000
AXPZ20 KNHC 210306
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS NATIONAL HURRICANE CENTER MIAMI FL
0405 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0300 UTC.

...SPECIAL FEATURE...

A 1007 MB LOW IS EMBEDDED WITHIN THE MONSOON TROUGH SW OF THE 
GULF OF TEHUANTEPEC NEAR 13N96W. THERE IS A BROAD AREA OF ACTIVE 
AND INCREASINGLY ORGANIZING DEEP CONVECTION AROUND THE LOW 
CENTER. THE LOW IS SITUATED BENEATH AN UPPER LEVEL ANTICYCLONE 
INDICATING FAVORABLE CONDITIONS FOR ADDITIONAL DEVELOPMENT. 
THERE IS A HIGH PROBABILITY OF TROPICAL CYCLONE FORMATION WITHIN 
THE NEXT 48 HOURS.
 
...ITCZ/MONSOON TROUGH...
THE MONSOON TROUGH AXIS EXTENDS FROM 09N80W TO 1007 MB LOW NEAR 
13N96W TO 10N105W TO 14N114W TO 1007 MB LOW NEAR 12N121W TO 
11N130W TO 1008 MB LOW NEAR 10N136W TO 10N140W. ISOLATED 
MODERATE CONVECTION IS FROM 05N TO 09N BETWEEN 81W AND 86W. 
SCATTERED MODERATE TO ISOLATED STRONG CONVECTION IS FROM 08N TO 
18N BETWEEN 90W AND 103W. SCATTERED MODERATE TO ISOLATED STRONG 
CONVECTION IS FROM 08N TO 13N BETWEEN 112W AND 115W.    

...DISCUSSION... 

1021 MB HIGH PRES CENTERED NEAR 30N144W CONTINUES TO WEAKEN 
AHEAD OF A DEEP LAYER TROUGH DIGGING EASTWARD FROM THE N CENTRAL 
PACIFIC. A WEAK RIDGE EXTENDS E-SE FROM THE HIGH TO NORTHERN 
BAJA CALIFORNIA. SCATTEROMETER DATA SHOWS GENERALLY LIGHT TO 
MODERATE TRADE WIND FLOW N OF 15N AND S OF THE SURFACE RIDGE. 
WINDS ARE NE AT 15 KT CLOSER TO THE MONSOON TROUGH...WITH LIGHT 
S TO SW FLOW S OF THE TROUGH AXIS. TWO WEAK LOWS EMBEDDED WITHIN 
THE MONSOON TROUGH ARE LOCATED NEAR 12N121W AND 10N136W. THEY 
HAVE 1007 MB AND 1008 MB RESPECTIVELY AND LACK SIGNIFICANT DEEP 
CONVECTION. WEAK LOW-LEVEL CONVERGENCE AND A LACK OF DEEP 
LAYERED MOISTURE IS SUPPRESSING CONVECTION ASSOCIATED WITH THE 
MONSOON TROUGH W OF 118W. NW SWELL REACHING AS HIGH AS 11 FT 
WITH PERIODS TO 17 SECONDS WILL PUSH INTO THE NW PORTION OF THE 
DISCUSSION AREA BY WED NIGHT AND CONTINUE INTO THU. 
ELSEWHERE...MODERATE S TO SW FLOW IS EXPECTED TO INCREASE 
TONIGHT AS THE THE 1007 MB LOW NEAR 13N96W DEEPENS...ALLOWING 
SEAS TO BUILD TO 10 FT. 25 KT GAP WINDS ARE ALSO FLOWING THROUGH 
THE GULF OF TEHUANTEPEC.

AN UPPER LEVEL HIGH IS CENTERED NEAR 16N142W AND EXTENDS E TO 
130W. ANOTHER UPPER LEVEL HIGH IS CENTERED S OF BAJA CALIFORNIA 
NEAR 21N110W AND EXTENDS E-W FROM 125W TO SW MEXICO NEAR 102W.  
A FAVORABLE LOW SHEAR ENVIRONMENT IS THUS OVER THE DEVELOPING 
LOW NEAR 13N96W. REFER TO SPECIAL FEATURES SECTION ABOVE FOR 
ADDITIONAL INFORMATION.   
$$
FORMOSA