000
AXPZ20 KNHC 240317
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC MON SEP 24 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0300 UTC.

...SPECIAL FEATURES...
HURRICANE MIRIAM AT 16.8N 111.3W AT 0300 UTC MOVING NW OR 310 
DEGREES AT 10 KT. MINIMUM CENTRAL PRES 983 MB WITH MAXIMUM 
SUSTAINED WIND SPEED 80 GUSTS TO 95 KT. FAVORABLE CONDITIONS 
ENHANCED SYSTEM INTO BECOMING A HURRICANE EARLIER AND LIKELY TO 
FURTHER ITS INTENSIFICATION TONIGHT AND MON. MIRIAM SHOULD 
CONTINUE MOVING NW THROUGH TUE THEN START TURNING INTO A MORE 
NORTHERLY HEADING INTO COOLER WATERS AND LESS FAVORABLE UPPER 
LEVEL ENVIRONMENT LATE TUE AND WEAKEN WED AND THU. NUMEROUS 
STRONG CONVECTION IN CLUSTERS WITHIN 210 NM OF CENTER. 
SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS 
MIATCMEP3/WTPZ23 KNHC FOR MORE DETAILS.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...
MONSOON TROUGH FROM 11N86W TO 09N99W TO 12N103W THEN RESUMES 
FROM 13N112W TO 11N128W THEN ITCZ TO BEYOND 09N140W. SCATTERED 
MODERATE CONVECTION WITHIN 210 NM N OF AXIS FROM 94W TO 100W AND 
WITHIN 150 NM S OF AXIS W OF 129W.

...DISCUSSION...
WELL DEFINED DEEP LAYER CYCLONE AT 30N142W SUPPORTS COLD FRONT 
APPROACHING NW CORNER OF BASIN. WEAKENING 45 KT JET STREAM 
ADVECTS A SWATH OF LIMITED AMOUNT OF MOISTURE DOWNSTREAM AND 
PARALLEL TO THE FRONT. CYCLONE EXPECTED TO SHIFT N STALLING 
FRONT AND LEAVING DRY AIR MASS IN ITS WAKE N OF 23N W OF 120W. 
BROAD UPPER LEVEL ANTICYCLONE PROVIDES MIRIAM WITH GOOD 
DIVERGENT OUTFLOW AND LIGHT VERTICAL SHEAR TO ENHANCE ITS 
INTENSIFICATION. ANTICYCLONE REMAINS STATIONARY WHILE MIRIAM 
MOVES NW AWAY INTO A MORE ADVERSE ENVIRONMENT BY WED.

...ELSEWHERE AT THE LOWER LEVELS... 
HIGH PRES CENTER 1028 MB AT 41N150W HAS RIDGE EXTEND TO 24N117W. 
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 LATE TUE.

$$
WALLY BARNES