[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 202343
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
705 PM EST THU JAN 20 2011

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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY
THROUGH 2300 UTC.

...THE ITCZ...

THE ITCZ AXIS IS CENTERED FROM BROAD LOW PRESSURE OVER GUINEA
ALONG 9N14W 2N25W CROSSING THE EQUATOR NEAR 34W TO 3S43W.
SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM EQ-4N
BETWEEN 23W-43W...AND S OF THE EQUATOR FROM EQ-2S BETWEEN
31W-37W...AS WELL AS ACROSS INLAND PORTIONS OF NE BRAZIL.

...DISCUSSION...

THE GULF OF MEXICO...
A LONGWAVE UPPER TROUGH ACROSS THE CENTRAL UNITED STATES IS
APPROACHING THE GULF OF MEXICO PROVIDING MAINLY WSWLY FLOW
ALOFT...AND CURRENTLY SUPPORTS A COLD FRONT THAT HAS PUSHED OFF
THE NW GULF COAST. AS OF 2100 UTC...THE FRONT EXTENDS FROM NEAR
LAKE CHARLES LOUISIANA AT 30N93W TO NE MEXICO NEAR 25N98W. A
THIN LINE OF SHOWERS IS JUST AHEAD OF THE FRONT WITH ISOLATED
SHOWERS WITHIN 90 NM EITHER SIDE OF THE FRONT. SURFACE
OBSERVATIONS ALREADY INDICATE NNW WINDS UP TO 30 KTS ARE BEHIND
THE FRONT...AND ARE EXPECTED TO REACH GALE FORCE WITHIN THE NEXT
6 HOURS. A SURFACE TROUGH IS IN THE NE GULF ALONG 29N86W TO
27N89W...AND MAY ACTUALLY BE THE REMNANTS OF AN OLD FRONTAL
BOUNDARY THAT HAS NOW LIFTED N. TOTAL PRECIPITABLE WATER IMAGERY
SHOWS A MOISTURE DISCONTINUITY WITH DRIER AIR TO THE N AND MORE
MOIST AIR TO THE S OF THE AXIS. RADAR IMAGERY INDICATES THAT
SCATTERED SHOWERS/POSSIBLE THUNDERSTORMS ARE WITHIN 100 NM
SE...30 NM NW OF THE TROUGH AXIS. A FEW ISOLATED SHOWERS ARE
ALSO NOTED ACROSS S FLORIDA AND OFF THE SW COAST OF THE
PENINSULA. EXPECT THE FRONTAL BOUNDARY TO CONTINUE TO PUSH
ACROSS THE BASIN WITH SHOWERS EXPECTED AHEAD AND ALONG THE AXIS
WITH STRONG WINDS BEHIND IT.

THE CARIBBEAN SEA...
A WEAK PRESSURE GRADIENT ACROSS THE CARIBBEAN SEA IS MAINTAINING
MODERATE TO FRESH TRADEWINDS ACROSS MUCH OF THE BASIN. MOSTLY
FAIR WEATHER IS ACROSS THE AREA DUE TO A DRY AND STABLE AIR
MASS COVERING THE BASIN WITH ZONAL WLY FLOW ALOFT AROUND A BROAD
UPPER LEVEL RIDGE. HOWEVER...AN AREA OF SCATTERED SHOWERS ARE IN
THE SE CARIBBEAN N OF VENEZUELA S OF 16N BETWEEN 65W-70W NEAR A
SURFACE TROUGH ALONG 66W S OF 16N. TOTAL PRECIPITABLE WATER
IMAGERY INDICATES AN AREA OF ENHANCED MOISTURE NEAR THIS TROUGH.
A SECOND AREA OF ENHANCED MOISTURE IN THE NW CARIBBEAN IS
ASSOCIATED WITH SCATTERED SHOWERS FROM 17N-20N BETWEEN 81W-84W.
EXPECT THE SURFACE TROUGH TO DRIFT WWD BRINGING SHOWERS WITH IT
WITH LITTLE CHANGE OVER THE REMAINDER OF THE BASIN FOR THE NEXT
24 HRS.

THE ATLANTIC OCEAN...
WHILE MUCH OF THE SW N ATLC IS EXPERIENCING MOSTLY FAIR
WEATHER...A COLD FRONT DRAPES ACROSS THE AREA ENTERING THE
DISCUSSION AREA NEAR 32N58W TO NEAR 25N71W PRODUCING SCATTERED
SHOWERS WITHIN 100 NM AHEAD OF THE FRONT E OF 64W. THIS PORTION
OF THE FRONT IS BEGINNING TO LOSE ITS UPPER LEVEL SUPPORT AS A
BROAD UPPER RIDGE MOVES ACROSS THE AREA WITH AXIS EXTENDING FROM
THE CENTRAL CARIBBEAN AND UP THE ERN SEABOARD. THE CENTRAL ATLC
IS DOMINATED BY SURFACE RIDGING AROUND A 1020 MB HIGH NEAR
29N40W MAINTAINING GENERALLY PLEASANT CONDITIONS. THIS RIDGE IS
SUPPORTED BY A SECOND UPPER LEVEL RIDGE ALONG 42W. ACROSS THE
ERN ATLC...AN UPPER LEVEL TROUGH WITH AXIS FROM E OF THE AZORES
ISLANDS TO NEAR 17N36W SUPPORTS A COLD FRONT W OF THE CAPE VERDE
ISLANDS ALONG 32N19W 28N21W 25N25W. ISOLATED SHOWERS ARE WITHIN
120 NM AHEAD OF THE FRONT.

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

$$
WALTON






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