000
AXPZ20 KNHC 201530
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC TUE SEP 20 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1500 UTC.

...SPECIAL FEATURE...

A 1008 MB LOW PRES EMBEDDED WITHIN THE MONSOON TROUGH ABOUT 200 
NM S-SE OF PUERTO ESCONDIDO MEXICO NEAR 13N96W HAS A BROAD AREA 
OF ACTIVE BUT POORLY ORGANIZED CONVECTION. CIRCULATION CENTER 
SHOWS UP WELL IN A 0004 UTC WINDSAT PASS AND A 0312 UTC ASCAT 
PASS...WITH WINDS REACHING 20 KT N OF THE LOW...WHERE SCATTERED 
MODERATE CONVECTION IS NOTED. IT IS EXPECTED TO DRIFT W OVER THE 
NEXT COUPLE OF DAYS. ENVIRONMENTAL CONDITIONS ARE AREA FAVORABLE 
FOR CONTINUED STRENGTHENING AND POSSIBLE TROPICAL CYCLOGENESIS.
 
...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH AXIS EXTENDS FROM 10N85W TO LOW PRES NEAR 
13N96W 1008 MB TO 10N105W...THEN RESUMES AT 12N118W TO LOW PRES 
NEAR 11N121W 1011 MB TO 13N126W TO LOW PRES NEAR 11N135W 1011 MB 
TO 09N140W. SCATTERED MODERATE TO STRONG CONVECTION NOTED N OF 
TROUGH AXIS TO COAST OF MEXICO BETWEEN 88W AND 92W AND WITHIN 
150 NM N OF THE TROUGH AXIS BETWEEN 93W TO 102W. 

SCATTERED MODERATE ISOLATED STRONG CONVECTION N OF 09N TO TROUGH 
AXIS BETWEEN 87W AND 98W AND WITHIN 90 NM OF LINE FROM COLOMBIA 
NEAR 06N77W TO 09N86W. 

SCATTERED MODERATE ISOLATED STRONG CONVECTION FROM 09N TO 13N 
BETWEEN 108W AND 112W. 

...DISCUSSION... 

1022 MB HIGH PRES CENTERED NEAR 32N139W 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. 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 11N121W AND 11N135W. BOTH ARE 1011 MB 
AND BOTH LACK SIGNIFICANT DEEP CONVECTION. WEAK LOW-LEVEL 
CONVERGENCE AND A LACK OF DEEP LAYER MOISTURE IS SUPPRESSING 
CONVECTION ASSOCIATED WITH THE TROUGH W OF 118W. NW SWELL 
REACHING AS HIGH AS 12 FT WITH PERIODS TO 15 SECONDS WILL PUSH 
INTO THE NW PORTION OF THE DISCUSSION AREA BY EARLY WED MORNING. 

AN UPPER RIDGE EXTENDS E-W ALONG 20N THROUGH CENTRAL MEXICO. A 
BREAK IN RIDGE IS EVIDENT NEAR 95W...PROVIDING A FAVORABLE LOW 
SHEAR ENVIRONMENT FOR THE DEVELOPING LOW PRES NEAR 13N96W. 
MODERATE S TO SW FLOW IS EXPECTED TO INCREASE THIS AFTERNOON AS 
THE LOW DEEPENS...ALLOWING SEAS TO BUILD TO 8 TO 10 FT S OF THE 
LOW FROM 04N TO 11N BETWEEN 95W AND 105W. THE DEEPENING LOW WILL 
ALSO ENHANCE N WINDS FLOWING THROUGH THE GULF OF TEHUANTEPEC... 
ALTHOUGH THIS WILL VEER MORE NE AND TAPER OFF THROUGH LATE WED 
AS THE LOW TRACKS FURTHER W...ALLOWING MORE SOUTHERLY FLOW TO 
PREVAIL THROUGH THE GULF OF TEHUANTEPEC.
  
$$
MUNDELL