000
AXPZ20 KNHC 181527
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC SAT JUL 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...
A TROPICAL WAVE IS ALONG 99W FROM 04N-13N MOVING W 15 TO 20 KT.  
SCATTERED MODERATE TO ISOLATED STRONG CONVECTION IS WITHIN 300 
NM E OF AXIS FROM 09N TO 11N.  
 
A TROPICAL WAVE IS ALONG 123W FROM 05N TO 15N MOVING W AT ABOUT  
15 KT. SCATTERED MODERATE CONVECTION IS NOTED WITHIN 120 NM 
EITHER SIDE OF WAVE AXIS. SOME OF THE COMPUTER MODELS SUGGEST 
THE DEVELOPMENT OF A LOW PRES ALONG THE WAVE AXIS IN ABOUT 36 TO 
48 HOURS. 

...ITCZ...
THE ITCZ AXIS IS ALONG 07N78W TO 07N110W TO 10N130W TO 09N140W. 
SCATTERED MODERATE TO ISOLATED STRONG FROM 04N TO 10N E OF 99W. 
SIMILAR CONVECTION IS NOTED WITHIN 200 NM N OF AXIS BETWEEN 105W 
AND 110W. THIS CONVECTIVE ACTIVITY HAS PERSISTED SINCE 
YESTERDAY. 

...DISCUSSION...
AN UPPER-LEVEL ANTICYCLONIC CIRCULATION IS CENTERED OVER NW 
MEXICO EXTENDING A RIDGE WWD OVER THE FORECAST AREA MAINLY N OF 
20N E OF 125W. ANOTHER RIDGE...ANCHORED ON AN UPPER-LEVEL HIGH 
LOCATED W OF AREA DOMINATES THE WEST PORTION PARTICULARLY SOUTH 
OF 25N AND W OF 128W PRODUCING MODERATE TO STRONG SUBSIDENCE AND 
IMPLIED DRY AIR. A DEEP LAYERED TROUGH IS WEST OF THE AREA WITH 
THE ASSOCIATED SW FLOW AFFECTING THE FAR NW CORNER OF THE 
DISCUSSION AREA. AN INVERTED TROUGH EXTENDS ALONG 19N107W 
16N115W THEN CONTINUES S AND SE TO NEAR 04N114W. JUST E OF THIS 
TROUGH THERE IS AN UPPER-LEVEL HIGH 13N103W. UPPER DIFFLUENCE 
BETWEEN THESE TO UPPER-LEVEL FEATURES IS HELPING TO INDUCE  
CONVECTION N OF THE ITCZ BETWEEN 105W AND 110W.

A WEAKENING SWIRL OF LOW CLOUDS...ANALYZED 1012 MB LOW PRES NEAR 
23N131W...IS ASSOCIATED WITH THE REMNANTS OF DOLORES. SE TO S 
WINDS OF 20 KT AND SEAS OF UP TO 9 FT ARE STILL NOTED WITHIN 
180 NM E SEMICIRCLE. THESE CONDITIONS ARE EXPECTED TO GRADUALLY 
DIMINISH AS THE REMNANTS OF DOLORES CONTINUES TO DISSIPATE. 
EXCEPT FOR THE REMNANTS OF DOLORES A WEAK SURFACE RIDGE IS NORTH 
OF 15N WEST OF 110W. PRES GRADIENT BETWEEN THIS RIDGE AND LOWER 
PRES OVER MEXICO IS PRODUCING NW WINDS OF 20 KT WITHIN 150 NM OF 
NORTHERN BAJA CALIFORNIA. A SMALL AREA OF FRESH TRADE WINDS IS 
NOTED FROM 10N TO 16N W OF 135W. 

GAP WINDS...EASTERLY TRADES AT 20 TO 25 KT...WITH SEAS TO 11 
FT...ARE EXPECTED TO CONTINUE TO SURGE THROUGH THE GULF OF 
PAPAGAYO FOR AT LEAST ONE MORE DAY. THESE WINDS ARE EXTENDING 
WESTWARD TO ALONG 110W. WINDS AND SEAS ARE FORECAST TO DIMINISH 
IN AREAL COVERAGE IN ABOUT 48 HOURS. FRESH TO STRONG NLY WINDS 
ARE ALSO EXPECTED TO SURGE THROUGH THE GULF OF TEHUANTEPEC 
DURING THE NEXT 48 HOURS. A RECENT QSCAT PASS SHOWS A COUPLE OF 
20-25 KT WIND BARBS IN THAT AREA.  

CROSS EQUATORIAL SOUTHEASTERLY AND SOUTHWESTERLY SWELLS AND 
SOUTHERLY LOW LEVEL FLOW AT 15 TO 20 KT IS RESULTING IN SEAS TO 
9 FT SPREADING N OVER THE WATERS S OF 08N W OF THE GALAPAGOS 
ISLANDS TO ALONG 130W. THESE CONDITIONS ARE EXPECTED TO PERSIST 
THROUGH 48 HOURS.  

$$
GR