000
AXPZ20 KNHC 091506
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC MON SEP 09 2013

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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1500 UTC.

...TROPICAL WAVES... 

THE SOUTHERN EXTENT OF WEAK TROPICAL WAVE IS FORECAST TO MOVE 
OFF THE COAST OF GUATEMALA AND SOUTHERN MEXICO LATE TONIGHT. 
THIS POORLY DEFINED WAVE IS MOVING THROUGH AN ALREADY ABUNDANT 
AREA OF MOISTURE AND IS HELPING TO FIRE OFF NEW CONVECTION OVER 
GUATEMALA...THE YUCATAN AND FAR SE MEXICO...INCLUDING THE GULF 
OF TEHUANTEPEC AND ADJACENT WATERS.
 
...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...

THE MONSOON TROUGH AXIS EXTENDS FROM 07N78W TO 15N93W TO LOW 
PRES NEAR 15N109W 1009 MB TO ANOTHER LOW PRES CENTER NEAR 
12N133W 1011 MB TO 11N140W. NO ITCZ IS PRESENT E OF 140W. 
SCATTERED MODERATE AND ISOLATED STRONG CONVECTION IS WITHIN 180 
NM S OF AXIS E OF 82W...AND WITHIN 120 NM N OF AXIS BETWEEN 102W 
AND 107W. 

...DISCUSSION... 

A 1009 MB LOW PRES AREA IS CENTERED ALONG THE MONSOON TROUGH 
NEAR 15N109W. THIS HAS FORMED OVER THE PAST 24 HOURS IN RESPONSE 
TO LOWER TO MID LEVEL TROUGHING TO THE NW. THE UPPER LEVEL FLOW 
ON THE EAST SIDE OF AN ANTICYCLONE ALOFT CENTERED NEAR 23N115W 
IS UNFAVORABLE TO FURTHER DEVELOPMENT OF THIS LOW PRES IN THE 
SHORT TERM. CONVECTION HAS BEEN PULSING AROUND THE PERIPHERY OF 
THE LOW...PARTICULARLY TO THE SOUTH OF THE LOW WHERE ASCAT DATA 
FROM THE PAST SEVERAL HOURS INDICATED FLOW INTO THE MONSOON 
TROUGH IS AROUND 15 TO 20 KT. THIS ENHANCED FLOW IS BOTH A 
RESULT OF AND A CONTRIBUTOR TO THE DEVELOPMENT OF THE LOW PRES. 
GLOBAL MODELS CONTINUE TO BE IN BROAD AGREEMENT SHOWING THE LOW 
PRES NOT DEEPENING APPRECIABLY BUT DRIFTING EASTWARD TOWARD THE 
COAST OF MEXICO. AN ALTIMETER PASS FROM LAST NIGHT SHOWED SEAS 
NEARING 7 FT IN THE AREA OF FRESH SW FLOW...BUT THIS LIKELY 
MISSED A MAXIMUM HEIGHT OF 8 FT INITIALIZED BY WW3 A LITTLE 
FARTHER EAST WHERE A GREATER FETCH SUPPORTS FULLY DEVELOPED SEAS.

LOOKING AHEAD...THE TROPICAL WAVE MOVING INTO SOUTHERN MEXICO 
WILL INTERACT WITH THE MONSOON TROUGH TO HELP ACCENTUATE 
CONVECTION IN THE AREA AND LOWER PRES...BUT UPPER FLOW WILL 
REMAIN UNFAVORABLE FOR FURTHER DEVELOPMENT.

FARTHER WEST...A MORE MODEST 1011 MB LOW PRES IS CENTERED ALONG 
THE MONSOON TROUGH NEAR 12N133W. SIMILAR TO ITS EASTERN 
COUNTERPART THIS LOW FORMED DUE MID LEVEL TROUGH INTERACTION 
WITH THE MONSOON TROUGH...BUT IS AN AREA OF MUCH DRIER AIR. 
CONVECTION IS VIRTUALLY NON EXISTENT...AND THE LOW IS EXPECTED 
TO DISSIPATE OVER THE NEXT 24 HOURS.

ELSEWHERE LIGHT TO MODERATE TRADE WINDS PERSIST. SEAS ARE 
GENERALLY 3 TO 5 FT. SOUTHERLY SWELL FROM THE SOUTHERN 
HEMISPHERE WILL CROSS THE EQUATOR TONIGHT...REACHING AS FAR N AS 
04N BETWEEN 100W AND 120W BY EARLY TUE. THE LONGER PERIOD SWELL 
THEN WILL MERGE WITH SHORTER PERIOD SEAS WHERE THE FRESH SW FLOW 
IS CONVERGING INTO THE MONSOON TROUGH...GENERALLY COVERING THE 
AREA S OF 12N BETWEEN 95W AND 115W BY LATE TUE.  

$$
CHRISTENSEN