000
AXPZ20 KNHC 072153
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
2205 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
2115 UTC.

...ITCZ/MONSOON TROUGH...
THE MONSOON TROUGH IS ALONG 14N90W TO 14N99W TO LOW PRES 17N107W 
TO 12N119W TO LOW PRES 10N134W TO 08N140W. SCATTERED MODERATE 
AND ISOLATED STRONG CONVECTION IS FROM 12N TO 16N BETWEEN 97W 
AND 105W...AND FROM 08N TO 13N BETWEEN 115W AND 125W.

...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 31N144W...AND A SECOND SHIFTING NE NEAR 
39N128W. BOTH OF THESE CYCLONES WILL LIFT OUT TO THE NE 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 W TO 120W. A SMALLER UPPER LEVEL 
ANTICYCLONE WAS TO THE W-SW NEAR 22N127W EXTENDING SW TO 154W. 
DRY AND STABLE AIR UNDER MODERATE TO STRONG SUBSIDENCE IS NOTED 
ON WATER VAPOR SATELLITE IMAGERY N OF 15N W OF 118W. THE BIG 
CHANGE IN THE UPPER PATTERN WILL BE REALIZED WITH A SIGNIFICANT 
WESTWARD 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 
16N W OF 118W. 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 03N TO THE MONSOON TROUGH 
AXIS BETWEEN 107W AND 133W WITH SEAS TO 10 FT. THESE SOUTHERLY 
WINDS ARE FORECAST TO SHIFT AND ENCOMPASS THE AREA WITHIN 240 NM 
S OF THE MONSOON TROUGH AXIS BETWEEN 110W AND 130W IN 24 
HOURS...AND FROM 10N TO 16N BETWEEN 106W AND 120W IN 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 NE WINDS ARE FORECAST TO FUNNEL THROUGH 
THE CHIVELA PASS AND INTO THE GULF OF TEHUANTEPEC REGION FOR THE 
DURATION OF THE FORECAST PERIOD.

$$
HUFFMAN