[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 222347
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT SAT OCT 22 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...WEATHER OBSERVATIONS...RADAR...AND METEOROLOGICAL
ANALYSIS.

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2300 UTC.

...SPECIAL FEATURES...

AN AREA OF LOW PRESSURE COVERS THE SW CARIBBEAN FOCUSED NEAR A
1005 MB LOW AT 13N81W. A STATIONARY FRONT CONTINUES TO SIT TO
THE N OF THE SYSTEM KEEPING A TROPICAL AIRMASS OVER THE LOW.
HOWEVER...SOME DRY AIR ALOFT IS SINKING IN FROM THE ATLC ACROSS
THE CENTRAL CARIBBEAN AND AROUND THE NE SIDE OF THE LOW...WHICH
COINCIDES WITH AN AREA LACKING CONVECTION. CURRENTLY SCATTERED
MODERATE/STRONG CONVECTION IS MAINLY NW OF THE LOW FROM 12N-16N
BETWEEN 82W-86W MERGING INTO THE CONVECTION ALONG THE FRONTAL
BOUNDARY. SCATTERED MODERATE CONVECTION IS ALSO S OF THE LOW
FROM 9N-12N BETWEEN 78W-84W. EVEN THOUGH CONVECTION REMAINS
DISORGANIZED...THIS SYSTEM STILL HAS A CHANCE TO FURTHER DEVELOP
OVER THE NEXT COUPLE OF DAYS AS IT DRIFTS NWD.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 14N17W
ALONG 11N24W 7N34W. SCATTERED MODERATE/STRONG CONVECTION IS
WITHIN 120 NM N OF THE AXIS...AS WELL AS WITHIN 200 NM S OF THE
AXIS BETWEEN 23W-34W. SIMILAR ACTIVITY IS ALSO FROM 2N-6N
BETWEEN 33W-38W.

...DISCUSSION...

GULF OF MEXICO...
A STABLE AND DRY AIRMASS CONTINUES TO SIT OVER THE GULF OF
MEXICO PROVIDING FAIR WEATHER BASIN WIDE. ALOFT...MAINLY WLY
FLOW DOMINATES...WHILE AT THE SURFACE RIDGING PREVAILS WITH AXIS
FROM LOUISIANA TO THE BAY OF CAMPECHE. SATELLITE IMAGERY
INDICATES AREAS OF STRATOCUMULUS CLOUDS S OF 26N WITH A FEW
ISOLATED SHOWERS OVER THE FAR SRN BAY OF CAMPECHE. SURFACE
RIDGING AND MOSTLY FAIR CONDITIONS ARE EXPECTED TO REMAIN ACROSS
THE BASIN FOR THE NEXT SEVERAL DAYS.

CARIBBEAN SEA...
DRY AIR FROM THE GULF OF MEXICO IS SEEPING INTO THE FAR NW
CARIBBEAN MAINTAINING FAIR CONDITIONS. HOWEVER...JUST E AND S A
STATIONARY FRONT IS PROVIDING UNSTABLE CONDITIONS. THE FRONT
EXTENDS FROM ERN CUBA NEAR 21N78W ALONG 19N81W 17N84W. SCATTERED
SHOWERS/THUNDERSTORMS ARE MAINLY SE OF THE AXIS WITHIN 100 NM. A
FEW SHOWERS/THUNDERSTORMS ARE ALSO NW OF THE FRONT WITHIN 75 NM
W OF 80W. ALOFT...AN UPPER LEVEL RIDGE EXTENDS FROM NEAR 18N83W
TOWARDS THE NE INTO THE ATLC. TO THE S...A BROAD AREA OF LOW
PRESSURE EXISTS AROUND THE MONSOON TROUGH WHICH EXTENDS ACROSS
SRN NICARAGUA FROM 12N85W TO 15N77W. THE MONSOON TROUGH EXTENDS
THROUGH A 1005 MB SURFACE LOW THAT IS MENTIONED IN THE SPECIAL
FEATURES SECTION. AS THE LOW DRIFTS N...POSSIBLE HEAVY SHOWERS
COULD OCCUR OVER PORTIONS OF NICARAGUA AND HONDURAS CAUSING THE
POTENTIAL FOR FLOODING AND MUDSLIDES. BESIDES THE CONVECTION
ASSOCIATED WITH THE LOW...SCATTERED SHOWERS/THUNDERSTORMS ARE
FROM 12N-15N BETWEEN 72W-77W. A FEW CLUSTERS OF STORMS ARE ALSO
NOTED OVER HISPANIOLA AND PUERTO RICO. ACROSS THE ERN
CARIBBEAN...MODERATE DRY AIR ALOFT IN SWLY FLOW IS KEEPING
CONDITIONS FAIR EVEN THOUGH A WEAK SURFACE TROUGH EXTENDS FROM
11N63W TO 16N70W. THE SURFACE TROUGH WILL LIKELY DISSIPATE OVER
THE NEXT 12-24 HOURS. MOIST CONDITIONS WILL REMAIN OVER THE WRN
CARIBBEAN IN ASSOCIATED WITH BOTH THE FRONTAL BOUNDARY AND THE
SURFACE LOW.

ATLANTIC OCEAN...
A BROAD LONGWAVE UPPER TROUGH IS MOVING ACROSS THE ERN CONUS AND
FAR WRN ATLC SUPPORTING A STATIONARY FRONT ENTERING THE
DISCUSSION AREA NEAR 32N69W CONTINUING TO THE CENTRAL BAHAMAS
NEAR 25N76W TO ERN CUBA NEAR 21N78W. STRONG DRY AIR ACCOMPANIES
THE UPPER TROUGH MAINTAINING MOSTLY FAIR CONDITIONS W OF THE
FRONTAL BOUNDARY BESIDES SOME LOW LEVEL CLOUDINESS AND POSSIBLE
ISOLATED SHOWERS THAT EXIST WITHIN 150 NM TO THE W. ISOLATED
SHOWERS ARE ALONG THE FRONTAL BOUNDARY AND WITHIN 160 NM E OF
THE AXIS. A WEAK UPPER RIDGE IS SANDWICHED BETWEEN THE BROAD
UPPER TROUGH AND AN UPPER LEVEL LOW NEAR 25N66W. THIS UPPER LOW
IS SUPPORTING A SURFACE TROUGH ALONG 30N68W TO 21N66W. NO SHOWER
ACTIVITY IS ALONG THE TROUGH AXIS. HOWEVER...DUE TO DIFFLUENCE
ALOFT...SCATTERED SHOWERS/THUNDERSTORMS ARE FARTHER E FROM
21N-25N BETWEEN 60W-65W...AND FROM 27N-31N BETWEEN 57W-62W. AN
UPPER LEVEL RIDGE DOMINATES THE CENTRAL AND MOST OF THE ERN ATLC
WITH AXIS EXTENDING FROM 10N51W TO 41N40W SUPPORTING A 1026 MB
HIGH NEAR 35N46W. TO THE S...E OF THE LESSER ANTILLES AND AROUND
THE BASE OF THE UPPER RIDGE...A 1006 MB SURFACE LOW SPINS NEAR
10N56W. ISOLATED SHOWERS/POSSIBLE THUNDERSTORMS ARE WITHIN 150
NM OF THE LOW CENTER. A SECOND WEAKER 1009 MB LOW IS FARTHER E
NEAR 16N43W WITH NO ASSOCIATED SHOWER ACTIVITY. HOWEVER...A
NARROW UPPER LEVEL TROUGH THAT EXTENDS E OF THE UPPER RIDGE AND
WRAPS AROUND THE ERN SIDE OF THE RIDGE IS PROVIDING DIFFLUENCE
ALOFT TO SUPPORT AREAS OF SCATTERED SHOWERS/POSSIBLE
THUNDERSTORMS FROM 7N-13N BETWEEN 36W-45W...AND FROM 12N-17N
BETWEEN 25W-37W. POSSIBLE ISOLATE SHOWERS CONTINUE TO THE NE
ACROSS NW AFRICA. THE UPPER TROUGH ALSO SUPPORTS A WEAK 1013 MB
SURFACE LOW NEAR 24N23W WITH A SURFACE TROUGH EXTENDING THROUGH
IT FROM 26N18W TO 23N26W.

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

$$
WALTON





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