000
AXPZ20 KNHC 060240
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC TUE SEP 06 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 
0215 UTC.

...ITCZ/MONSOON TROUGH...
MONSOON TROUGH FROM 11N86W TO 15N103W TO A 1009 MB LOW PRES NEAR 
11N124W TO 11N140W. SCATTERED MODERATE CONVECTION IS NOTED FROM 
07N TO 10N BETWEEN 99W AND 111W. SIMILAR CONVECTION IS N OF THE 
MONSOON TROUGH TO THE COAST OF MEXICO FROM 91W TO 102W. A 
CLUSTER OF MODERATE TO ISOLATED STRONG CONVECTION IS WITHIN 45 
NM OF 17.5N107W. 

...DISCUSSION...

THE BROAD MIDDLE TO UPPER LEVEL TROUGH THAT WAS AFFECTING THE NW 
CORNER OF THE AREA IS WEAKENING AND LIFTING OUT TO THE NE. ITS 
AXIS CURRENTLY EXTENDS FROM 30N128W TO 21N132W. AN ANTICYCLONIC 
CIRCULATION CENTERED OVER THE STATE OF CHIHUAHUA MEXICO HAS A 
RIDGE EXTENDING SW TO NEAR 20N131W. THIS SYSTEM IS COVERING 
NORTHERN MEXICO MAINLY N OF 24N WHERE IS PRODUCING MODERATE TO 
STRONG UPPER LEVEL SUBSIDENCE. SOUTH OF THIS RIDGE...NE TO E 
FLOW ALOFT PERSISTS. UPPER DIFFLUENCE S OF THE RIDGE AXIS IS 
HELPING TO SUPPORT SCATTERED MODERATE CONVECTION N OF 07N 
BETWEEN 90W AND 110W.   

AT THE SURFACE...WEAK RIDGE DOMINATES THE NW PART OF THE AREA 
PRODUCING MAINLY LIGHT WINDS. AS A RESULT...TRADE WINDS REMAIN 
BELOW 20 KT E OF 140W...WITH SEA HEIGHTS OF 6 TO 7 FT. THE 
SURFACE RIDGE IS FORECAST TO BUILD BACK IN ACROSS THE NW PART OF 
THE AREA LATE TODAY. 

FURTHER SOUTH...LIMITED AREA OF FRESH 20 KT SW MONSOONAL FLOW IS 
FOUND FROM 05N TO 10N BETWEEN 95W AND 105W. THESE LOCALLY 
STRONGER MONSOONAL WINDS ARE INDUCING SPEED CONVERGENCE...AND 
CORRESPONDS WITH THE AREAS WHERE THERE IS ACTIVE CONVECTION. THE 
AREAL EXTENT AND STRENGTH OF THE MONSOONAL FLOW WILL LIKELY 
INCREASE BEGINNING LATE TODAY. COMPUTER MODEL DEPICTS A LARGE 
CYCLONIC GYRE ALONG THE MONSOON TROUGH N OF 12N BETWEEN 100W AND 
110W. THE COMBINATION OF THIS CYCLONIC GYRE AND THE PRESENCE OF 
A HIGH PRES OVER THE WESTERN GULF OF MEXICO WILL BRING SOME 
INCREASE IN WINDS AND SEAS ACROSS THE GULF OF TEHUANTEPEC AND TO 
THE WEST TO AROUND 100W BEGINNING TONIGHT.  

LONG PERIOD CROSS EQUATORIAL SWELL PREVAILS S OF 15N E OF 125W 
WITH COMBINED SEAS OF 8 TO 11 FT.

$$
GR