[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 172353
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
705 PM EST MON DEC 17 2012

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...WEATHER OBSERVATIONS...RADAR...AND METEOROLOGICAL
ANALYSIS.

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2315 UTC.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 08N13W TO
08N16W. THE INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM
08N16W TO 04N30W TO 02N45W. WIDELY SCATTERED MODERATE CONVECTION
IS FROM 02N-06N BETWEEN 05W-18W. SCATTERED MODERATE CONVECTION
IS FROM THE EQUATOR TO 07N BETWEEN 20W-44W...AND FROM 06N-10N
BETWEEN 44W-49W.

...DISCUSSION...

GULF OF MEXICO...
A BROAD MIDDLE TO UPPER LEVEL TROUGH IS NOTED ON WATER VAPOR
IMAGERY PROGRESSING EASTWARD OVER THE LOWER MISSISSIPPI RIVER
VALLEY AND NW GULF WITH AXIS EXTENDING FROM 36N88W TO 24N101W.
THIS TROUGHING SUPPORTS A COLD FRONT ANALYZED FROM THE SOUTH-
CENTRAL LOUISIANA COAST NEAR 30N91W S-SW TO THE MEXICO COAST
NEAR 23N98W. EXAMINING MOSAIC DOPPLER RADAR IMAGERY AND
LIGHTNING DATA...IT APPEARS THE FRONT REMAINS MOSTLY DRY WITH
THE MAIN IMPACTS OF A SIGNIFICANT WIND SHIFT AND MUCH COOLER AND
DRIER AIRMASS FOLLOWING IN WAKE OF THE FRONT. TO THE EAST OF THE
FRONT...SURFACE PRESSURE ANALYSIS INDICATES TROUGHING COVERS
MUCH OF THE NORTHERN GULF N OF 28N...CENTRAL GULF BETWEEN 90W-
93W...AND SW GULF S OF 24N BETWEEN 90W-96W. A SURFACE TROUGH IS
ANALYZED FROM THE FLORIDA PANHANDLE SW TO 26N94W AND IS
PROVIDING MOST OF THE FOCUS FOR SCATTERED SHOWERS AND ISOLATED
TSTMS OCCURRING WITHIN 120 NM EITHER SIDE OF THE BOUNDARY.
ANOTHER SURFACE TROUGH EXTENDS FROM 24N94W TO 19N96W IN THE SW
GULF WITH INCREASED CLOUDINESS AND POSSIBLE ISOLATED SHOWERS S
OF 23N W OF 94W. THE COLD FRONT IS FORECAST TO SWEEP EAST OF THE
BASIN BY LATE TUESDAY WITH HIGH PRESSURE DOMINATING ANCHORED BY
A HIGH CENTERED IN THE VICINITY OF THE NE GULF WATERS.

CARIBBEAN SEA...
CONDITIONS ACROSS THE CARIBBEAN SEA BASIN REMAIN FAIRLY TRANQUIL
THIS EVENING AS WATER VAPOR IMAGERY INDICATES VERY DRY AIR AND
SUBSIDENCE PREVAILS. AN UPPER LEVEL ANTICYCLONIC CIRCULATION IS
CENTERED NEAR 22N76W AND INFLUENCES MUCH OF THE NW CARIBBEAN.
OVER THE EASTERN CARIBBEAN...AN UPPER LEVEL TROUGH AXIS EXTENDS
FROM THE CENTRAL ATLC FROM 20N54W TO 16N65W TO 14N79W. AT THE
SURFACE...A PAIR OF WEAK TROUGHS ARE ANALYZED FROM 14N-18N ALONG
64W...AND FROM 16N80W TO 20N81W. ISOLATED SHOWERS ARE OCCURRING
OVER THE NE CARIBBEAN N OF 16N BETWEEN 61W-65W...AND FROM
16N-20N BETWEEN 79W-83W. OTHERWISE...TRADE WINDS PREVAIL IN THE
RANGE OF 10 TO 20 KT WITH LITTLE CHANGE EXPECTED THROUGH MIDWEEK.

ATLANTIC OCEAN...
WITH A BROAD MIDDLE TO UPPER LEVEL TROUGH CURRENTLY LOCATED OVER
THE SE CONUS AND APPROACHING FROM THE WEST...AN UPPER LEVEL
ANTICYCLONIC CIRCULATION IS CENTERED OVER THE SW NORTH ATLC NEAR
22N76W AND EXTENDS A RIDGE AXIS N-NE TO BEYOND 32N70W. AT THE
SURFACE HOWEVER...A SURFACE RIDGE ANCHORED BY A 1020 MB HIGH
CENTERED NEAR 24N55W IS EXPECTED TO SHIFT EAST WITH INCREASED
SOUTHWESTERLY WINDS N OF 29N W OF 60W TO IMPACT THE SW NORTH
ATLC WATERS. CURRENTLY...SCATTERED SHOWERS AND ISOLATED TSTMS
ARE BEGINNING TO SHIFT OFFSHORE AND REMAIN WEST OF A LINE FROM
29N81W TO 32N76W. FARTHER EAST...A WEAKENING SURFACE TROUGH IS
ANALYZED ON THE SOUTHEASTERN PERIPHERY OF THE PREVIOUSLY
MENTIONED SURFACE RIDGE FROM 30N46W TO 26N52W TO 24N61W.
ISOLATED SHOWERS ARE OCCURRING WITHIN 90 NM EITHER SIDE OF THE
BOUNDARY. FINALLY...AN UPPER LEVEL TROUGH AXIS EXTENDS FROM
32N43W TO 16N61W AND SUPPORTS A SURFACE TROUGH ANALYZED FROM
32N36W TO 22N46W. THE TROUGHING REPRESENTS A WEAKNESS IN THE
SUBTROPICAL RIDGING ACROSS THE CENTRAL AND EASTERN ATLC WITH
WIDELY SCATTERED SHOWERS AND ISOLATED TSTMS OCCURRING WITHIN 240
NM EITHER SIDE OF A LINE FROM 32N35W TO 20N41W TO 10N58W.

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

$$
HUFFMAN




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