[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 170547
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
105 AM EST SAT NOV 17 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0515 UTC.

...TROPICAL WAVES...
TROPICAL WAVE IS ALONG 56W S OF 17N MOVING W 15 KT. NIGHT
CHANNEL VIS IMAGERY REVEALS SLIGHT LOW-LEVEL TURNING IN THE
THIN LOW-LEVEL CLOUDS. THE ONLY AREA OF SHOWER ACTIVITY AT THE
MOMENT IS NEAR THE INTERSECTION OF THE ITCZ FROM 9N-10N BETWEEN
57W-58W. BUOY DATA IN THE REGION SHOWS AN SLP MINIMUM NEAR THE
WAVE AXIS AND A RECENT QSCAT PASS DEPICTS A SLIGHT INCREASE IN
THE ELY TRADES ALONG AND TO THE E OF THE WAVE.

TROPICAL WAVE IS IN THE CENTRAL CARIBBEAN ALONG 75W S OF 19N
MOVING W 10-15 KT. THE MIMIC TPW ANIMATION PROVIDES A BIT OF
HISTORY ON THIS WAVE SHOWING A WELL DEFINED...ALBEIT
NARROW...MOISTURE PLUME TRACKING ACROSS THE CARIB THU AND EARLY
FRI. THIS MOISTURE AREA...WHICH IS THOUGHT TO REPRESENT MUCH OF
THE WAVE ENERGY...HAS BEEN PULLED TO THE NE BY A STRONG COLD
FRONT OVER THE LAST SEVERAL HOURS. THE LEFT OVER PORTION OF THE
WAVE APPEARS WEAK AND IS PRODUCING ISOLATED SHOWERS AT BEST IN
ITS VICINITY.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 8N13W 6N25W 7N40W 9N54W 8N62W.
SCATTERED MODERATE CONVECTION IS WITHIN 120 NM N OF THE AXIS
BETWEEN 26W-36W AND WITHIN 240 NM S OF THE AXIS BETWEEN 34W-38W.
ISOLATED MODERATE IS WITHIN 90 NM EITHER SIDE OF THE AXIS
BETWEEN 42W-48W.

DISCUSSION...

THE GULF OF MEXICO...
SFC HIGH PRES CONTINUES TO SHIFT SE CENTERED JUST S OF THE FL
PANHANDLE NEAR 30N87W...ANALYZED 1021 MB. IT IS A VERY CHILLY
NIGHT ACROSS THE SOUTHEAST ON THE E SIDE OF THE HIGH WITH TEMPS
NEAR THE FREEZING MARK IN INLAND PORTIONS OF NW FLORIDA. THE
AIRMASS MODIFIES FURTHER W ESPECIALLY W OF 92W WHERE LOW-LEVEL
RETURN FLOW HAS SET UP. FAIR WEATHER EXISTS ACROSS THE ENTIRE
AREA WITH SATELLITE IMAGERY SHOWING COOL AIR STRATOCUMULUS
CLOUDS AS THE PRIMARY MOISTURE SOURCE IN THE CENTRAL AND E GULF
AND SOME PATCHY LOW TO MID LEVEL CLOUDS IN THE BAY OF
CAMPECHE...POSSIBLY ASSOCIATED WITH A VERY WEAK SFC TROUGH. IN
THE MID AND UPPER LEVELS...MODEST RIDGING AND ABUNDANT STABLE
AIR COVERS THE REGION.

THE CARIBBEAN SEA...
STRONG COLD FRONT THAT SWEPT THROUGH THE GULF OF MEXICO THU AND
FRI IS GRADUALLY LOSING ITS IDENTITY IN THE NW CARIBBEAN
...ANALYZED FROM WRN CUBA TO THE CENTRAL YUCATAN. COOL AIR HAS
WORKED ITS WAY AS FAR S AS THE NRN YUCATAN WITH TEMPS IN THE
LOWER 60'S F IN CANCUN. THERE IS SOME PATCHY LOW-LEVEL
CLOUDINESS AND ISOLATED SHOWERS WITHIN 60 NM OF THE FRONT.
FARTHER S...IR IMAGERY SHOWS SMALL CLUSTERS OF SHOWERS AND
ISOLATED TSTMS IN THE SW CARIB FROM 9N-12N BETWEEN 79W-83W
ASSOCIATED WITH LOW-LEVEL CONFLUENCE NEAR THE ITCZ. SIMILAR
WEATHER IS OCCURRING OVER PUERTO RICO AND HISPANIOLA TIED TO THE
TAIL END OF A PRE-FRONTAL TROUGH. SAN JUAN DOPPLER RADAR SHOWS
MUCH OF THE STRONGER ACTIVITY BOTH N AND SW OF THE ISLAND AT THE
MOMENT. SCATTERED SHOWERS ARE ALSO MAKING THEIR WAY TOWARD THE
WINDWARD ISLANDS TRIGGERED BY APPROACHING WEAK TROPICAL WAVE.
THE REMAINDER OF THE AREA IS RELATIVELY TRANQUIL WITH MODERATE
DRY AIR AND SW TO ZONAL FLOW OVERHEAD.

THE ATLANTIC OCEAN...
MID AND UPPER LEVEL TROUGHING DOMINATES MUCH OF THE WRN ATLC
EXTENDING SWD FROM A POLAR VORTEX. THIS UPPER SYSTEM IS
SUPPORTING A FAIRLY STRONG COLD FRONT WHICH EXTENDS FROM 32N60W
ACROSS THE SE BAHAMAS. THE COMBINATION OF SFC HIGH PRES BEHIND
THE FRONT AND A VERY DRY ENVIRONMENT ALOFT IS PROVIDING FAIR AND
COOL WEATHER ACROSS THE SW ATLC. NIGHT CHANNEL VIS IMAGERY SHOWS
A LARGE AREA OF SCATTERED STRATOCUMULUS CLOUDS...INDICATIVE OF
THE COOL AIRMASS IN PLACE. SOME ACTIVE WEATHER LIES IN A
DIFFLUENT ZONE ALOFT BETWEEN THE TROUGH AND A RIDGE AXIS ALONG
51W/52W. IR IMAGES AND LIGHTNING DATA REVEAL SCATTERED SHOWERS
AND TSTMS N OF 21N BETWEEN 53W-61W AND S OF 20N BETWEEN 64W-68W.
A SFC TROUGH FROM 27N58W TO THE DOMINICAN REPUBLIC...WHICH
SHOWED UP FAIRLY WELL IN AN EARLIER QSCAT PASS...IS ENHANCING
SOME OF THIS WEATHER ESPECIALLY S OF 20N.

PART OF THE CENTRAL ATLC...BETWEEN 40W AND 52W...IS DOMINATED BY
DEEP LAYER RIDGING WHICH IS ONLY ADVECTING SOME DEBRIS HIGH
LEVEL CLOUDINESS. THE PATTERN QUICKLY CHANGES THEME IN THE E
ATLC WHERE LARGE SCALE DEEP LAYER TROUGHING IS IN PLACE ANCHORED
BY AN UPPER LOW NEAR 36N29W. A MID-LEVEL DISTURBANCE TO THE S OF
THE UPPER LOW IS GENERATING SCATTERED SHOWERS AND TSTMS FROM
24N-27N BETWEEN 29W-34W. THIS LARGE SCALE UPPER TROUGH IS
SUPPORTING A 1006 MB LOW W OF THE MADEIRA ISLANDS WHICH HAS A
TRAILING COLD FRONT ALONG 32N21W 25N29W 24N38W. A SWLY JET
BRANCH HAS SET UP NEAR THE BASE OF THE TROUGH AND THEN RUNS NE
ALONG 14N47W 17N30W 24N22W GENERATING AND ADVECTING MID HIGH
LEVEL CLOUDINESS WITHIN 150 NM SE OF THE JET AXIS.

$$
CANGIALOSI




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