[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 181137
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
705 AM EST SAT NOV 18 2006

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHEASTERN
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...WEATHER OBSERVATIONS...RADAR...
AND METEOROLOGICAL ANALYSIS.

BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1115 UTC.

...TROPICAL WAVES...
A TROPICAL WAVE IS ALONG 54W S OF 16N MOVING W NEAR 10 KT. THE
WAVE IS INTERACTING WITH AN UPPER TROUGH THAT DIGS INTO THE DEEP
TROPICS ALONG 58W. SWLY WINDS AHEAD OF THE TROUGH ARE SHEARING
THE SHOWER ACTIVITY WELL TO THE E/NE OF THE WAVE. A 1011 MB
SURFACE LOW HAS DEVELOPED VERY CLOSE TO THE NORTHERN END OF THE
WAVE. LATEST NIGHT CHANNEL VIS IMAGERY SHOWS A WELL DEFINED
SWIRL OF LOW LEVEL CLOUDS NEAR 18N51W. WIDELY SCATTERED SHOWERS
ARE ASSOCIATED WITH THE WAVE...WHILE AN AREA OF SCATTERED
MODERATE CONVECTION IS JUST EAST OF THE LOW PRESSURE FROM
16N-20N BETWEEN 47W-51W. THIS LOW PRESSURE WILL MOVE MAINLY
NORTH DURING THE NEXT 12-24 HOURS.

A WEAK TROPICAL WAVE IS IN THE CENTRAL CARIBBEAN ALONG 72W S OF
18N MOVING W 10 TO 15 KT. THIS WAVE IS GENERATING A COUPLE OF
CLUSTERS OF MODERATE CONVECTION OVER WESTERN VENEZUELA. ONE OF
THEM IS OVER LAKE MARACAIBO. ISOLATED SHOWERS ARE ALSO SEEN OVER
HISPANIOLA AND THE COASTAL WATERS.

...THE ITCZ...
THE ITCZ AXIS IS CENTERED ALONG 10N14W 5N30W 6N40W 9N52W. THE
ITCZ IS PRETTY ACTIVE EARLY THIS MORNING WITH SCATTERED MODERATE
TO ISOLATED STRONG CONVECTION MAINLY NORTH OF THE AXIS...AND
FROM 4N-9N BETWEEN 20W-40W. SIMILAR CONVECTION IS ALSO FOUND
WITHIN 100 NM ON EITHER SIDE OF THE AXIS BETWEEN 48W-48W.

...DISCUSSION...
THE GULF OF MEXICO...
A BROAD DEEP LAYERED TROUGH EXTENDS ALONG THE EASTERN U.S./GULF
OF MEXICO NORTH OF 24N. THE BASE OF THE TROUGH REACHES SOUTH
FLORIDA. ABUNDANT UPPER LEVEL MOISTURE IS BEEN ADVECTED FROM
T.S. SERGIO AND THE ITCZ IN THE EPAC ACROSS SOUTHERN MEXICO AND
THE YUCATAN PENINSULA INTO CUBA AND THE BAHAMAS. THIS PLUME OF
MOISTURE IS SLOWLY SWEEPING SE CLEARING THE GULF. DRY AND STABLE
AIR ALOFT...RESULTING IN MODERATE TO STRONG SUBSIDENCE DOMINATES
MOST OF THE AREA WHERE COOL/DRY CONDITIONS WITH LIGHT LOW-LEVEL
WINDS PREVAIL. A 1019 MB SURFACE HIGH CENTERED OVER LOUISIANA
COVERS THE ENTIRE GULF. A REINFORCING FRONT WILL MOVE ACROSS THE
GULF ON SUNDAY FOLLOWED BY STRONG NLY WINDS AND BUILDING SEAS.
THESE WEATHER CONDITIONS ARE EXPECTED TO PERSIST THROUGH
TUESDAY. ON THIS DAY...THE GFS MODEL DEVELOPS A LOW PRESSURE
EAST OF FLORIDA. THE PRESSURE GRADIENT WILL TIGHTEN BETWEEN THIS
LOW AND THE HIGH PRESSURE OVER THE GULF...RESULTING IN STRONG
NLY WINDS OVER THE EASTERN GULF OF MEXICO...THE FLORIDA
PENINSULA AND THE NW CARIBBEAN.

THE CARIBBEAN SEA...
A BROAD UPPER RIDGE DOMINATES MOST OF THE CARIBBEAN WATERS AND
CENTRAL AMERICA FROM AN UPPER HIGH NOW LOCATED NEAR 13N79W. A
STATIONARY FRONT REMAINS OVER THE NW CARIBBEAN AND CENTRAL
CUBA/BAHAMAS GENERATING SCATTERED SHOWERS AND ISOLATED TSTMS. AN
AREA OF MODERATE TO ISOLATED STRONG CONVECTION HAS DEVELOPED
AHEAD OF THE FRONT AND VERY CLOSE TO THE CARIBBEAN PLAINS OF
COSTA RICA AND NICARAGUA. THIS CONVECTIVE ACTIVITY COVERS FROM
9N-17N BETWEEN 80W-84W. A DIFFLUENT PATTERN ALOFT IS ENHANCING
THIS SHOWER/TSTM ACTIVITY. THE REMAINDER OF THE BASIN IS QUIET
WITH STABLE AIR ALOFT...PARTICULARLY THE ERN CARIBBEAN. ONLY
SCATTERED SHOWERS ARE SEEN EMBEDDED IN THE TRADE WINDS. THE
STATIONARY FRONT WILL GRADUALLY WEAKEN TO A FRONTAL TROUGH. A
REINFORCING COLD FRONT MOVING THROUGH THE GULF OF MEXICO ON
SUNDAY WILL CAUSE WINDS TO INCREASE OVER THE WESTERN CARIBBEAN
MON THROUGH WED.

THE ATLANTIC OCEAN...
THE BASE OF A BROAD DEEP LAYERED TROUGH THAT LIES ACROSS THE
EASTERN U.S. EXTENDS ACROSS THE ERN GULF...THE STATE OF FLORIDA
AND THE FAR W ATLC. THE ASSOCIATED FRONTAL SYSTEM ENTERS THE
AREA NEAR 32N71W THEN CONTINUES SW ACROSS THE CENTRAL BAHAMAS
AND CUBA WHERE IT BECOMES STATIONARY. INSTABILITY ASSOCIATED
WITH THE FRONTAL BOUNDARY ALONG WITH A DIFFLUENT PATTERN ALOFT
ARE GENERATING PATCHES OF SCATTERED MODERATE CONVECTION WITHIN
80-100 NM AHEAD OF THE FRONT FROM 23N-29N. A NARROW UPPER RIDGE
EXTENDS FROM THE CARIBBEAN ACROSS CUBA AND THE BAHAMAS INTO THE
REMAINDER OF THE W ATLC TO 32N66W AND BEYOND. A LARGE CUT OFF
UPPER LOW IS EAST OF THE RIDGE NEAR 28N56W. AN UPPER TROUGH
EXTENDS SW FROM THIS LOW INTO THE DEEP TROPICS NEAR 11N-58W.
VERY DRY AIR LIES TO THE W AND S OF THE UPPER LOW EXTENDING
INTO THE ERN CARIBBEAN. A LARGE AREA OF SCATTERED SHOWERS AND
ISOLATED TSTMS EXISTS AHEAD OF THIS TROUGH FROM 20N-32N BETWEEN
45W-56W. A 1012 MB SURFACE LOW REMAINS NEAR 29N60W. ANOTHER
UPPER RIDGE EXTENDS NORTH FROM THE TROPICS ALONG 42W. THE FLOW
THEN BECOMES NEARLY ZONAL E OF 30W. A 1027 MB SURFACE HIGH
LOCATED WELL NORTH OF THE AREA EXTENDS A RIDGE OVER THE EASTERN
ATLC GIVING THE REGION MOSTLY FAIR WEATHER. AN UPPER LOW WITH
SOME SHOWERS IS APPROACHING THE MADEIRA/CANARY ISLANDS.

$$
GR





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