[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 150542
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
105 AM EST FRI DEC 15 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
0515 UTC.

...THE ITCZ...
ITCZ AXIS IS ALONG 7N11W 4N26W 3N40W EQ50W. SMALL CLUSTERS OF
SCATTERED MODERATE CONVECTION ARE WITHIN 120 NM EITHER SIDE OF
THE AXIS E OF 41W.

...DISCUSSION...
THE GULF OF MEXICO...
A SFC TROUGH REMAINS OVER THE E GULF ALONG 85W FROM 22N-27N
DRIFTING E. A FAIRLY EXTENSIVE SHIELD OF SHOWERS AND TSTMS ARE
LOCATED TO THE E OF THE TROUGH AXIS ACROSS S FLORIDA...MOSTLY S
OF LAKE OKEECHOBEE AS DEPICTED ON DOPPLER RADAR. THE TAIL END OF
A STALLED FRONT STRETCHES ACROSS THE FL/GA BORDER. LOW-LEVEL
CONVERGENCE NEAR THE FRONT IS PRODUCING SCATTERED SHOWERS AND
TSTMS OFF THE NE COAST OF FLA. GFS SHOWS THE SFC TROUGH MERGING
WITH THE FRONTAL BOUNDARY AND PUSHING INTO THE ATLC LATER TODAY.
THE UPPER LEVEL FLOW IS A RATHER UNIFORM SWLY ACROSS THE GULF
JUST E OF A SHORTWAVE TROUGH LOCATED ABOVE E TEXAS AND NRN
MEXICO. A PLUME OF HIGH LEVEL MOISTURE...ASSOCIATED WITH THE
SUBTROPICAL JET ORIGINATING AT THE BASE OF THE TROUGH...IS
ADVECTED A CONSIDERABLE AMOUNT OF CLOUDINESS ACROSS THE CENTRAL
AND NRN GULF. BROWNSVILLE DOPPLER RADAR INDICATES SCATTERED
SHOWERS AND TSTMS NEAR THE EDGE OF ITS RADAR RANGE IN THE W GULF
EMBEDDED IN THIS MOISTURE PLUME. WEAK SFC HIGH PRES IS LOCATED
IN THE N GULF KEEPING WINDS RATHER LIGHT. THIS HIGH WILL SLIDE
TO THE E AND STRENGTHEN THRU THE WEEKEND AS THE SFC
TROUGH/FRONTAL BOUNDARY MOVES OUT OF THE AREA.

THE CARIBBEAN SEA...
CONDITIONS ACROSS THE CARIBBEAN ARE FAIRLY QUIET THIS MORNING.
THE ONLY AREA OF ANY MENTIONABLE CLOUDINESS IS IN THE EXTREME
WRN PORTION WHERE MULTILAYERED CLOUDS AND ISOLATED SHOWERS COVER
A GOOD PORTION OF CENTRAL AMERICA AND THE CARIBBEAN SEA W OF
85W. THIS CLOUDINESS IS MAINLY CONTRIBUTED TO THE SFC TROUGH IN
THE E GULF AND AN AREA OF WEAK UPPER LEVEL DIFFLUENCE BETWEEN AN
UPPER LEVEL HIGH OVER NRN COLOMBIA AND ANOTHER IN THE EPAC.  THE
REMAINDER OF THE CARIBBEAN IS STABLE WITH PLENTY OF DRY AIR ALOFT
NOTED ON WATER VAPOR IMAGERY...WITH THE DRIEST AIR OVER THE ERN
CARIBBEAN WHERE UPPER LEVEL CONFLUENCE IS STRONGEST. THE TYPICAL
LOW-LEVEL CLOUD STREAKS...UNDERNEATH THE MID-LEVEL CAP...EVEN
APPEAR RATHER THIN BASED ON SHORTWAVE IR IMAGES. TRADE WINDS ARE
MOSTLY IN THE 15-20 KT RANGE AND LITTLE CHANGE OR SOME SLACKING
IS EXPECTED THRU SAT AS A WEAKNESS IN THE SUBTROPICAL RIDGE
DEVELOPS TO THE N OF THE AREA.

THE ATLANTIC OCEAN...
THE UPPER LEVEL PATTERN IS MUCH LESS AMPLIFIED THAN IT HAS BEEN
THE PAST COUPLE DAYS. IN THE WRN AND CNTRL ATLC...DEBRIS
MOISTURE ASSOCIATED WITH A SFC TROUGH AND FRONTAL BOUNDARY IN
THE EXTREME W ATLC AND E GULF IS SPREADING TO ABOUT 70W MAINLY N
OF 23N. AS THE UPPER LEVEL FLOW DEVELOPS A NLY COMPONENT...ON
THE E SIDE OF A SLIGHT RIDGE AXIS ALONG 70W...THE UPPER
ATMOSPHERE DRIES OUT CONSIDERABLY. THIS DRY STABLE AIR ALOFT
COVERS A LARGE PORTION OF THE REGION BETWEEN 40W-70W. A SMALL
UPPER LEVEL LOW APPEARS TO BE FORMING NEAR 20N56W BUT THIS
FEATURE IS EMBEDDED IN THE DRY AIR MENTIONED ONLY MOISTENING THE
AIR SLIGHTLY. AT THE SFC...A 1031 MB HIGH CENTERED NEAR 28N47W
DOMINATES THE REGION HELPING TO PRODUCE MOSTLY FAIR WEATHER
BETWEEN 40W-70W. IN THE E ATLC...A 1011 MB SFC LOW IS LOCATED
NEAR 29N34W WITH A COLD FRONT DRAPED SWD FROM THE LOW ALONG
25N33W 19N39W. MOISTURE APPEARS MOST ORGANIZED ON THE N SIDE OF
THE LOW AND E OF THE COLD FRONT WITHIN 120 NM OF A PRE-FRONTAL
TROUGH FROM 31N28N TO 21N33W. THE MOST SIGNIFICANT WEATHER
EFFECT IS THE STRONG WINDS AS A TIGHT PRES GRAD HAS SET UP
BETWEEN THIS LOW AND THE HIGH TO IT'S NW PRODUCING GALE FORCE
WINDS IN THE REGION BETWEEN THE LOW AND 40W N OF 28N. THE
REMAINDER OF THE SUBTROPICAL E ATLC IS UNDER A NARROW UPPER
RIDGE KEEPING CONDITIONS RATHER TRANQUIL E OF 25W. IN THE
TROPICAL ATLC...EXTENSIVE ZONAL FLOW ON THE N SIDE OF VERY BROAD
RIDGING IS THE RULE WITH CONVECTION CONFINED TO THE ITCZ. GFS
SUGGESTS THAT THE PATTERN MAY BECOME MORE AMPLIFIED IN THE E
ATLC OVER THE WEEKEND WITH A LARGE UPPER LOW DEVELOPING NEAR
30N30W.

$$
CANGIALOSI




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