000
AXPZ20 KNHC 071531
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC WED SEP 07 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 
1515 UTC.

...ITCZ/MONSOON TROUGH...
THE MONSOON TROUGH IS ALONG 09N78W TO 10N85W TO LOW PRES 18N106W 
TO LOW PRES 17N108W TO 11N115W TO LOW PRES 10N134W TO 06N140W. 
SCATTERED MODERATE AND ISOLATED STRONG CONVECTION IS N OF 03N E 
OF 84W...WITHIN 60 NM OF 11N86W...WITHIN 60 NM OF A LINE FROM 
14N99W TO 17N104W...AND WITHIN 180 NM OF A LINE FROM 08N113W TO 
13N123W.

...DISCUSSION...
ALOFT...A STRONG LONGWAVE TROUGH IS ACROSS THE CENTRAL PACIFIC N 
OF 30N ALONG ABOUT 155W. TWO UPPER LEVEL CYCLONES LIE TO THE SE 
OF THIS TROUGH...THE FIRST SHORTWAVE IS LOCATED NE OF THE 
HAWAIIAN ISLANDS NEAR 31N146W...AND A SECOND SHIFTING NE NEAR 
39N131W. BOTH OF THESE CYCLONES WILL LIFT OUT TO THE NE DURING 
THE NEXT FEW DAYS. TWO ANTICYCLONIC CIRCULATIONS TO THE SE OF 
THE SHORTWAVES FORM PERSISTENT RIDGING...EXTENDING FROM A LARGE 
UPPER LEVEL ANTICYCLONE OVER NORTHERN MEXICO NEAR 26N105W WITH A 
RIDGE AXIS EXTENDING W TO 120W. A SMALLER UPPER LEVEL 
ANTICYCLONE WAS TO THE W-SW NEAR 26N133W EXTENDING SW TO 150W. 
DRY AND STABLE AIR UNDER MODERATE TO STRONG SUBSIDENCE IS NOTED 
ON WATER VAPOR SATELLITE IMAGERY N OF 15N W OF 120W. THE BIG 
CHANGE IN THE UPPER PATTERN WILL BE REALIZED WITH A SIGNIFICANT 
WWD EXPANSION OF THIS RIDGE TO 150W BY EARLY FRI...FORCING ALL 
UPSTREAM SHORTWAVE ENERGY N OF THE AREA. NE TO E FLOW ALOFT 
PERSISTS S OF THE UPPER RIDGING ACROSS MUCH OF THE REMAINDER OF 
THE DISCUSSION AREA AND IS MAINTAINING A MODESTLY SHEARED UPPER 
LEVEL ENVIRONMENT CONDUCIVE FOR CONVECTION. 

AT THE SURFACE...A BROAD RIDGE OF HIGH PRES COVERS THE AREA N OF 
15N W OF 115W. WITH A WEAK PRES GRADIENT IN PLACE...TRADES 
REMAIN LESS THAN 20 KT ACROSS THE NE PACIFIC WATERS. AN AREA OF 
20 TO 25 KT S TO SW WINDS EXISTS FROM 04N TO 10N BETWEEN 95W AND 
127W WITH SEAS TO 11 FT IN SW SWELL. THESE SOUTHERLY WINDS ARE 
FORECAST TO SHIFT AND ENCOMPASS THE AREA FROM 07N TO 12N BETWEEN 
105W AND 118W IN 24 HOURS...AND FROM 10N TO 15N BETWEEN 105W AND 
115W IN 48 HOURS. ALSO OF NOTE...WITH STRONG NORTHERLY WINDS 
EXPECTED ACROSS PORTIONS OF THE SOUTHWESTERN GULF OF MEXICO... 
THESE 20 TO 25 KT NE WINDS ARE FORECAST TO FUNNEL THROUGH THE 
CHIVELA PASS AND INTO THE GULF OF TEHUANTEPEC REGION THROUGH THE 
FORECAST PERIOD.

A COMPLEX 1009 MB LOW WITH MEAN CENTER NEAR 17N107W REMAINS 
EMBEDDED WITHIN THE MONSOON TROUGH INDUCING WINDS IN THE RANGE 
OF 20 TO 25 KT WITHIN 210 NM OF THE CENTER. LITTLE CHANGE IS 
EXPECTED WITHIN THE NEXT 24 TO 48 HOURS.

$$
HUFFMAN