000
AXPZ20 KNHC 310952
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC WED AUG 31 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 
094500 UTC.

...SPECIAL FEATURES...
SURFACE LOW PRESSURE IS ANALYZED AT 1003 MB AT 17N102W. 
SCATTERED MODERATE TO STRONG CONVECTION IS FLARING WITHIN 120 NM 
OF CENTER. THIS DISTURBANCE HAS THE POTENTIAL TO BECOME A 
TROPICAL CYCLONE AS IT MOVES WEST NORTHWEST TO NEAR 18.5N105W 
TONIGHT AND NEAR 20N107.5W THU NIGHT. LOCALLY HEAVY RAINFALL IS 
POSSIBLE OVER PACIFIC COAST OF MEXICO FROM 17N TO 22N.

...ITCZ/MONSOON TROUGH...
THE MONSOON TROUGH EXTENDS E TO W ALONG 09N FROM COLOMBIA TO 
COSTA RICA...THEN TURNS NW PARALLELING THE PACIFIC COAST OF  
CENTRAL AMERICA COAST 17N95W...THEN TURNS W OFFSHORE TO THE 
DEVELOPING SURFACE LOW AT 17N102W...THEN THE TROUGH AXIS 
CONTINUES W ALONG 14N114W TO 15N128W..TURNING SW TO 10N140W. 
SCATTERED MODERATE ISOLATED STRONG CONVECTION IS NOTED ALONG THE 
MONSOON TROUGH AXIS WITHIN 120 NM OF THE COAST FROM 07N82W TO 
16N96W...THEN N OF THE PREVIOUSLY CONVECTION DIRECTLY ASSOCIATED 
WITH THE SURFACE LOW WITHIN ABOUT 120 NM OF 19N106W. SIMILAR 
CONVECTION IS NOTED WITHIN 120 NM EITHER SIDE OF A LINE FROM 
13N119W TO 06N131W...AND ALSO WITHIN 60 NM OF 05N92W.

...DISCUSSION...
AN UPPER TROUGH IS SWINGING SE INTO THE N PORTION OF THE 
DISCUSSION AREA FROM 32N132W TO 29N136W. AN UPPER LEVEL 
ANTICYCLONE CENTERED OVER THE TEXAS PANHANDLE RIDGES SW ACROSS 
THE NORTHERN BAJA CALIFORNIA PENINSULA THROUGH 16N140W...TO A 
SHARP CREST AT 14N150W. THE UPPER LEVELS APPEAR VERY DRY NW OF A 
LINE FROM 22N105W TO 12N140W. 

AN UPPER TROUGH ALONG THE SE CONUS CONTINUES SW ACROSS THE GULF 
OF MEXICO THROUGH UPPER CYCLONES AT 29N86W AND 27N95W...THROUGH 
AN UPPER CYCLONE OVER OLD MEXICO AT 24N102W...AND THROUGH UPPER 
CYCLONES OVER THE TROPICAL PACIFIC AT 20N115W...15N128W AND 
07N139W. IMMEDIATELY SE OF THIS TUTT IS UPPER RIDGING... 
ORIENTATED NE TO SW...THROUGH UPPER ANTICYCLONES AT 25N79W... 
22N85W...AND 19N93W CONTINUING SW OVER THE DEEP TROPICAL PACIFIC 
TO YET ANOTHER UPPER ANTICYCLONE AT 11N124W. FURTHER SE AN UPPER 
TROUGH EXTENDS FROM AN UPPER CYCLONE OVER COLOMBIA AT 06N73W TO 
ANOTHER UPPER CYCLONE OVER THE TROPICAL PACIFIC AT 01N86W. DRY 
UPPER AIR IS NOTED SE OF A LINE FROM PANAMA TO THE GALAPAGOS 
ISLANDS. THE UPPER RIDGING BETWEEN 80W AND 130W IS ROUGHLY IN 
PHASE WITH THE LOW LEVEL MONSOON TROUGH ALLOWING THE DENSE 
DEBRIS MOISTURE FROM ENHANCED CONVECTION TO FAN OUT OVER THE 
AREA FROM 05N TO 20N BETWEEN 80W AND 110W...AND WITHIN 180 NM 
EITHER SIDE OF A LINE FROM 13N110W TO 13N123W TO 07N133W.

AT THE SURFACE...A RIDGE DOMINATES THE NW CORNER OF THE FORECAST 
AREA WITH N TO NE WINDS AT 15 TO 20 KT SPREADING SE OVER THE 
PACIFIC WATERS W OF A LINE FROM 32N118W TO 10N140W. THE 
ASSOCIATED NORTHERLY SWELL IS MIXING WITH CROSS EQUATORIAL 
SOUTHERLY SWELL RESULTING IN COMBINED SEAS TO 9 FT. THE 
NORTHERLY WINDS WILL DIMINISH BELOW 20 KT ON THU...BUT OPPOSING 
SWELL WILL CONTINUE OVER THE ENTIRE WATERS N OF 20N...AND FROM 
12N TO 20N TO THE W OF 130W THROUGH THU NIGHT.
 
THESE LONG PERIOD CROSS EQUATORIAL SOUTHERLY SWELLS WILL ALSO 
SPREAD NE TO THE CENTRAL AMERICAN COAST S OF 20N WITH SEAS TO 11 
FT IN THE AREAS OF ENHANCED SOUTHWESTERLY MONSOON FLOW...JUST TO 
THE S OF THE DEVELOPING SURFACE LOW. 

$$
NELSON