOISTURE FROM THE EPAC THROUGH MEXICO INTO
THE GULF.

CARIBBEAN SEA...
THE REMNANT LOW OF T.D. OLGA CONTINUES TO SPIN ACROSS THE
CARIBBEAN SEA BETWEEN THE ISLE OF YOUTH CUBA AND THE CAYMAN
ISLANDS. AS OF 2100 UTC...A 1010 MB LOW WAS ANALYZED NEAR
19.5N81.5W. THE LAST FEW VIS SATELLITE IMAGERY FOR THE DAY SHOWS
VERY CLEAR THE LOW LEVEL CYCLONIC CIRCULATION...BUT CONVECTION
IS CONFINED TO A FEW SMALL BANDS N AND NE OF THE CENTER.
MOISTURE ASSOCIATED WITH THIS LOW EXTENDS NWD REACHING SOUTH
FLORIDA WHERE IS GENERATING SOME SHOWER ACTIVITY. LIGHTNING DATA
DEPICTS SCATTERED TSTMS OVER CENTRAL CUBA WHILE SOME SHOWER
ACTIVITY IS ALSO OBSERVED EAST OF JAMAICA. THE CAYMAN ISLANDS
ARE REPORTING MAINLY LIGHT SHOWERS AND SUSTAINED WINDS UP TO 22
KT. THIS LOW...REMNANTS OF OLGA IS EXPECTED TO CONTINUE TO MOVE
WWD AND WILL PROBABLY BE ABSORBED BY AN APPROACHING COLD FRONT
ENTERING THE NW CARIBBEAN EARLY SUN. ELSEWHERE...FRAGMENTS OF
LOW LEVEL MOISTURE ARE MOVING ACROSS THE LEEWARD ISLANDS INTO
THE UK/US VIRGIN ISLANDS AND PUERTO RICO UNDER THE TRADE WIND
FLOW. THE SAN JUAN DOPPLER RADAR REVEALS SCATTERED SHOWERS AND
ISOLATED TSTMS OVER THOSE ISLANDS AND THE SURROUNDING COASTAL
WATERS. ALOFT...A RIDGE DOMINATES MOST THE WEST AND CENTRAL
CARIBBEAN WITH AN UPPER TROUGH ENTERING THE EASTERN PORTION OF
THE BASIN FROM THE CENTRAL ATLC.

ATLANTIC OCEAN...
BANDS OF SHOWERS/TSTMS...ASSOCIATED WITH THE REMNANTS OF T.D.
OLGA...ARE AFFECTING THE STRAITS OF FLORIDA...THE FLORIDA KEYS
AND SOUTH FLORIDA. DOPPLER RADAR DATA DEPICTS THE STRONGEST
TSTMS MOVING WWD ACROSS THE UPPER/MIDDLE KEYS. AN INVERTED
TROUGH EXTENDS NWD FROM THE REMNANTS OF OLGA TO SOUTH-CENTRAL
FLORIDA. THIS TROUGH WILL CONTINUE TO MOVE WWD IN TANDEM WITH
THE 1010 MB SFC LOW...REMNANTS OF OLGA...LOCATED OVER THE
CARIBBEAN SEA. THE REMAINDER OF THE DISCUSSION AREA IS DOMINATED
BY MODERATE TO STRONG SFC RIDGING SUPPORTED BY A 1026 MB HIGH
CENTERED SE OF BERMUDA NEAR 29N61W. THERE IS A SLIGHT WEAKNESS
IN THE RIDGE DUE TO THE PRESENCE OF A SFC TROUGH THAT EXTENDS
FROM 31N33W TO 25N42W AND A LARGE INVERTED TROUGH NEAR THE
MADEIRA AND CANARY ISLANDS. PATCHES OF MAINLY LOW LEVEL CLOUDS
ARE ASSOCIATED WITH THESE TROUGHS. AN AREA OF MODERATE
CONVECTION REMAINS BETWEEN THE WINDWARD ISLANDS AND THE N COAST
OF SOUTH AMERICA COVERING FROM 6N-11N BETWEEN 55W-61W. A
DIFFLUENT PATTERN ALOFT IS HELPING TO INDUCE THIS SHOWER/TSTM
ACTIVITY THAT IS ALSO FOUND OVER THE GUYANAS. THE MID AND UPPER
PATTERN CONSISTS OF A LONGWAVE RIDGE/TROUGH N OF 16N WITH A
SERIES OF EMBEDDED SHORTWAVES E OF ABOUT 50W. IN THE DEEP
TROPICS...THE FLOW ALOFT IS FAIRLY ZONAL AND QUITE STRONG. A
JETSTREAM BRANCH WITH CORE WINDS OF 70-90 KT CROSS JUST N OF THE
CAPE VERDE ISLANDS.

$$
GR


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