[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 281750
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
105 PM EST THU DEC 27 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1715 UTC

...THE ITCZ...

ITCZ AXIS IS CENTERED ALONG 7N10W 6N20W 4N30W 2N40W EQUATOR AT
47W INTO NE BRAZIL. SCATTERED MODERATE CONVECTION IS WITHIN 80
NM EITHER SIDE OF AXIS 29W-36W. CLUSTERS OF MODERATE CONVECTION
ARE N OF AXIS FROM 4N-7N BETWEEN 42W-52W. UPPER DIFFLUENCE IS
ENHANCING THIS CONVECTIVE ACTIVITY.

...DISCUSSION...

THE GULF OF MEXICO...
A NEW COLD FRONT HAS ENTERED THE NW CORNER OF THE GULF THIS
MORNING. AS OF 1500 UTC...THE FRONT STRETCHES ACROSS CENTRAL
LOUISIANA AND THE NW PORTION OF THE GULF TO NEAR TAMPICO MEXICO.
MOSAIC DOPPLER RADAR FROM THE SE U.S. REVEALS A NARROW LINE OF
SHOWERS WITH EMBEDDED TSTMS ASSOCIATED WITH THE FRONTAL
BOUNDARY. THIS FRONT WILL EXTEND FROM THE FLORIDA PANHANDLE TO
THE BAY OF CAMPECHE SATURDAY MORNING BEFORE BECOMING DIFFUSE AND
DISSIPATE SUN. IN THE MID AND UPPER LEVELS...A JETSTREAM CUTS
ACROSS THE REGION ADVECTING A PLUME OF MOISTURE FROM THE EPAC
ACROSS THE DEEP SOUTH TO SE U.S..AN UPPER TROUGH OVER THE
CENTRAL PLAINS IS SUPPORTING THE ABOVE MENTIONED COLD FRONT.
MODERATE RETURN FLOW IS SEEN AHEAD OF THE FRONT WHILE NLY WINDS
OF 20 TO 25 KT ARE BLOWING BEHIND THE FRONT. LOOKING AHEAD...A
STRONGER COLD FRONT IS IN STORE FOR THE BEGINNING OF THE NEW
YEAR. THIS FRONT IS EXPECTED TO MOVE RAPIDLY OFF THE TEXAS COAST
LATE MON AND EXTEND FROM THE FLORIDA PANHANDLE TO BAY OF
CAMPECHE EARLY TUE FOLLOWED BY STRONG NLY FLOW AND MUCH COOLER
TEMPERATURES. GALE FORCE WINDS ARE EXPECTED OVER THE WESTERN
GULF TUE AND PROBABLY WED WHEN THE COLD FRONT IS EXPECTED TO
MOVE ACROSS SOUTH FLORIDA.

THE CARIBBEAN SEA...
MORE OF THE SAME...THE CARIBBEAN REMAINS TYPICALLY TRANQUIL FOR
THIS TIME OF YEAR UNDER THE INFLUENCE OF A MID/UPPER-LEVEL RIDGE
WHICH IS PRODUCING STRONG SUBSIDENCE. THIS RIDGE...ANCHORED ON A
HIGH JUST SOUTH OF JAMAICA ALSO COVERS CENTRAL AMERICA AND
SOUTHERN MEXICO...INCLUDING THE YUCATAN PENINSULA/CHANNEL.
POCKETS OF LOW LEVEL MOISTURE WITH LIGHT TO MODERATE SHOWERS
ARE BEING CARRIED BY THE TRADE WINDS ACROSS THE BASIN...MORE
CONCENTRATED SOUTH OF PUERTO RICO AND HISPANIOLA. SCATTERED
MODERATE CONVECTION HAS DEVELOPED ACROSS THE SW CARIBBEAN DUE TO
SOME LOW-LEVEL CONVERGENCE...AIDED BY A DIFFLUENT PATTERN ALOFT.
THIS SHOWER ACTIVITY IS SPREADING OVER PARTS OF PANAMA...COSTA
RICA AND NICARAGUA. HIGH PRESSURE BUILDING N OF THE AREA WILL
MAINTAIN MODERATE TO STRONG TRADE WINDS ACROSS THE SEA THROUGH
MONDAY. THE GFS COMPUTER MODEL SHOWS ELY WINDS OF UP TO 30 KT
JUST OFF THE COLOMBIAN COAST SAT AND SUN.

THE ATLANTIC OCEAN...
HIGHLY AMPLIFIED DEEP LAYER RIDGE/TROUGH/RIDGE PATTERN EXISTS
ACROSS THE DISCUSSION AREA. THE W ATLC IS DOMINATED BY RIDGING
WITH THE MID AND UPPER AXIS EXTENDING NWD FROM THE CARIBBEAN
THROUGH BERMUDA. A SUBTROPICAL JETSTREAM IS RIDING ON THE N
PERIPHERY OF THIS ANTICYCLONE BRINGING SOME UPPER LEVEL
MOISTURE/HIGH CLOUDS. A DEEP LAYERED TROUGH REMAINS STUCK OVER
THE CENTRAL ATLANTIC EXTENDING SW FROM A CUT-OFF LOW NEAR 26N38W
TO JUST EAST OF THE WINDWARD ISLANDS. AT THE SURFACE...A 1011 MB
LOW CONTINUES TO MEANDER NEAR 26N38W WITH A TROUGH EXTENDING S
THEN SW TO NEAR TRINIDAD AND TOBAGO. A ROPE CLOUD DEFINES THIS
TROUGH ON VIS SAT IMAGERY. A QUIKSCAT PASS FROM AROUND 1200 UTC
SHOWED VERY CLEAR THE CYCLONIC CIRCULATION. SCATTERED MODERATE
CONVECTION IS WITHIN 120 NM N OF THE LOW CENTER AND WITHIN 75 NM
AHEAD OF THE TROUGH N OF 24N. A COUPLE OF 1026 MB HIGHS CENTERED
NEAR 34N71W AND 30N57W ARE DOMINATING THE AREA W OF 50W. THE FAR
E ATLC IS ALSO DOMINATED BY RIDGING ANCHORED ON A HIGH OVER THE
IBERIAN PENINSULA. HOWEVER...THERE IS QUITE A BIT MORE
CLOUDINESS WITH EMBEDDED SHOWERS IN THIS AREA DUE TO AN UPPER
JET CROSSING THE AREA. THIS JETSTREAM LIES SE OF THE
AFOREMENTIONED UPPER TROUGH.

$$
GR


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