000
AXPZ20 KNHC 041543
TWDEP 

TROPICAL WEATHER DISCUSSION  
NWS NATIONAL HURRICANE CENTER MIAMI FL
1605 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1500 UTC.

...SPECIAL FEATURES...
HURRICANE EUGENE AT 16.8N 118.9W AT 04/1500 UTC MOVING W-NW OR 
285 DEGREES AT 12 KT WITH CENTRAL PRES 954 MB. MAXIMUM SUSTAINED 
WINDS ARE 105 KT WITH GUSTS TO 130 KT. EUGENE IS A CATEGORY 
THREE HURRICANE ON THE SAFFIR-SIMPSON HURRICANE WIND SCALE.  
QUICKER WEAKENING IS FORECAST DURING THE NEXT 48 HOURS...AND 
EUGENE SHOULD WEAKEN TO A TROPICAL STORM ON FRIDAY. THE TROPICAL 
CYCLONE IS IN A LOW-SHEAR ENVIRONMENT BUT IS BEGINNING TO MOVE 
INTO COOLER WATERS. SCATTERED MODERATE TO ISOLATED STRONG 
CONVECTION LIES WITHIN 90 NM S OF THE CENTER AND 45 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 08N84W TO 1006 MB LOW PRES NEAR 
15N100W THEN CONTINUES FROM 12N122W TO 10N130W. ITCZ AXIS 
EXTENDS FROM 10N130W TO 08N140W. SCATTERED MODERATE CONVECTION 
LIES WITHIN 140 NM NW QUADRANT OF LOW PRES NEAR 15N100W.

...DISCUSSION...
THE 1028 MB SUBTROPICAL HIGH IS CENTERED NW OF THE AREA NEAR 
36N151W. IT HAS BEEN DISPLACED WESTWARD THE LAST FEW DAYS BY 
MEAN TROUGHING OFF THE W COAST OF THE UNITED STATES. AS A 
RESULT...THE FRESH TRADE WINDS HAVE BEEN PRIMARILY FOUND W OF 
130W. HOWEVER...THE PRES GRADIENT BETWEEN THE SUBTROPICAL RIDGE 
TO THE N AND HURRICANE EUGENE TO THE S HAS INCREASED ENOUGH OVER 
THE LAST FEW HOURS FOR FRESH N TO NE WINDS TO EXPAND OVER MUCH 
OF THE AREA N OF 27N.   

AN UPPER ANTICYCLONE IS CENTER OVER CENTRAL BAJA CALIFORNIA AT 
26N114W EXTENDING A RIDGE SW TO AROUND 23N128W. EUGENE IS MOVING 
W-NW AROUND THE SOUTHERN PERIPHERY OF THIS RIDGE. THIS SYSTEM  
WILL SLOWLY SHIFT NORTHWARD OVER THE NEXT FEW DAYS AND WILL HELP 
STEER HURRICANE EUGENE INTO COOLER WATERS. ANOTHER RIDGE AXIS 
EXTENDS S ACROSS N AND CENTRAL MEXICO TO NEAR ACAPULCO. THIS 
RIDGE IS HELPING TO INDUCE CONVECTION ALONG THE MEXICAN COAST 
FROM 19N TO 23N AND NW OF THE LOW PRES NEAR 15N100W. 

AN EARLIER ASCAT PASS CAPTURED THE EASTERN SIDE OF HURRICANE 
EUGENE. THE FRESH TO STRONG WINDS EXTEND AS FAR AS 240 NM NE 
QUADRANT AND 450 NM SE QUADRANT ACCORDING TO THE PASS. FRESH TO 
STRONG S TO SW WINDS CONTINUES TO FEED INTO EUGENE FROM N OF 
04N BETWEEN 113W AND 128W. 

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.

SHOWERS AND A FEW THUNDERSTORMS JUST OFF THE SOUTHWESTERN COAST 
OF MEXICO ARE ASSOCIATED WITH A 1006 MB LOW PRESSURE SYSTEM
CENTERED NEAR 15N100W OR ABOUT 150 MPH SOUTH OF ZIHUATANEJO.  
ENVIRONMENTAL CONDITIONS DO NOT APPEAR 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 BETWEEN 5 AND 10 MPH. AN EARLIER ASCAT PASS SHOWED 
25 KT WINDS WITHIN 45 NM OF THE LOW CENTER. 

$$
GR