[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 161133
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
705 AM EST SAT DEC 16 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 4N25W 5N37W 3N52W. SMALL CLUSTERS OF
ISOLATED MODERATE CONVECTION ARE WITHIN 180 NM EITHER SIDE OF
THE AXIS E OF 37W. SCATTERED MODERATE IS WITHIN 120 NM N OF THE
AXIS BETWEEN 41W-46W.

...DISCUSSION...
THE GULF OF MEXICO...
AN UPPER LEVEL SHORTWAVE TROUGH CONTINUES TO SLOWLY MOVE E NOW
LOCATED FROM MISSISSIPPI SOUTHWESTWARD TO N CENTRAL MEXICO. A
SUBTROPICAL JET ORIGINATES AT THE BASE OF THE TROUGH AND RACES
ACROSS SOUTH CENTRAL FLORIDA AND INTO THE W ATLC WITH CORE WINDS
FROM 80 TO 100 KT...STRONGEST IN THE WRN ATLC...BASED ON CIMSS
SATELLITE DERIVED WINDS. COPIOUS MOISTURE IS ASSOCIATED WITH
THIS UPPER LEVEL JET COVERING THE GULF E OF 86W. A SFC
TROUGH...ANALYZED FROM THE NW BAHAMAS ACROSS THE STRAITS OF
FLORIDA TO THE NRN YUCATAN PENINSULA IS DEEPENING THE MOISTURE
ACROSS THE SE GULF. IN FACT...DOPPLER RADAR FROM MIAMI AND KEY
WEST DEPICT A LARGE SHIELD OF SCATTERED SHOWERS AND TSTMS MOVING
OVER S FLORIDA WHERE IT LOOKS LIKE IT WILL BE A PRETTY RAINY
DAY. BUT THE DRIER AIR IS NOT THAT FAR AWAY WITH PLENTY OF IT
BEING ADVECTED INTO THE WRN AND CNTRL GULF W OF 90W. A 1020 MB
SFC HIGH IS LOCATED IN THE N GULF NEAR PENSACOLA. THIS WEAK PRES
PATTERN IS PRODUCING LIGHT NE TO ELY WINDS. THE SFC HIGH WILL
SLIDE E...STRENGTHEN AND BECOME NEARLY STATIONARY OFF THE SE
COAST LATE THIS WEEKEND INCREASING ELY WINDS SLIGHTLY. THE
MOISTURE IN THE E GULF WILL CONTINUE TO MOVE E WITH THE
SHORTWAVE TROUGH EVENTUALLY CLEARING THE ENTIRE REGION SOMETIME
TONIGHT.

THE CARIBBEAN SEA...
CONDITIONS ACROSS THE CARIBBEAN ARE QUIET THIS MORNING. THE ONLY
AREA OF ANY MENTIONABLE CLOUDINESS IS IN THE EXTREME NW PORTION
WHERE BROKEN MULTILAYERED CLOUDS AND ISOLATED SHOWERS COVER THE
AREA N OF 19N W OF 80W. THIS CLOUDINESS IS MAINLY CONTRIBUTED TO
THE TAIL END OF A SFC TROUGH IN THE NRN YUCATAN PENINSULA AND
STRONG UPPER LEVEL WINDS ON THE N PERIPHERY OF AN UPPER HIGH
CENTERED IN THE SRN CARIBBEAN NEAR 15N77W. THE REMAINDER OF THE
AREA 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 IS EXPECTED THRU THE WEEKEND.
THE WINDS WILL LIKELY INCREASE SOME IN THE NW CARIB EARLY NEXT
WEEK AS MODERATE HIGH PRES BECOMES NEARLY STATIONARY TO THE N OF
THE AREA. LOW-LEVEL MOISTURE MAY INCREASE SLIGHTLY IN THE ERN
CARIBBEAN LATER TODAY AND SUN BUT OVERALL MAINLY DRY CONDITIONS
ARE EXPECTED TO PREVAIL.

THE ATLANTIC OCEAN...
THE UPPER LEVEL PATTERN HAS BECOME A LITTLE MORE AMPLIFIED TODAY
AND BASICALLY CONSISTS OF A LONGWAVE RIDGE/TROUGH PATTERN.
STARTING IN THE WRN AND CENTRAL ATLC...WIDESPREAD
MOISTURE...PRODUCED BY STRONG UPPER LEVEL WINDS E OF A SHORTWAVE
TROUGH IN THE GULF AND A WEAKENING FRONTAL BOUNDARY/SFC TROUGH
DRAPED ACROSS THE BAHAMAS AND THE STRAITS OF FLORIDA...IS
SPREADING TO ABOUT 55W MAINLY N OF 24N. THE ATMOSPHERE
CONSIDERABLY DRIES OUT E OF 55W AS THE UPPER LEVEL FLOW DEVELOPS
A NLY COMPONENT ON THE W SIDE OF A LARGE TROUGH IN THE E ATLC.
THIS DRY STABLE AIR ALOFT COVERS A LARGE PORTION OF THE REGION
BETWEEN 25W-55W. AT THE SFC...A 1029 MB HIGH CENTERED NEAR
38N42W DOMINATES THE REGION E OF THE OLD FRONTAL BOUNDARY
HELPING TO PRODUCE MOSTLY FAIR WEATHER. COMPUTER MODELS SHOW THE
MOISTURE PLUME SLOWLY THINNING AND PRESSING TO THE SE OVER THE
NEXT COUPLE DAYS AS THE SHORTWAVE TROUGH MOVES THRU THE REGION.

IN THE E ATLC...AN OCCLUDED 1004 MB SFC LOW IS LOCATED NEAR
33N29W. A WEAKER 1010 MB LOW HAS FORMED TO THE S OF THIS MAIN
ONE NEAR 26N29W WITH A SFC TROUGH CONNECTING THESE SYSTEMS.
MODELS SHOW THE WEAKER SRN LOW PULLING NWD AND BECOMING ABSORBED
BY THE LARGER AND STRONGER LOW TO THE N LATER TODAY. THE
ASSOCIATED COLD FRONT ENTERS THE AREA NEAR 32N26W AND EXTENDS
SWD ALONG 24N27W 16N34W. MOISTURE IS MOST ORGANIZED WELL N OF
THE OCCLUDED LOW...OUTSIDE OF THE DISCUSSION AREA. SCATTERED
SHOWERS ARE WITHIN 150 NM AHEAD OF THE COLD FRONT N OF 20N. THE
MOST SIGNIFICANT WEATHER EFFECT ASSOCIATED WITH THIS LOW PRES
SYSTEM IS THE STRONG WINDS AND HIGH SEAS...AS A TIGHT PRES GRAD
EXISTS BETWEEN THIS LOW AND THE HIGH TO IT'S NW PRODUCING NEAR
GALE FORCE CONDITIONS IN THE REGION BETWEEN THE LOW AND 40W N OF
25N. STRONGER WINDS EXIST TO THE N OF THE AREA WHERE THE GRAD IS
TIGHTER. THESE STRONG NLY WINDS HAVE CREATED SIGNIFICANT SWELL
PRODUCING COMBINED SEAS OF 14-18 FT IN THE REGION OUTLINED. THE
REMAINDER OF THE SUBTROPICAL E ATLC IS UNDER A NARROW UPPER
RIDGE WITH THE AXIS ALONG 16W KEEPING CONDITIONS RATHER TRANQUIL
ACROSS THE CANARY ISLANDS AND WRN AFRICA. 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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