Eastern Pacific Basin Tropical Discussion Atlantic | Pacific

000
AXPZ20 KNHC 170951
TWDEP 

TROPICAL WEATHER DISCUSSION      
NWS NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC THU MAY 17 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0845 UTC.

...SPECIAL FEATURES...
ALETTA WAS DOWNGRADED TO A TROPICAL DEPRESSION AT 17/0900 UTC. 
AT THIS TIME...IT IS CENTERED NEAR 11.7N 114.6W MOVING W-NW OR 
295 DEG AT 3 KT. ESTIMATED MINIMUM CENTRAL PRES 1005 MB. MAXIMUM 
SUSTAINED WINDS 30 KT GUSTS TO 40 KT. PLEASE REFER TO THE LATEST 
PUBLIC ADVISORY TCPEP1/WTPZ31 KNHC FOR MORE DETAILS. SCATTERED 
MODERATE TO ISOLATED STRONG CONVECTION IS WITHIN 75 NM OF THE 
CENTER. ALETTA WILL CONTINUE TO WEAKEN DURING THE NEXT 48 HOURS 
AS VERTICAL SHEAR INCREASES AND DRY AIR APPROACHES. IN FACT... 
THE 0528 UTC HIGH RESOLUTION ASCAT PASS PROVIDED OBSERVATIONS OF 
20 TO 25 KT WINDS IN ASSOCIATION WITH ALETTA. THE STRONGEST 
WINDS ARE IN THE NE QUADRANT. 

SHOWER ACTIVITY ASSOCIATED WITH A BROAD LOW PRESSURE AREA... 
ANALYZED NEAR 12N101W 1008 MB ON THE 0600 UTC SURFACE MAP 
REMAINS POORLY ORGANIZED. SATELLITE IMAGERY SHOWS SCATTERED 
MODERATE TO ISOLATED STRONG CONVECTION JUST N OF THE LOW CENTER 
TO THE COAST OF MEXICO NEAR ACAPULCO BETWEEN 98W AND 101W. 
ENVIRONMENTAL CONDITIONS ARE FORECAST TO BECOME MORE CONDUCIVE 
FOR SLOW DEVELOPMENT DURING THE NEXT FEW DAYS. GLOBAL MODELS 
SHOW A DEEPENING LOW PRES SYSTEM DURING THE UPCOMING WEEKEND. A 
SURGE OF NLY WINDS FROM THE GULF OF TEHUANTEPEC COULD ADD 
VORTICITY TO THE PRE-EXISTING CIRCULATION. THIS SYSTEM HAS A 
MEDIUM CHANCE OF BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 
HOURS AS IT MOVES SLOWLY TO THE NORTHWEST.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...
MONSOON TROUGH FROM 07N78W TO LOW PRES NEAR 12N101W 1008 MB THEN 
RESUMES FROM 08N115W TO 05N123W. ITCZ FROM 05N123W TO 06N131W TO 
03N140W. SCATTERED MODERATE ISOLATED STRONG WITHIN 60 NM EITHER 
SIDE OF TROUGH E OF 83W TO THE COAST OF COLOMBIA. SIMILAR 
CONVECTION IS NOTED N OF 10N BETWEEN 85W AND 88W.

...DISCUSSION...

ALOFT...A TROUGH/RIDGE/TROUGH PATTERN DOMINATES THE N WATERS. A 
DEEP LAYER TROUGH CROSSES 30N140W AND EXTENDS SW TO A CUT-OFF 
LOW NEAR 21N146W. THE RIDGE WITH AXIS ROUGHLY ALONG 124W 
CONTINUES TO DOMINATE THE N PORTION OF THE DISCUSSION AREA. S 
AND SW WINDS BETWEEN THE TROUGH AND THE RIDGE ARE TRANSPORTING 
ABUNDANT MID/UPPER LEVEL MOISTURE ACROSS THE NW CORNER OF THE 
AREA. STRONG MID/UPPER LEVEL SUBSIDENCE AND IMPLIED DRY AIR MASS 
COVERS THE AREA N OF 20N E OF 120W INCLUDING THE BAJA CALIFORNIA 
PENINSULA AND NW MEXICO. A TROUGH IS NOTED IS THIS AREA 
EXTENDING FROM NW MEXICO TO NEAR 18N120W. AN ANTICYCLONIC 
CIRCULATION REMAINS CENTERED OVER CENTRAL AMERICA WITH A RIDGE 
DOMINATING THE WATERS E OF 110W. THIS FEATURE IS HELPING TO 
SUPPORT THE CONVECTIVE ACTIVITY NEAR THE MONSOON TROUGH AND THE 
LOW PRES AT 12N101W. 

A WEAK HIGH PRES RIDGE EXTENDING FROM 32N133W TO AROUND 20N120W 
IS SUPPORTING MODERATE NW WINDS N OF 28N W OF THE BAJA CALIFORNIA
PENINSULA...WITH NLY SWELL MAINTAINING SEAS OF 6-7 FT IN NE 
PORTION OF THE DISCUSSION AREA. NE TRADE WINDS W OF 115W ARE 
RELATIVELY WEAK AND ARE EXPECTED TO REMAIN GENTLE TO MODERATE 
THROUGH THE WEEKEND DUE TO A WEAK SUBTROPICAL RIDGE N OF 30N AND 
NEAR-NORMAL PRESSURES WITHIN THE NEAR-EQUATORIAL TROUGH.

HIGH PRES BUILDING SOUTHWARD ALONG THE GULF COAST OF MEXICO WILL 
INDUCE 20-25 KT N-NE WINDS INTO THE GULF OF TEHUANTEPEC THROUGH 
EARLY FRI.

$$
GR