000
AXPZ20 KNHC 080308
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC THU SEP 08 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
2115 UTC.

...ITCZ/MONSOON TROUGH...
MONSOON TROUGH ACROSS EXTREME SW CARIBBEAN EXTENDING NW ACROSS 
COSTA RICA AND W NICARAGUA TO 13.5N90W TO 14N99W TO LOW PRES 
17N108W TO 13N115W TO LOW PRES 11N133W TO BEYOND 08N140W. 
SCATTERED TO LOCALLY NUMEROUS MODERATE TO STRONG N OF 06N E OF 
87W. SCATTERED MODERATE ISOLATED STRONG WITHIN 210 NM S OF 
MONSOON TROUGH BETWEEN 95W AND 123W. 

...DISCUSSION...
ALOFT...A STRONG LONGWAVE TROUGH IS ACROSS THE CENTRAL PACIFIC N 
OF 30N ALONG ABOUT 155W. TWO SHORT WAVES LIE TO THE SE OF THIS 
TROUGH EMBEDDED IN THE SWLY FLOW ON E SIDE OF TROUGH AXIS. THE 
FIRST SHORTWAVE CONTINUES TO ELONGATE AND STRETCHES FROM THE 
HAWAIIAN ISLANDS NNE...WHILE A SECOND WELL DEFINED UPPER CYCLONE 
WAS NEAR 32N142W MOVING NE. BOTH OF THESE CYCLONES WILL LIFT OUT 
TO THE NE AND OVER THE RIDGE TO THE EAST DURING THE NEXT FEW 
DAYS. TWO ANTICYCLONIC CIRCULATIONS TO THE SE OF THESE 
SHORTWAVES FORM PERSISTENT RIDGING...EXTENDING FROM A LARGE 
UPPER LEVEL ANTICYCLONE OVER NORTHERN MEXICO NEAR 26N106W WITH A 
RIDGE AXIS EXTENDING WSW TO 21N120W. A SMALLER UPPER LEVEL 
ANTICYCLONE WAS TO THE W NEAR 25N130W EXTENDING SW TO 150W. 
DRY AND STABLE AIR UNDER MODERATE TO STRONG SUBSIDENCE IS NOTED 
ON WATER VAPOR SATELLITE IMAGERY N OF 18N W OF 122W. WEDGED IN 
BETWEEN THESE TWO HIGH CELLS WAS A WEAKENING MID LEVEL CYCLONE 
NEAR 24N122W SHIFTING SLOWLY W. A CHANGE IN THE UPPER PATTERN 
WILL BE REALIZED BY FRI AS THE EASTERN MOST ANTICYCLONE 
COLLAPSES AND SINKS SW...AND THE WESTERN ANTICYCLONE SHIFTS W TO 
ALONG 136W. THIS WILL ALLOW BROAD UPPER TROUGHING TO ENCOMPASS 
ALL OF NORTH AMERICA N OF 26-27N. NE TO E FLOW ALOFT PERSISTS S 
OF THE PRESENT RIDGE 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 
16N W OF 118W....CENTERED ON A 1022 MB HIGH NEAR 41N132W. WITH A 
WEAK PRES GRADIENT IN PLACE...TRADES REMAIN LESS THAN 20 KT 
ACROSS THE NE PACIFIC WATERS...EXCEPT FOR AN AREA OF 20 KT WINDS 
ACROSS THE NW SEMICIRCLE OF LOW PRES CENTER EMBEDDED IN THE 
MONSOON TROUGH...LOCATED NEAR 11N133W. AN AREA OF 20 TO 25 KT S 
TO SW WINDS EXISTS FROM 06N TO THE MONSOON TROUGH AXIS BETWEEN 
110W AND 132W WITH SEAS TO 10 FT. THIS BROAD AREA OF WINDS WILL 
CONTINUE TO PRODUCE AN ELONGATED ZONE OF ACTIVE TSTMS WITH AREAS 
OF HEAVY RAIN THROUGH THU...AND WILL THEN SHIFT AND ENCOMPASS 
THE AREA WITHIN 240 NM S OF THE MONSOON TROUGH AXIS BETWEEN 110W 
AND 130W IN 24 HOURS...AND THEN DIMINISH BELOW 20 KT BY 48 
HOURS. ALSO OF NOTE...WITH STRONG NORTHERLY WINDS EXPECTED 
ACROSS PORTIONS OF THE SOUTHWESTERN GULF OF MEXICO DUE TO 
TROPICAL STORM NATE...20 TO 25 KT NLY WINDS ARE EXPECTED TO 
FUNNEL THROUGH THE CHIVELA PASS AND INTO THE GULF OF TEHUANTEPEC 
REGION THROUGH 48 HOURS BEFORE NATE BEGINS TO MOVE NW AND AWAY 
FROM THE REGION. 

MARINE CONDITIONS ACROSS THE AREA ARE OTHERWISE DOMINATED BY 
FADING SRN HEMI SW SWELL THAT HAS BEGIN TO MIX WITH SELY SWELL 
GENERATED ACROSS THE SE PACIFIC. THIS SELY SWELL WILL CONTINUE 
TO MOVE THROUGH THE AREA WATERS THROUGH SAT...WHILE A NEW PULSE 
OF SW SWELL ENTERS THE AREA SAT.

$$
STRIPLING