000
AXPZ20 KNHC 232150
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC SUN SEP 23 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...
TROPICAL STORM MIRIAM AT 16.1N 110.5W AT 2100 UTC MOVING NW OR 
305 DEGREES AT 9 KT.  MINIMUM CENTRAL PRES 994 MB WITH MAXIMUM 
SUSTAINED WIND SPEED 60 GUSTS TO 75 KT.  OVERALL ENVIRONMENT 
REMAINS FAVORABLE FOR CONTINUING DEVELOPMENT AND MIRIAM IS 
EXPECTED TO GAIN MORE STRENGTH TONIGHT AND BECOME A HURRICANE 
TONIGHT.  MIRIAM SHOULD CONTINUE MOVING NW THROUGH MON INTO 
COOLER WATERS AND LESS FAVORABLE ENVIRONMENT BY MON NIGHT.  
NUMEROUS STRONG CONVECTION IN CLUSTERS WITHIN 180 NM OF CENTER.  
SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS 
MIATCMEP3/WTPZ23 KNHC FOR MORE DETAILS.

...TROPICAL WAVES...
TROPICAL WAVE EXTENDS N FROM 14N96W MOVING W AT 10 KT. 
NO SIGNIFICANT CONVECTION ASSOCIATED WITH WAVE.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...
MONSOON TROUGH FROM 08N84W TO 12N102W.  ITCZ EXTEND FROM 12N125W 
TO BEYOND 06N140W. SCATTERED MODERATE CONVECTION WITHIN 90 NM S 
OF FROM 94W TO 96W AND WITHIN 90 NM N OF AXIS W OF 135W.

...DISCUSSION...
WELL DEFINED DEEP LAYER CYCLONE AT 29N142W SUPPORTS COLD FRONT 
APPROACHING NW CORNER OF BASIN.  WEAKENING 50 KT JET STREAM 
ADVECTS A SWATH OF LIMITED AMOUNT OF MOISTURE DOWNSTREAM AND 
PARALLEL TO THE FRONT.  CYCLONE EXPECTED TO SHIFT N-NE STALLING 
FRONT AND LEAVING DRY AIR MASS IN ITS WAKE N OF 20N W OF 120W.  
BROAD UPPER LEVEL ANTICYCLONE PROVIDES MIRIAM WITH GOOD 
DIVERGENT OUTFLOW AND LIGHT VERTICAL SHEAR TO ENHANCE ITS 
DEVELOPMENT.  ANTICYCLONE REMAINS STATIONARY WHILE MIRIAM MOVES 
NW AWAY INTO A MORE ADVERSE ENVIRONMENT BY MON NIGHT.

...ELSEWHERE AT THE LOWER LEVELS... 
HIGH PRES CENTER 1027 MB AT 36N136W HAS RIDGE EXTEND TO 25N123W. 
APPROACHING COLD FRONT STALLS OVER NW CORNER OF BASIN BUT ITS 
LARGE NW SWELLS SPREAD INTO E PAC EVENTUALLY MERGING WITH SE 
SWELLS MOVING ACROSS EQUATOR.  SEAS EXPECTED TO BUILD TO 12 FT 
IN CONFUSED SEAS WITH HIGHEST SEAS NEAR NW PART.

STRONG GAP WINDS ACROSS GULF OF TEHUANTEPEC EXPECTED TO DIMINISH 
IN STRENGTH AND COVERAGE BY TUE.

$$
WALLY BARNES