000
AXPZ20 KNHC 132129
TWDEP 

TROPICAL WEATHER DISCUSSION   
NWS NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC WED APR 13 2011

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

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
2100 UTC.

...ITCZ...
THE INTERTROPICAL CONVERGENCE ZONE AXIS IS ANALYZED FROM 04N77W 
TO 1010 MB LOW PRES NEAR 6N90W TO 3N98W TO 6N110W TO 2N126W 
TO 4N140W. SCATTERED MODERATE CONVECTION IS S OF 06N BETWEEN 
82W AND 96W. SIMILAR CONVECTION IS WITHIN 200 NM N OF AXIS W OF 
135W. 

...DISCUSSION...
A RIDGE/TROUGH/RIDGE PATTERN DOMINATES MOST OF THE FORECAST 
AREA. AN UPPER LEVEL RIDGE COVERS THE NW CORNER. THE UPPER LEVEL 
TROUGH ENTERS THE REGION THROUGH NORTHERN BAJA CALIFORNIA AND 
EXTENDS SW TO NEAR 20N130W. A 95-100 KT JETSTREAM IS SE OF THE 
TROUGH AXIS FROM 25N119W ACROSS NORTHERN BAJA CALIFORNIA INTO 
THE SW UNITED STATES. MODERATE TO STRONG UPPER LEVEL SUBSIDENCE 
AND IMPLIED DRY AIR MASS IS NOTED N OF 18N W OF 120W. A LARGE 
UPPER-LEVEL ANTICYCLONIC CIRCULATION IS CENTERED NEAR THE 
ISTHMUS OF TEHUANTEPEC. S TO SW FLOW BETWEEN THIS ANTICYCLONE 
AND THE TROUGH IS ADVECTING MID TO UPPER LEVEL MOISTURE FROM 
ITCZ CONVECTION TOWARD SOUTHERN BAJA CALIFORNIA INTO NORTHERN 
MEXICO.

A 1030 MB SURFACE HIGH PRES LOCATED NEAR 31N132W EXTENDS A RIDGE 
OVER THE FORECAST WATERS AND DOMINATES MAINLY THE AREA N OF 12N 
W OF 108W. A BROAD AREA OF TRADE WINDS IN THE 20 TO 25 KT RANGE 
IS OBSERVED ON THE SOUTHERN PERIPHERY OF THE RIDGE COVERING 
ROUGHLY THE REGION FROM 05N TO 25N W OF 120W. THESE WINDS ARE 
ALLOWING SEAS TO BUILD TO 11-12 FT. THE HIGH PRES IS FORECAST TO 
REMAIN NEARLY STATIONARY OVER THE NEXT 24 HOURS THEN WILL DRIFT 
EWD. LITTLE CHANGE IS EXPECTED IN THE STRENGTH AND AREAL EXTENT 
OF THESE TRADE WINDS THROUGH FRI MORNING. WINDS ARE FORECAST TO 
INCREASE TO 20-25 KT W OF BAJA CALIFORNIA PENINSULA IN ABOUT 24 
HOURS AS PRES GRADIENT TIGHTENS BETWEEN THE HIGH PRES AND LOWER 
PRES OVER NE MEXICO. ALSO EXPECT INCREASING WINDS UP TO 25 KT  
ACROSS THE GULF OF CALIFORNIA BY THU.  

A WEAK 1011 MB LOW PRES IS ANALYZED NEAR 9N109W. THE CONVECTIVE 
ACTIVITY ASSOCIATED WITH THIS SYSTEM HAS DIMINISHED AND IS 
CURRENTLY LOCATED NW OF THE CENTER DUE TO STRONG SE WINDS ALOFT. 
THE CENTER IS DEFINED BY A SWIRL OF LOW CLOUDS ON VISIBLE 
SATELLITE PICTURES. AS PREVIOUSLY MENTIONED...ANOTHER 1010 MB 
LOW PRES IS EMBEDDED WITHIN THE ITCZ NEAR 6N90W. 

GAP WINDS...
WINDS WILL CONTINUE TO PULSE TO 20 KT ACROSS THE GULF OF 
PAPAGAYO THROUGH THU MORNING WITH SEAS REMAINING JUST BELOW 8 
FT. THE LARGEST AREAL EXTENT OF THE 20 KT WINDS WILL BE IN THE 
EARLY MORNING HOURS WITH THE AID OF NOCTURNAL DRAINAGE FLOW.

WINDS HAVE DIMINISHED BELOW 20 KT ACROSS THE GULF OF TEHUANTEPEC.

$$
GR