[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 312326
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
705 PM EST SUN DEC 31 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
2315 UTC.

...THE ITCZ...
ITCZ AXIS IS ALONG 6N10W 2N26W 1N40W TO THE EQUATOR AND 50W.
SCATTERED MODERATE CONVECTION IS WITHIN 60 NM EITHER SIDE
BETWEEN 12W-16W. ISOLATED MODERATE IS WITHIN 240 NM N OF THE
AXIS BETWEEN 33W-44W.

...DISCUSSION...
THE GULF OF MEXICO...
A COLD FRONT ENTERED THE NW CORNER OF THE GULF NEARLY 48 HOURS
AGO AND CONTINUES TO SLOWLY INCH EASTWARD. AS OF 21Z...THE FRONT
WAS ANALYZED FROM PENSACOLA FLORIDA TO S MEXICO ALONG 31N87W
24N91W 18N94W. DOPPLER RADAR FROM THE SE U.S. SHOWS A STRONG
BAND OF NUMEROUS SHOWERS AND TSTMS AHEAD OF THE FRONT ACROSS THE
FL PANHANDLE AND THE BIG BEND AREA NWD INTO GEORGIA. IR IMAGERY
SUGGESTS THAT SIMILAR ACTIVITY IS LIKELY OCCURRING FURTHER SE
WITHIN 90 NM EITHER SIDE OF THE FRONT BETWEEN 25N-30N. THE SE
GULF AND MUCH OF THE FL PENINSULA STILL LIES UNDER MID TO UPPER
LEVEL RIDGING WITH DRY AIR IN PLACE. HOWEVER...SOME MOISTENING
WILL OCCUR AS THE FRONT NEARS AND THE RIDGE CONTINUES TO RETREAT
E. SHIP...BUOY AND QSCAT DATA SHOWS SLY WINDS MAINLY WITHIN THE
15-20 KT RANGE WHICH IS ADVECTING A WARM AND HUMID AIRMASS FOR
THE MIDDLE OF WINTER. BEHIND THE FRONT...CONSIDERABLE CLOUDINESS
AND SCATTERED SHOWERS ARE LINGERING FOR ABOUT 200 NM W OF THE
BOUNDARY WITH CLEARING SKIES CONFINED TO THE FAR NW PORTION. SFC
WINDS ARE NLY IN THE 15-25 KT RANGE...STRONGEST CLOSEST TO THE
FRONT. THE AIRMASS BEHIND THE FRONT IS NOTICEABLY COOLER BUT FAR
FROM COLD WITH TEMPS GENERALLY IN THE 60'S AND LOW 70'S. DEW
POINTS HAVE DROPPED OFF TO THE UPPER 30'S F ACROSS THE NW GULF
COAST WHERE THE CLOUDS HAVE CLEARED. OVER THE NEXT COUPLE OF
DAYS...THE FRONT WILL CONTINUE ITS SLOW MOTION...WEAKEN
CONSIDERABLY AND EVENTUALLY BECOME STATIONARY DRAPED E-W ACROSS
THE AREA. THE ASSOCIATED MOISTURE WILL LIKELY THIN OUT AS SFC
HIGH PRES BUILDS IN.

THE CARIBBEAN SEA...
AN AMPLIFIED UPPER LEVEL RIDGE/TROUGH PATTERN EXISTS IN THE
REGION. THE UPPER RIDGE AXIS LIES ROUGHLY ALONG 82W AND COVERS
THE CARIB W OF 75W. THE REMAINDER OF THE AREA IS UNDER A
WELL-DEFINED CENTRAL ATLC TROUGH. UPPER LEVEL CONFLUENCE BETWEEN
THESE BROAD FEATURES IS PRODUCING WIDESPREAD DRY AND STABLE AIR
IN THE MID AND UPPER LEVELS. THIS SINKING...STABLE AIR IS
KEEPING THE WX CONDITIONS VERY QUIET WITH NO AREAS OF
SIGNIFICANT DEEP CLOUDINESS OR SHOWER ACTIVITY NOTED ON IR
IMAGERY. WHILE CONVECTION IS NOT A CONCERN...STRONG TRADES WINDS
ARE. SFC OBSERVATIONS SHOW WINDS BETWEEN 20-30 KT ...STRONGEST N
OF THE COLOMBIAN COAST. THESE WINDS ARE PRODUCING HAZARDOUS SEAS
UP TO 14 FT. THE STRONG LOW-LEVEL FLOW IS ALSO STIRRING UP
ENOUGH INSTABILITY TO FORM SHALLOW QUICK MOVING SHOWERS...AS
NOTED ON SAN JUAN'S 88-D. TRADE WINDS ARE EXPECTED TO REMAIN ON
THE STRONG SIDE THRU MUCH OF NEXT WEEK AS THE PRES GRAD REMAINS
TIGHT. MAINLY DRY CONDITIONS ARE ALSO EXPECTED TO PERSIST AS THE
UPPER TROUGH IN THE CENTRAL ATLC MOVES OUT AND THE MID TO UPPER
RIDGE BUILDS E.

THE ATLANTIC OCEAN...
A LONG WAVE RIDGE/TROUGH/RIDGE PATTERN IS ESTABLISHED ACROSS THE
SUBTROPICAL ATLC. STARTING IN THE W ATLC...AN AMPLIFIED MID TO
UPPER RIDGE IS ALIGNED FROM THE NW CARIB NWD ACROSS THE BAHAMAS
INTO THE NE U.S. BROKEN CLOUDINESS...STREAMING FROM THE
GULF...IS ROTATING AROUND THE THE RIDGE STAYING N OF THE
DISCUSSION AREA. A VERY BROAD MID TO UPPER LEVEL TROUGH IS
COVERING A LOT OF OCEAN BETWEEN 38W AND 73W. THIS TROUGH HAS
SHARPENED AND BECOME MORE ELONGATED SINCE YESTERDAY AS SHORT
WAVES CONTINUE TO ROTATE THRU. THERE APPEAR TO BE A FEW WEAK SFC
FEATURES ASSOCIATED WITH THIS BROAD TROUGH. THE CLEAREST
BOUNDARY IS A COLD FRONT WHICH IS JUST ENTERING THE AREA ALIGNED
E-W ALONG 31N/32N BETWEEN 58W-71W. THIS FRONT ACTS AS A SURGE IN
NLY WINDS. ANOTHER WEAK BOUNDARY IS A LINGERING SFC TROUGH WHICH
IS AHEAD OF THE FRONT ALONG 29N59W 28N68W 28N74W. THIS FEATURE
IS AWFULLY WEAK...GENERATING MAYBE ISOLATED SHOWERS WITHIN 90 NM
BUT A CLEAR LOW CLOUD LINE AND EVEN SOME VEERING IN THE WINDS...
WHICH IS THE REASON FOR ANALYZING THIS FEATURE. TWO OTHER WEAK
SFC TROUGHS...WHICH ARE ILL-DEFINED...ARE LOCATED FURTHER E.
LOW-LEVEL LIFTING ALONG WITH MOIST SWLY UPPER LEVEL FLOW IS
GENERATING A SWATH OF MOISTURE BETWEEN 40W-51W N OF 21N.  A
LARGE MID TO UPPER LEVEL RIDGE COVERS THE REMAINDER OF THE
SUBTROPICAL ATLC E OF 38W ANCHORED BY A HIGH CENTER 150 NM S OF
THE CANARY ISLANDS NEAR 26N18W. THE SW PORTION OF THIS RIDGE IS
ERODED BY A WEAKENING...NWD MOVING UPPER LOW CENTERED NEAR
24N33W. STRONG SWLY FLOW...TO THE E OF THE UPPER LOW...IS
GENERATING AND DRAWING MOISTURE NWD LIKELY PRODUCING SCATTERED
SHOWERS BETWEEN 25W-31W MAINLY FROM 23N-30N. MAINLY FAIR WEATHER
EXISTS OVER MUCH OF THE OCEAN NOT OUTLINED. IN THE DEEP
TROPICS...EXTENSIVE WLY FLOW ON THE N SIDE OF A BROAD UPPER
RIDGE IS THE RULE WITH CONVECTION CONFINED TO THE ITCZ.

$$
CANGIALOSI




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