[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 200003
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
705 PM EST MON NOV 19 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
2245 UTC.

...ITCZ/MONSOON TROUGH...
THE MONSOON TROUGH EXTENDS ACROSS WEST AFRICA TO THE COAST OF
GUINEA-BISSAU AT 12N16W TO 8N21W. THE ITCZ BEGINS AT 8N21W AND
CONTINUES ALONG 8N34W 10N47W 7N59W. SCATTERED MODERATE/STRONG
CONVECTION IS FROM 5N-9N BETWEEN 20W-34W. ISOLATED MODERATE
CONVECTION IS FROM 9N-11N BETWEEN 52W-56W.

...DISCUSSION...

GULF OF MEXICO...
UPPER LEVEL RIDGING COVERS THE GULF OF MEXICO PROVIDING MOSTLY
NORTHWESTERLY FLOW ALOFT. DRY AIR CONTINUES TO COVER THE
MAJORITY OF THE AREA PROVIDING FAIR WEATHER. THE UPPER RIDGE
SUPPORTS A SURFACE RIDGE ACROSS THE SE CONUS WHICH EXTENDS
ACROSS THE NORTHERN GULF AND INTO THE SW GULF. HOWEVER...AN
UPPER LEVEL TROUGH IN THE WEST ATLC SUPPORTS A WEAK COLD FRONT
THAT EXTENDS THROUGH THE BAHAMAS TO THE FLORIDA STRAITS INTO THE
FAR SE GULF ALONG 23N81W 24N86W. NE WINDS UP TO 20 KT ARE NORTH
OF THE FRONT. A SURFACE TROUGH IS ALSO TO THE WEST EXTENDING
ACROSS THE YUCATAN PENINSULA ALONG 23N90W TO 18N85W. ISOLATED
SHOWERS ARE WITHIN 120 NM OF THE TROUGH AXIS WITH POSSIBLE
ISOLATED SHOWERS WITHIN 60 NM SOUTH OF THE FRONT. THE TROUGH IS
EXPECTED TO DRIFT WEST WITH POSSIBLE SHOWERS NEAR IT WHILE THE
FRONT CONTINUES SOUTH. SURFACE RIDGING WILL REMAIN ACROSS THE
NORTHERN GULF.

CARIBBEAN SEA...
DRY AIR ALOFT COVERS THE NW CARIBBEAN AROUND THE BASE OF AN
UPPER LEVEL TROUGH THAT IS ACROSS THE W ATLC. THE DRY AIR IS
HELPING PROVIDE FAIR CONDITIONS EXCEPT FOR A FEW ISOLATED
SHOWERS NORTH OF HONDURAS NEAR A SURFACE TROUGH THAT EXTENDS
FROM THE YUCATAN PENINSULA TO THE NW CARIBBEAN ALONG 23N90W TO
18N85W. MOIST SOUTHWESTERLY FLOW ALOFT COVERS THE CENTRAL
CARIBBEAN BETWEEN THE UPPER TROUGH OVER THE FAR NW CARIBBEAN AND
AN UPPER LEVEL RIDGE COVERING THE EASTERN CARIBBEAN ALONG 66W.
ISOLATED SHOWERS EXTEND FROM COSTA RICA AND PANAMA ALL THE WAY
ACROSS HISPANIOLA WITH MORE SCATTERED ACTIVITY WITH ISOLATED
THUNDERSTORMS ACROSS THE SW CARIBBEAN FROM 11N-14N BETWEEN
76W-82W. THIS STRONGER ACTIVITY IS ENHANCED BY THE MONSOON
TROUGH THAT EXTENDS THROUGH PANAMA TO A SPOT 1008 MB SURFACE LOW
NEAR 10N79W. SHOWERS/THUNDERSTORMS ARE ALSO NOTED OVER PUERTO
RICO. THE REMAINDER OF THE EASTERN CARIBBEAN IS EXPERIENCING
MOSTLY FAIR WEATHER DUE TO THE DRY AIR ALOFT AROUND THE EAST
SIDE OF THE UPPER RIDGE. ONLY A FEW WIDELY ISOLATED SHOWERS ARE
EMBEDDED WITHIN THE 10-15 KT TRADEWIND FLOW. LITTLE CHANGE IS
EXPECTED EXCEPT FOR A WEAK COLD FRONT CURRENTLY THROUGH THE
STRAITS OF FLORIDA IS EXPECTED TO DIP SOUTH INTO THE NW
CARIBBEAN. POSSIBLE ISOLATED SHOWERS WILL BE ALONG IT.

ATLANTIC OCEAN...
AN UPPER LEVEL LOW JUST NORTH OF THE DISCUSSION AREA OFF THE
SOUTHEAST UNITED STATES COAST SUPPORTS A SERIES OF LOW PRESSURE
SYSTEMS AT THE SURFACE. FIRST...A 1012 MB SURFACE LOW IS
CENTERED NEAR 30N77W. A WEAK COLD FRONT EXTENDS FROM THE LOW
CENTERED SOUTHWARD ACROSS THE BAHAMAS TO THE FLORIDA STRAITS
ALONG 26N77W TO 23N81W. NO SHOWERS ACCOMPANY THE FRONT...BUT
STRONG NORTHERLY WINDS OF 20-25 KT ARE WEST OF THE LOW CENTER
WITH EVEN STRONGER WINDS ALONG THE US COAST NORTH OF THE
DISCUSSION AREA. THIS LOW IS EXPECTED TO DISSIPATE AS TWO OTHER
LOWS MERGE TO FORM ONE MAIN LOW WHICH WILL CONTINUE TO MOVE THE
FRONT SE FOLLOWED BY A SECONDARY FRONT WHICH WILL SWEEP IN
BEHIND IT. OF THE OTHER TWO LOWS...ONLY ONE IS IN THE DISCUSSION
AREA NEAR 32N68W WITH A SURFACE TROUGH EXTENDING FROM THE CENTER
TO NEAR 27N70W. THIS LOW IS EXPECTED TO MOVE NORTH TO MERGE WITH
THE THIRD LOW. DIFFLUENCE ALOFT BETWEEN THE UPPER LOW OVER THE
WEST ATLC AND AN UPPER LEVEL RIDGE EXTENDING FROM THE EASTERN
CARIBBEAN INTO THE CENTRAL ATLC IS SUPPORTING WIDESPREAD
SHOWERS/POSSIBLE THUNDERSTORMS FROM 20N-30N BETWEEN
59W-66W...AND FROM 19N-24N BETWEEN 66W-71W NEAR A SURFACE TROUGH
ALONG 24N68W TO 18N68W. THE UPPER RIDGE SUPPORTS WEAK SURFACE
RIDGING ACROSS THE CENTRAL ATLC. HOWEVER...A BROAD UPPER LEVEL
TROUGH OVER THE NORTH CENTRAL ATLC SUPPORTS A COLD FRONT THAT
SPREADS FROM THE NE ATLC TO NEAR 32N42W 32N59W WHERE IT
CONTINUES TO THE THIRD LOW OVER THE WESTERN ATLC. ISOLATED
SHOWERS ARE WITHIN 60 NM OF THE FRONT AXIS. AN UPPER LEVEL LOW
IS SOUTH OF THE BROAD UPPER TROUGH NEAR 17N42W SUPPORTING A
SURFACE TROUGH ALONG 20N41W TO 11N47W. SCATTERED SHOWERS ARE
EAST OF THE AXIS FROM 12N-17N BETWEEN 40W-43W...AND FROM 15N-19N
BETWEEN 34W-36W. WEAK SURFACE RIDGING AROUND A 1020 MB HIGH NEAR
30N19W COVERS THE FAR EASTERN TROPICAL ATLC.

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

$$
WALTON





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