000
AXPZ20 KNHC 202149
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC THU SEP 19 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
2100 UTC.

...SPECIAL FEATURES...
SURFACE LOW PRES DEVELOPED EMBEDDED IN MONSOON TROUGH AT 13N103W 
1008 MB.  IT IS EXPECTED TO DRIFT W-NW AND INTENSIFY REACHING 
14N105W LATE TONIGHT AND 15N108W FRI NIGHT.  TROPICAL CYCLONE 
FORMATION EXPECTED WITHIN NEXT 36-48 HRS.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...
MONSOON TROUGH EXTEND FROM 09N84W TO 1008 MB LOW PRES 13N103W TO 
10N114W TO 11N122W TO 09N128W.  ITCZ AXIS EXTEND FROM 08N134W TO 
BEYOND 06N140W. SCATTERED MODERATE ISOLATED STRONG CONVECTION 
WITHIN 150 NM N SEMICIRCLE OF LOW PRES CENTER AT 13N103W. 
SCATTERED MODERATE CONVECTION S OF AXIS TO 07N FROM 103W TO 
110W.  ISOLATED MODERATE CONVECTION WITHIN 150 NM OF 08N132W. 
 
...DISCUSSION...
BROAD DOUBLE BARREL ANTICYCLONES...ONE AT 16N133W AND ANOTHER AT 
22N128W...COVER LARGE PORTION OF E PAC MAINTAINING DRY STABLE 
AIR MASS N OF ITCZ/MONSOON TROUGH AND W OF 115W.  TROPICAL 
MOISTURE ADVECTS NE ON WRN PERIPHERY OF RIDGE N OF 20N W OF 
135W.  SINGLE ANTICYCLONE AT 15N98W PROVIDES LOW SHEAR 
ENVIRONMENT AND GOOD OUTFLOW OVER SURFACE LOW PRES CENTER AT 
13N103W.  WITH PLENTY OF HEAT ENERGY AVAILABLE AS SEA SURFACE 
TEMPERATURES REMAIN ABOVE 28 DEG CELSIUS...LOW PRES IS EXPECTED 
TO INTENSIFY INTO TROPICAL CYCLONE IN 36-48 HRS. 

...ELSEWHERE IN THE LOWER LEVELS...
WEAKENING TROUGH...REMNANTS OF LANE...FROM 24N134W TO 19N136W 
DRIFT W WITH FRESH NE WINDS W OF AXIS.  TROUGH EXPECTED OUT OF 
BASIN IN 24-30 HRS.  SECOND SURFACE TROUGH FROM 11N130W TO 
07N132W EMBEDDED BETWEEN MONSOON TROUGH AND ITCZ DRIFTS W INTO  
A DRIER REGION WITH LITTLE OR NO CHANCE OF INTENSIFICATION. 

FRESH N WINDS FORCED ACROSS CHIVELAS PASS IN MEXICO EMERGE AS 
STRONG N TO NE WINDS IN GULF OF TEHUANTEPEC.  WINDS EXPECTED TO 
INCLUDE GUSTS TO NEAR GALE FORCE THROUGH FORECAST PERIOD.
 
$$
WALLY BARNES