000
AXPZ20 KNHC 090306
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC FRI SEP 09 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 W ACROSS COSTA 
RICA TO NEAR 09N84W TO 15N93W TO 15N98W TO 18N106W TO 18N111W TO 
11N119W TO LOW PRES 13N131W TO 12N137W WHERE IT TRANSITIONS TO 
ITCZ TO BEYOND 10N140W. SCATTERED MODERATE ISOLATED STRONG FROM 
06N TO 14N BETWEEN 95W AND 120W. SCATTERED MODERATE ISOLATED 
STRONG FROM 05N TO 11N E OF 93W. SCATTERED MODERATE TO STRONG 
WITHIN 210 NM NW OF THE AXIS BETWEEN 114W AND 119W. 

...DISCUSSION...
ALOFT...A STRONG LONGWAVE TROUGH IS ACROSS THE NORTH-CENTRAL 
PACIFIC N OF 30N ALONG ABOUT 165W AND HAS ATTAINED A MORE NNE TO 
SSW ALIGNMENT IN THE PAST24 HOURS. 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 AND 
EVENING. ANY LEFTOVER ENERGY CONTINUES TO ELONGATE AND STRETCH N 
OF THE HAWAIIAN ISLANDS NEAR 30N155W...AND NORTH OF THE AREA 
ALONG 36N AND 131W. A RIDGE ENCOMPASSES MUCH OF THE NORTHWESTERN 
PORTION OF THE DISCUSSION AREA TO THE SE OF THE LONGWAVE TROUGH 
AND REMAINS ANCHORED BY TWO ANTICYCLONIC CIRCULATIONS. ONE IS 
CENTERED NEAR 26N106W AND GRADUALLY FLATTENING...AND THE OTHER  
MORE DOMINANT CENTER IS LOCATED FARTHER WEST NEAR 28N132W. 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 24N125W 
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...CURRENTLY ANALYZED BY CIMSS/NESDIS AS LESS THAN 20 
KT EXCEPT FOR SMALL AREA AT 20 KT CENTERED NEAR 13N108W.  

AT THE SURFACE...A BROAD RIDGE OF HIGH PRES COVERS THE AREA N OF 
18N W OF 115W....CENTERED BY A 1026 MB HIGH NEAR 40N133W. WHILE 
A WEAK PRESSURE GRADIENT REMAINS IN PLACE...TRADES REMAIN LESS 
THAN 20 KT ACROSS THE NE PACIFIC WATERS...EXCEPT ACROSS THE NW 
QUADRANT OF THE LOW PRES CENTER AT 13N131W. AN AREA OF 20 TO 25 
KT S TO SW WINDS EXISTS FROM 10N TO 15N BETWEEN 108W AND 120W 
WITH SEAS TO 11 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 NLY WINDS ARE EXPECTED TO 
FUNNEL THROUGH THE CHIVELA PASS AND INTO THE GULF OF TEHUANTEPEC 
REGION THROUGH 36 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.

$$
STRIPLING