000
AXPZ20 KNHC 070300
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
0405 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0200 UTC.

...ITCZ/MONSOON TROUGH...
MONSOON TROUGH EXTENDS FROM EXTREME SW CARIBBEAN WWD AND EXITS W 
COAST OF COSTA RICA NEAR 10.5N86W TO 14N94W TO 14N102W TO 
17N107W TO LOW PRES AT 11N125W TO LOW PRES AT 10N133W TO BEYOND 
09N140W. SCATTERED MODERATE TO STRONG CONVECTION NOTED E OF 78W. 
SCATTERED MODERATE ISOLATED STRONG CONVECTION NOTED N OF 10N TO 
COAST OF MEXICO BETWEEN 90W AND 102W. SCATTERED TO LOCALLY 
NUMEROUS MODERATE ISOLATED STRONG CONVECTION NOTED WITHIN 90 NM 
OF LINE 11N101W TO 08.5N109W TO 08.5N111W TO 12N120W TO 
10.5N127W. 

...DISCUSSION...
ALOFT...A SIGNIFICANT PATTERN CHANGE IS EVOLVING FINALLY ACROSS 
THE EASTERN PACIFIC. A STRONG LONGWAVE TROUGH IS ACROSS THE 
CENTRAL PACIFIC N OF 30N ALONG ABOUT 159W. TWO UPPER CYCLONES 
LIE TO THE SE OF THIS TROUGH...THE FIRST WAS BECOMING ELONGATED 
N-NE OF THE HAWAIIAN ISLANDS...AND A SECOND SHIFTING NE NEAR 
38N133W. BOTH OF THESE CYCLONES WILL LIFT OUT TO THE NE DURING 
THE NEXT FEW DAYS. TWO ANTICYCLONIC CIRCULATIONS TO THE SE OF 
THIS FORM PERSISTENT RIDGING...EXTENDING FROM A LARGE UPPER 
ANTICYCLONE OVER NORTHERN MEXICO NEAR 28N105W WITH A RIDGE AXIS 
EXTENDING W TO 121W. A SMALLER UPPER ANTICYCLONE WAS TO THE SW 
NEAR 23N126W EXTENDING W TO 143W. CONTINUING TO 22N140W. A WEAK 
INVERTED UPPER TROUGH IS WEDGED BETWEEN THE ANTICYCLONES 
EXTENDING FROM 20N115W TO 26N121W. DRY AND STABLE AIR UNDER 
MODERATE TO STRONG SUBSIDENCE IS NOTED ON WATER VAPOR SATELLITE 
IMAGERY N OF 15N W OF 123W. THE BIG CHANGE IN THE UPPER PATTERN 
WILL BE REALIZED WITH A SIGNIFICANT WWD EXPANSION OF THIS RIDGE 
TO 145W BY LATE THU...FORCING ALL UPSTREAM SHORTWAVE ENERGY N OF 
THE AREA. NE TO E FLOW ALOFT PERSISTS S OF THE UPPER RIDGING 
ACROSS THE MAJORITY OF THE REMAINDER OF THE DISCUSSION AREA AND 
IS MAINTAINING A MODESTLY SHEARED UPPER ENVIRONMENT CONDUCIVE 
FOR ACTIVE CONVECTION. 

AT THE SURFACE...A BROAD RIDGE OF HIGH PRES COVERS THE AREA N OF 
16N W OF 120W. WITH A WEAK PRES GRADIENT IN PLACE...TRADES 
REMAIN LESS THAN 20 KT ACROSS THE NE PACIFIC WATERS. AN AREA OF 
20 KT S TO SW WINDS EXISTS 05N TO 11N BETWEEN 110W AND 132W WITH 
SEAS TO 9 FT IN A BROAD MIX OF SWELL. THESE SOUTHERLY WINDS ARE 
FORECAST TO SHIFT AND ENCOMPASS THE AREA FROM 06N TO 12N BETWEEN 
100W AND 118W...ALONG WITH SE TO S 20 TO 25 KT WINDS S OF 10N 
BETWEEN 118W AND 134W WITH SEAS BUILDING TO 10 FT IN 24 
HOURS...WITH S TO SW 20 KT WINDS FROM 06N TO 12N BETWEEN 107W 
AND 117W IN 48 HOURS.

A PAIR OF 1009 MB LOWS WERE EMBEDDED WITHIN THE MONSOON TROUGH 
AT 123.5W AND 133.5W...AND LIKELY WERE INDUCING SW WINDS TO 25 
KT ACROSS THEIR SE QUADRANTS. BY 24 HOURS 20 TO 25 KT WINDS WILL 
BECOME CONFINED TO THE AREA N OF 15N BETWEEN 94.5W AND 98W WHILE 
SHIFTING TO THE N TO NE WHERE THEY WILL LINGER THROUGH 48 HOURS. 

OTHERWISE...LONG PERIOD CROSS EQUATORIAL SWELL PRODUCING SEAS TO 
9 FT DOMINATES THE REMAINDER OF THE AREA S OF 13N BETWEEN 90W 
AND 130W AND S OF 06N BETWEEN 78W AND 87W. THE COVERAGE OF THIS 
SWELL WILL NOT VARY MUCH THROUGH THE NEXT 48 HOURS. BROKEN TO 
OVERCAST STRATOCUMULUS CLOUDS BLANKET THE AREA N OF 15N W OF 
115W.

$$
STRIPLING