000
AXPZ20 KNHC 180355
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC TUE AUG 18 2009

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

BASED ON 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0300 UTC.

...TROPICAL WAVES...
TROPICAL WAVE N OF 10N ALONG 95W MOVING W AT 15 KT. ASSOCIATED 
SCATTERED MODERATE CONVECTION QUICKLY DIMINISHING. 

TROPICAL WAVE FROM 08N TO 16N ALONG 108W MOVING W AT 15 
KT...ALONG THE LEADING EDGE OF AN AREA OF HIGH PRECIPITABLE 
WATER VALUES. HOWEVER NORTHERLY FLOW ALOFT IS SUPPRESSING 
CONVECTIVE DEVELOPMENT...AND NO SIGNIFICANT CONVECTION IS NOTED 
WITH THIS TROPICAL WAVE.

TROPICAL WAVE FROM 07N-15N ALONG 123W MOVE W AT 15 KT. THE WAVE 
HAS BEEN ANALYZED OVER THE PAST SEVERAL DAYS IN A AREA OF 
PERSISTENT CONVECTION TRAILING AN UPPER LEVEL LOW MIGRATING 
WESTWARD.

...ITCZ...
AXIS ALONG 08N82W TO 12N95W TO 10N105W TO 10N128W TO 12N135W TO 
11N140W. SCATTERED MODERATE ISOLATED STRONG CONVECTION FROM 05N 
TO 08N BETWEEN 85W AND 90W.

...DISCUSSION...
FAIRLY AMPLIFIED PATTERN CONTINUES OVER THE DISCUSSION AREA WITH 
AN UPPER ANTICYCLONE CENTERED NEAR 23N134W...JUST TO THE WEST OF 
AN UPPER LOW CENTERED NEAR 19N124W. THE DRY SUBSIDENT N TO NE 
DEEP LAYER FLOW BETWEEN THESE TWO SYSTEMS IS SUPPRESSING ANY 
ORGANIZED CONVECTION ALONG THE ITCZ W OF 130W. VISIBLE SATELLITE 
IMAGERY HINTS OF A WEAK TROUGH JUST NORTH OF THE ITCZ ALONG 
139W. THIS THEORY IS BOLSTERED BY AN ASCAT PASS FROM AROUND 20Z 
SHOWING WEAK CYCLONIC TURNING. THIS IS LIKELY THE SURVIVING 
REMNANT OF T.D. NINE-E FROM SEVERAL DAYS AGO...REMAINING IN THE 
SAME GENERAL LOCATION AS HURRICANE GUILLERMO MOVED WESTWARD TO 
THE NORTH. 

FURTHER NORTH...A 1030 MB SURFACE HIGH PRES AREA IS 
CENTERED 1000 NM N OF HAWAII. A SURFACE RIDGE EXTENDS FROM THE 
HIGH TO ALMOST THE SOUTHERN BAJA PENINSULA. SCATTEROMETER AND 
SHIP OBSERVATIONS SHOW A BROAD SWATH OF 20 KT NW FLOW TO BETWEEN 
THE SURFACE TROUGH AND THE RIDGE. RECENT SHIP OBSERVATIONS N OF 
25N W OF 130W INDICATE THAT SEAS ARE STILL RUNNING 8 TO 12 FT 
OVER THE FAR NW PORTION OF THE DISCUSSION AREA...IN DECAYING NE 
SWELL IN THE WAKE OF GUILLERMO...NOW A DYING TROPICAL STORM 
AROUND 600 NM ENE OF HAWAII. AN EARLIER ALTIMETER PASS FROM 08Z 
SHOWED A SWATH OF 9 TO 14 FT SEAS IN THE SAME AREA.

RECENT SHIP OBSERVATIONS FROM OFF THE BAJA COAST SHOW MAXIMUM 
WINDS TO ONLY 15 KT. THIS AREA HAD SEEN WINDS TO 20 KT OVER THE 
PAST COUPLE OF DAYS...ON THE WESTERN PERIPHERY OF THE SURFACE 
RIDGE. MODELS INDICATE SOME SPORADIC SMALL AREAS OF 20 KT WINDS 
OVER THE NEXT COUPLE OF DAYS...BUT THIS MAY BE A LITTLE OVERDONE 
CONSIDERING THE SURFACE RIDGE IS NOT EXPECTED TO BUILD 
APPRECIABLY.

MEANWHILE MODEST CONVECTION CONTINUES ALONG THE ITCZ BETWEEN 
120W AND 125W...TRAILING WESTWARD ON THE SE SIDE OF THE UPPER 
LOW NEAR 19N124W.

SOUTH OF THE ITCZ...SUCCESSIVE ASCAT AND QUIKSCAT PASSES HAVE 
BEEN SHOWING PATCHES OF 20 KT WINDS OVER THE WARMER WATERS A 
LITTLE TO THE NORTH OF THE EQUATOR AND SOUTH OF THE ITCZ. 
ALTIMETER PASSES SHOWED SEAS TO 8 FT...MOST LIKELY IN SOUTHERLY 
SWELL. LATEST WAVEWATCH III GUIDANCE DEPICTS LONG PERIOD 
SOUTHERLY SWELL OF UP TO 6 TO 7 FT MIGRATING NORTH ACROSS THE 
AREA OVER THE NEXT SEVERAL DAYS...REACHING THE MEXICAN AND 
CENTRAL AMERICAN COASTS BY LATE THU/EARLY FRI...CREATING THE 
POTENTIAL FOR HIGH SURF CONDITIONS.

$$
CHRISTENSEN