000
AXPZ20 KNHC 100304
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC SAT SEP 10 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...
THE MONSOON TROUGH EXTENDS FROM THE FAR SW CARIBBEAN ACROSS 
COSTA RICA AND ENTERS THE EPAC NEAR 10N85W TO 09N89W TO 07N91W 
TO 09N103W WHERE IT HAS FRACTURED FROM THE REMAINDER OF THE 
TROUGH...THEN RESUMES AGAIN FROM 18N103W TO 19N110W TO LOW PRES 
16N117W TO LOW PRES 13.5N131W TO BEYOND 10N1410W. SCATTERED 
MODERATE CONVECTION NOTED FROM 03N TO 07N E OF 87W...AND FROM 
04N TO 14N BETWEEN 92W AND 106W.  

...DISCUSSION...
AN UPPER ANTICYCLONE IS CENTERED AT 29N139W WITH A RIDGE ESE TO 
25N128W...AND MORE PROMINENT RIDGE EXTENDING SW TO JUST BEYOND 
THE HAWAIIAN ISLANDS. AN ENERGETIC LONGWAVE TROUGH PERSISTS 
ACROSS THE N CENTRAL PACIFIC TO THE NW OF THIS RIDGE...WHICH HAS 
ALLOWED THE CREST OF THE RIDGE TO BUILD NNE AND OFFSHORE OF THE 
PACIFIC NW COASTS. AN UPPER LEVEL CYCLONE HAS BECOME CUT OFF 
FROM THE MAIN FLOW ACROSS THE NW U.S. WITH A SHORTWAVE TROUGH 
ROTATING SE AND EXTENDING INTO THE AREA TO NEAR 28N125W. A 
SECOND UPPER ANTICYCLONE WAS CENTERED OVER CENTRAL MEXICO ALONG 
23N EARLIER TODAY BUT HAS BEGUN TO COLLAPSE AS FORECAST BY THE 
GLOBAL MODELS. ASSOCIATED RIDGING STILL PERSISTS FROM SOUTHERN 
MEXICO ALONG 22-24N WWD TO NEAR 23N120W...AND IS SEPARATED FROM 
THE DOMINANT RIDGE ABOVE BY AN INVERTED MIDDLE TO UPPER TROUGH 
ALONG 125W FROM 15N TO 25N. TO THE SOUTH OF THESE FEATURES E TO 
NE UPPER LEVEL FLOW PERSISTS ACROSS THE DEEP TROPICS...FROM 
CENTRAL AND SOUTH AMERICA TO 140W. CIMSS/NESDIS ANALYSIS SHOWS 
MILD ELY VERTICAL WIND SHEAR ACROSS THE DEEP TROPICS...GENERALLY 
AT 15 KT OR LESS. THE SHORTWAVE MOVING SE ACROSS NE PORTIONS OF 
THE AREA IS FORECAST TO DEEPEN ACROSS SRN CALIFORNIA AND DIG S 
AND SW...AND GRADUALLY FORM A BROAD UPPER TROUGH FROM CALIFORNIA 
TO NEAR 24N125W BY SUN NIGHT.  

LITTLE CHANGE HAS OCCURRED AT THE SURFACE DURING THE PAST 24 
HOURS...WITH A WEAK HIGH PRES RIDGE ACROSS W AND NW PORTIONS 
EXTENDING FROM A 1028 MB HIGH NEAR 37N138W TO NEAR 23N120W. THIS 
CONTINUES TO YIELD NELY TRADES AT LESS THAN 20 KT ACROSS THE 
AREA...WITH THE ONLY AREAS OF 20 KT WINDS AND GREATER ACROSS THE 
OPEN PACIFIC OCCURRING AROUND THE TWO LOW CENTERS EMBEDDED IN 
THE MONSOON TROUGH. DEEPENING SURFACE LOW PRESSURE ACROSS SRN 
CALIFORNIA AND SW ARIZONA IS INDUCING SLY WINDS TO 20 KT ACROSS 
N PORTIONS OF THE GULF OF CALIFORNIA...WHICH IS EXPECTED TO 
PERSIST THROUGH SUNDAY NIGHT BEFORE DIMINISHING. OTHERWISE... 
LIGHT TO MODERATE MONSOONAL FLOW CONTINUES S OF THE TROUGH S OF 
10N E OF 105W. 

GAP WINDS...TROPICAL STORM NATE CONTINUES TO MEANDER SLOWLY 
ACROSS THE BAY OF CAMPECHE RESULTING IN NORTHERLY WINDS AT 20 KT 
TO FUNNEL THROUGH THE CHIVELA PASS AND INTO THE GULF OF 
TEHUANTEPEC REGION. THESE FRESH NORTHERLY WINDS ARE EXPECTED TO 
END LATE SUNDAY AFTERNOON. 

OTHERWISE...MARINE CONDITIONS ACROSS THE AREA ARE 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 PROPAGATE THROUGH THE TROPICAL WATERS REINFORCED BY 
ANOTHER PULSE OF SW SWELL ENTERING THE AREA THIS MORNING.

$$
STRIPLING