000
AXPZ20 KNHC 231527
TWDEP 

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

...SPECIAL FEATURES...
TROPICAL STORM MIRIAM CENTERED NEAR 15.6N 109.6W AT 1500 UTC 
MOVING NW OR 305 DEGREES AT 7 KT. MINIMUM CENTRAL PRESSURE IS 
996 MB. MAXIMUM SUSTAINED WIND SPEED 55 KT GUSTS TO 65 KT. THE 
ATMOSPHERIC AND OCEANIC CONDITIONS ARE EXPECTED TO BE QUITE 
CONDUCIVE FOR MIRIAM TO GAIN MORE STRENGTH DURING THE NEXT 
COUPLE OF DAYS. THE FORECAST CALLS FOR MIRIAM TO BECOME A 
HURRICANE BY TONIGHT. THE STORM SHOULD CONTINUE MOVING 
NORTHWESTWARD FOR THE NEXT COUPLE OF DAYS. MIRIAM HAS 
BECOME BETTER ORGANIZED OVERNIGHT WITH SMALL CENTRAL DENSE 
OVERCAST AND BANDING FEATURES MORE DISTINCT. NUMEROUS STRONG 
CONVECTION IS WITHIN 150 NM OF CENTER. SEE LATEST NHC 
FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMEP3/WTPZ23 KNHC 
FOR MORE DETAILS.

...TROPICAL WAVES...
TROPICAL WAVE EXTENDS ALONG THE GULF OF TEHUANTEPEC INTO THE E 
PACIFIC TO NEAR 12N95W MOVING W AT 10-15 KT. NO SIGNIFICANT 
CONVECTION ASSOCIATED WITH THE WAVE.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...
MONSOON TROUGH FROM 11N86W TO 9N95W TO 12N100W. THE ITCZ FROM 
9N124W TO 9N140W. SCATTERED MODERATE ISOLATED STRONG CONVECTION 
WITHIN 90 NM S OF W OF 136W.

...DISCUSSION...
UPPER LEVEL CYCLONIC CIRCULATION IS CENTERED NEAR 16N129W. AN 
UPPER LEVEL RIDGE EXTENDS FROM 21N110W TO 32N135W. EXCEPT FOR 
SCATTERED TO BROKEN HIGH CLOUDS N OF 20N W OF 133W STRONG 
SUBSIDENCE WITH DRY STABLE AIR AT THE MIDDLE AND UPPER LEVELS IS 
N OF 20N W OF 115W. BROAD UPPER LEVEL ANTICYCLONIC CIRCULATION 
CENTERED NEAR 16N100W RIGHT NEXT TO TROPICAL STORM MIRIAM 
MAINTAINS LIGHT UPPER LEVEL WIND SHEAR AND GOOD DIVERGENT 
OUTFLOW FOR MIRIAM TO CONTINUE TO DEVELOP.

HIGH PRES RIDGE COVERS THE AREA N OF 20N W OF 125W. AN AREA  
15-20 KT  TRADE WINDS ON SOUTHEASTERN PERIPHERY OF RIDGE FROM 
10N TO 18N W OF 133W. TRADES EXPECTED TO DIMINISH WITHIN 24 
HOURS AS HIGH PRES WEAKENS AND COLD FRONT MOVES CLOSER THEN 
STALLS JUST NW PORTION OF THE DISCUSSION AREA. NW SWELL 
GENERATED BEHIND FRONT WILL BUILD SEAS TO 11 FT ACROSS WESTERN 
PORTIONS OF THE AREA. 

NLY WINDS 20-25 KT CONTINUE TO BLOW THROUGH THE GULF OF 
TEHUANTEPEC. THE WINDS ARE EXPECTED TO DECREASE TO LESS THAN 20 
KT BY TUE.

$$
DGS