000
AXPZ20 KNHC 130948
TWDEP 

TROPICAL WEATHER DISCUSSION   
NWS NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC FRI MAY 13 2011

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

BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0945 UTC.

...ITCZ...
THE ITCZ AXIS IS ANALYZED ALONG 11N103W TO 11N110W TO 04N140W. A 
SURFACE LOW NEAR 11N103W IS ESTIMATED AT 1010 MB...BUT LACKS 
CONVECTION AT THE MOMENT. SCATTERED MODERATE ISOLATED STRONG 
CONVECTION IS OBSERVED WITHIN 180 NM SE OF A LINE FROM 09N83W TO 
05N90W...AND ALSO WITHIN 60 NM OF 09N109W...AND WITHIN 60 NM OF 
07N122W.

...DISCUSSION...
AN UPPER LEVEL CYCLONE IS CENTERED AT 29N125W AND IS RACING NE 
WHILE TRAILING AN UPPER TROUGH SW TO A BASE AT 15N137W. UPPER 
MOISTURE IS NOTED OVER THE N SEMICIRLCE OF THE CYCLONE AS FAR N 
AS CENTRAL CALIFORNIA. A SECOND UPPER TROUGH IS APPROACHING FROM 
THE NW ALONG 32N139W TO 30N146W...AND IS PRECEDED BY A 150 NM 
WIDE BAND OF UPPER MOISTURE. OTHERWISE DRY UPPER AIR IS NOTED 
FROM 18N TO 27N BETWEEN 140W AND 130W...AND ALSO EXTENDING NE 
WITHIN 90 NM EITHER SIDE OF A LINE FROM 22N130W TO BEYOND 
32N116W MERGING WITH DRY UPPER AIR OBSERVED OVER OLD MEXICO N OF 
20N...AND OVER MOST OF SOUTHERN TEXAS...OVER SW NEW MEXICO AND 
OVER ALL OF ARIZONA.

AN UPPER CYCLONE HAS CUT OFF OVER THE DEEP TROPICAL PACIFIC AT 
04N132W. CONVECTION ALONG THE ITCZ WAS ENHANCED EARLIER FROM 
03N137W TO 04N145W. THE DEBRIS MOISTURE IS NOW EVAPORATING ALONG 
THE SAME LINE AS THE UPPER LEVELS APPEAR VERY DRY ELSEWHERE S OF 
10N BETWEEN 127W AND 137W.

AN UPPER ANTICYCLONE IS CENTERED NEAR 15N97W WITH AN UPPER RIDGE 
EXTENDING SW TO 03N77W...AND AN UPPER RIDGE EXTENDING E TO OVER 
NICARAGUA. A RIDGE ALSO EXTENDS NW TO A GENTLE CREST AT 30N112W. 
A BAND OF UPPER MOISTURE IS SPREADING NE ALONG THE PERIPHERY OF 
THIS UPPER RIDGE...WITHIN 150 NM EITHER SIDE OF A LINE FROM 
14N130W TO OVER THE SOUTHERN BAJA CALIFORNIA PENINSULA TO NEAR 
26N110W WHERE THE MOISTURE SEEMS TO EVAPORATE. DEBRIS MOISTURE 
FROM ITCZ CONVECTION BETWEEN 106W AND 122W IS ADVECTED NE UNDER 
THE RIDGE ACROSS OLD MEXICO TO THE S OF 20N. A LARGE AREA OF 
ITCZ DEBRIS MOISTURE IS NOTED OVER THE DEEP TROPICS FROM 03N TO 
12N BETWEEN 10W AND 75W...WITH SOME OF THE MOISTURE SPREADING NE 
ACROSS CENTRAL AMERICA AND OVER THE CARIBBEAN S OF 15N.

AT THE LOW LEVELS A FRONT HAS STALLED ALONG 31N BETWEEN 127W AND 
143W WITH A SURFACE RIDGE BRIDGING THE FRONT ALONG 32N140W TO 
NEAR 15N110W. NORTHERLY FLOW NE OF THE RIDGE ALONG THE W COAST 
OF THE BAJA CALIFORNIA PENINSULA HAS DIMINISHED BELOW 20 
KT...BUT IS EXPECTED TO INCREASE TO 15 TO 20 KT AGAIN ON SAT 
NIGHT. A SMALL AREA OF NE TRADES AT 15 TO 20 KT IS OBSERVED FROM 
09N TO 16N TO THE W OF 136W WITH LITTLE CHANGE EXPECTED FOR THE 
NEXT COUPLE OF DAYS. 

A MONSOON TROUGH IS ANALYZED FROM THE GULF OF PANAMA TO 07N98W. 
SOUTHERLY FLOW TO THE S OF THE TROUGH IS EXPECTED TO INCREASE TO 
20 KT ON SAT NIGHT WITH SEAS BUILDING TO ABOUT 8 FT IN THE 
VICINITY OF 05N84W.    

$$
NELSON