[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 102351
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
705 PM EST SAT NOV 10 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 ITCZ EXTENDS FROM THE COAST OF GUINEA-BISSAU NEAR 11N16W
ACROSS THE TROPICAL ATLC THROUGH 9N26W 14N38W...THEN CONTINUES
THROUGH 12N45W TO 9N16W. SCATTERED MODERATE TO STRONG CONVECTION
IS NORTH OF THE ITCZ IN AN AREA FROM 9N TO 13N BETWEEN 20W AND
34W...WITH THE GREATEST CONCENTRATION OF CONVECTION FROM 11N TO
14N BETWEEN 29W AND 34W. SCATTERED MODERATE ISOLATED STRONG
CONVECTION WAS NOTED WITHIN 90-120 NM EITHER SIDE OF THE AXIS
BETWEEN 34W AND 47W. AN UPPER LEVEL TROUGH IN THE EASTERN ATLC
IS HELPING ENHANCE THE CONVECTION E OF 34W.

...DISCUSSION...

GULF OF MEXICO...
FAIR WEATHER PREVAILS ACROSS THE GULF OF MEXICO WITH PATCHES OF
MAINLY STRATOCUMULUS CLOUDS WITH LOCAL OVERCAST CONDITIONS OVER
THE NORTHERN GULF OF MEXICO EXTENDING NORTHWARD OVER THE UPPER
TEXAS AND LOUISIANA COASTS. AN ADDITIONAL CONCENTRATION OF LOW
CLOUDS WAS NOTED ACROSS THE SOUTHEAST GULF FROM THE FLORIDA STRAITS
TO NORTH OF THE YUCATAN PENINSULA. THE FAIR WEATHER IS
ATTRIBUTED TO SURFACE RIDGING AND DRY AIR ALOFT AROUND THE
EASTERN HALF OF AN UPPER LEVEL RIDGE WITH MEAN AXIS ALONG 90W/91W.
EAST TO SOUTHEAST WINDS ARE AROUND THE SURFACE RIDGE RANGING
FROM 10-15 KT WITH SOME 20 KT WINDS NOTED NEAR THE FLORIDA
STRAITS AND NEAR THE TEXAS COAST IN INCREASING RETURN FLOW. SURFACE
RIDGING IS EXPECTED TO REMAIN ACROSS THE BASIN OVER THE NEXT 24
HOURS WITH WINDS INCREASING TO 20-25 KT W OF 90W LATER TONIGHT
AND SUN. A COLD FRONT IS EXPECTED TO EMERGE INTO THE NW GULF
OVERNIGHT SUN INTO MON WITH STRONG NORTHERLY WINDS IN ITS WAKE.

CARIBBEAN SEA...
DRY AIR ALOFT COVERS A GOOD PORTION OF THE CARIBBEAN THIS
EVENING AROUND THE BASE OF AN UPPER LEVEL TROUGH SWEEPING ACROSS
THE SW NORTH ATLANTIC AND EXTENDING DEEP INTO THE CARIBBEAN
ALONG 75W TO A BASE NEAR 11N78W. FAIR WEATHER EXISTED TO THE W
OF THE TROUGH AXIS. UPPER LEVEL DIFFLUENCE EAST OF THE TROUGH
AXIS WAS SUPPORTING AN INCREASE IN CLOUD COVER WITH ISOLATED
THUNDERSTORMS OVER HISPANIOLA AND PUERTO RICO. THIS TROUGH WAS
PROVIDING SOME SUPPORT FOR A WEAKENING COLD FRONT OVER
HISPANIOLA WHICH TRANSITIONED TO A SHEAR AXIS FROM HAITI ACROSS
IN THE CARIBBEAN ALONG 18N76W TO 12N82W. A 1518 UTC ASCAT PASS
INDICATED THE BOUNDARY IS WEAK WITH LITTLE DIFFERENCE IN WIND
SPEEDS ACROSS THE AXIS. WINDS WERE GENERALLY OUT OF THE NE AT
20 KT...WITH ISOLATED AREAS OF 25 KT WINDS NEAR THE WINDWARD
PASSAGE. WEAK CONVERGENCE ALONG THE SHEAR AXIS STILL SUPPORTS
ISOLATED SHOWERS WITHIN 120 NM EITHER SIDE OF THE FEATURE.
STRONG NE WINDS ARE EXPECTED TO REMAIN ACROSS THE WESTERN AND
CENTRAL CARIBBEAN UNTIL LATE SUN BEFORE DECREASING SUN NIGHT AND
MON.

ATLANTIC OCEAN...
SURFACE RIDGING EXTENDS FROM THE EASTERN CONUS INTO THE ATLC
WEST OF 65W MAINTAINING MOSTLY FAIR CONDITIONS ACROSS THE AREA.
MODERATE TO STRONG NE WINDS WERE ADVECTING PATCHES OF BROKEN TO
OVERCAST STRATOCUMULUS ACROSS THE AREA INTO TH FLORIDA EAST
COAST. AT THE UPPER LEVELS...DRY AIR WAS SPREADING INTO THE AREA
AS IT SPILLS AROUND THE WESTERN SIDE OF AN UPPER LEVEL TROUGH
EXTENDING FROM 32N68W TO EASTERN CUBA. THE UPPER TROUGH
CONTINUES TO SUPPORT A COLD FRONT THAT HAS NOW PUSHED INTO THE
CENTRAL ATLC. THE FRONT ENTERS THE DISCUSSION AREA NEAR 31N53W
AND CONTINUES THROUGH 23N60W TO 20N66W WHERE IT BECOMES A
STATIONARY FRONT TO THE NORTH COAST OF HISPANIOLA. SCATTERED
SHOWERS AND THUNDERSTORMS ARE FOCUSED WITHIN 180-240 NM E OF THE
FRONT FROM 20N TO 27N. A SECONDARY FRONT LIES JUST N OF THE AREA
TO 31N66W BUT WAS ONLY EXPECTED TO CLIP THE DISCUSSION AREA.
FURTHER E...A NARROW UPPER LEVEL RIDGE WITH AXIS ALONG 50W
EXTENDED FROM THE DEEP TROPICS TO 31N. A SHARP UPPER LEVEL
TROUGH WAS NOTED E OF THE RIDGE WITH AN ELONGATED UPPER LEVEL
CYCLONE NEAR 26N39W. VERY DRY AIR ALOFT WAS WRAPPING AROUND THE
W SIDE OF THE TROUGH BETWEEN 40W AND 47W. AT THE SURFACE A
BROAD SURFACE RIDGE WAS ANCHORED BY A 1035 MB AZORES HIGH. THE
RIDGE IS PROVIDING GENERALLY FAIR CONDITIONS ACROSS THE EASTERN
ATLC EXCEPT FOR SOME AREAS OF MULTILAYERED CLOUDS AND EMBEDDED
SHOWERS AND THUNDERSTORMS FROM 19N TO 26N BETWEEN 32W AND 37W.
ADDITIONALLY MODERATE TO STRONG EASTERLY WINDS WERE NOTED S OF
THE RIDGE WITH A 2042 UTC ASCAT PASS INDICATING AN AREA OF NE
WINDS OF 25 KT FROM 19N TO 24N BETWEEN 40W AND 45W...GENERALLY
TO THE NW OF A SURFACE TROUGH ALONG 41W FROM 16N TO 22N. THE
AFOREMENTIONED UPPER LEVEL TROUGH WAS RESPONSIBLE FOR ENHANCING
CONVECTION JUST NORTH OF THE ITCZ REGION WHICH IS DESCRIBED IN
THE ITCZ SECTION ABOVE.

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

$$
COBB





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