000
AXPZ20 KNHC 091552
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC FRI SEP 09 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 
1545 UTC.

...ITCZ/MONSOON TROUGH...
THE MONSOON TROUGH EXTENDS W ACROSS COSTA RICA FROM 10N80W TO 
10N86W...THEN TURNS SW OVER THE PACIFIC TO 07N99W. A SECOND 
SEGMENT OF THE MONSOON TROUGH IS ANALYZED FROM THE PACIFIC COAST 
OF MEXICO AT 18N100W TO A SURFACE LOW AT 16N118W...CONTINUING SW 
TO ANOTHER SURFACE LOW AT 13N130W...THE TROUGH EXTENDS FURTHER 
SW TO 11N138W WHERE LOW LEVEL WINDS INDICATE THAT THE ITCZ 
BEGINS AND CONTINUES SW TO BEYOND 10N140W. SCATTERED MODERATE 
ISOLATED STRONG IS NOTED WITHIN 30 NM EITHER SIDE OF A LINE FROM 
05N80W TO 06N85W...AND WITHIN THE AREA BOUNDED BY 04N TO 10N 
BETWEEN 91W AND 104W. 

SIMILAR CONVECTION IS NOTED NEAR AN UPPER CYCLONE WITHIN 30 NM OF 
22N106.5W...AND IN ASSOCIATION WITH THE PREVIOUSLY DESCRIBED 
SURFACE LOWS EMBEDDED ALONG THE MONSOON TROUGH AXIS AT 19N109W 
AND 17N119W.

...DISCUSSION...

AN UPPER ANTICYCLONE IS CENTERED AT 30N137W WITH A RIDGE SE TO A 
CREST AT OVER THE SE GULF OF MEXICO JUST TO THE W OF TROPICAL 
STORM NATE. ANTICYCLONIC FLOW...AND DRY UPPER AIR...DOMINATES 
THE DISCUSSION AREA TO THE N OF 17N EXCEPT FOR A SMALL 
CONVECTIVE CLUSTER DISSIPATING ALONG THE PACIFIC COAST OF MEXICO 
AT 22N106W WHICH IS ASSOCIATED WITH A SMALL UPPER CYCLONE. THE 
ASSOCIATED SURFACE RIDGE EXTENDS ALONG 32N132W TO 23N115W. AN 
UPPER TROUGH HAS PENETRATED THE NE PORTION OF THE UPPER RIDGE 
FROM 32N126W TO 29N129W. SOME UPPER MOISTURE IS SWINGING E 
THROUGH THIS UPPER SHORTWAVE TROUGH...ACROSS SE CALIFORNIA... 
SOUTHERN ARIZONA AND OVER THE TEXAS PANHANDLE. A SECOND UPPER 
SHORTWAVE TROUGH IS PROGRESSING THROUGH THE LONGWAVE TROUGH... 
ANCHORED OVER THE CENTRAL CONUS...WITH CONVECTION PREVIOUSLY 
ENHANCED OVER NW OLD MEXICO. THE DEBRIS MOISTURE IS NOW 
SPREADING E ALONG 28N BETWEEN 108W AND 98W.

AN UPPER TROUGH DISSECTS THE GULF OF MEXICO FROM NE TO SW 
THROUGH AN UPPER CYCLONE NEAR TS NATE. THE UPPER TROUGH 
CONTINUES SW ACROSS OLD MEXICO THROUGH AN UPPER CYCLONE AT  
21N107W...TO ANOTHER CYCLONE AT 17N119W...TO ANOTHER AT 13N132W 
TO FINALLY ANOTHER CYCLONE JUST W OF THE AREA AT 11N144W. THE 
UPPER RIDGE SEEMS TO BRIDGE THROUGH THIS NARROW UPPER TROUGH 
RESULTING IN NORTHEASTERLY UPPER FLOW OVER THE TROPICS BETWEEN 
100W AND 140W WITH THE UPPER LEVELS APPEARING MOIST FROM 17N TO 
THE EQUATOR BETWEEN 100W AND 125W.

ANOTHER UPPER TROUGH EXTENDS SW ACROSS THE SE PORTION THE AREA 
TROUGH ILL DEFINED UPPER CYCLONES AT 13N76W...06N85W AND 
02N101W. THE UPPER FLOW IS GENERALLY NE OVER THE DEEP TROPICS E 
OF 100W WITH UPPER DEBRIS MOISTURE ADVECTED SW ACROSS THE 
EQUATOR.

GAP WINDS...TROPICAL STORM NATE CONTINUES TO DRIFT W ACROSS THE 
BAY OF CAMPECHE RESULTING IN NORTHERLY WINDS AT 20 TO 25 KT 
FUNNELING THROUGH THE CHIVELA PASS AND INTO THE GULF OF 
TEHUANTEPEC REGION THROUGH TONIGHT. 

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 SAT.

$$
NELSON