000
AXPZ20 KNHC 010949
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC THU SEP 01 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0945 UTC.

...ITCZ/MONSOON TROUGH...
THE MONSOON TROUGH EXTENDS W ALONG 10N FROM 75W TO 83W...THEN 
TURNS NW ALONG THE CENTRAL AMERICAN MEXICAN COAST THROUGH THE 
GULF OF TEHUANTEPEC AND CONTINUING INLAND TO THE REMNANTS OF 
TROPICAL DEPRESSION EIGHT E NEAR 20N104W. THE TROUGH AXIS THEN
TURNS SW OVER THE PACIFIC TO 15N112W...NW TO 17N125W...FINALLY   
SW TO JUST BEYOND 10N140W. SCATTERED MODERATE ISOLATED STRONG 
CONVECTION...ACCOMPANIED BY NUMEROUS LIGHTNING STRIKES...IS 
OBSERVED TO THE N OF 03N E OF 80W AND ALSO OVER THE CARIBBEAN 
S OF 12N TO THE W OF 74W. 

SIMILAR CONVECTION IS NOTED ALONG THE CENTRAL AMERICAN COAST 
FROM 83W TO 87W AND EXTENDING 180 NM OFFSHORE THE CENTRAL 
AMERICAN COAST ACROSS THE GULF OF TEHUANTEPEC BETWEEN 91W 
AND 100W...AND WITHIN 120 NM OF MEXICAN COAST FROM 18N TO 23N. 
SIMILAR CONVECTION IS OBSERVED OVER THE PACIFIC WITHIN 30 NM OF 
16N108W.  

BROKEN TO OVERCAST MULTILAYERED CLOUDS ARE OBSERVED FROM 09N TO 
16N BETWEEN 105W AND 125W...WITH SCATTERED MODERATE AND ISOLATED 
STRONG CONVECTION NOTED IN THE AREA FROM 10N TO 14N BETWEEN 112W 
AND 123W.

...DISCUSSION...
AN UPPER LEVEL TROUGH EXTENDS FROM 32N126W TO AN UPPER CYCLONE 
AT 28N129W...WITH THE TROUGH CONTINUING THROUGH 18N131W TO A 
BASE AT 15N135W. THIS TROUGH HAS SPLIT AN UPPER RIDGE INTO TWO 
SEGMENTS. THE EASTERN RIDGE EXTENDS SW FROM AN UPPER LEVEL 
ANTICYCLONE CENTERED OVER SE OKLAHOMA...ACROSS NW OLD MEXICO AND 
THE BAJA CALIFORNIA PENINSULA TO 22N127W. AN UPPER ANTICYCLONE 
HAS CUT W OF THE AREA AT 20N144W WITH ITS ENVELOPE OF 
ANTICYCLONIC FLOW EXTENDING E INTO THE AREA NEAR 18N138W. 
CONVECTION WAS ENHANCED UNDER THE MEXICAN UPPER RIDGE...WITH 
DEBRIS MOISTURE NOW SPREADING W OVER THE NORTHERN GULF OF 
CALIFORNIA...AND ALSO TURNING NE AROUND THE RIDGE PERIPHERY INTO 
A PLUME SPREADING NE ACROSS EASTERN ARIZONA...OVER ALL OF NEW 
MEXICO...THEN EVAPORATING OVER WESTERN TEXAS. OTHERWISE THE 
UPPER LEVELS APPEAR VERY DRY N OF 17N W OF 110W AND FROM 11N TO 
17N W OF 130W. 

AT THE SURFACE...A RIDGE DOMINATES THE DISCUSSION AREA N OF 20N 
W OF 118W. NORTHERLY WINDS AT 15 TO 20 KT ARE OBSERVED NW OF 
LINE FROM 32N122W TO 17N140W WITH SEAS 8 TO 10 FT IN MIXING N 
AND S SWELL. ALTHOUGH WINDS ARE LESS THAN 20 KT ELSEWHERE TO THE 
N OF 20N AND ALSO IN THE AREA FROM 10N TO 20N TO THE W OF 
132W...SEAS ARE REPORTED TO 8 FT PRIMARILY DUE TO MIXING N AND S 
SWELL. MONSOONAL SW FLOW AT 20 KT...SEAS 9 TO 10 FT...IS 
OBSERVED IN THE AREAS FROM 10N TO 15N BETWEEN 100W AND 108W AND 
FROM 09N TO 12N BETWEEN 108W AND 120W. CROSS EQUATORIAL SW SWELL 
IS NOTED ELSEWHERE S OF 20N RESULTING IN COMBINED SEAS OF 8 TO 
10 FT. BOTH THE SOUTHERLY AND NORTHERLY SWELLS ARE FORECAST TO 
SUBSIDE OVER THE NEXT FEW DAYS. A WEAKENING COLD FRONT WILL MOVE 
INTO THE NW PORTION OVER THE WEEKEND.
 
$$
NELSON