[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 130005
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
705 PM EST MON DEC 12 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 2345 UTC.

...THE ITCZ...
ITCZ AXIS IS ALONG 7N11W 4N30W 3N52W. SCATTERED MODERATE
CONVECTION LIES FROM 2N-7N BETWEEN 20W-35W. SIMILAR CLUSTER
NOTED OFF NE SOUTH AMERICA NEAR 1N49W.

...DISCUSSION...
THE GULF OF MEXICO...
A WEAK COLD FRONT IS MOVING THROUGH THE NW GULF BETWEEN SE
LOUISIANA AND 24N96W AS OF 2100 UTC. A WIND SHIFT AND DEWPOINT
GRADIENT IS NOTED WITH THIS BOUNDARY...THOUGH VERY LITTLE TEMP
GRADIENT IS EVIDENT. THIS FRONT IS MUCH TAMER THAN THE LAST
SEVERAL HAVE BEEN...WITH NW/N FLOW ONLY TO 10 KT BEHIND THE
FRONT. A PREFRONTAL TROUGH IS ANALYZED ALONG 29N89W 25N91W. THIS
TROUGH IS MARKED BY A LINE OF SHOWERS WITH EMBEDDED TSTMS WITHIN
50NM OF THE AXIS. ANOTHER SFC TROUGH EXTENDS THROUGH THE NW
CARIBBEAN...NE YUCATAN...AND INTO THE SRN MIDDLE GULF WATERS TO
24N88W. THIS TROUGH HAS A SMALL CLUSTER OF MODERATE CONVECTION
WITH IT NEAR 23N86W. GFS SUGGESTS A WEAK LOW WILL DEVELOP FROM
THIS IN THE SE GULF LATER IN THE WEEK AND EVENTUALLY MOVE ACROSS
FLORIDA. TODAYS GUIDANCE IS LESS ROBUST WITH THIS FEATURE THAN
IT WAS YESTERDAY IN THE GULF...AND NOW PREFERS TO DEEPEN THE LOW
IN THE SW NORTH ATLC. SW TO W UPPER FLOW PERSISTS OVER THE
GULF...W OF AN UPPER RIDGE EXTENDING N THROUGH THE BAHAMAS. THE
PVA AHEAD OF A SHORTWAVE UPPER TROUGH EXPECTED TO MOVE THROUGH
THE GULF FRI EXPECTED TO PROVIDE THE ENERGY FOR THE
AFOREMENTIONED SFC LOW PROGGED.

THE CARIBBEAN SEA...
MAIN FEATURE IN THE CARIBBEAN THIS EVENING IS THE SFC TROUGH IN
THE NW PORTION...EXTENDING THROUGH THE NE YUCATAN AND INTO THE
GULF. THE LAST FEW GOES 12 VISIBLE PICTURES SHOW CLEAR CYCLONIC
TURNING IN THE LOW CLOUD FIELD ABOUT THE TROUGH AXIS. SEE GULF
SECTION ABOVE AND MIAMIMATS FOR FORECAST NOTES ON THIS FEATURE.
TRADE WINDS OVER THE NW CARIBBEAN ARE SLOWLY DIMINISHING AS THE
W ATLC HIGH PRES AREA MOVES E. WINDS OVER THE CENTRAL CARIBBEAN
REMAIN ON THE FRESH TO STRONG SIDE DUE TO A SLIGHTLY STRONGER
GRADIENT WITH THE HIGH AND LOWER PRESSURE OVER COLOMBIA. NO
MAJOR CHANGES ARE EXPECTED OVER THE CARIBBEAN WATERS THROUGH THE
END OF THE WEEK WITH THE PRES GRADIENT EXPECTED TO REMAIN QUASI
CONSTANT. ALOFT...AN UPPER RIDGE DOMINATES WITH THE AXIS
EXTENDING N FROM ITS ORIGIN NEAR 11N77W THROUGH ERN CUBA.

THE ATLANTIC OCEAN...
AN AMPLIFIED UPPER RIDGE/TROUGH/RIDGE PATTERN DOMINATES THE ATLC
WATERS N OF 15N. A SMALL UPPER LOW IS EMBEDDED IN THIS PATTERN
NNW OF THE CAPE VERDE ISLANDS NEAR 24N31W. NEARLY ZONAL UPPER
FLOW DOMINATES THE DEEP TROPICS S OF 15N. THE SRN PERIPHERY OF
SFC HIGH PRESSURE DOMINATES THE SW NORTH ATLC WATERS BEHIND A
CENTRAL ATLC COLD FRONT ENTERING THE AREA AT 32N45W TO 22N57W.
SCATTERED MODERATE CONVECTION IS AHEAD OF THIS FRONT FROM
25N-30N BETWEEN 40W-45W. A SFC TROUGH IS ANALYZED ALONG 22N43W
12N48W...AND IS MARKED BY A WEAK LOW LEVEL CONFLUENT ZONE WHICH
IS PRODUCING MOSTLY LOWER TO MID CLOUDS WITH POSSIBLE ISOLATED
SHOWERS WITHIN 90 NM OF THE AXIS. THE REMAINDER OF THE E ATLC
SFC PATTERN IS DOMINATED BY THE SRN PORTION OF A 1030 MB HIGH
NEAR 36N24W...OR JUST SE OF THE AZORES. A WEAK COLD FRONT MOVES
OFF THE GEORGIA/N FLORIDA COAST LATE WED BUT QUICKLY STALLS JUST
OFFSHORE THROUGH FRI. AS INDICATED ABOVE...THE GFS IS SHOWING A
LESS AGGRESSIVE LOW DEVELOPMENT SCENARIO OVER THE GULF OF MEXICO
ALTHOUGH IT STILL SHOWS SPIN-UP OVER THE W ATLC LATE FRI THROUGH
SUN. THIS SEEMS A LITTLE OVERDONE WITH THE ENSEMBLE MEAN THE
CURRENT PREFERRED SOLUTION.

$$
WILLIS




This weather bulletin was brought to you by:
www.nashvilleweather.net