000
AXPZ20 KNHC 200921
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS NATIONAL HURRICANE CENTER MIAMI FL
1005 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0845 UTC.

...SPECIAL FEATURE...

A 1009 MB LOW PRES AREA IS CENTERED ALONG THE MONSOON TROUGH 
NEAR 13N97W...OR ABOUT 200 NM SOUTHEAST OF PUERTO ESCONDIDO 
MEXICO. THIS FEATURE SHOWS UP WELL IN A 00 UTC WINDSAT PASS AND 
A 03 UTC ASCAT PASS. WINDS AREA REACHING 20 KT ON THE N SIDE OF 
THE LOW...WHERE SCATTERED MODERATE CONVECTION IS NOTED. THIS LOW 
IS EXPECTED TO DRIFT W OVER THE NEXT COUPLE OF DAYS THROUGH AN 
AREA FAVORABLE FOR CONTINUED STRENGTHENING AND POSSIBLE TROPICAL 
CYCLONE FORMATION.
 
...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH AXIS EXTENDS FROM 14N90W TO LOW PRES NEAR 
13N97W 1009 MB THEN ENDING NEAR 09N105W. THE MONSOON TROUGH 
RESUMES OVER THE PACIFIC AT 16N110W TO LOW PRES NEAR 12N120W 
1010 MB TO LOW PRES NEAR 11N135W 1011 MB TO 09N140W. SCATTERED 
MODERATE CONVECTION NOTED WITHIN 180 NM S OF TROUGH AXIS BETWEEN 
85W AND 95W...AND OVER FORECAST WATERS WITHIN 240 NM N OF AXIS 
BETWEEN 90W AND 100W.

SCATTERED MODERATE ISOLATED STRONG CONVECTION ALSO WITHIN 90 NM 
OF MEXICAN COAST FROM 18N TO 21N.

...DISCUSSION... 

W OF 110W...A 1023 MB SURFACE HIGH PRES AREA CENTERED NEAR 
31N137W CONTINUES TO WEAKEN AHEAD OF A DEEP LAYER TROUGH DIGGING 
EASTWARD FROM THE N CENTRAL PACIFIC. A SURFACE RIDGE EXTENDS 
FROM THE HIGH PRES THROUGH NORTHERN BAJA. SCATTEROMETER DATA 
FROM THE PAST 12 HOURS HAS SHOWN GENERALLY LIGHT TO MODERATE 
TRADE WIND FLOW N OF 15N AND S OF THE SURFACE RIDGE. WINDS ARE 
NE AT 15 TO 20 KT CLOSER TO THE MONSOON TROUGH...WITH LIGHT 
SOUTHERLY FLOW S OF THE TROUGH AXIS. THE WEAK CONVERGENCE AND 
GENERAL LACK OF DEEP LAYER MOISTURE IS SUPPRESSING CONVECTIVE 
DEVELOPMENT W OF 125W ALONG THE TROUGH. NW SWELL REACHING AS 
HIGH AS 12 FT WITH PERIODS TO 15 SECONDS WILL PUSH INTO THE NW 
DISCUSSION AREA BY LATE TUE NIGHT/EARLY WED MORNING. 

E OF 110W...AN UPPER RIDGE EXTENDS E-W ALONG ROUGHLY 20N THROUGH 
CENTRAL MEXICO. A SERIES OF SHORT WAVE TROUGH OVER THE CENTRAL 
UNITED STATES AND NORTHERN MEXICO HAVE CREATED A BREAK IN THE 
UPPER RIDGE NEAR 95W. THIS PROVIDES A FAVORABLE LOW SHEAR 
ENVIRONMENT FOR THE DEVELOPING LOW PRES NEAR 13N97W. TOGA-TAO 
BUOYS S OF THE LOW ALONG WITH SCATTEROMETER DATA FROM THE PAST 
12 HOURS SHOW GENERALLY MODERATE...15 KT...S TO SW FLOW. THIS 
WILL INCREASE TODAY AS THE LOW DEEPENS...ALLOWING SEAS TO BUILD 
ACCORDINGLY TO 8 TO 10 FT IN A BAND S OF THE LOW FROM 04N TO 11N 
BETWEEN 95W AND 105W. THE DEEPENING LOW WILL ALSO PROMOTE GAP 
WIND FLOW IN 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.
  
$$
CHRISTENSEN