000
AXPZ20 KNHC 181537
TWDEP 

TROPICAL WEATHER DISCUSSION      
NWS NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC FRI MAY 18 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...
AT 1500 UTC...TROPICAL DEPRESSION ALETTA CENTERED NEAR 14.2N 
113.5W AND MOVING NE OR 45 DEG AT 5 KT. THE ESTIMATED MINIMUM 
CENTRAL PRES WAS 1006 MB. MAXIMUM SUSTAINED WINDS WERE 30 KT 
GUSTS TO 40 KT. PLEASE REFER TO THE LATEST PUBLIC ADVISORY 
TCPEP1/WTPZ31 KNHC FOR MORE DETAILS. SCATTERED MODERATE TO 
STRONG CONVECTION WITHIN 90 NM NE QUADRANT OF TROPICAL 
DEPRESSION ALETTA. ALETTA WILL GRADUALLY WEAKEN DURING THE NEXT 
48 HOURS AS DRY AIR AND SHEAR ALOFT BEGIN TO TAKE THEIR TOLL ON 
THE SYSTEM.

BROAD AREA OF LOW PRES IS EMBEDDED WITHIN THE MONSOON TROUGH AND 
CENTERED NEAR 12N101W. CONVECTIVE ACTIVITY ASSOCIATED WITH THE 
DISTURBANCE IS WITHIN 180 NM NE QUADRANT OF LOW. THE LOW IS 
UNDER AN UPPER RIDGE THAT EXTENDS FROM AN ANTICYCLONE OVER 
CENTRAL AMERICA. THIS PATTERN IS EXPECTED TO CHANGE LITTLE 
OVER THE NEXT FEW DAYS. THE SLOW MOVING LOW PRES SYSTEM IS 
EXPECTED TO INTENSIFY IN AN ENVIRONMENT OF FAVORABLE UPPER LEVEL 
DIFFLUENCE. THERE IS A MEDIUM CHANCE OF THE LOW BECOMING A 
TROPICAL CYCLONE DURING THE NEXT 48 HOURS.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...
MONSOON TROUGH FROM 8N82W TO 1007 MB LOW PRES NEAR 12N101W TO 
14N110W. ITCZ FROM 8N119W 5N130W TO 6N140W. SCATTERED MODERATE 
TO STRONG CONVECTION FROM 3N-10N BETWEEN 92W-110W.

...DISCUSSION...
AN UPPER LEVEL TROUGH OVER THE FAR NW PORTION OF THE AREA FROM 
31N136W TO A CYCLONIC CIRCULATION JUST W OF THE AREA NEAR 
22N142W. A FLATTENING RIDGE IS E OF THE TROUGH. EXCEPT FOR SOME 
HIGH CLOUDS FROM 20N-26N W OF 125W STRONG SUBSIDENCE WITH 
DRY/STABLE AIR AT THE MIDDLE AND UPPER LEVELS OF THE ATMOSPHERE 
IS ACROSS THE AREA N OF 20N E OF 120W. UPPER LEVEL ANTICYCLONIC 
CIRCULATION IS CENTERED OVER CENTRAL AMERICA WITH A RIDGE 
EXTENDING WESTWARD TO 15N115W. UPPER LEVEL DIFFLUENT FLOW WITHIN 
THIS AREA IS ENHANCING CONVECTION IN THIS MOIST AIRMASS FROM
3N-15N E OF 110W.

THE PRES GRADIENT WILL REMAIN STRONG ENOUGH ON THE E SIDE OF THE 
HIGH N OF THE AREA TO GENERATE 20 KT N WINDS WELL OFF THE BAJA 
PENINSULA N OF 25N BETWEEN 119W-125W TODAY AND TOMORROW...WITH 
NLY SWELL KEEPING SEAS OVER 8 FT INTO SUN.

THE PRES GRADIENT BETWEEN HIGHER PRES OVER THE GULF OF MEXICO 
AND THE LOW PRES NEAR 12N101W IS PRODUCING NLY WINDS 20-25 KT 
THROUGH THE GULF OF TEHUANTEPEC. THE HIGH WEAKENS AND WIND 
DECREASE TO BELOW 20 KT TONIGHT.

$$
DGS