000
AXPZ20 KNHC 021532
TWDEP 

TROPICAL WEATHER DISCUSSION  
NWS NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC TUE AUG 02 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 
1430 UTC.

...SPECIAL FEATURES...
HURRICANE EUGENE LOCATED AT 14.0N 109.6W AT 02/1500Z MOVING W-NW 
OR 285 DEGREES AT 13 KT...WITH CENTRAL PRES 973 MB. MAXIMUM 
SUSTAINED WINDS 85 WITH GUSTS TO 105 KT. NUMEROUS STRONG 
CONVECTION LIES WITHIN 90 NM NE AND 210 SW OF THE CENTER OF 
EUGENE. THE CURRENT FORECAST CALLS FOR EUGENE TO GENERALLY 
MAINTAIN ITS CURRENT MOTION AND INTENSIFY SLIGHTLY OVER THE NEXT 
24 HOURS BEFORE BEGINNING TO ENCOUNTER COOLER WATER AND BEGIN A 
GRADUAL WEAKENING TREND. 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 09N79W TO 07N83W TO 1008 MB LOW 
PRES NEAR 14N94W THEN CONTINUES FROM 12N114W TO 1007 MB LOW PRES 
NEAR 11N119W TO 1008 MB LOW PRES NEAR 10N131W TO 08N136W. ITCZ 
AXIS EXTENDS FROM 08N136W TO BEYOND 06N140W. SCATTERED MODERATE 
WITHIN 120 NM S OF MONSOON TROUGH FROM 84W TO 87W. SIMILAR 
CONVECTION IS NOTED FROM 10N TO 11N BETWEEN 114W AND 117W.

...DISCUSSION...
THE DEEP LAYERED NORTHERN STREAM TROUGH THAT SAT ALONG 130W AND 
WEAKENED THE SUBTROPICAL RIDGE DURING THE LAST FEW DAYS HAS 
CONTINUED TO WEAKEN DURING THE PAST 12 HOURS...WITH THE MAIN 
ENERGY NOW MOVING N OF THE AREA. THIS IS LEAVING A WEAK MIDDLE 
TO UPPER LEVEL TROUGH EXTENDING FROM NEAR 30N129W TO VERY WEAK 
MID LEVEL CYCLONE NEAR 21N141W. AT THE SURFACE...THE SUBTROPICAL 
HIGH HAS BUILT ENOUGH RIDGING OVER WESTERN WATERS TO INCREASE 
THE PRES GRADIENT BETWEEN IT AND THE ITCZ...ALLOWING FOR FRESH 
NE TRADE WINDS TO RETURN W OF 130W. AN OVERNIGHT 0254 UTC 
WINDSAT PASS SHOWS 20 KT WINDS FROM 12N TO 20N W OF 136W. THESE 
TRADES WILL BUILD SLIGHTLY FARTHER NE DURING THE NEXT DAY OR 
TWO. 

A SLOWLY WEAKENING ANTICYCLONE ALOFT LIES NEAR 22N128W AND 
EXTENDS A NARROW RIDGE NE THROUGH NORTHERN BAJA CALIFORNIA TO 
ANOTHER ANTICYCLONE OVER WESTERN NEW MEXICO. JUST TO THE SE OF 
THIS RIDGE LIES A WEAK UPPER LEVEL CYCLONE NEAR 29N117W WITH 
TROUGH EXTENDING SW TO A MIDDLE TO UPPER LEVEL CYCLONE NEAR THE 
ITCZ ALONG 13N127W. A SECOND BROADER RIDGE AXIS ALOFT CONTINUES 
TO DOMINATE THE CENTRAL AND S CENTRAL U.S. AND NORTHERN GULF OF 
MEXICO...AND EXTENDS SW ACROSS MOST OF THE N HALF OF MEXICO.  
HURRICANE EUGENE IS S OF THIS SECOND RIDGE AND LIES ON THE 
SOUTHERN PERIPHERY OF ABOUT 20 KT OF E-NE SHEAR. WHILE THERE 
REMAINS AMPLE DEEP CONVECTION NEAR THE CENTER...THIS SHEAR IS 
FORCING THE BULK OF THE DEEP CONVECTION ASSOCIATED WITH EUGENE 
TO BE DISPLACED ACROSS THE SW SEMICIRCLE OF THE CIRCULATION. 
CLOSER TO THE RIDGE AXIS...SCATTERED MODERATE TO STRONG 
CONVECTION LIES WITHIN 90 NM OF THE MEXICAN COAST FROM 20N TO 
23N. THE UPPER CYCLONE AND ASSOCIATED TROUGH IS EXPECTED TO WEAK 
TODAY AS IT SHIFTS NW...THE TWO RIDGE AXES ALOFT WILL GRADUALLY 
MERGE...WITH A NEW ANTICYLONE EXPECTED TO DEVELOP OVER NW MEXICO 
TONIGHT. E OF 100W...NE TO ELY WINDS ALOFT WERE PRODUCING VERY 
LIGHT WIND SHEAR ALOFT...AND HELPING TO MAINTAIN ACTIVE DEEP 
CONVECTION OFF THE MEXICAN COAST N OF 20N BETWEEN 93W AND 100W.

A 0504 UTC OVERNIGHT ASCAT PASS CAPTURED THE SHRINKING AREA OF 
FRESH TO STRONG SW WINDS FEEDING INTO EUGENE FROM N OF 05N. A 
JASON2 PASS FROM 0410 UTC SHOWS SEAS ABOVE 12 FT EXTEND AT LEAST 
180 NM IN THE NE QUADRANT AND 90 NM IN THE SW QUADRANT WITH SEAS 
AS HIGH AS 18 FT OBSERVED. THE FORECAST MODELS SUGGEST THE AREA 
OF 12 FT SEAS IN THE SE QUADRANT STILL EXTENDS AT LEAST 240 NM 
FROM THE CENTER OF EUGENE WITH SW SWELL STILL ENHANCING THE 
SEAS. A NEW PULSE OF LONG PERIOD SW SWELL IS CURRENTLY CROSSING 
THE EQUATOR...AND WILL REACH EUGENE LATER TODAY. THE AREA OF SW 
WINDS AND INCREASED SEAS S OF EUGENE WILL LIFT NW IN TANDEM WITH 
THE SYSTEM OVER THE NEXT FEW DAYS. 

A 1008 MB SURFACE LOW IS ANALYZED JUST SW OF THE GULF OF 
TEHUANTEPEC NEAR 14N95W...IN THE REGION OF DEEP CONVECTION NOTED 
ABOVE BETWEEN 93W AND 100W. THE CYCLONIC CIRCULATION ASSOCIATED 
WITH THIS LOW EMBEDDED IN THE MONSOON TROUGH IS AIDING IN LOW 
LEVEL MOISTURE CONVERGENCE OVER THE REGION...WHILE SPEED 
DIVERGENCE ALOFT IS ENHANCING AND SUSTAINING THE DEEP CONVECTION 
THERE. THIS LOW IS FORECAST TO SHIFT SLOWLY W OVER THE NEXT 48 
HOURS AND REMAIN A FOCUS FOR ACTIVE CONVECTION...BEFORE REACHING 
100W AND GRADUALLY WEAKENING THU.

$$
STRIPLING