[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 202320
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
705 PM EST WED DEC 20 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
2300 UTC.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 6N10W 4N48W 3N53W. SCATTERED
MODERATE CONVECTION FROM 2N TO 5N BETWEEN 38W AND 47W.

...DISCUSSION...
GULF OF MEXICO...
SHORT WAVE TROUGH IS ENTERING THE WESTERN GULF OF MEXICO W OF
93W...ROUNDING THE BASE OF A STRONG UPPER LOW PRES SYSTEM
CENTERED OVER ERN COLORADO. COPIOUS MID AND UPPER LEVEL MOISTURE
CONTINUES TO STREAM FROM S TO N AHEAD OF THE TROUGH BETWEEN 87W
AND 94W. AN UPPER LEVEL RIDGE CENTERED OVER S FLORIDA REMAINS IN
PLACE OVER THE ERN GULF...AND MAINTAINING GENERALLY DRY AND
STABLE CONDITIONS IN THE MID AND UPPER LEVELS E OF 87W. AT THE
SURFACE...A COLD FRONT IS MOVING E TOWARD THE TEXAS COAST...AND
SHOULD PUSH INTO THE WESTERN GULF WATERS LATE TONIGHT. BUOYS AND
SHIP OBSERVATIONS REPORT MODERATE TO FRESH E TO SE WINDS E OF
90W ON THE PERIPHERY OF HIGH PRES CENTERED OVER THE MID ATLC
STATES. MODERATE TO FRESH SLY WINDS ARE EVIDENT W OF 90W AHEAD
OF A 1008 MB LOW PRES CENTER OVER NE MEXICO. MOIST SWLY FLOW
AHEAD OF THE SHORT WAVE IS RIDING OVER WEDGE OF HIGH PRES OVER
SE UNITED STATES...PROVIDING ENOUGH ISENTROPIC LIFT TO ALLOW
SCATTERED SHOWERS AND A FEW THUNDERSTORMS OVER MISSISSIPPI DELTA
AREA AND ADJACENT COASTAL WATERS N OF 27N. THE FRONT WILL STALL
OVER THE CENTRAL GULF ON FRI...FOLLOWED BY A STRONGER
REINFORCING SHOT THIS WEEKEND IN RESPONSE TO ANOTHER SHORT WAVE
TROUGH PUSHING DOWN THE FRONT RANGE OF THE ROCKIES. ALTHOUGH
THERE IS STILL SOME UNCERTAINTY IN TIMING AND INTENSITY...THE
STRONGER PUNCH BRING GALE FORCE WINDS TO GULF WATERS THIS
WEEKEND.

CARIBBEAN SEA...
AN UPPER LEVEL LOW PRES SYSTEM IS CENTERED NEAR 19N80W...JUST W
OF JAMAICA. UPPER LEVEL DIFFLUENCE IS PROMOTING SCATTERED
CONVECTION BETWEEN JAMAICA AND HAITI AND TO A LESSER EXTENT OVER
EASTERN CUBA AND THE WINDWARD PASSAGE. DRY MID AND UPPER AIR
CONTINUES TO ADVECT SWD ON THE W SIDE OF THE UPPER LOW...KEEPING
GENERALLY STABLE CONDITIONS OVER THE REMAIN OF THE CARIBBEAN
BASIN...WITH SWLY UPPER FLOW PREVAILING ACROSS THE BASIN S OF
THE LOW. SURFACE OBSERVATIONS SHOW GENERALLY LIGHT TO MODERATE
ELY FLOW ACROSS THE CARIBBEAN...AT THE BASE OF HIGH PRES TO THE
N. THIS FLOW WILL INCREASE AS HIGH PRES BUILDS TO THE N OVER THE
NEXT COUPLE OF DAYS. MEANWHILE THE UPPER LOW WILL OPEN INTO A
TROUGH AND SHIFT NE OF HISPANIOLA BY THIS WEEKEND...AS UPPER
RIDGE BUILDS OVER THE WESTERN GULF.

ATLANTIC OCEAN...
UPPER LOW REMAINS CENTERED W OF CAPE VERDE ISLANDS NEAR 28N23W
WITH ASSOCIATED 1016 MB SURFACE LOW REMAINING STATIONARY AND
WEAKENING. W OF THIS...DEEP LAYER RIDGE WITH 1023 MB SURFACE
PRES IS CENTERED NEAR 31N39W. AN UPPER TROUGH EXTENDS FROM
27N64W TO THE SOUTHERN BAHAMAS NEAR 23N72W. SOME EVIDENCE OF A
SURFACE REFLECTION OF THIS EXTENDING FROM 22N67W TO 28N56W.
SCATTERED MODERATE CONVECTION IS EVIDENT WITHIN 180 NM SE OF THE
SURFACE TROUGH. N OF THIS...SATELLITE IMAGERY AND SHIP
OBSERVATIONS SHOW NLY SURGE WITH AN APPROACHING COLD FRONT
EXTENDING FROM 30N59W TO 29N71W THEN BECOMING STATIONARY TO THE
GEORGIA COAST. FRESH TO STRONG N TO NE WINDS FOLLOW BEHIND THE
FRONT...BUT WILL DIMINISH THIS WEEKEND AHEAD OF ANOTHER FRONT
EMERGING OFF THE COAST. MEANWHILE...MODERATE TO FRESH ELY
SURFACE FLOW PERSISTS OVER THE TROPICAL ATLC S OF 20N...AT THE
BASE OF THE RIDGE OVER THE CENTRAL ATLC. THIS WILL DIMINISH
BRIEFLY ON THU AS THE RIDGE WEAKENS AHEAD OF THE COLD FRONT
PUSHING E...BUT WILL INCREASE AGAIN FRI INTO THE WEEKEND AS HIGH
PRES STRENGTHENS. FURTHER S...UPPER RIDGE CENTERED NEAR 4N41W IS
ENHANCING SCATTERED CONVECTION ALONG THE ITCZ W OF 38W.

$$
CHRISTENSEN


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