[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 180549
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
105 AM EST MON DEC 18 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0530 UTC.

...THE ITCZ...
ITCZ AXIS IS ALONG 9N13W 8N30W 6N40W 2N52W. ISOLATED MODERATE
CONVECTION IS WITHIN 300 NM S OF THE AXIS BETWEEN 24W-30W AND
WITHIN 180 NM EITHER SIDE OF THE AXIS BETWEEN 37W-43W.

...DISCUSSION...
THE GULF OF MEXICO...
MAINLY FAIR WEATHER EXISTS ACROSS THE GULF OF MEXICO UNDER THE
INFLUENCE OF A MID TO UPPER LEVEL RIDGE ANCHORED OVER THE
REGION. PLENTY OF DRY AIR ALOFT LIES ABOVE THE AREA WITH THE
MOST STABLE CONDITIONS ABOVE THE N AND E PORTIONS WHERE UPPER
LEVEL CONFLUENCE IS STRONGEST. SOME HIGH CLOUDINESS IS BEGINNING
TO STREAM INTO THE BAY OF CAMPECHE. THIS CLOUDINESS MAY SPREAD
NE THRU THE DAY...BUT WILL NOT BE A WEATHER CONCERN. AT THE
SFC...RIDGING EXTENDS ACROSS THE GULF FROM A NEARLY STATIONARY
1027 MB HIGH IN THE W ATLC. THIS PATTERN IS PRODUCING 15-20 KT E
WINDS IN THE MIDDLE AND E GULF AND LIGHTER RETURN FLOW IN THE
WRN GULF. THE WEAK SFC TROUGH THAT HAS BEEN IN THE E GULF HAS
BECOME VERY FAINT AND WAS REMOVED FROM THE 00 Z ANALYSIS BUT
PATCHY LOW/MID LEVEL CLOUDS AND SHALLOW ISOLATED SHOWERS REMAIN
S OF 26N BETWEEN 84W-88W. LOOKING AHEAD OVER THE NEXT FEW
DAYS...COMPUTER MODELS SHOW THE MID-UPPER LEVEL RIDGE HOLDING IN
PLACE KEEPING CONDITIONS PRETTY QUIET ACROSS THE AREA. HIGH PRES
AT THE SFC WILL STRENGTHEN AND SHIFT W WHICH WILL INCREASE THE
WINDS AND SEAS SLIGHTLY.

THE CARIBBEAN SEA...
THE TAIL END OF A WEAKENING SFC TROUGH STRETCHES ACROSS THE
BAHAMAS AND CUBA. MULTILAYER CLOUDINESS AND ISOLATED SHOWERS
NEAR THE TROUGH ARE BEGINNING TO BREAK UP AS DRIER AIR PIVOTS
INTO THE REGION...DUE TO THE MID/UPPER LEVEL SHORTWAVE TROUGH IN
THE W ATLC SHIFTING SE. THE REMAINDER OF THE CARIBBEAN IS UNDER
A WEAK MID LEVEL RIDGE WITH PLENTY OF DRY STABLE AIR
ALOFT...ESPECIALLY S OF 17N. THERE ARE PATCHES OF LOW LEVEL
CLOUDS AND EMBEDDED SCATTERED SHOWERS UNDERNEATH THE STRONG MID
LEVEL CAP IN THE E CARIBBEAN...MAINLY E OF THE DOMINICAN
REPUBLIC AND N OF 13N. TRADE WINDS ARE MOSTLY IN THE 15-20 KT
RANGE...EXCEPT FOR SLIGHTLY STRONGER WINDS IN THE SW CARIB WHERE
THE PRES GRAD IS A LITTLE TIGHTER. OVER THE NEXT FEW
DAYS...LITTLE CHANGE IN STRENGTH OF THE TRADES IS EXPECTED AS
THE SFC PATTERN REMAINS SIMILAR. GFS SHOWS THE SHORTWAVE IN THE
ATLC PULLING SE WHICH MAY DRAG A LITTLE MOISTURE INTO THE N
CENTRAL AND E CARIB.

THE ATLANTIC OCEAN...
IN THE WRN AND CENTRAL ATLC...A MID TO UPPER LEVEL SHORTWAVE
TROUGH STRETCHES FROM JUST E OF BERMUDA TO THE E BAHAMAS. DRY
STABLE AIR ALOFT COVERS THE AREA W OF THE SHORTWAVE AXIS
INCLUDING FLORIDA AND THE GULF OF MEXICO. STRONG WLY WINDS IS
SPREADING A PLUME OF MOISTURE COVERING A LOT OF REAL ESTATE IN
AN E-W FASHION E OF THE TROUGH AXIS FROM 20N-26N BETWEEN
30W-70W. AT THE SFC...A WEAK 1017 MB LOW IS LOCATED NEAR 29N51W
WITH A COLD FRONT EXTENDING FROM THE LOW SWWD ALONG 26N56W
23N67W THEN AS A SFC TROUGH ACROSS THE S BAHAMAS AND CUBA. THIS
SFC LOW/FRONTAL BOUNDARY IS PROVIDING LIFT WHICH IS DEEPENING
THE MOISTURE PLUME. A 1027 MB HIGH PRES SYSTEM IS CENTERED TO
THE N AND W OF THE FRONTAL BOUNDARY AND IS NEARLY STATIONARY 220
NM WNW OF BERMUDA NEAR 34N69W. IN THE TROPICAL AND E ATLC...ONE
OF THE MAIN FEATURES IS A STRONG UPPER LEVEL TROPICAL JETSTREAM
WHICH IS LOCATED BETWEEN TROUGHING IN THE CENTRAL ATLC AND BROAD
RIDGING OVER AFRICA. THIS 90-110 KT JET APPROXIMATELY RUNS ALONG
8N42W 18N27W TO THE CANARY ISLANDS. CONSIDERABLE MOISTURE LIES
TO THE S AND E OF THE JET AXIS WHILE UPPER LEVEL CONFLUENCE IS
PROVIDING A STABLE ENVIRONMENT WITHIN 300 NM W OF THE JET AXIS.
THE OTHER MAIN FEATURE IS THE LONG LIVED SLOW MOVING LARGE 1001
MB OCCLUDED LOW PRES SYSTEM CENTERED NEAR 35N32W. THE ASSOCIATED
COLD FRONT WHICH LIES WELL E OF THE LOW CENTER IS DISSIPATING
ALONG 32N21W 24N25W 16N31W. THE NRN BRANCH OF THE DISSIPATING
FRONT IS LOCATED IN THE MOIST REGION OF THE TROPICAL JET
MENTIONED AND IS ENHANCING SHOWER ACTIVITY N OF 26N BETWEEN
20W-24W. GFS SHOWS THE OCCLUDED LOW FINALLY WEAKENING AND
PULLING N IN RESPONSE TO THE FAST MOVING COLD FRONT IN THE
CENTRAL ATLC.

$$
CANGIALOSI




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