000
AXPZ20 KNHC 312202
TWDEP 

TROPICAL WEATHER DISCUSSION    
NWS NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC SUN JUL 31 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.

...SPECIAL FEATURES...
TROPICAL STORM EUGENE CENTERED AT 11.0N 101.1W AT 31/2100 MOVING 
W OR 280 DEGREES AT 8 KT WITH CENTRAL PRES 1002 MB.  MAXIMUM 
SUSTAINED WINDS 40 GUSTS TO 50 KT.  DEEP CONVECTION AROUND 
CENTER OF EUGENE IS UNDER WEAK DIVERGENT FLOW BUT WITH LITTLE 
OR NO WIND SHEAR AS ANTICYCLONIC FLOW TRIES TO GET ESTABLISHED 
OVER REGION.  MID-LEVEL RIDGE STEERS EUGENE W-NW OVER NEXT FEW 
DAYS AS IT GRADUALLY STRENGTHENS OVER WARM E PAC SEA SURFACE 
TEMPERATURES AND COULD EVEN REACH MINIMAL HURRICANE FORCE WINDS 
LATE TUE BEFORE ENTERING AREA WITH ADVERSE UPPER LEVEL 
ENVIRONMENT...COOLER SEA TEMPERATURES AND DRIER AIR MASS SAPPING 
ITS STRENGTH.  SEE LATEST NHC PUBLIC ADVISORY UNDER AWIPS/WMO 
HEADERS TCPEP5/WTPZ35 KNHC AND FULL FORECAST/ADVISORY UNDER 
AWIPS/WMO HEADERS TCMEP5/WTPZ25 FOR MORE DETAILS.

...ITCZ/MONSOON TROUGH...
MONSOON TROUGH AXIS EXTENDS FROM 10N85W TO 13N95W THEN CONTINUES 
TO 11N105W TO 12N115W TO 1008 MB LOW PRES AT 10N124W TO 11N124W 
TO 10N140W.  SCATTERED MODERATE ISOLATED STRONG CONVECTION 
WITHIN 180 NM S OF AXIS FROM 115W TO 135W.

...DISCUSSION...
DEEP AMPLITUDE UPPER LEVEL TROUGH CUTS INTO NW CORNER OF E PAC 
FROM 32N132W TO 13N140W.  LARGE ANTICYCLONIC GYRE COMBINES WITH 
TROUGH TO KEEP A VERY DRY AIR MASS OVER REGION N OF MONSOON 
TROUGH AND W OF 115W.  ILL-DEFINED UPPER LEVEL RIDGE TRYING TO 
ESTABLISH OVER EUGENE BRINGS UNUSUAL LARGE AREA OF NE WINDS 
ALOFT ACROSS E PAC S OF 10N AND A VERY MOIST MODERATE EASTERLY 
FLOW E OF 110W N OF 10N.  

ELSEWHERE AT THE LOW LEVELS...
WEAK SURFACE TROUGH FROM 32N125W TO 28N130W WEAKENS AS IT MOVES 
E AND DISSIPATES MON.  BROAD AND WEAKENING HIGH PRES CENTER 1030 
MB FOLLOWS IN WAKE OF TROUGH ESTABLISHES A MODERATE NE BREEZE  
FROM 10N-15N W OF 135W WHICH BECOME A FRESH NE BREEZE LATE MON 
AND TUE. 

INCREASED PRES GRADIENT BETWEEN GULF OF MEXICO AND TROPICAL 
STORM EUGENE IN THE E PAC PROMPTING N FLOW ACROSS CHIVELAS PASS 
INTO GULF OF TEHUANTEPEC.  WINDS INCREASE A STRONG BREEZE BUT 
ARE SHORT-LIVED AS EUGENE DRIFT W AWAY FROM AREA. 

APPROACHING ATLANTIC TROPICAL WAVE ALONG 88W EXPECTED TO BECOME 
CAUGHT IN MONSOON FLOW MON AND DISSIPATE.

$$
WALLY BARNES