000
AXPZ20 KNHC 210916
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC WED SEP 21 2011

TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM 
THE EQUATOR TO 32N...EAST OF 140W. THE FOLLOWING INFORMATION IS 
BASED ON SATELLITE IMAGERY...WEATHER OBSERVATIONS...RADAR...AND 
METEOROLOGICAL ANALYSIS.

BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0900 UTC.

...SPECIAL FEATURE...

TROPICAL DEPRESSION NINE-E HAS FORMED NEAR 13.4N 96.5W AT 
21/0900 UTC OR 150 NM SSE OF PUERTO ESCONDIDO MEXICO MOVING WNW 
OR 285 DEGREES AT 4 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 
1006 MB. MAXIMUM SUSTAINED WIND SPEED IS 30 KT WITH GUSTS TO 40 
KT. SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS 
MIATCMEP4/WTPZ24 KNHC FOR MORE DETAILS. STRONG BANDS OF 
CONVECTION ARE DEVELOPING IN A BROAD ARC WITHIN 180 NM N 
SEMICIRCLE AND WITHIN 120 NM SW QUADRANT OF THE STORM...COVERING 
MUCH OF THE GULF OF TEHUANTEPEC. 
 
...ITCZ/MONSOON TROUGH...
THE MONSOON TROUGH AXIS EXTENDS FROM 10N102W TO LOW PRES NEAR 
11N111W 1009 MB TO 14N115W TO LOW PRES NEAR 13N120W TO LOW PRES 
NEAR 10N136W 1010 MB TO 09N140W. SCATTERED MODERATE CONVECTION 
FROM 08N TO 11N BETWEEN 98W AND 115W. SCATTERED MODERATE 
ISOLATED STRONG CONVECTION WITHIN 120 NM S OF TROUGH AXIS 
BETWEEN 113W AND 115W. 

...DISCUSSION... 

ASCAT DATA FROM 0430 UTC AND REPORTS FROM TOGA-TAO BUOYS SHOW 15 
TO 20 KT S TO SW WINDS IN A BROAD AREA S OF THE MONSOON TROUGH 
FROM 03N TO 09N BETWEEN 95W AND 115W. CONVERGENCE RELATED TO 
THIS FLOW IS RESULTING IN A BAND CONVECTION ALONG THE MONSOON 
TROUGH AND SW OF T.D. 16 FROM 08N TO 11N BETWEEN 98W AND 103W. 

A SMALL UPPER LEVEL CYCLONIC CIRCULATION IS BARELY VISIBLE ON 
WATER VAPORY IMAGERY NEAR 13N120W...OVER THE MONSOON TROUGH...S 
OF AN UPPER RIDGE ORIENTED E-W ALONG 20N. SUBTLE CYCLONIC 
TURNING IS ALSO NOTED IN THE MID LEVELS ON GOES DERIVED HIGH 
DENSITY WINDS AS WELL IN THE SAME AREA. DIVERGENCE ALOFT RELATED 
TO THIS FEATURE IS AIDING DEVELOPMENT OF A SMALL BUT PERSISTENT 
STRONG AREA OF CONVECTION WITHIN 120 NM S OF THE MONSOON TROUGH 
AXIS BETWEEN 113W AND 115W. A 1009 MB LOW PRES SYSTEM IS NOTED 
JUST UPSHEAR TO THE E OF THE CONVECTION NEAR 11N111W. FURTHER W 
ANOTHER WEAK 1010 MB LOW IS NOTED ALONG THE MONSOON TROUGH NEAR 
13N120W...AND IS LIKELY THE LOW LEVEL REFLECTION OF THE UPPER 
LOW. 

ANOTHER DEEP LAYER BUT FAIRLY WEAK CYCLONE IS NOTED FURTHER 
W...SUPPORTING A 1010 MB SURFACE LOW ALONG THE MONSOON TROUGH 
NEAR 10N136W. A LACK OF DEEP LAYER MOISTURE IS INHIBITING 
CONVECTION ALONG THE MONSOON TROUGH W OF 115W. A 0610 UTC ASCAT 
SHOWED A SMALL AREA OF 20 KT WINDS WITHIN 60 NM ON THE N 
SEMICIRCLE OF THIS LOW. THE LOW AND ASSOCIATED AREA OF WINDS 
WILL SHIFT W OF 140W OVER THE NEXT 24 HOURS. 

FURTHER N...WINDS WILL REMAIN LIGHT TO MODERATE AS A SURFACE 
HIGH PRES AREA BUILDS E. HOWEVER NW SWELL UP TO 10 FT WILL 
PROPAGATE S OF 32N AND E OF 140W WITHIN 24 HOURS.

$$
CHRISTENSEN