[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 271743
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 7N12W 3N25W 2N35W EQUATOR AT 49W...
INTO NE BRAZIL. WIDELY SCATTERED MODERATE CONVECTION IS WITHIN
80-100 NM EITHER SIDE OF AXIS EAST OF 30W. SIMILAR CONVECTION
IS FROM THE EQUATOR TO THE AFRICAN COAST BETWEEN THE PRIME
MERIDIAN AND 9W.

...DISCUSSION...

THE GULF OF MEXICO...
THE COLD FRONT THAT MOVED ACROSS THE GULF 24 HOURS AGO WITH A
LINE OF VIGOROUS SHOWERS AND TSTMS HAS WEAKENED...AND A SFC
TROUGH WAS ANALYZED ON THE 1200 UTC MAP EXTENDING FROM THE
FLORIDA PANHANDLE THROUGH THE CENTRAL GULF TO THE COAST OF
MEXICO BETWEEN TUXPAN AND JALAPA. A QUIKSCAT PASS FROM THIS
MORNING AND SFC OBSERVATIONS SHOWED CLEARLY THE WINDS SHIFT
ASSOCIATED WITH THE TROUGH...REMNANT OF THE FRONTAL BOUNDARY.
SELY FLOW OF 10 TO 15 KT IS SEEN AHEAD OF THE TROUGH WITH NELY
FLOW UP TO 15 KT BEHIND THE TROUGH AXIS. THESE WINDS WILL
RAPIDLY VEER TO THE SE AND SOUTH AHEAD OF THE NEXT STORM SYSTEM
CURRENTLY DEVELOPING OVER THE SOUTHERN ROCKIES. THIS LOW WILL
MOVE NE THROUGH THE CENTRAL PLAINS WITH A NEW COLD FRONT
ENTERING THE NW PORTION OF THE GULF FRIDAY MORNING. THIS FRONTAL
SYSTEM IS ALSO FORECAST TO DISSIPATE OVER ERN GULF EARLY SUN. A
STRONGER COLD FRONT IS IN STORE FOR NEW YEAR EVE. THIS FRONT IS
EXPECTED TO MOVES RAPIDLY OFF THE TEXAS COAST EARLY MON AND
EXTEND FROM THE FLORIDA PANHANDLE TO E BAY OF CAMPECHE LATE MON
FOLLOWED BY STRONG NLY FLOW AND MUCH COOLER TEMPERATURES. UPPER
LEVEL MOISTURE IS BEING TRANSPORTED BY A SUBTROPICAL JETSTREAM
FROM THE EPAC ACROSS CENTRAL MEXICO AND THE GULF INTO THE W
ATLC. NEARLY ZONAL FLOW DOMINATES THE ENTIRE GULF.

THE CARIBBEAN SEA...
THE CARIBBEAN REMAINS TYPICALLY TRANQUIL FOR THIS TIME OF YEAR
UNDER THE INFLUENCE OF A MID/UPPER-LEVELS RIDGE WHICH IS
PRODUCING STRONG SUBSIDENCE. NO AREAS OF ORGANIZED CONVECTION
ARE PRESENT. ONLY PATCHES OF LOW LEVEL MOISTURE WITH MAINLY
LIGHT SHOWERS DOT THE REGION. SURFACE HIGH PRESSURE BUILDING N
OF THE AREA WILL MAINTAIN MODERATE TRADE WINDS ACROSS THE BASIN
THROUGH THE UPCOMING WEEKEND. THE GFS COMPUTER MODEL SHOWS ELY
WINDS OF UP TO 30 KT JUST OFF THE COLOMBIAN COAST SAT AND SUN.

THE ATLANTIC OCEAN...
A 1014 MB SURFACE LOW CONTINUES TO MEANDER NEAR 26N38W WITH A
TROUGH EXTENDING SW TO 20N45W. SCATTERED MODERATE CONVECTION IS
OBSERVED WITHIN 90 NM OF THE TROUGH. HIGH PRESSURE DOMINATES
MOST OF THE SUBTROPICAL NORTH ATLANTIC WITH A 1026 MB HIGH
CENTERED AT 31N55W. FARTHER TO THE WEST...A WEAKENING FRONTAL
BOUNDARY ENTERS THE AREA NEAR 31N70W THEN CONTINUES SW TO THE NW
BAHAMAS. A BROKEN BAND OF MAINLY LOW CLOUDS IS ASSOCIATED WITH
THE FRONT. THE WEATHER PATTERN ALOFT HAS CHANGED LITTLE SINCE
CHRISTMAS EVE. THE AREA CONTINUES TO BE PRIMARILY DOMINATED BY A
COUPLE OF FEATURES. THE FIRST ONE IS THE BROAD UPPER RIDGE THAT
EXPANDS FROM THE CARIBBEAN SEA INTO THE W ATLC TO BEYOND 31N65W.
A SUBTROPICAL JETSTREAM IS RIDING ON THE N PERIPHERY OF THIS
ANTICYCLONE. THE SECOND ONE IS THE DEEP LAYERED TROUGH THAT
REMAINS STUCK OVER THE CENTRAL ATLC EXTENDING SW  FROM A CUT-OFF
LOW NEAR 26N38W TO JUST EAST OF THE WINDWARD ISLANDS. AMPLE
UPPER LEVEL MOISTURE IS OBSERVED AHEAD OF THE TROUGH AXIS. A
JETSTREAM BRANCH LOCATED SE OF THIS TROUGH IS ENHANCING
ADDITIONAL WIDESPREAD MODERATE CONVECTION FROM 14N-25N EAST OF
27W.

$$
GR




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