[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 170038
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
705 PM EST SUN DEC 16 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

...ITCZ...
ITCZ AXIS ALONG 7N11W 4N19W 2N35W 1N45W EQUATOR50W.  SCATTERED
MODERATE CONVECTION WITHIN 240 NM S OF AXIS FROM 40W-46W.

DISCUSSION...
GULF OF MEXICO...
LONGWAVE UPPER LEVEL TROUGH ACROSS BASIN SUPPORTS STRONG FAST
MOVING COLD FRONT THAT HAS JUST EXITED EASTERN BORDER OF GULF.
STRONG N TO NW WINDS BEHIND FRONT...TO GALE FORCE IN SW GULF S
OF 20N W OF 92W.  WIDESPREAD BROKEN TO OVERCAST STRATOCUMULUS
CLOUDS ENGULF ENTIRE BASIN...INDICATIVE OF COOL STABLE AIRMASS
BUT ALL CONVECTION NOW E OF BASIN.  WINDS EXPECTED BELOW GALE
FORCE WITHIN NEXT 12 HOURS AS FRONT MOVES FURTHER E ALLOWING
HIGH PRES TO SLACKEN GRADIENT WITH DRY WEATHER ACROSS ENTIRE
REGION THRU MON.

CARIBBEAN SEA...
COLD FRONT FROM WESTERN CUBA TO BAY ISLANDS IN HONDURAS CARRIES
ONLY SIGNIFICANT CONVECTION IN WESTERN CARIBBEAN AS DRY
SUBSIDING AIR MASS UNDER MID TO UPPER LEVEL RIDGE HAS BEEN IN
PLACE SINCE...WHAT ONCE WAS TROPICAL STORM...OLGA WENT THROUGH.

NOT EVEN LOW-LEVEL CONVERGENCE ALONG PRE-FRONTAL TROUGH EXTEND
FROM WESTERN CUBA TO NICARAGUA-HONDURAS BORDER IS ABLE TO
GENERATE ANY SIGNIFICANT CONVECTION.  REMAINDER OF BASIN REMAIN
QUIET WITH ONLY ISOLATED SHOWERS EMBEDDED IN EASTERLY TRADES.
UPPER LEVEL TROUGH CROSSES EASTERN CARIBBEAN FROM LEEWARD
ISLANDS IN THE NORTHEAST TO WESTERN VENEZUELA.  ONLY NOTED
MOISTURE IN BASIN RIDES SW WINDS ALOFT S OF 14N E OF 68W.
LITTLE SIGNIFICANT MOISTURE AVAILABLE ELSEWHERE DUE TO STRONG
SUBSIDENCE N OF 17N E OF 72W.

ATLANTIC OCEAN...
SCATTERED CONVECTION WITHIN 90 NM E OF COLD FRONT ACROSS
SOUTHWEST NORTH ATLANTIC FROM 31N78W TO EXTREME SOUTHEAST
FLORIDA TO NORTHWEST CUBA TO NORTHEAST YUCATAN PENINSULA.  GALE
FORCE SW WINDS AHEAD OF FRONT TO 70W THROUGH TONIGHT DIMINISHING
BY EARLY MON.  STRONGEST TSTMS NOW OVER NORTHEAST BAHAMAS AND N
OF AREA OFF CAROLINA COASTLINE.  STATIONARY HIGH PRESSURE CENTER
1023 MB AT 28N54W SHOULD YIELD TO STRONG FRONT SHIFTING EAST AS
STRONG NORTHEASTERLY FLOW DOMINATES FLOW BEHIND FRONT.  BROKEN
LOW TO MID LEVEL CLOUDINESS WITHOUT SIGNIFICANT CONVECTION
EXPECTED AS AIR MASS BECOMES STABLE.

UPPER LEVEL TROUGHING THAT CROSSES EASTERN CARIBBEAN EXTENDS
FURTHER NE ACROSS CENTRAL AND EASTERN ATLANTIC WELL INTO
NORTHWEST AFRICA.  STRONG SW FLOW ALOFT ON LEE SIDE OF TROUGH
WITH JET CORE OF 115 KT BRINGS SWATH OF ITCZ TROPICAL MOISTURE
INTO CONTINENT NORTH OF 13N.  WEAK LOW PRESSURE 1014 MB AT
24N21W HAS TROUGH ANALYZED ACROSS CANARY ISLANDS TO 231N16W
REMAINS UNDER SUBSIDING SIDE OF UPPER TROUGH UNABLE TO UTILIZE
MOISTURE FOR ANY CONVECTION.

$$
WALLY BARNES

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