[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 212359
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
705 PM EST THU DEC 21 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...
METEOROLOGICAL ANALYSIS...WEATHER OBSERVATIONS...AND RADAR.

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2330 UTC.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 6N10W 4N30W 6N47W 4N54W. SCATTERED
MODERATE CONVECTION FROM 3N TO 7N BETWEEN 37W AND 47W.

...DISCUSSION...
GULF OF MEXICO...
DYNAMIC WEATHER PATTERN CONTINUES OVER THE NW GULF THIS
AFTERNOON. BROAD UPPER TROUGH EXTENDS FROM A CUTOFF UPPER LOW
OVER KANSAS TO SOUTHERN BAJA. AHEAD OF THIS TROUGH...UPPER AIR
ANALYSIS SHOWS RIGHT FRONT QUADRANT OF A 120 KT SW JET NOSING
INTO THE NW GULF WATERS FROM CENTRAL MEXICO...ACCOMPANIED BY
ABUNDANT DEEP LAYER MOISTURE. AT THE SURFACE...A 1013 MB LOW IS
EMERGING OFF THE S TEXAS COAST BETWEEN BRO AND CRP...WITH A
STATIONARY BOUNDARY EXTENDING TO THE NE TOWARD LCH. THESE
FACTORS ARE SUPPORTING WIDESPREAD THUNDERSTORM ACTIVITY ACROSS
THE NW GULF AS EVIDENCED BY AREAS RADAR IMAGERY...FROM S TEXAS
TO COASTAL ALABAMA. ELSEWHERE OVER THE GULF W OF 85W ONLY
SCATTERED CIRRUS DECKS ARE EVIDENT ON VISIBLE IMAGERY UNDER
FLATTENING UPPER RIDGE AXIS OVER THE CENTRAL GULF. OVER THE
EASTERN GULF...UPPER TROUGH EXTENDS ALONG 82W...AIDING WEAK
SHOWER DEVELOPMENT NEAR 26N85W. AT THE SURFACE...BUOY AND SHIP
OBSERVATIONS SHOW MODERATE TO FRESH SE FLOW ACROSS THE GULF ON
THE PERIPHERY OF 1030 MB HIGH PRES CENTERED OVER THE CAROLINAS.
SLIGHTLY STRONGER E TO SE WINDS ARE EVIDENT IN THE STRAITS OF
FLORIDA...AT THE BASE OF THE HIGH PRES. LOOKING AHEAD...THE
FRONT WILL SHIFT E AND STALL FROM THE FLORIDA BIG BEND TO
MATAMOROS MEXICO BY SAT. MEANWHILE A REINFORCING SHORT WAVE WILL
PUSH DOWN THE ROCKIES THROUGH SAT...AND INTO THE NW GULF BY LATE
SAT. WINDS WILL INCREASE OVER THE WESTERN GULF TO GALE FORCE
BEHIND THE SECOND FRONT.

CARIBBEAN SEA...
SURFACE OBSERVATIONS ARE SHOWING FRESH ELY TRADES ACROSS THE
CARIBBEAN E OF 80W...WITH MODERATE SE WINDS OVER THE NW
CARIBBEAN...AND LIGHT ELY NEAR THE CENTRAL AMERICAN COAST.
ALOFT...UPPER TROUGH EXTENDS FROM CENTRAL CUBA TO WESTERN
PANAMA. WEAK CONVECTION IS EVIDENT ON VISIBLE IMAGERY UNDER THE
TROUGH AXIS N OF 12N...LIKELY AIDED BY MODEST LOW LEVEL SPEED
CONVERGENCE ACROSS THE CARIBBEAN. OTHERWISE DRY MID AND UPPER
LEVEL AIR IS ADVECTING SWD ON THE W SIDE OF THE TROUGH...KEEPING
FAIRLY STABLE CONDITIONS IN PLACE ACROSS THE BASIN. UPPER LEVEL
ISOTACH ANALYSIS SHOWS 50 TO 60 KT SWLY FLOW ALOFT FROM EASTERN
PANAMA TO THE LEEWARD ISLANDS...BETWEEN THE TROUGH TO THE NW AND
A PERSISTENT UPPER RIDGE CENTERED OVER SOUTHERN
GUYANA...BRINGING SCATTERED CIRRUS DECKS ACROSS THE EASTERN
CARIBBEAN. FORECAST CALLS FOR FRESH TO STRONG ELY WINDS OVER THE
EASTERN CARIBBEAN THIS WEEKEND AS HIGH PRES BUILDS TO THE N. A
COLD FRONT WILL PENETRATE TROUGH THE YUCATAN CHANNEL AND INTO
THE NW CARIBBEAN EARLY NEXT WEEK...FOLLOWED BY FRESH TO STRONG
NLY WINDS.

ATLANTIC OCEAN...
WATER VAPOR IMAGERY SHOWS SOMEWHAT AMPLIFIED UPPER AIR PATTERN
ACROSS THE SUBTROPICAL ATLC. UPPER TROUGH IS EVIDENT FROM 32N48W
TO 23N60W...AHEAD OF A FLAT UPPER RIDGE EMERGING OFF THE U.S.
SOUTHEAST COAST N OF THE BAHAMAS. LIGHT CONVECTION IS EVIDENT ON
THE DIVERGENT E SIDE OF THE UPPER TROUGH FROM 25N TO 32N BETWEEN
43W AND 49W...ALONG A SURFACE FRONT THAT EXTENDS FROM 32N41W TO
A 1019 MB LOW PRES AREA NEAR 25N53W. A SURFACE TROUGH EXTENDS
FROM THE LOW SW TO 21N63W. S OF THE RIDGE...A WEAK UPPER TROUGH
AND LOW LEVEL SPEED CONVERGENCE DUE TO FRESH TO STRONG ELY
TRADES ARE PROMOTING SCATTERED LIGHT TO MODERATE CONVECTION OVER
THE SOUTHERN BAHAMAS AND TURKS AND CAICOS ISLANDS. THE TRADE
WINDS ARE ON THE SOUTHERN PERIPHERY OF 1030 MB SURFACE HIGH PRES
N OF THE AREA. FURTHER E...FAIRLY STABLE CONDITIONS PERSIST
UNDER AN UPPER RIDGE AXIS CENTERED ALONG 28W...WITH AN
ASSOCIATED 1024 MB SURFACE HIGH AHEAD OF THE FRONT. AN
STATIONARY UPPER TROUGH REMAINS E OF THE RIDGE FROM CENTRAL
SPAIN TO 21N20W. AN ASSOCIATED WEAKENING 1018 MB SURFACE LOW
REMAINS CENTERED W OF THE CAPE VERDE ISLANDS NEAR 27N27N.
MEANWHILE THE TROPICAL ATLC S OF 20N...AFTERNOON QUIKSCAT DATA
SHOW GENERALLY MODERATE NELY TRADE FLOW ACROSS THE ATLC.
ALOFT...UPPER RIDGE REMAIN IN PLACE FROM GUYANA EWD ALONG 3N TO
15W. WLY UPPER LEVEL WINDS OF 50 TO 60 KT PERSIST N OF THE RIDGE
AXIS. THE RIDGING IS ENHANCING CONVECTION ALONG THE ITCZ W OF
37W.

$$
CHRISTENSEN




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