[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 151128
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
705 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1115 UTC.

...THE ITCZ...
ITCZ AXIS IS ALONG 7N12W 5N27W 2N40W EQ50W. SMALL CLUSTERS OF
SCATTERED MODERATE CONVECTION ARE WITHIN 120 NM EITHER SIDE OF
THE AXIS E OF 44W.

...DISCUSSION...
THE GULF OF MEXICO...
THE SFC TROUGH THAT HAS BEEN NEARLY STATIONARY IN THE GULF OVER
THE PAST COUPLE DAYS HAS NOW BEGUN TO MOVE E IN RESPONSE TO AN
APPROACHING UPPER LEVEL SHORTWAVE. IT APPEARS THAT THE SFC
TROUGH IS MERGING WITH THE STALLED BOUNDARY IN THE WRN ATLC. AS
OF 09 UTC...THE TROUGH WAS ANALYZED FROM MELBOURNE FLORIDA TO
FORT MYERS STRETCHING TO THE NE YUCATAN PENINSULA. THIS FEATURE
MAY BE TRANSITIONING INTO A COLD FRONT AS THERE IS A FEW DEGREE
TEMP AND DEWPOINT GRAD ACROSS FLORIDA...BUT BECAUSE THIS IS
OFTEN THE NORM AND DUE TO VERY HIGH RH VALUES BEHIND THE
BOUNDARY IT REMAINS ANALYZED AS A TROUGH AT THIS TIME. A LINE OF
SCATTERED SHOWERS AND TSTMS HAS MOVED S AND E OF MAINLAND S FLA
AND NOW EXTEND FROM THE KEYS TO THE BAHAMAS. THE UPPER LEVEL
FLOW IS MAINLY SWLY ACROSS THE GULF JUST E OF THE SHORTWAVE
TROUGH MENTIONED WHICH IS LOCATED ABOVE E TEXAS AND NE MEXICO. A
PLUME OF MID AND HIGH LEVEL MOISTURE...ASSOCIATED WITH THE
SUBTROPICAL JET ORIGINATING AT THE BASE OF THE TROUGH...IS
ADVECTED ACROSS THE CENTRAL AND NRN GULF. THIS MOISTURE
CONTINUES ABOVE THE SFC TROUGH IN FLORIDA AND INTO THE WRN ATLC.
BROWNSVILLE DOPPLER RADAR INDICATES SCATTERED SHOWERS AND TSTMS
NEAR THE EDGE OF ITS RADAR RANGE IN THE W GULF EMBEDDED IN THIS
MOISTURE PLUME. A 1018 MB SFC HIGH PRES IS LOCATED IN THE N GULF
JUST S OF LOUISIANA NEAR 29N91W KEEPING WINDS RATHER LIGHT. THIS
HIGH WILL SLIDE E AND STRENGTHEN THRU THE WEEKEND AS THE SFC
TROUGH AND SHORTWAVE UPPER TROUGH MOVE OUT OF THE AREA. THIS
WILL ALLOW DRIER CONDITIONS TO RETURN.

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 BROKEN MULTILAYERED CLOUDS AND ISOLATED
SHOWERS COVER A PORTION OF THE YUCATAN PENINSULA AND THE
CARIBBEAN SEA W OF 85W N OF 16N. 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. THIS WEAK UPPER DIFFLUENCE IS
ALSO SPARKING ISOLATED TO SCATTERED SHOWERS ACROSS PORTIONS OF
PANAMA AND COSTA RICA. 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 RELAXING IN THESE WINDS
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...FLORIDA AND THE E GULF IS SPREADING TO
ABOUT 68W MAINLY N OF 23N. FOR DETAILS REFER TO THE GULF OF
MEXICO SECTION ABOVE. THE ATMOSPHERE CONSIDERABLY DRIES OUT E OF
68W AS THE UPPER LEVEL FLOW DEVELOPS A NLY COMPONENT ON THE E
SIDE OF THE WEAK RIDGE. THIS DRY STABLE AIR ALOFT COVERS A LARGE
PORTION OF THE REGION BETWEEN 35W-68W. A SMALL UPPER LEVEL LOW
APPEARS TO BE FORMING NEAR 18N58W BUT THIS FEATURE IS EMBEDDED
IN THE DRY AIR MENTIONED ONLY MOISTENING THE AIR SLIGHTLY IN ITS
VICINITY. AT THE SFC...A 1031 MB HIGH CENTERED NEAR 37N46W
DOMINATES THE REGION HELPING TO PRODUCE MOSTLY FAIR WEATHER. IN
THE E ATLC...AN OCCLUDED 1008 MB SFC LOW IS LOCATED NEAR 29N33W.
A COLD FRONT ORIGINATES ABOUT 180 NM E OF THE LOW AND EXTENDS
ALONG 30N30W 24N31W 16N37W. MOISTURE APPEARS MOST ORGANIZED WELL
N OF THE LOW...OUTSIDE OF THE DISCUSSION AREA...AND WITHIN 240
NM AHEAD OF THE COLD FRONT. THE MOST SIGNIFICANT WEATHER EFFECT
ASSOCIATED WITH THIS LOW PRES SYSTEM 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. THESE GALE FORCE WINDS ARE NOT EXPECTED TO LAST
MUCH LONGER AS THE OCCLUDED LOW GETS ABSORBED BY A DEVELOPING
LARGER AND STRONGER LOW TO ITS N ALONG THE SAME FRONTAL
BOUNDARY. THIS WILL LIKELY KEEP THE STRONGEST WINDS N OF THE
AREA. 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.

$$
CANGIALOSI




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