[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 222333
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
705 PM EST SAT DEC 22 2007

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHERN
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 CENTERED ALONG 8N13W 4N27W 4N38W 8N54W 9N62W.
SCATTERED MODERATE CONVECTION IS WITHIN 150 NM OF THE AXIS
BETWEEN 36W-45W AND WITHIN 90 NM OF THE AXIS BETWEEN 51W-55W.
SIMILAR CONVECTION IS FROM 4N-6N BETWEEN 25W-26W.

...DISCUSSION...

THE GULF OF MEXICO...
A COLD FRONT HAS ENTERED THE NW CORNER FROM CENTRAL LOUISIANA TO
THE MEXICAN COAST NEAR 23N98W THEN NWD ALONG THE E SLOPES OF THE
SIERRA MADRE TO 26N100W...AT 21Z. THIS FRONT IS OBTAINING
SUPPORT FROM A DEEP LAYERED LOW OVER THE SRN PLAINS WHICH IS
PRODUCING WINTRY WEATHER ON IT'S BACK SIDE. DOPPLER RADAR AND
LIGHTNING DATA DETECT A WELL DEFINED LINE OF SCATTERED TSTM
ACTIVITY WITHIN 45 NM AHEAD OF THE FRONT N OF 28N. THIS ACTIVITY
THINS OUT SUBSTANTIALLY S OF 28N. TEMPS HAVE BEEN UNSEASONABLY
WARM TODAY AHEAD OF THE FRONT...AND ARE NOW FALLING BACK TO AND
BELOW TYPICAL LEVELS AS THE BOUNDARY PASSES. A QUICK SHOT OF NLY
GALE FORCE WINDS ARE ANTICIPATED IN THE SW GULF BEGINNING LATER
TONIGHT INTO THE FIRST HALF OF TOMORROW. STILL WARM AND HUMID IN
THE WARM SECTION BETWEEN THE AFOREMENTIONED COLD FRONT AND A
WARM FRONT FROM 24N88W TO THE NEW ORLEANS AREA. BROKEN
CLOUDINESS AND POSSIBLE ISOLATED SHOWERS ACCOMPANY THE WARM
FRONT. THE E GULF IS FAIRLY TRANQUIL THIS EVENING WITH ONLY
PATCHY CLOUDS AND A COUPLE OF LIGHT SHOWERS ON THE FLA E COAST
BLOWING IN FROM THE ATLC.

THE CARIBBEAN SEA...
MID TO UPPER RIDGE IS PARKED OVER THE W CARIB WITH THE FLOW ALOFT
BECOMING ZONAL E OF ABOUT 75W. ABUNDANT STRONG SUBSIDENCE IS
NOTED NEARLY EVERYWHERE PROVIDING NICE WEATHER ACROSS MOST OF
THE REGION. HOWEVER...THERE ARE A COUPLE EXCEPTIONS. ONE IS IN
THE CENTRAL CARIB N OF VENEZUELA WHERE SCATTERED SHOWERS ARE
POSSIBLE S OF 15N BETWEEN 67W-72W...ASSOCIATED WITH A WEAK SFC
TROUGH. SLIGHTLY DEEPER PRECIP...ALSO SCATTERED IN NATURE...IS
IN THE SW CARIB S OF 12N BETWEEN 76W-82W ENHANCED BY THE ITCZ
AND SLIGHTLY DIFFLUENT FLOW ALOFT. TRADE WIND FLOW IS LIGHT TO
MODERATE AREA-WIDE...EXCEPT NEAR 20 KT IN THE VICINITY OF THE
COLOMBIAN COAST.

THE ATLANTIC OCEAN...
MAIN FEATURE IN THE W ATLC IS A COMPLEX AREA OF LOW PRES.
EARLIER...WE ANALYZED THIS SYSTEM AS SERIES OF LOWS DUE TO
SEVERAL SWIRLS ROTATING ABOUT A CENTER. HOWEVER...SINCE THEN A
LOW APPEARS TO BE DOMINATE NEAR 29N69W...1009 MB...WITH A TROUGH
HANGING WSW TO SOUTH FLORIDA. THIS LOW IS VERTICALLY STACKED AS
WATER VAPOR IMAGES REVEAL AN UPPER CENTER NEARLY OVERHEAD. MOST
OF THE DEEP CLOUDINESS...SCATTERED SHOWERS AND TSTMS ARE
SITUATED TO THE E OF THE CENTER IN AN UPPER DIFFLUENT ZONE FROM
25N-32N BETWEEN 60W-67W. AN ASSOCIATED COLD FRONT EXTENDS FROM
30N67W TO 23N72W THEN DISSIPATING ACROSS CENTRAL CUBA. SCATTERED
SHOWERS ARE TSTMS ARE WITHIN 60 NM AHEAD OF THE FRONT N OF 24N.

THERE ARE A COUPLE OF WEAK FEATURES IN THE CENTRAL ATLC. ONE IS
THE TAIL END OF A OLD FRONTAL BOUNDARY WHICH APPEARS TO BE
LIFTING NWD ALONG 32N38W 28N48W 27N55W. LITTLE SIGNIFICANT
CLOUDINESS IS ALONG THIS WEAK BOUNDARY. A SMALLER SCALE INVERTED
SFC TROUGH IS IN THE TROPICS E OF THE NRN LEEWARDS ALONG 58W
FROM 16N-21N. NIGHT CHANNEL VIS IMAGERY SHOWS DISTINCT TURNING
IN THE LOW-LEVEL CLOUDS BUT LITTLE IN THE WAY OF DEEP
CONVECTION. SCATTERED SHOWERS ARE LIKELY WITHIN 180 NM E OF THE
AXIS. THE E ATLC IS THE QUIETEST PART OF THE BASIN WITH SFC
HIGH PRES AND ZONAL FLOW ALOFT DOMINATING THE WX PATTERN. THIS
IS PRODUCING MAINLY FAIR WEATHER...ONLY PATCHY MID-HIGH LEVEL
CLOUDINESS...AND MODERATE NE TO E TRADES.

$$
CANGIALOSI




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