[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 281739
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
105 PM EST FRI NOV 28 2008

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHERN SECTIONS
OF SOUTH AMERICA...AND 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.

...THE ITCZ...
THE ITCZ AXIS IS ANALYZED ALONG 6N11W 3N25W 5N40W 8N48W 6N58W. A
SURFACE TROUGH IS EMBEDDED WITHIN THE ITCZ AND EXTENDS FROM
13N47W TO 8N50W. SCATTERED MODERATE CONVECTION IS OCCURRING
WITHIN 120 NM WEST SIDE OF THIS SURFACE TROUGH BETWEEN 10N-12N.
ELSEWHERE...SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS
WITHIN 70 NM EITHER SIDE OF THE ITCZ AXIS BETWEEN 20W-37W.
SCATTERED MODERATE CONVECTION IS FROM 5N-10N BETWEEN 30W-37W.

...DISCUSSION...

GULF OF MEXICO...
AS OF 1500 UTC...THE GULF REMAINS UNDER THE INFLUENCE OF A
SURFACE RIDGE ANCHORED ON A 1021 MB HIGH LOCATED OVER CENTRAL
FLORIDA JUST N OF LAKE OKEECHOBEE. THIS FEATURE IS PRODUCING
MOSTLY FAIR WEATHER OVER THE ENTIRE REGION. SLY RETURN FLOW HAS
DEVELOPED OVER THE WESTERN GULF AS THIS SFC HIGH CONTINUES TO
MOVED EWD. ALOFT...AN UPPER LEVEL RIDGE COVERS THE AREA WITH
STRONG UPPER LEVEL WINDS ACROSS THE NORTHERN PERIPHERY OF THE
RIDGE OVER THE SE CONUS AND N GULF WATERS. UPPER LEVEL MOISTURE
CONTINUES STREAMING ACROSS THE N GULF...WHILE MODERATE TO STRONG
SUBSIDENCE IS PRESENT OVER THE S GULF. LOOKING AHEAD...A STRONG
COLD FRONT IS FORECAST TO MOVE OUT OF THE TEXAS COAST SATURDAY
MORNING...AND WILL EXTEND FROM THE FLORIDA PANHANDLE TO THE BAY
OF CAMPECHE SUNDAY AFTERNOON. WINDS ARE EXPECTED TO INCREASE ON
EITHER SIDE OF THE FRONT...REACHING NEAR GALE FORCE. IN THE WAKE
OF THE FRONT A RELATIVELY COOLER AND DRIER AIR MASS WILL INVADE
THE GULF WITH N TO NW SURFACE WINDS. TRANQUIL WEATHER CONDITIONS
ARE IN PLACE OVER SOUTH FLORIDA WHERE A VERY STABLE ATMOSPHERE
PREVAILS...BUT CHANGES ARE IN STORE FOR SUNDAY AS THE COLD FRONT
APPROACHES THE AREA. THE RISK OF TSTMS IS ALREADY IN THE
FORECAST DUE TO INCREASING MOISTURE WITH SWLY WINDS ALOFT.

CARIBBEAN SEA...
IN THE SW CARIBBEAN...A 1010 MB SURFACE LOW IS CENTERED N OF
PANAMA NEAR 10N78W. THE CLOUD PATTERN IS EXHIBITING THE CYCLONIC
CIRCULATION ASSOCIATED WITH THIS LOW. NLY WINDS ON THE WEST SIDE
OF THE LOW ARE ADVECTING LOW LEVEL MOISTURE WITH EMBEDDED
SHOWERS INTO WESTERN PANAMA AND COSTA RICA...WHILE CONVECTION IS
ON INCREASE ACROSS THE PACIFIC SIDE OF THESE COUNTRIES DUE TO
THE CLOSE PROXIMITY OF THE EPAC ITCZ. THE TAIL END OF AN OLD
FRONTAL BOUNDARY...ANALYZED AS A SURFACE TROUGH OVER THE
TROPICAL CENTRAL ATLC...IS PRODUCING SCATTERED SHOWERS OVER THE
SOUTHERN WINDWARD ISLANDS AND THE FAR NE OF VENEZUELA. PATCHES
OF LOW LEVEL MOISTURE EMBEDDED IN THE TRADE WIND FLOW ARE NOTED
ACROSS THE REMAINDER OF THE BASIN...MORE CONCENTRATED JUST SOUTH
OF HISPANIOLA AND NEAR CABO GRACIAS A DIOS NICARAGUA. SIMILAR
CLOUDINESS IS ALSO AFFECTING THE ABC ISLANDS...AND THE ISLANDS
LOCATED JUST OFFSHORE VENEZUELA. IN THE UPPER LEVELS...A MAINLY
ZONAL FLOW DOMINATES THE REGION. THE SURFACE RIDGE N OF THE AREA
WILL SHIFT E AND SLOWLY WEAKEN...ALLOWING TRADEWINDS TO DECREASE
ACROSS MUCH OF THE BASIN DURING THE UPCOMING WEEKEND. ON THE
OTHER HAND...SE TO S WINDS WILL INCREASE OVER THE NW CARIBBEAN
BEGINNING ON SUN IN ADVANCE OF A GULF OF MEXICO COLD FRONT
EXPECTED TO REACH WESTERN CUBA AND THE NW CARIBBEAN EARLY MON
MORNING. NW WINDS OF 15-20 KT WILL FOLLOW THE FRONT...KEEPING
TEMPERATES ACROSS CUBA ON THE COOL SIDE.

ATLANTIC OCEAN...
SURFACE HIGH PRES CENTERED OVER CENTRAL FLORIDA EXTENDS A RIDGE
OVER THE W ATLC AND THE BAHAMAS PRODUCING MOSTLY FAIR WEATHER. A
WEAKENING COLD FRONT ENTERS THE REGION NEAR 31N54W THEN
CONTINUES SW TO NEAR 23N67W. ISOLATED SHOWERS ARE WITHIN 30 NM
OF THE FRONT. A 1001 MB LOW CONTINUES TO SPIN OVER THE CENTRAL
ATLANTIC AND IS CURRENTLY CENTERED NORTH OF AREA NEAR 32N37W.
THIS LOW IS ACCOMPANIED BY SHOWERS AND SQUALLS...AND THE CLOUD
PATTERN IS EXHIBITING SOME SUBTROPICAL-LIKE CHARACTERISTICS.
THIS SYSTEM IS MOVING NORTHWARD OVER COOLER WATERS AND FURTHER
DEVELOPMENT IS NOT ANTICIPATED. A SFC TROUGH EXTENDS FROM THIS
LOW INTO THE FORECAST AREA ALONG 31N32W 29N29W 25N26W. AN AREA
OF SHOWERS WITH EMBEDDED TSTMS IS WITHIN 120 NM AHEAD OF THIS
TROUGH N OF 26N. ANOTHER SURFACE TROUGH...REMNANTS OF AN OLD
FRONTAL BOUNDARY...RUNS FROM 18N42W TO 9N60W AND IS GENERATING
SOME SHOWER ACTIVITY OVER THE SOUTHERN WINDWARD ISLANDS. THE E
ATLC IS UNDER THE INFLUENCE OF A SURFACE RIDGE CENTERED WELL N
OF THE DISCUSSION AREA. IN THE UPPER LEVELS...A RIDGE DOMINATES
MUCH OF THE W ATLC. A DEEP LAYERED TROUGH LIES ALONG 62W WITH
THE BASE OF THE TROUGH REACHING THE NE CARIBBEAN. A JET STREAM
BRANCH WITH CORE WINDS OF AROUND 90 KT ROUNDS THE BASE OF THIS
TROUGH WHICH IS SUPPORTING THE AFOREMENTIONED WEAKENING COLD
FRONT. A CUT-OFF LOW REMAINS NEAR 32N40W. AN UPPER-LEVEL RIDGE
CENTERED NEAR 8N38W DOMINATES THE TROPICS AND IS HELPING TO
INDUCE CONVECTION ALONG THE ITCZ AXIS.

$$
GR





This weather bulletin was brought to you by:
www.nashvilleweather.net