[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 032338
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
705 PM EST TUE JAN 03 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
2330 UTC.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH REMAINS INLAND OVER AFRICA. THE ITCZ EXTENDS
WSW FROM THE COAST OF SIERRA LEONE NEAR 8N12W ALONG 5N30W TO THE
COAST OF BRAZIL NEAR EQ50W. SCATTERED WEAK TO ISOLATED MODERATE
CONVECTION IS WITHIN 100 NM ON EITHER SIDE OF THE AXIS BETWEEN
20W-40W.

...DISCUSSION...

GULF OF MEXICO...
WATER VAPOR IMAGERY DEPICTS A VERY DRY ATMOSPHERE ACROSS THE
GULF THIS EVENING...AS AN UPPER RIDGE APPROACHES THE S CENTRAL
CONUS SUPPORTING SURFACE RIDGING OVER THE N GULF STATES. MARINE
OBSERVATIONS INDICATE A LIGHT ANTICYCLONIC FLOW N OF 25N...
AROUND A 1033 MB HIGH CENTERED OVER THE CENTRAL LOUISIANA COAST
NEAR 29N92W. THE LIGHT ANTICYCLONIC FLOW BECOMES NORTHERLY 10-20
KT S OF 25N...HELPING TO MAINTAIN A FAIRLY DEEP LAYER OF COLD
AIR ACROSS THE AREA. THIS FLOW IS BANKING UP SOME LOW LEVEL
MOISTURE OVER THE FAR SW BASIN...WITH A FEW POSSIBLE ISOLATED
SHOWERS WITHIN 75 NM OFF THE COAST OF MEXICO FROM THE CITY OF
TAMPICO TO LAGUNA DE TERMINOS. OTHERWISE...THE AIRMASS MOVING
OVER RELATIVELY WARMER WATERS IS GENERATING A BROAD AREA OF LOW
LEVEL STRATOCUMULUS CLOUDS SEEN ON VISIBLE IMAGERY S OF 27N.
MEDIUM RANGE COMPUTER MODELS SUGGEST THE SURFACE RIDGE WILL MOVE
TO THE NRN FLORIDA PENINSULA OVER THE NEXT 24-36 HRS MAINTAINING
FAIR WEATHER CONDITIONS ACROSS THE AREA AND PROMOTING A WARMING
TREND TO THE WRN AND N CENTRAL BASINS.

CARIBBEAN SEA...
THE COLD FRONT MOVING ACROSS THE WRN N ATLC EXTENDS SW INTO THE
NW CARIBBEAN ACROSS THE WINDWARD PASSAGE ALONG 20N74W TO THE ERN
COAST OF HONDURAS NEAR 15N84W. WHILE THE FRONT HAS BROUGHT
NORTHERLY WINDS 20-30 KT TO THIS REGION...A FAIRLY DRY
ATMOSPHERE OVER IT HAS LIMITED THE CONVECTION ASSOCIATED WITH
IT...KEEPING MOST OF THE ACTIVITY WITHIN 60 NM ON EITHER SIDE OF
THE BOUNDARY S OF 17N. A SIX HOUR LOOP OF VISIBLE IMAGERY
INDICATES THE FRONT HAS REDUCED ITS FORWARD MOVEMENT.
FURTHERMORE...CURRENT THETA-E FROM MODEL DATA SUGGEST THAT
FRONTOLISIS MAY BE OCCURRING OR SOON TO OCCUR WITH THIS
BOUNDARY. THESE CONDITIONS SUGGEST THE FRONT WILL CONTINUE TO
WEAKEN AND BECOME NEARLY STATIONARY DURING THE NEXT 24 HOURS.
OTHERWISE...DRY AIR ALOFT AND STRONG SUBSIDENCE REMAINS
ELSEWHERE ACROSS THE BASIN SUPPRESSING DEEP CONVECTION OVER MOST
OF THE DISCUSSION AREA. THE ONLY AREA OF WEAK CONVECTION IS
NOTICED OVER THE N CENTRAL BASIN N OF 14N BETWEEN 68W-74W. AN
EARLIER ASCAT PASS AND SURFACE OBSERVATIONS INDICATED 15-20 KT
TRADEWINDS OVER THE ENTIRE CARIBBEAN SEA E OF THE FRONT...WITH
THE STRONGEST WINDS REACHING UP TO 25 KT ALONG THE COAST OF
COLOMBIA.

ATLANTIC OCEAN...
AN UPPER LEVEL LONGWAVE/TROUGH MOVES OFF THE SE CONUS SEABOARD
SUPPORTING A COLD FRONT THAT ENTERS THE REGION ALONG 32N65W
EXTENDING S-SW ACROSS THE SE BAHAMAS ALONG 22N74W AND INTO THE
NW CARIBBEAN SEA ALONG THE WINDWARD PASSAGE. THE COMBINATION OF
LOW LEVEL CONVERGENCE OF NW AND SOUTHERLY WINDS AND UPPER LEVEL
DIFFLUENCE ALONG THE BOUNDARY IS GENERATING SCATTERED HEAVY
SHOWERS AND THUNDERSTORMS WITHIN 50 NM ON EITHER SIDE OF IT. THE
PRESSURE GRADIENT BETWEEN THE STRONG SURFACE RIDGE OVER THE N
CENTRAL GULF OF MEXICO AND THE DEEP LAYER TROUGH IS GENERATING
AN AREA OF GALE FORCE WINDS BEHIND THE FRONT N OF 27N TO 80W
GENERATING SEAS 14 TO 21 FT IN NW SWELL. AS THE FRONT CONTINUES
TO TRACK EASTWARD...THE ACTIVITY IS EXPECTED TO DECREASE BELOW
GALE FORCE CRITERIA OVER THE NEXT 18 HRS. OTHERWISE...AN UPPER
LEVEL ANTICYCLONE COVERING THE CENTRAL BASIN BETWEEN 40W-60W...
AND A STRONG 1034 MB HIGH CENTERED OFF THE COAST OF PORTUGAL
NEAR 38N11W ARE DOMINATING THE REMAINDER OF THE DISCUSSION AREA
WITH FAIR WEATHER. THE SURFACE RIDGE ALONG WITH LOWER PRESSURES
NEAR THE ITCZ CONTINUE TO GENERATE A SOMEWHAT TIGHT SURFACE
PRESSURE GRADIENT THAT COVERS A BROAD AREA IN THE S CENTRAL
BASIN FROM 10N-22N BETWEEN 30N-55W WITH MOSTLY ENE WINDS AT 20
KT.

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

$$

GARCIA




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