000
AXPZ20 KNHC 150250
TWDEP 

TROPICAL WEATHER DISCUSSION      
NWS NATIONAL HURRICANE CENTER MIAMI FL
0405 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0215 UTC.

...SPECIAL FEATURE...
NEWLY UPGRADED TROPICAL STORM ALETTA WAS LOCATED NEAR 10.5N 
108.5W 1004 MB AT 0300 UTC MAY 15 MOVING W OR 280 DEG AT 10 KT. 
MAXIMUM SUSTAINED WINDS 35 KT GUSTS 45 KT. CONVECTION HAS 
INCREASE THIS EVENING NEAR THE CENTER OF ALETTA...WITH 
THUNDERSTORM TOPS COOLING. THE IMPROVED SATELLITE PRESENTATION 
SUGGEST THE SYSTEM HAS INCREASED TO TROPICAL STORM STRENGTH. THE 
CORE OF ALETTA IS SMALL AND EXPECTED TO MOVE WEST TO WEST 
NORTHWEST OVER THE NEXT 48 HOURS. AFTER THAT...ADVERSE UPPER 
LEVEL WINDS TO THE WEST ARE EXPECTED TO WEAKEN THIS SYSTEM 
RATHER QUICKLY...SO THERE IS A SHORT WINDOW OF OPPORTUNITY FOR 
THIS SYSTEM TO FURTHER INTENSIFY. 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 EXTENDS FROM 07N76W TO 10.5N85W TO LOW PRES NEAR 
08N92W 1007 MB TO 12N102W...WHERE T.S. ALETA HAS SEPARATED FROM 
TROUGH...THEN TROUGH RESUMES FROM NEAR 09N105W TO 07N112W TO LOW 
PRES NEAR 07N123W 1008 MB TO 05N125W...THEN TRANSITIONS TO ITCZ 
CONTINUING ON TO BEYOND 03N140W. SCATTERED TO LOCALLY NUMEROUS 
MODERATE TO STRONG CONVECTION IS NOTED WITHIN 120 NM EITHER SIDE 
OF TROUGH BETWEEN 81W AND 87W. SCATTERED TO NUMEROUS MODERATE TO 
STRONG CONVECTION NOTED WITHIN 150 NM N AND 30 NM S OF TROUGH 
BETWEEN 95W AND 102W. SCATTERED MODERATE CONVECTION NOTED WITHIN 
150 NM N OF ITCZ W OF 136W.
 
...DISCUSSION...
ALOFT...FLAT MID/UPPER LEVEL RIDGE IS HOLDING ITS POSITION N OF 
20N ALONG ABOUT 125W N TO 31N WHILE SHORTWAVE ENERGY WITHIN A 
SHARP LONGWAVE TROUGH PERSISTING W OF 140W SHIFTS NE THROUGH 
TROUGH. TROPICAL RIDGING TO THE SE CONTINUES ALONG AND N OF THE 
MONSOON TROUGH...WITH UPPER ANTICYCLONE CENTERED NEAR 
12N88W...AND HAS SHIFTED SLIGHTLY WWD PAST 24 HOURS IN RESPONSE 
TO WWD SHIFTING DEEP CONVECTIVE OUTBURST CURRENTLY BETWEEN 88W 
AND 96W...ALTHOUGH CONVECTION HAS DIMINISHED PAST COUPLE OF 
HOURS THERE. LIGHT ANTICYCLONIC SHEAR ALONG S SIDE OF RIDGE 
PROVIDING FAVORABLE ENVIRONMENT FOR DEEP CONVECTIVE GROWTH. 
RIDGE EXTENDS NE ACROSS W CARIB TO BEYOND THE BAHAMAS...AND W-NW 
TO NEAR 17N116W.

AT LOWER LEVELS...HIGH PRES CENTER 1024 MB AT 28N131W EXTENDS 
RIDGE SE TO NEAR 18N110W.  PRES GRADIENT BETWEEN CENTER AND WEAK 
LOW PRES OVER SOUTHERN CALIFORNIA IS MAINTAINING FRESH TO STRONG 
NW BREEZE TO 25 KT ALONG BAJA CALIFORNIA W COAST S TO 24N WITH 
SEAS TO 9 FT. THIS HIGH PRES IS FORECAST TO SHIFT NW AND 
REORGANIZE JUST N OF AREA DURING THE 48 HOURS...AND WILL 
MAINTAIN FRESH TO STRONG NWLY WINDS ACROSS BAJA CALIFORNIA NORTE 
N OF 28N INTO THE WEEKEND. 

STATIONARY FRONT OVER THE ERN BAY OF CAMPECHE AND A WAVE LIKE 
FEATURE ALONG ABOUT 92W IN THE EPAC ARE COMBINING TO MAINTAIN 
STRONG NLY WINDS ACROSS CHIVELA PASS AND EXITING THROUGH GULF OF 
TEHUANTEPEC. WINDS HAVE DROPPED FROM GALE FORCE TO 30 KT LATE 
THIS AFTERNOON AND EVENING...AND WILL DIMINISH TO A NARROW PLUME 
OF 20-25 KT BY TUE AFTERNOON...AND THEN BLOW AROUND 20 KT 
CONFINED JUST TO THE BAY THROUGH 48 HOURS.  

FRESH ELY WINDS OVER GULF OF PAPAGAYO HAVE DIMINISHED TO LESS 
THAN 20 KT THIS EVENING.

THE WAVE LIKE DISTURBANCE ALONG ABOUT 92W HAS SHOWN SOME MIDDLE 
LEVEL CYCLONIC TURNING IN SATELLITE IMAGERY THIS AFTERNOON AND 
EVENING. THIS FEATURE IS EXPECTED TO CONTINUE TO PRODUCE ACTIVE 
CONVECTION FOR THE NEXT FEW DAYS AS IT SHIFTS SLOWLY WWD.

$$
STRIPLING