000
AXPZ20 KNHC 042135
TWDEP 

TROPICAL WEATHER DISCUSSION  
NWS NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC THU AUG 04 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 
2100 UTC.

...SPECIAL FEATURES...
HURRICANE EUGENE AT 17.2N 120.1W AT 04/2100 UTC MOVING W-NW OR 
285 DEGREES AT 12 KT WITH ESTIMATED CENTRAL PRES OF 966 MB. 
MAXIMUM SUSTAINED WINDS ARE 95 KT WITH GUSTS TO 115 KT. EUGENE 
IS NOW A CATEGORY TWO HURRICANE ON THE SAFFIR-SIMPSON HURRICANE 
WIND SCALE. ADDITIONAL WEAKENING IS FORECAST DURING THE NEXT 48 
HOURS...AND EUGENE COULD BECOME A TROPICAL STORM BY LATE FRIDAY 
AS IT BEGINS TO MOVE OVER WATERS COLDER THAN 24C AND INTO A 
DRIER...MORE STABLE ENVIRONMENT. SCATTERED MODERATE TO ISOLATED 
STRONG CONVECTION LIES WITHIN 90 NM S OF THE CENTER AND 30 NM N 
OF CENTER. 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 10N86W TO 1007 MB LOW PRES NEAR 
16N101W THEN CONTINUES FROM 12N122W TO 08N140W. THE ITCZ AXIS IS 
WEST OF AREA. SCATTERED MODERATE CONVECTION LIES WITHIN 120 NM 
NW QUADRANT OF LOW PRES NEAR 16N101W.

...DISCUSSION...
A 1029 MB HIGH PRES CENTERED NW OF THE AREA NEAR 37N152W EXTENDS 
A RIDGE OVER THE NORTHERN FORECAST WATERS MAINLY N OF 20N AND W 
OF 120W. PRES GRADIENT BETWEEN THE RIDGE TO THE N AND HURRICANE 
EUGENE TO THE S HAS INCREASED ENOUGH TO PRODUCE FRESH N TO NE 
WINDS OVER A LARGE AREA N OF 18N W OF 120W. AN EARLIER WINDSAT 
PASS AND THE 1843 UTC ASCAT PASS CONFIRMED THESE CONDITIONS. IN 
ADDITION...FRESH TRADE WINDS ARE BLOWING ON THE SOUTHERN 
PERIPHERY OF THE RIDGE W OF 130W.

AN UPPER ANTICYCLONE IS CENTER OVER CENTRAL BAJA CALIFORNIA AT 
28112W EXTENDING A RIDGE SW TO 21N128W THEN MAINLY S TO 12N132W. 
EUGENE IS MOVING W-NW AROUND THE SOUTHERN PERIPHERY OF THIS 
RIDGE. ANOTHER RIDGE AXIS EXTENDS S ACROSS N AND CENTRAL MEXICO 
TO NEAR ACAPULCO. THIS RIDGE IS HELPING TO INDUCE SOME 
CONVECTION ALONG THE MEXICAN COAST FROM 18N TO 24N AND NW OF THE 
LOW PRES NEAR 16N101W. THE MOST RECENT ASCAT PASS PROVIDED 
OBSERVATIONS OF THESE WIND SPEEDS.

THE 1656 UTC ASCAT PASS CAPTURED THE EASTERN SIDE OF HURRICANE 
EUGENE. THE FRESH TO STRONG WINDS EXTEND AS FAR AS 210 NM NE 
QUADRANT AND 360 NM SE QUADRANT ACCORDING TO THE PASS. FRESH TO 
STRONG S TO SW WINDS CONTINUES TO FEED INTO EUGENE FROM N OF 04N 
BETWEEN 115W AND 120W. 

CROSS-EQUATORIAL SWELL IS RAISING SEAS TO ABOVE 9 FT IN S 
CENTRAL WATERS. SW SWELL WILL CONTINUE TO KEEP WAVE HEIGHTS IN 
THE 8 TO 10 FT RANGE THROUGH THE NEXT COUPLE OF DAYS.

A WEAK AREA OF LOW PRESSURE REMAINS CENTERED JUST OFF THE 
SOUTHWESTERN COAST OF MEXICO AND ABOUT 130 MILES SOUTH OF 
ZIHUATANEJO. THIS SYSTEM IS PRODUCING DISORGANIZED SHOWER AND 
THUNDERSTORM ACTIVITY PARTICULARLY TO THE NW QUADRANT.  
ENVIRONMENTAL CONDITIONS ARE NOT CONDUCIVE FOR DEVELOPMENT...AND 
THIS SYSTEM HAS A LOW CHANCE OF BECOMING A TROPICAL CYCLONE 
DURING THE NEXT 48 HOURS AS IT MOVES WEST-NORTHWESTWARD NEAR 10 
MPH. THE 1656 UTC ASCAT PASS SUGGESTS THAT THE LOW HAS OPENED UP 
INTO A TROUGH OR BECAME ELONGATED. 

$$
GR