000
AXPZ20 KNHC 211539
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC FRI SEP 21 2012

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 0900 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1500 UTC.

...SPECIAL FEATURES...
SURFACE LOW PRES 1006 MB EMBEDDED IN MONSOON TROUGH AT 14N105W. 
IT IS EXPECTED TO DRIFT W-NW AND INTENSIFY REACHING 15N108W SAT 
AND 16N111W SUN. SCATTERED MODERATE TO STRONG CONVECTION IS FROM 
10-15N BETWEEN 105W-110W. THE CONVECTION IS GETTING A LITTLE 
BETTER ORGANIZED. TROPICAL CYCLONE FORMATION EXPECTED WITHIN 
NEXT 24-48 HOURS.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...
MONSOON TROUGH FROM 9N85W TO 8N90W TO 1006 MB LOW PRES 14N105W 
TO 1009 MB LOW PRES NEAR 15N115W TO 11N125W. ITCZ 11N125W 9N135W 
TO 7N140W. SCATTERED MODERATE TO STRONG CONVECTION FROM 7N-15N 
BETWEEN 95W-102W AND WITHIN 100 NM S OF AXIS FROM 129W-135W.
 
...DISCUSSION...
BROAD ANTICYCLONIC CIRCULATION IS CENTERED NEAR 14N139W WITH 
RIDGE FROM THE CIRCULATION CENTER NE TO 32N117W. A 55-70 KT JET 
STREAM BETWEEN THE RIDGE AND AN UPPER LEVEL TROUGH NW OF THE 
DISCUSSION AREA FROM 26N140W TO 30N131W IS ADVECTING HIGH LEVEL 
MOISTURE ALONG THE WESTERN PERIPHERY OF THE RIDGE. OTHERWISE DRY 
STABLE AIR MASS ACROSS THE AREA N OF 12N W OF 115W. SECOND UPPER 
LEVEL ANTICYCLONIC CIRCULATING NEAR 15N105W PROVIDES LOW SHEAR 
ENVIRONMENT AND GOOD OUTFLOW OVER SURFACE LOW PRES CENTER 
DISCUSSED ABOVE. THE LOW HAS A HIGH CHANCE OF DEVELOPING 
INTO A TROPICAL CYCLONE.

WEAKENING LOW PRES 1009 MB AT 16N114W WITH TROUGH FROM THE LOW N 
TO 21N114W. NO SIGNIFICANT WEATHER ASSOCIATED THE THE LOW AND 
TROUGH. OTHERWISE SURFACE RIDGE COVERS THE AREA N OF 17N W OF 
120W. ELY TRADES TO 20 KT ALONG THE SOUTHERN PERIPHERY OF THE 
RIDGE FROM 10N-20N W OF 134W.

STRONG NLY WINDS...IN THE 20-25 KT RANGE...BLOWING THROUGH THE 
GULF OF TEHUANTEPEC WILL CONTINUE THROUGH THE NEXT 48 HOURS.

$$
DGS