000
AXPZ20 KNHC 181610
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC TUE AUG 18 2009

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.

...TROPICAL WAVES...
TROPICAL WAVE N OF 08N ALONG 99W MOVE W AT 15 KT APPROACHES 
SLIGHTLY LESS ADVERSE UPPER CONDITIONS WITH MODERATE DIFFLUENT 
FLOW JUST N OF 13N WHICH IS EXPECTED TO ENHANCE ITS CONVECTION 
WITHIN NEXT 12-24 HRS.  ALTHOUGH SOME CYCLONIC ROTATION NOTED IN 
SYSTEM...ENVIRONMENT TURNS MORE ADVERSE AFTER THAT AND MODEL 
GUIDANCE DOES NOT SEE SIGNIFICANT INTENSIFICATION FOR SYSTEM. 
 
TROPICAL WAVE FROM 07N TO 15N ALONG 111W MOVE W AT 15 KT WITH  
ISOLATED MODERATE CONVECTION NEAR ITCZ INTERSECTION.  ADVERSE NE 
WIND SHEAR MAKES ANY SIGNIFICANT ORGANIZATION OF WAVE 
UNLIKELY.

TROPICAL WAVE FROM 07N TO 15N ALONG 125W MOVE W AT 15 KT WITH 
SCATTERED MODERATE ISOLATED STRONG CONVECTION FLARING WITHIN 240 
NM E OF AXIS.  THERE IS MODERATELY FAVORABLE CONDITION ALOFT S 
OF 12N NEAR ITCZ...BUT DRY STRONG SW SHEAR JUST NW OF AXIS WILL 
INHIBIT CONVECTION N OF 13N-14N.  MODEL GUIDANCE SOLUTION FAVOR 
DEVELOPMENT OF CYCLONIC CIRCULATION S OF 10N AS AXIS CROSSES 
140W.

...ITCZ...
AXIS ALONG 07N78W TO 10N96W TO 10N114W TO 08N140W.  SCATTERED 
MODERATE ISOLATED STRONG CONVECTION WITHIN 180 NM S OF AXIS E OF 
94W AND WITHIN 240 NM OF AXIS W OF 130W.  REMAINDER CONVECTION 
ASSOCIATED WITH TROPICAL WAVES. 

RAPIDLY DIMINISHING SCATTERED MODERATE ISOLATED STRONG 
CONVECTION FROM 20N-22N E OF 88W ASSOCIATED WITH SURFACE TROUGH 
OVER MEXICO.

...DISCUSSION...
UPPER LEVEL RIDGE CREST CROSS NW CORNER OF BASIN FROM 24N140W TO 
32N129W FEEDS STRONG DRY AIR MASS TO DOWNSTREAM CYCLONE AT 
20N127W.  DRY AIR MASS REACH AS FAR S AS 13N INHIBITING 
CONVECTION AHEAD OF TROPICAL WAVE ALONG 125W.  CYCLONE ADVECTS 
ABUNDANT MOISTURE FROM E SIDE OF WAVE AXIS NORTHWARD.  

DOWNSTREAM ANTICYCLONE AT 21N116W BRINGING STRONG SHEAR TO N 
HALF OF WAVE AXIS ALONG 112W.  SHARP INVERTED TROUGH ALONG 103W 
INDUCING MODERATE UPPER LEVEL DIFFLUENCE TO N HALF OF TROPICAL 
WAVE ALONG 99W ENHANCING ITS CONVECTION N OF 14N. 

ELSEWHERE AT THE SURFACE...

HIGH PRES 1031 MB HAS RIDGE EXTEND TO 10N115W.  FRESH NW WINDS  
ALONG W COAST OF BAJA CALIFORNIA PENINSULA EXPECTED THROUGHOUT 
FORECAST PERIOD.  S WINDS S OF ITCZ BRING FRESH BREEZE OF CROSS 
EQUATORIAL WARM MOIST WINDS WITH LONG PERIOD SWELLS NEAR 8 FT. 

$$
WALLY BARNES