000
AXPZ20 KNHC 121529
TWDEP 

TROPICAL WEATHER DISCUSSION   
NWS NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC THU MAY 12 2011

TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM 
THE EQUATOR TO 32N...EAST OF 140W.

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1500 UTC.

...ITCZ...
THE INTERTROPICAL CONVERGENCE ZONE AXIS IS ALONG 09N104W TO 
06N125W TO 04N140W. NO SIGNIFICANT CONVECTION. SCATTERED 
MODERATE TO ISOLATED STRONG CONVECTION IS NOTED N OF 03N E OF 
94W IN A WEAK MONSOONAL FLOW. 

...DISCUSSION...
A TROUGH/RIDGE PATTERN DOMINATES THE FORECAST REGION. A CUT-OFF 
LOW IS CENTERED NEAR 26N129W WITH A TROUGH EXTENDING SW TO 
23N140W. AN 70-90 KT JETSTREAM IS SE OF THE CYCLONIC CIRCULATION 
FROM 20N130W TO 25N120W THEN ACROSS CENTRAL BAJA CALIFORNIA AND 
THROUGH NORTHERN MEXICO. A BROAD ANTICYCLONIC CIRCULATION IS 
NEAR 13N104W AND DOMINATES THE AREA S OF 20N E OF 115W INCLUDING 
SOUTH-CENTRAL MEXICO AND NORTHERN CENTRAL AMERICA. A DIFFLUENT 
PATTERN ALOFT BETWEEN THIS ANTICYCLONE AND THE TAIL END OF A 
TROUGH EXTENDING ACROSS THE CENTRAL CARIBBEAN INTO THE EPAC 
THROUGH PANAMA IS HELPING TO MAINTAIN THE CONVECTION IS OF 
94W.     

HIGH PRES NW OF AREA EXTENDS A RIDGE OVER THE FORECAST WATERS 
COVERING THE REGION N OF 15N W OF 113W. THE RIDGE COMBINED WITH 
LOW PRES OVER MEXICO IS PRODUCING NW WINDS OF 20 KT ALONG THE 
COAST OF BAJA CALIFORNIA. AN EARLIER ASCAT PASS AND A FEW SHIP 
OBSERVATIONS VERIFIED THE PRESENCE OF THESE WINDS WHICH ARE  
FORECAST TO BE BELOW 20 KT IN ABOUT 6 HOURS. AN AREA OF FRESH 
TRADE WINDS IS ALSO NOTED ON THE SOUTHERN PERIPHERY OF THE RIDGE 
PARTICULARLY FROM 07N TO 17N W OF 128W. THE RIDGE IS EXPECTED TO 
WEAKEN AS A COLD FRONT MOVES INTO THE NW CORNER OF THE AREA THIS 
SAT. AS A RESULT...THE AREAL EXTENT OF THE TRADES WILL DECREASE.

A WEAK 1009 MB LOW PRES IS WITHIN THE ITCZ NEAR 9N104W. FIRST 
LIGHT VISIBLE IMAGERY SHOWS A WELL DEFINED SWIRL OF LOW CLOUDS 
ASSOCIATED WITH THE LOW CENTER WHILE MOST OF THE CONVECTIVE 
ACTIVITY IS TO THE W OF THE CENTER COVERING FROM 9N-12N BETWEEN 
104W-107W. 

$$
GR