[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 122357
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
705 PM EST SAT JAN 12 2008

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...
THE ITCZ AXIS IS CENTERED ALONG 8N13W 4N23W 2N33W CROSSING THE
EQUATOR NEAR 37W TO 2S45W. SCATTERED MODERATE CONVECTION IS WITHIN
75 NM OF THE AXIS BETWEEN 27W-30W AND FROM THE EQUATOR TO 2N BETWEEN
12W-17W.

...DISCUSSION...

THE GULF OF MEXICO...
A WEAK FRONTAL BOUNDARY IS STALLED ACROSS THE NRN HALF FROM THE BIG
BEND AREA OF FLORIDA TO NRN MEXICO ALONG 29N83W 25N97W. A 1010 MB
LOW IS ANALYZED AT THE TAIL END OF THE FRONT BASED ON LOW PRES
VALUES IN THE NEARBY LAND AND BUOY OBS...BUT HAS LITTLE CLOUD
SIGNATURE. COMBINATION OF MOSAIC DOPPLER RADAR AND LIGHTNING DATA
SUGGEST SCATTERED SHOWERS AND TSTMS WITHIN 60 NM N OF THE STATIONARY
FRONT. THE FRONT HAS LITTLE UPPER SUPPORT AT THE MOMENT AS WATER
VAPOR IMAGES AND DERIVED UPPER WINDS SHOW WIDESPREAD SWLY FLOW
AREA-WIDE. HOWEVER...SUPPORT IS ON THE WAY AS A LARGE UPPER TROUGH
OVER THE CENTRAL U.S. SHIFTS E. THIS TROUGH IS SUPPORTING A COLD
FRONT CURRENTLY OVER E TEXAS. MODEL GUIDANCE SHOWS THESE BOUNDARIES
MERGING AND SWEEPING THROUGH THE MAJORITY OF THE AREA WITHIN THE
NEXT 24-36 HOURS BRINGING COOLER CONDITIONS TO THE REGION.

THE CARIBBEAN SEA...
SUBSIDENT MID TO UPPER RIDGE LIES ABOVE THE ENTIRE ZONE LIMITING THE
DEVELOPMENT OF CONVECTION OR DEEP CLOUDINESS. PATCHES OF LOW LEVEL
CLOUDS ARE STREAMING FROM W TO E ACROSS THE SEA. THE THICKEST
PATCHES ARE S OF 17N E OF 68W AND FROM 14N-19N BETWEEN 79W-82W. THE
STEERING FOR THESE LOW-LEVEL CLOUD AREAS ARE THE TRADES WINDS WHICH
ARE MAINLY MODERATE...EXCEPT LIGHT AND SELY IN THE NW PORTION.
OVERALL...LITTLE CHANGE IS EXPECTED UNTIL A FRONT MOVES INTO THE NW
CORNER ON MON.

THE ATLANTIC OCEAN...
A WEAK 1013 MB LOW PRES SYSTEM IS DRIFTING N CENTERED NEAR 27N60W.
WHILE THE LOW-LEVEL CIRCULATION IS EASILY EVIDENT...THE SYSTEM IS
DEVOID OF CONVECTION. AN EARLIER ASCAT PASS CAPTURED THE CIRCULATION
WELL REVEALING WINDS MOSTLY LESS THAN 20 KT. NWP MODELS SHOW A
CONTINUED NWD DRIFT AS IT OPENS INTO A TROUGH OVER THE NEXT DAY OR
TWO...EVENTUALLY BEING ABSORBED BY A MUCH LARGER EXTRATROPICAL LOW.
DENSE CLOUDINESS AND EMBEDDED SCATTERED SHOWERS/ISOLATED TSTMS LIE
WELL TO THE E OF THE SFC LOW N OF 22N BETWEEN 46W-53W IN AN UPPER
DIFFLUENT ZONE.

THE W ATLC W OF 60W IS UNDER SWLY UPPER FLOW AND WEAK SFC RIDGING.
THIS PATTERN IS PRODUCING SCATTERED CLOUDS AT DIFFERENT LEVELS BUT
NOT AMOUNTING TO MUCH SIGNIFICANT WEATHER. MUCH STRONGER SFC RIDGING
LIES OVER THE E ATLC WITH A FAIRLY WELL DEFINED TROUGH ALOFT
EXTENDING FROM THE MADEIRA ISLANDS NEAR 32N17W TO 22N35W. SWIFT MID
TO UPPER ZONAL FLOW LIES OVER THE TROPICAL BELT. THIS OVERALL
PATTERN IS ALSO NOT AMOUNTING TO MUCH SENSIBLE WEATHER WITH ONLY A
SWATH OF MID-HIGH LEVEL CLOUDS AND POSSIBLE SHOWERS FROM 10N-16N E
OF 50W.

$$
CANGIALOSI




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