000
AXPZ20 KNHC 092124
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
2205 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
2115 UTC.

...ITCZ/MONSOON TROUGH...
THE SOUTHERN SEGMENT OF THE MONSOON TROUGH EXTENDS W ACROSS 
COSTA RICA FROM 10N80W TO 10N86W...THEN TURNS SW OVER THE 
PACIFIC TO 07N100W. A SECOND...NORTHERN SEGMENT OF THE 
MONSOON TROUGH IS ANALYZED FROM THE PACIFIC COAST OF MEXICO AT 
18N100W TO A 1008 MB SURFACE LOW AT 16N118W...CONTINUING SW TO A 
1010 MB SURFACE LOW AT 13N131W. THE TROUGH EXTENDS FURTHER SW TO 
10N140W WHERE LOW LEVEL WINDS INDICATE THAT THE ITCZ BEGINS.

SCATTERED MODERATE ISOLATED STRONG CONVECTION IS MOVING OFF THE 
COAST OF COLOMBIA N OF 06N AND ALSO NOTED WITHIN 30 NM EITHER 
SIDE OF A LINE FROM 05N82W TO 05N86W...AND WITHIN 60 NM EITHER 
SIDE OF A LINE FROM 06N92W TO 06N100W TO 10N104W. SIMILAR 
CONVECTION...ASSOCIATED WITH AN UPPER CYCLONE...IS DISSIPATING 
ALONG THE PACIFIC COAST OF MEXICO WITHIN 30 NM OF 22N106W...AND 
IN ASSOCIATION WITH THE PREVIOUSLY DESCRIBED SURFACE LOWS 
EMBEDDED ALONG THE MONSOON TROUGH AXIS AT 19N110W...18N112W AND 
WITHIN 90 NM OF 16N119W AND 12N131W. SCATTERED MODERATE 
CONVECTION IS OBSERVED WITHIN 60 NM OF 12N99W AND WITHIN 30 NM 
OF 11N105W.

...DISCUSSION...

AN UPPER ANTICYCLONE IS CENTERED AT 31N136W WITH A RIDGE SE TO A 
CREST AT OVER THE SE GULF OF MEXICO TO 20N101W WHICH IS JUST W 
OF TROPICAL STORM NATE. ANTICYCLONIC FLOW...AND DRY UPPER AIR... 
DOMINATES THE DISCUSSION AREA TO THE N OF 15N EXCEPT FOR THE 
SMALL CONVECTIVE CLUSTER DISSIPATING ALONG THE PACIFIC COAST OF 
MEXICO AT 22N106W. THE ASSOCIATED SURFACE RIDGE EXTENDS FROM 
32N132W TO 23N115W. AN UPPER TROUGH HAS PENETRATED THE NE 
PORTION OF THE UPPER RIDGE FROM 32N124W TO 28N129W. SOME UPPER 
MOISTURE IS SWINGING E THROUGH THIS UPPER SHORTWAVE TROUGH 
ACROSS SE CALIFORNIA...ALL OF ARIZONA AND OVER THE NW TEXAS.
A SECOND UPPER SHORTWAVE TROUGH IS PROGRESSING THROUGH THE 
LONGWAVE TROUGH THAT IS ANCHORED OVER THE CENTRAL CONUS...WITH 
DEBRIS MOISTURE FORM FORMER CONVECTION SPREADING E ALONG 28N 
BETWEEN 108W AND 98W.

AN UPPER TROUGH DISSECTS THE GULF OF MEXICO FROM NE TO SW 
CONTINUING SW ACROSS OLD MEXICO THROUGH AN UPPER CYCLONES AT  
22N107W AND 17N120W AND 12N132W TO YET ANOTHER CYCLONE W OF THE 
AREA AT 07N155W. THE UPPER RIDGE SEEMS TO BRIDGE THROUGH THIS 
NARROW UPPER TROPOSPHERIC TROUGH RESULTING IN NORTHEASTERLY 
UPPER FLOW OVER THE TROPICS BETWEEN 100W AND 140W. THE UPPER 
LEVELS APPEAR MOIST FROM 18N TO THE EQUATOR BETWEEN 100W AND 
130W.

ANOTHER UPPER TROUGH EXTENDS SW ACROSS THE SE PORTION THE AREA 
TROUGH ILL DEFINED UPPER CYCLONES AT 13N76W...05N85W AND 02N94W. 
THE UPPER FLOW IS ALSO 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 KT TO FUNNEL 
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