000
AXPZ20 KNHC 271553
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC THU SEP 27 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1500 UTC.

...SPECIAL FEATURES...
TROPICAL STORM MIRIAM CENTERED NEAR 22.2N 116.3W AT 27/1500 UTC 
MOVING NW AT 5 KT. MAXIMUM SUSTAINED WINDS 35 KT GUSTS 45 KT AND 
ESTIMATED MINIMUM CENTRAL PRESSURE 1000 MB. MIRIAM CONTINUES TO 
WEAKEN DUE TO THE COMBINATION OF VERTICAL WIND SHEAR...DRY MID 
LEVEL AIR AND COOL SEA SURFACE TEMPERATURES. IT IS EXPECTED TO 
BECOME A DEPRESSION WITHIN THE NEXT 12 HOURS AND A REMNANT LOW 
BY FRI MORNING. SWELLS GENERATED BY MIRIAM AFFECTING COASTS OF 
THE SOUTH-CENTRAL BAJA PENINSULA WILL SUBSIDE THROUGH FRIDAY. 
SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS 
MIATCMEP3/WTPZ23 KNHC FOR MORE DETAILS.

A DEVELOPING AREA OF LOW PRESSURE EMBEDDED WITHIN THE MONSOON 
TROUGH IS CENTERED NEAR 16N107W WITH AN ESTIMATED PRESSURE OF 
1007 MB. SATELLITE IMAGERY SHOWS A BROAD LINEAR AREA OF ACTIVE 
CONVECTION EXTENDING W-SW FROM THE CIRCULATION CENTER INDICATED 
BY WEAK CYCLONIC TURNING IN THE DEEP CONVECTION. ENVIRONMENTAL 
CONDITIONS ARE CONDUCIVE FOR SOME DEVELOPMENT AS THE LOW MOVES 
NORTH-NORTHWESTWARD THE NEXT COUPLE OF DAYS...AND MAY BECOME A 
TROPICAL CYCLONE DURING THE NEXT 48 HOURS. NUMEROUS MODERATE 
ISOLATED STRONG CONVECTION WITHIN 240 NM N AND SW OF THE CENTER. 
DEEP MOISTURE ASSOCIATED WITH THIS DISTURBANCE WILL SPREAD INTO 
S PORTIONS OF BAJA CALIFORNIA...SOUTHERN GULF OF CALIFORNIA AND 
COASTAL MEXICO...WITH LOCALLY HEAVY RAIN POSSIBLE.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...
MONSOON TROUGH EXTENDS FROM 10N85W TO 12N101W...THEN RESUMES FROM
14N113W TO 10N127W TO 10N140W. SCATTERED MODERATE CONVECTION 
WITHIN 150 NM S OF TROUGH BETWEEN 88W AND 99W. SCATTERED 
MODERATE ISOLATED STRONG CONVECTION FROM 10N TO 14N BETWEEN 107W 
AND 119W. SCATTERED MODERATE CONVECTION FROM 09N TO 11N BETWEEN 
127W AND 131W. 

...DISCUSSION...
SUBTROPICAL HIGH CENTERED NEAR 34N141W 1023 MB EXTENDS A RIDGE 
SE AND ACROSS THE NW WATERS TO NEAR 24N122W. MODERATE TRADE 
WINDS ARE NOTED ON THE SOUTHERN PERIPHERY OF THE RIDGE BY RECENT 
SCATTEROMETER PASSES...WITH 7-8 FT SEAS IN MIXED NW SWELL AND NE 
WIND WAVES. LIGHT TO MODERATE W-SW WINDS ELSEWHERE E OF 110W ARE 
MAINTAINING A MOIST CONVECTIVELY UNSTABLE REGIME S OF THE TROUGH 
THAT IS EXPECTED TO REMAIN CONVECTIVELY ACTIVE THE NEXT FEW DAYS 
AS AN UPPER RIDGE REMAINS IN PLACE OVER THE MONSOON TROUGH AXIS.

TWO AREAS OF SWELL MOVING THROUGH THE REGION IN ADDITION TO SEAS 
GENERATED BY T.S. MIRIAM WILL CONTINUE TO AFFECT THE DISCUSSION 
AREA THROUGH TONIGHT. MODERATE LONG PERIOD SWELLS ARE SPREADING 
ACROSS THE WATERS NW OF MIRIAM. WHILE CROSS-EQUATORIAL SW SWELLS 
MOVING THROUGH SE PORTIONS ARE REACHING THE COAST OF MEXICO AND 
CENTRAL AMERICA...WITH ANOTHER STRONG PULSE TO FOLLOW TONIGHT... 
MERGING WITH 8-10 FT SEAS W OF 105W. SWELLS GENERATED BY MIRIAM 
AFFECTING COASTS OF THE SOUTH-CENTRAL BAJA PENINSULA WILL CREATE 
SMALL BUT STRONG SURF ALONG EXPOSED COASTLINES S OF 27N TODAY. 
ADDITIONAL PULSES OF NW SWELL WILL REACH THE NW CORNER OF THE 
DISCUSSION AREA FRI NIGHT AND SAT...BUILDING SEAS TO 9 FT.   

$$
MUNDELL