000
AXPZ20 KNHC 130316
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC TUE SEP 13 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 
0200 UTC.

...ITCZ/MONSOON TROUGH...
MONSOON TROUGH CONTINUES TO REALIGN DUE TO INTERACTION WITH 
TROPICAL WAVE ACROSS CENTRAL AMERICA AND EXTENDS FROM NEAR 
14.5N93W TO 10N102W TO 1010 MB LOW PRES AT 11N108W TO 1011 MB 
LOW PRES AT 17N118.5W WHERE IT TERMINATES. ITCZ BEGINS NEAR 
11N120W TO 1011 MB LOW PRES AT 10.5N139W. SCATTERED MODERATE TO 
STRONG CONVECTION IS NOTED N OF 05N E OF 79W. SCATTERED MODERATE 
CONVECTION IS NOTED N OF 06N BETWEEN 88W AND 98W. 

...DISCUSSION...
ALOFT...A RIDGE/TROUGH/RIDGE PATTERN CONTINUES ACROSS THE 
DISCUSSION AREA TONIGHT WITH UPPER LEVEL ANTICYCLONE CENTERED 
OVER N CENTRAL MEXICO NEAR 25N100W ANCHORING A LARGE UPPER RIDGE 
EXTENDING WSW TO 130W. THIS RIDGE IS FORECAST TO REMAIN IN PLACE 
FOR THE NEXT 24 HOURS BEFORE BEGINNING TO ERODE W OF 120W.  
UPPER LEVEL FLOW S OF THE RIDGE CONTINUES TO YIELD E TO NE WINDS 
E OF 112W BECOMING E TO SE WINDS W OF 112W. 

AT THE SURFACE...A WEAK HIGH PRES RIDGE CONTINUES ACROSS THE NW 
WATERS...CENTERED ON A 1023 MB HIGH NEAR 36N135W...AND IS  
PRODUCING MAINLY LIGHT TO MODERATE NE TRADEWINDS W OF 120W. 
A 1013 MB LOW IS CENTERED OVER SW ARIZONA WITH A SURFACE TROUGH 
EXTENDING S FROM THE LOW AND INTO THE GULF OF CALIFORNIA AT 
27N111W. THE PRES GRADIENT  BETWEEN THIS SEMIPERMANENT TROUGH 
AND THE HIGH IS PRODUCING WINDS NEAR 20 KT OFF THE W COAST OF 
BAJA CALIFORNIA N OF 27N. THIS PATTERN WILL PERSIST THROUGH 24 
HOURS BEFORE SPREADING S OF 25N BY 48 HOURS. REMNANT MOISTURE 
FROM NATE HAD MOVED W ACROSS CENTRAL MEXICO AND EXITED INTO THE 
PACIFIC WATERS NEAR THE MARIAS ISLANDS...WHERE SCATTERED SHOWERS 
AND THUNDERSTORMS WERE OBSERVED THIS AFTERNOON...BUT HAVE SINCE 
DIMINISHED CONSIDERABLY.

BROAD CYCLONIC FLOW IS NOTED IN SATELLITE IMAGERY AROUND A 
TROPICAL WAVE ALONG 90W MOVING SLOWLY ACROSS CENTRAL AMERICA AND 
THE ADJACENT PACIFIC WATERS. ABUNDANT MOISTURE AND FAVORABLE  
UPPER LEVEL CONDITIONS WILL ALLOW FOR THIS WAVE TO CONTINUE TO 
PRODUCE WIDESPREAD SHOWERS AND SCATTERED THUNDERSTORMS AS IT 
CONTINUES TO MOVE SLOWLY W THE NEXT FEW DAYS. JUST AHEAD OF THIS 
WAVE...NELY FLOW OVER THE SOUTHERN GULF OF MEXICO IS FUNNELING 
THROUGH THE CHIVELA PASS INTO THE GULF OF TEHUANTEPEC... 
RESULTING IN FRESH 20 KT WINDS. GUIDANCE SUGGESTS WINDS WILL 
INCREASE ACROSS THE GULF OF TEHUANTEPEC TO 25 KT TONIGHT THROUGH 
WED BEFORE GRADUALLY DIMINISHING WED NIGHT AND THU MORNING.

THE THREE LOW PRESSURE CENTERS MENTIONED ABOVE EMBEDDED WITHIN 
THE MONSOON TROUGH AND ITCZ WILL CONTINUE TO SLOWLY WEAKEN 
WITHIN THE NEXT 48 HOURS...WHILE THE EASTERN MOST LOW NEAR 
11N108W WILL BECOME STATIONARY. 

LIGHT TO MODERATE S TO SW WINDS PRESENTLY PREVAIL ACROSS THE 
DEEP TROPICS S OF THE MONSOON TROUGH AND ARE NOT EXPECTED TO 
INCREASE MUCH IN THE NEXT FEW DAYS.

$$
STRIPLING