000
AXPZ20 KNHC 151528
TWDEP 

TROPICAL WEATHER DISCUSSION      
NWS NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC TUE MAY 15 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 FEATURE...
TROPICAL STORM ALETTA IS CENTERED NEAR 10.6N 109.6W AT 15/1500 
UTC MOVING W OR 280 DEG AT 8 KT...AND THIS GENERAL MOTION IS 
EXPECTED TO DURING THE NEXT 48 HOURS. ESTIMATED MINIMUM CENTRAL 
PRESSURE IS 1004 MB. MAXIMUM SUSTAINED WIND SPEED IS 35 KT GUSTS 
45 KT. PLEASE SEE THE LATEST PUBLIC ADVISORY UNDER AWIPS/WMO 
HEADER MIATCPEP1/WTPZ31 KNHC FOR MORE DETAILS. NUMEROUS STRONG 
CONVECTION IS NOTED WITHIN 240 NM NE QUADRANT AND 150 NM NW 
QUADRANT. THE FORECAST CALLS FOR ONLY A MODEST INTENSIFICATION 
DURING THE NEXT 24 HOURS BEFORE INCREASING SOUTHWESTERLY 
VERTICAL SHEAR BEGINS TO PREVENT ANY FURTHER DEVELOPMENT. WINDS 
ARE EXPECTED TO INCREASE AND PEAK NEAR 45 KT TUE NIGHT OR EARLY 
WED MORNING...BEFORE WEAKENING COMMENCES. 

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...
MONSOON TROUGH FROM 11N86W TO 11N105W THEN RESUMES AT 08N11W TO 
04N126W. ITCZ FROM 04N126W TO 03N140W. NUMEROUS MODERATE TO 
STRONG CONVECTION FROM 06N-13N BETWEEN 85W-98W.

...DISCUSSION...
MID/UPPER LEVEL RIDGE WITH AXIS ALONG 32N131W TO 20N124W 
CONTINUES TO DOMINATE THE N PORTION OF THE DISCUSSION AREA  
WHILE A SHARP LONGWAVE TROUGH PERSISTS W OF 140W. S AND SW WIND 
FLOW AHEAD OF THE TROUGH IS TRANSPORTING MID/UPPER LEVEL 
MOISTURE FROM THE TROPICS MAINLY W OF 125W. AN ANTICYCLONIC 
CIRCULATION REMAINS CENTERED OVER NORTHERN CENTRAL AMERICA WITH 
A RIDGE COVERING THE DISCUSSION AREA E OF 110W. A DIFFLUENT 
PATTERN ALOFT ASSOCIATED WITH THIS FEATURE CONTINUES TO SUPPORT 
THE DEVELOPMENT STRONG CONVECTION FROM 6N-13N BETWEEN 85W-98W.

A SURFACE 1024 MB HIGH PRES LOCATED NEAR 32N135W WITH A RIDGE 
EXTENDING FROM THE HIGH SE TO NEAR 20N116W. PRES GRADIENT 
BETWEEN THIS HIGH AND A TROUGH OVER SOUTHERN CALIFORNIA AND 
WESTERN MEXICO IS MAINTAINING 20 KT NW WINDS E OF 120W TO THE W 
COAST OF BAJA CALIFORNIA N OF 24N. THIS HIGH PRES IS FORECAST TO 
REMAIN NEARLY STATIONARY DURING THE NEXT 24 HOURS.

STATIONARY FRONT OVER THE ERN BAY OF CAMPECHE WITH HIGH PRES 
BUILDING BEHIND THE FRONT HAVE TIGHTENED THE PRES GRADIENT 
ACROSS SOUTHERN MEXICO RESULTING IN NLY WINDS 20-25 KT THROUGH 
THE GULF OF TEHUANTEPEC. THE WINDS ARE FORECAST TO DECREASE TO  
BELOW 20 KT TONIGHT.  

OF NOTE...TODAY MARKS THE BEGINNING OF THE TROPICAL SEASON IN 
THE EASTERN NORTH PACIFIC...AND ALETTA...THE FIRST TROPICAL 
CYCLONE OF THE SEASON HAS ALREADY FORMED. LONG-TERM AVERAGES OF 
TROPICAL STORMS...HURRICANES AND MAJOR HURRICANES IN THIS BASIN 
ARE 15...9...AND 4 RESPECTIVELY.

$$
DGS