[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 221746
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT SAT SEP 22 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1015 UTC.

...SPECIAL FEATURES...

POST-TROPICAL CYCLONE NADINE IS CENTERED OVER THE NORTHEASTERN
ATLC ANALYZED AS A 987 MB SURFACE LOW WNW OF THE CANARY ISLANDS
NEAR 31N27W MOVING SE AT 5-10 KT. REGENERATION INTO A TROPICAL
CYCLONE IS POSSIBLE OVER THE NEXT COUPLE OF DAYS AS IT
APPROACHES SLIGHTLY WARMER WATERS. ISOLATED MODERATE CONVECTION
IS NEAR THE LOW CENTER AND TO THE NORTH FROM 31N-32N BETWEEN
24W-27W.

...TROPICAL WAVES...

TROPICAL WAVE IS ALONG 15N44W TO 11N49W MOVING W NEAR 20 KT. THE
WAVE LIES WITHIN A HORIZONTALLY ELONGATED AREA OF DEEP LAYER
MOISTURE. VISIBLE SATELLITE IMAGERY ALSO INDICATES LOW-LEVEL
CYCLONIC FLOW IS AROUND THE WAVE AXIS. SCATTERED
MODERATE/ISOLATED STRONG CONVECTION IS FROM 12N-14N BETWEEN
45W-48W. SIMILAR ACTIVITY IS FARTHER WEST FROM 12N-14N BETWEEN
52W-55W.

TROPICAL WAVE EXTENDS FROM THE SE GULF OF MEXICO AT 24N87W TO
THE E PACIFIC NEAR 11N90W. THE WAVE WAS EXTENDED INTO THE E
PACIFIC WHERE IT IS SHOWING A STRONGER SIGNAL. THE NORTHERN
PORTION OF THE WAVE HAS LOST MOST OF ITS ENERGY TO A LARGE UPPER
LEVEL TROUGH ACROSS THE GULF OF MEXICO AND EASTERN CONUS. THE
UPPER TROUGH IS STILL SUPPORTING A SURFACE TROUGH ALONG WITH A
BROAD AREA OF SHOWERS/THUNDERSTORMS. THE WAVE HAS BEGUN TO MOVE
WEST OF THE UPPER TROUGH AND NO LONGER HAS ANY CONVECTION
ASSOCIATED WITH IT IN THE GULF OR ACROSS THE YUCATAN PENINSULA.
AS TIME GOES ON...THE NORTHERN HALF OF THE WAS WILL LIKELY
DISSIPATE AS THE SOUTHERN PORTION CONTINUES IN THE E PACIFIC.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS ACROSS W AFRICA TO A 1011 MB SURFACE
LOW ALONG THE COAST OF SENEGAL AT 14N17W AND CONTINUES OVER ATLC
WATERS ALONG 10N23W 7N33W. THE ITCZ BEGINS AT 7N33W AND
CONTINUES ALONG 7N38W 9N47W 7N61W. SCATTERED MODERATE/ISOLATED
STRONG CONVECTION IS FROM 6N-8N BETWEEN 14W-24W. NO OTHER DEEP
CONVECTION IS NOTED.

...DISCUSSION...

GULF OF MEXICO...
AN UPPER LEVEL TROUGH DOMINATES THE EASTERN CONUS AND GULF OF
MEXICO TODAY EXTENDING FROM SOUTHERN ALABAMA NEAR 32N89W TO THE
SOUTHERN TIP OF TEXAS NEAR 27N99W. THIS PATTERN IS PROVIDING
SOUTHWESTERLY FLOW ACROSS THE ENTIRE BASIN. DRY AIR ALOFT IS
COVERING THE MAJORITY OF THE AREA...EXCEPT IN THE AREA OF
STRONGEST DIFFLUENCE COVERING THE SOUTHERN HALF OF THE BASIN AND
EXTENDING INTO THE WEST ATLC. AT THE SURFACE...A SURFACE TROUGH
CONTINUES IN THE SW GULF ALONG 23N95W SUPPORTING SCATTERED
SHOWERS/THUNDERSTORMS FROM 20N-25N BETWEEN 93W-97W. A TROPICAL
WAVE IS OVER THE YUCATAN PENINSULA...BUT IS NOT CAUSING ANY
ACTIVE WEATHER AT THIS TIME. SEE TROPICAL WAVE SECTION FOR MORE
DETAILS. A FEW ISOLATED SHOWERS/THUNDERSTORMS STILL CONTINUE
OVER THE SE GULF INCLUDING SOUTH FLORIDA AND THE FLORIDA
STRAITS. THE NORTHERN GULF IS MOSTLY CLEAR AND DRY INFLUENCED BY
A SURFACE RIDGE THAT IS BEGINNING TO FORM TO THE NORTH. EXPECT
SHOWERS/THUNDERSTORMS TO REMAIN OVER THE SOUTHERN HALF OF THE
BASIN.

CARIBBEAN SEA...
UPPER LEVEL DIFFLUENCE AROUND AN UPPER TROUGH IN THE GULF OF
MEXICO ALONG WITH SURFACE CONFLUENCE AROUND A SURFACE TROUGH
ALONG 21N85W TO 16N84W IS HELPING SUPPORT AN AREA OF HEAVY
SHOWERS AND THUNDERSTORMS OVER WESTERN CUBA AND THE NW CARIBBEAN
FROM 18N-23N BETWEEN 82W-85W. STRONG SHOWERS/THUNDERSTORMS ALSO
COVER THE EXTREME SW CARIBBEAN NEAR THE MONSOON TROUGH THAT HAS
SHIFTED NORTH SOME AND EXTENDS FROM CENTRAL COSTA RICA TO
NORTHERN COLOMBIA ALONG 11/12 N. A LARGE CLUSTER OF ACTIVITY IS
FROM 9N-12N BETWEEN 76W-80W. MORE SCATTERED ACTIVITY IS FROM
10-15N BETWEEN 81W-84W...INCLUDING PORTIONS OF NICARAGUA. THE
REMAINDER OF THE BASIN HAS MOSTLY CLEAR SKIES DUE TO DRY AIR
ALOFT BETWEEN AN UPPER LEVEL RIDGE EXTENDING FROM THE NW
CARIBBEAN TO THE W ATLC...AND A BROAD UPPER LEVEL LOW CENTERED
IN THE EASTERN CARIBBEAN NEAR 13N62W. TRADEWIND FLOW OF 15-20 KT
IS PRESENT ACROSS MUCH OF THE BASIN. EXPECT MOIST CONDITIONS TO
REMAIN ACROSS THE SW CARIBBEAN AND ACROSS CENTRAL AMERICA FOR
THE NEXT 24 HOURS.

ATLANTIC OCEAN...
AN UPPER LEVEL TROUGH COVERING THE EASTERN CONUS IS SUPPORTING A
LARGE AREA OF SHOWERS/THUNDERSTORMS OFF THE SE CONUS COAST. A
SURFACE TROUGH IS ANALYZED FROM 30N77W TO 25N78W HELPING ENHANCE
THE ACTIVITY. SHOWERS/THUNDERSTORMS EXTEND FROM THE NW BAHAMAS N
OF 26N BETWEEN 75W-81W. AN UPPER LEVEL RIDGE IS TO THE E
EXTENDING FROM CENTRAL CUBA TO NEAR 36N68W PROVIDING FAIR
CONDITIONS ACROSS THE REMAINDER OF THE W ATLC. AN UPPER LEVEL
LOW NEAR 32N61W IS SUPPORTING A NON-TROPICAL SURFACE LOW NORTH
OF THE DISCUSSION AREA. A SURFACE TROUGH EXTENDS AROUND THE LOW
AND ENTERS THE AREA ALONG 32N57W TO 29N62W. ISOLATED SHOWERS ARE
N OF 29N BETWEEN 57W-63W. A SECOND AREA OF SCATTERED
SHOWERS/THUNDERSTORMS IS FARTHER SOUTH FROM 23N-26N BETWEEN
53W-59W. UPPER LEVEL RIDGING COVERS THE REMAINDER OF THE CENTRAL
ATLC CENTERED NEAR 35N41W WITH UPPER LEVEL RIDGING COVERING THE
REMAINDER OF THE TROPICAL ATLC AS WELL. AN UPPER LEVEL TROUGH
COVERS THE FAR NE ATLC SUPPORTING A SURFACE LOW OFF THE COAST OF
SPAIN ALONG WITH POST-TROPICAL NADINE STILL SPINNING NEAR 31N27W
WITH GALE FORCE WINDS IN THE NW QUADRANT. ONLY A FEW SHOWERS ARE
NEAR THE CENTER OF THE SYSTEM.

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

$$
WALTON










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