[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 171159
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
705 AM EST FRI DEC 17 2010

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHERN SECTIONS OF
SOUTH AMERICA...AND 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.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 09N13W 07N30W TO THE EQUATOR NEAR
50W. ISOLATED MODERATE CONVECTION IS FROM 03N-07N BETWEEN
12W-17W. WIDELY SCATTERED MODERATE CONVECTION IS WITHIN 120 NM
EITHER SIDE OF A LINE FROM 01N29W TO 09N40W. ISOLATED MODERATE
CONVECTION IS FROM 01N-04N BETWEEN 38W-43W.

...DISCUSSION...

GULF OF MEXICO...
UPPER LEVEL RIDGING AND STRONG SUBSIDENCE IS NOTED ALOFT ON
WATER VAPOR IMAGERY ACROSS THE EASTERN GULF THIS MORNING.
HOWEVER...THE UPPER LEVEL RIDGE IS GIVING WAY TO AN UPPER LEVEL
TROUGH PROGRESSING ACROSS NEW MEXICO AND WEST TEXAS ALONG 104W
THAT IS SUPPORTING A COLD FRONT ANALYZED FROM VERMILION BAY NEAR
30N92W SE TO NEAR BROWNSVILLE TEXAS AND INLAND OVER NORTHERN
MEXICO. OVERALL THE FRONT LACKS ANY SIGNIFICANT CONVECTION...
HOWEVER...LOW-LEVEL ADVECTION AND CONVERGENCE OF MOISTURE ON
S-SW RETURN FLOW LOCATED ON THE WESTERN PERIPHERY OF A WESTERN
ATLC SURFACE RIDGE IS GENERATING ISOLATED SHOWERS WITHIN 180 NM
SE OF THE COLD FRONT. LOOKING AHEAD FOR THE UPCOMING WEEKEND...
THE WEAK FRONTAL BOUNDARY IS FORECAST TO SWEEP ACROSS THE GULF
BY LATE SATURDAY AND INTRODUCE NORTHERLY WINDS TO 20 KT OVER THE
REGION THROUGH EARLY SUNDAY.

CARIBBEAN SEA...
VERY STRONG SUBSIDENCE AND DRY AIR ALOFT IS NOTED ACROSS THE NW
CARIBBEAN THAT CONTINUES TO SUPPORT A SURFACE RIDGE EXTENDING
FROM THE W ATLC AND FLORIDA PENINSULA TO THE GULF OF HONDURAS N
OF 15N AND W OF 80W. OVERALL STABLE CONDITIONS PERSIST AS A
RESULT...WITH MOSTLY SCATTERED TO BROKEN STRATOCUMULUS CLOUDS
NOTED ON SATELLITE IMAGERY THIS MORNING. ON THE SOUTHERN
PERIPHERY OF THE SURFACE RIDGE OVER THE EASTERN AND CENTRAL
CARIBBEAN...A SHEAR LINE IS ANALYZED FROM THE MARTINIQUE PASSAGE
TO 14N67W TO 15N73W. AN RECENT 17/0202 UTC ASCAT PASS CAPTURED
STRONGER NE WINDS OVER THE NE CARIBBEAN NORTH OF THE SHEAR
LINE...THEN GENERALLY LIGHTER E-NE TRADES SOUTH OF THE SHEAR
LINE AXIS. LOW-LEVEL SPEED CONVERGENCE IN VICINITY OF THIS
BOUNDARY IS PROVIDING FOCUS FOR ISOLATED SHOWERS N OF THE SHEAR
LINE BETWEEN 63W-74W. ELSEWHERE...A SURFACE TROUGH IS ANALYZED
FROM THE NORTHERN COAST OF COLOMBIA NEAR 09N76W TO 17N76W. NEAR
THE NORTHERN PORTION OF THE TROUGH AXIS...STRONGER LOW-LEVEL
CONVERGENCE...DUE PARTIALLY TO STRONGER NE WINDS FUNNELING
THROUGH THE WINDWARD PASSAGE...IS GENERATING SCATTERED SHOWERS
AND ISOLATED TSTMS FROM 15N-20N BETWEEN 74W-78W.

ATLANTIC OCEAN...
MOSTLY DRY AIR AND STRONG SUBSIDENCE RESIDES WITHIN WESTERLY
ZONAL UPPER LEVEL FLOW ACROSS THE W ATLC W OF 45W THAT CONTINUES
TO SUPPORT A BROAD SURFACE RIDGE ANCHORED BY A 1021 MB HIGH
CENTERED NEAR 27N67W. MOSTLY FAIR CONDITIONS ARE FOUND WITHIN
THE INFLUENCE OF THIS FEATURE THIS MORNING. OVER THE CENTRAL
ATLC...AN UPPER LEVEL TROUGH AND MID-LEVEL LOW IS NOTED ON WATER
VAPOR IMAGERY NORTH OF THE DISCUSSION AREA IN THE VICINITY OF
37N47W THAT SUPPORTS A COLD FRONT ENTERING THE REGION NEAR
32N44W THEN EXTENDING SW TO 25N48W. MOST OF THE FRONT S OF 25N
HAS BECOME DIFFUSE WITH A SURFACE TROUGH TRAILING S-SW ALONG
26N47W TO 17N51W. ISOLATED SHOWERS REMAIN WITHIN 120 NM EAST OF
THE COLD FRONT S OF 31N...WITH MORE ENHANCED DEEPER CONVECTION
EXTENDING WITHIN 120 NM EAST OF THE FRONT N OF 31N. FARTHER
EAST...AN UPPER LEVEL LOW CENTERED NEAR 34N19W CONTINUES TO
IMPACT MUCH OF THE EASTERN ATLC E OF 30W DRIVING A STRONG 988 MB
LOW CENTERED WEST OF THE MADEIRA ISLANDS NEAR 33N20W. THIS
PARTIALLY OCCLUDED LOW EXTENDS A COLD FRONT INTO THE AREA ALONG
32N13W ACROSS THE EASTERNMOST CANARY ISLANDS NEAR 28N15W THEN
BECOMING MORE DIFFUSE ALONG 23N20W 21N27W. ISOLATED SHOWERS ARE
MAINLY OCCURRING WITHIN 120 NM EAST OF THE FRONT.

FOR ADDITIONAL INFORMATION PLEASE VISIT
HTTP://WWW.HURRICANES.GOV/MARINE

$$
HUFFMAN



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