000
AXPZ20 KNHC 082156
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
2205 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...
THE MONSOON TROUGH IS ALONG 09N84W TO 15N93W TO 15N99W TO 
19N107W TO 18N112W TO 12N119W TO LOW PRES 13N131W TO 10N138W. 
THE INTERTROPICAL CONVERGENCE ZONE AXIS IS ALONG 10N138W TO 
09N140W. SCATTERED MODERATE AND ISOLATED STRONG CONVECTION IS 
FROM 04N TO 13N E OF 103W...WITHIN 120 NM OF THE AXIS BETWEEN 
94W AND 109W...AND WITHIN 210 NM OF THE AXIS BETWEEN 111W AND 
123W.

...DISCUSSION...
ALOFT...A STRONG LONGWAVE TROUGH IS ACROSS THE NORTH-CENTRAL 
PACIFIC N OF 30N ALONG ABOUT 160W. SHORT WAVE ENERGY RIDING 
SOUTHWESTERLY WINDS HAS ALL BUT BEEN ABSORBED BACK INTO THE MEAN 
FLOW ON THE SE PERIPHERY OF THE TROUGHING THIS AFTERNOON. ANY 
LEFTOVER ENERGY CONTINUES TO ELONGATE AND STRETCH N OF THE 
HAWAIIAN ISLANDS NEAR 30N155W...AND NORTH OF THE AREA ALONG 40N 
INTO NORTHERN CALIFORNIA. A RIDGE ENCOMPASSES MUCH OF THE 
NORTHWESTERN PORTION OF THE DISCUSSION AREA TO THE SE AND 
REMAINS ANCHORED BY TWO ANTICYCLONIC CIRCULATIONS. ONE IS 
CENTERED NEAR 25N107W...AND THE OTHER IS LOCATED FARTHER WEST 
NEAR 27N132W. THE RIDGING IS EXPECTED TO PERSIST WITH DRY AND 
STABLE AIR UNDER MODERATE TO STRONG SUBSIDENCE N OF 20N W OF 
105W. IN BETWEEN THESE TWO HIGHS WAS A WEAKENING MID LEVEL 
TROUGH NEAR 24N123W SHIFTING SLOWLY WESTWARD. A CHANGE IN THE 
UPPER PATTERN WILL BE REALIZED BY FRI AS THE EASTERNMOST 
ANTICYCLONE COLLAPSES AND SINKS SW...AND THE WESTERN ANTICYCLONE 
SHIFTS W TO ALONG 137W. THIS WILL ALLOW BROAD UPPER LEVEL 
TROUGHING TO ENCOMPASS ALL OF NORTH AMERICA N OF 28N. 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. 

AT THE SURFACE...A BROAD RIDGE OF HIGH PRES COVERS THE AREA N OF 
18N W OF 115W....CENTERED BY A 1025 MB HIGH NEAR 36N135W. WHILE 
A WEAK PRESSURE GRADIENT REMAINS 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 10N TO 15N BETWEEN 109W AND 119W WITH 
SEAS TO 12 FT. THIS BROAD AREA OF WINDS WILL CONTINUE TO PRODUCE 
AN ELONGATED ZONE OF ACTIVE TSTMS WITH AREAS OF HEAVY RAIN 
THROUGH EARLY FRI...AND WILL THEN GRADUALLY EXPAND AND ENCOMPASS 
THE AREA FROM 11N TO 19N BETWEEN 102W AND 115W IN 24 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 N WINDS ARE EXPECTED TO FUNNEL THROUGH THE 
CHIVELA PASS AND INTO THE GULF OF TEHUANTEPEC REGION THROUGH 48 
HOURS BEFORE NATE BEGINS TO MOVE N-NW AND AWAY FROM THE REGION. 

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

$$
HUFFMAN