[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 172357
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
705 PM EST MON DEC 17 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2315 UTC

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 7N10W 2N25W 1N35W 1N52W. WIDELY
SCATTERED MODERATE CONVECTION IS WITHIN 80-100 NM EITHER SIDE OF
AXIS EAST OF 32W. SCATTERED MODERATE CONVECTION IS FROM 4N-11N
BETWEEN 43W-55W...ENHANCED BY A DIFFLUENT PATTERN ALOFT
ASSOCIATED WITH AN ANTICYCLONE OVER NORTHERN SOUTH AMERICA.

DISCUSSION...
GULF OF MEXICO...
A COOL AND DRY AIRMASS IS IN PLACE ACROSS THE REGION THIS
EVENING UNDER THE INFLUENCE OF A 1029 MB HIGH LOCATED OVER THE
LOWER MISSISSIPPI VALLEY. THE LEADING EDGE OF THIS AIRMASS IS A
STRONG COLD FRONT THAT CURRENTLY EXTENDS OVER THE W ATLC AND THE
NW CARIBBEAN. BRISK N TO NE WINDS ARE BLOWING ACROSS THE E GULF
AND THE YUCATAN PENINSULA...WHERE THE PRES GRADIENT IS TIGHTEST
BETWEEN THE ABOVE MENTIONED HIGH PRES AND THE FRONT. WINDS SHIFT
TOWARD THE E IN THE W GULF MODIFYING THE TEMPS THERE. BROKEN TO
OVERCAST COLD AIR STRATOCUMULUS CLOUDS COVER MOST OF THE GULF. A
COOL TONGUE REGION IS SEEN ON SATELLITE IMAGERY ACROSS FLORIDA
REACHING WESTERN CUBA. THIS WEATHER PATTERN COULD PRODUCE LOW
TEMPERATURES NEAR 50 F...10 C IN PARTS OF THE PROVINCES OF
HAVANA AND MATANZAS IN CUBA UNDER CLEAR SKIES. IN THE MID AND
UPPER LEVELS...STRONG ZONAL FLOW DOMINATES THE AREA. A
SUBTROPICAL JETSTREAM IS TRANSPORTING ABUNDANT UPPER-LEVEL
MOISTURE  FROM THE EPAC ACROSS NORTHERN MEXICO INTO TEXAS AND
THE GULF. LOOKING AHEAD...SFC HIGH PRES WILL CONTINUE TO SHIFT E
ALLOWING ELY FLOW TO DEVELOP AREA-WIDE TOMORROW WHICH WILL WARM
TEMPS BACK TO CLIMO. THE NEXT COLD FRONT IS FORECAST TO MOVE IN
LATE IN THE WEEK.

CARIBBEAN SEA...
A COLD FRONT TRAILS ACROSS THE BAHAMAS...EASTERN CUBA...THE
CAYMAN ISLANDS AND NORTHERN HONDURAS. THE FRONT IS FORECAST TO
STALL OVER THIS AREA TONIGHT AND DISSIPATE TOMORROW. A 120-140
NM WIDE BAND OF CLOUDS WITH EMBEDDED SHOWERS/RAIN IS ASSOCIATED
WITH THE FRONT. COOL AIR HAS FILTERED WELL S INTO THE NW CARIB
AND WESTERN CUBA WHERE SAT PICTURES SHOW OVERCAST COLD AIR
STRATOCUMULUS CLOUDS. NLY WINDS OF 20-25 KT ARE BEHIND THE
FRONT...PARTICULARLY OVER THE GULF OF HONDURAS. A PRE-FRONTAL
TROUGH IS ANALYZED AROUND 80W/81W S OF 18N. LOW-LEVEL CLOUDINESS
WITH ISOLATED SHOWERS ARE ALONG THE TROUGH AXIS. E OF THE
FRONT...THE TRADE WINDS PREVAIL...CARRYING POCKETS OF LOW LEVEL
MOISTURE WITH MAINLY LIGHT SHOWERS ACROSS THE EAST AND CENTRAL
CARIBBEAN. ALOFT...A RIDGE/TROUGH PATTERN COVERS THE WHOLE AREA.
AN UPPER-LEVEL HIGH IS NEAR CABO GRACIAS A DIOS IN NICARAGUA...
WHILE AN UPPER TROUGH EXTENDS FROM THE LEEWARD ISLANDS TO
NORTHERN COLOMBIA. STRONG SWLY WINDS AHEAD OF THIS TROUGH ARE
HELPING TO INDUCE SOME CLOUDINESS WITH ISOLATED SHOWERS OVER THE
SE CARIBBEAN.

ATLANTIC OCEAN...
A STRONG COLD FRONT CROSS JUST SE OF BERMUDA AND ENTERS THE AREA
NEAR 31N65W...THEN CONTINUES SW ACROSS THE CENTRAL BAHAMAS AND
EASTERN CUBA INTO THE CARIBBEAN SEA TO N HONDURAS. SCATTERED
SHOWERS AND ISOLATED TSTMS ARE WITHIN 140 NM OF THE FRONT MAINLY
N OF 25N. MUCH COOLER AND DRIER AIRMASS IS BEING ADVECTED IN
BEHIND THE FRONT WITH BROKEN TO OVERCAST STRATOCUMULUS CLOUDS.
ANOTHER COLD FRONT...A WEAK ONE...EXTENDS ACROSS THE EAST AND
CENTRAL ATLC ALONG 31N22W 26N30W 25N40W TO 30N49W. A NARROW BAND
OF MAINLY LOW CLOUDS AND POSSIBLE SHOWERS IS RELATED TO THIS
SYSTEM. CONVECTIVE ACTIVITY IS MORE CONCENTRATE AHEAD OF THE
FRONT N OF 27N AND BETWEEN THE CANARY/MADEIRA ISLANDS AND THE
FRONT ITSELF. A 1027 MB HIGH LOCATED N OF AREA IS BETWEEN THE
FRONTAL BOUNDARIES. A WEAK 1015 MB LOW IS NEAR 21N23W. A SWIRL
OF LOW CLOUDS IS ASSOCIATED WITH THIS LOW.

IN THE UPPER-LEVELS... A TROUGH/RIDGE/TROUGH PATTERN DOMINATES
THE FORECAST AREA. AN UPPER TROUGH COVERS THE EASTERN U.S.
MOVING INTO THE W ATLC. THIS TROUGH SUPPORTS THE STRONG COLD
FRONT PREVIOUSLY MENTIONED. AN UPPER RIDGE ANCHORED IN THE
CARIBBEAN EXTENDS NE ACROSS EASTERN CUBA AND HISPANIOLA ONTO THE
CENTRAL ATLC TO BEYOND 31N43W. A HIGHLY ELONGATED MID TO UPPER
TROUGH EXTENDS FROM THE FAR EAST ATLC ALONG 20N ENTERING THE E
CARIBBEAN THROUGH THE LEEWARD ISLANDS. STRONG ZONAL FLOW
ALOFT...OR JUST SOUTH OF WEST...LIES ABOVE MOST OF THE TROPICS.

$$
GR





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