000
AXPZ20 KNHC 181618
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC SUN MAY 18 2008

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 
1530 UTC.

...TROPICAL WAVES...

A TROPICAL WAVE EXTENDS FROM 02N THROUGH WESTERN PANAMA ALONG 
82.5W. THIS FEATURE REMAINS WEAK AND DIFFICULT TO DISTINGUISH IN 
SPORADIC ONGOING CONVECTION IN THE VICINITY. SOME REPOSITIONING 
IS POSSIBLE IN SUBSEQUENT ANALYSES OR THE FEATURE MAY EVEN BE 
DROPPED IF NO ORGANIZED PATTERN BECOMES DISCERNIBLE.

...ITCZ...

ITCZ AXIS IS ALONG 07N78W TO 09N106W TO 08N113W 
TO 09N123W TO 04N140W. SCATTERED MODERATE TO ISOLATED STRONG 
CONVECTION WITHIN 120 NM N OF AXIS BETWEEN 81W AND 83W...AND 
WITHIN 90 NM N OF AXIS BETWEEN 88W AND 91W. SCATTERED MODERATE 
CONVECTION WITHIN 75NM N OF AXIS BETWEEN 128W AND 130W.

SCATTERED MODERATE CONVECTION IS OBSERVED WITHIN N OF 12N 
BETWEEN 94W AND 97W.   

...DISCUSSION...

AMPLIFIED UPPER PATTERN CONTINUES WITH AN UPPER CYCLONE CENTERED 
NEAR 26N139W...WEST OF AN UPPER RIDGE AXIS EXTENDING FROM AN 
UPPER ANTICYCLONE NEAR 10N118W TO 30N125W. A BROAD AREA OF 
SOUTHERLY FLOW ALOFT BETWEEN THESE FEATURES IS PROVIDING UPPER 
EXHAUST TO SCATTERED POCKETS OF MODERATE CONVECTION ALONG THE 
ITCZ W OF 120W. EAST OF THE UPPER RIDGE...AN UPPER TROUGH 
EXTENDS FROM THE TEXAS THROUGH AND UPPER CYCLONE OVER NW MEXICO 
NEAR 27N110W. STABLE NORTHERLY FLOW IS EVIDENT BETWEEN THE RIDGE 
AND TROUGH...DRYING OUT THE MID LEVELS OF THE ATMOSPHERE EAST OF 
THE RIDGE AXIS NORTH OF 15N. AN ANOTHER UPPER RIDGE AXIS IS 
NOTED SOUTHEAST AND PARALLEL TO THE UPPER TROUGH...FROM AN UPPER 
ANTICYCLONE OVER GUATEMALA TO THE UPPER ANTICYCLONE NEAR 
10N118W...PROVIDING OUTFLOW TO CONVECTION ALONG THE ITCZ EAST OF 
110W. 

MEANWHILE TRADES ARE FAIRLY LIGHT AT THE SURFACE SOUTH OF WEAK 
HIGH PRESSURE WELL NORTH OF THE AREA. LONG PERIOD SOUTHERLY 
SWELL IS MIGRATING ACROSS THE EQUATOR SOUTH OF 10N. A COUPLE OF 
SHIP REPORTS EARLIER THIS MORNING INDICATED SEAS IN EXCESS OF 8 
FT N OF 20N W OF 125W. THIS IS HIGHER THAN WAVEWATCH OR UKMET 
WAVE MODEL INITIALIZATIONS...AND IF ACCURATE INDICATE LARGER 
THAN ANTICIPATED NW SWELL IN THE AREA. THIS WILL DECAY TO BELOW 
8 FT WITHIN THE NEXT COUPLE DAYS. LITTLE CHANGE IS EXPECTED 
ELSEWHERE THROUGH TUESDAY.

LOOKING AHEAD TO MIDWEEK...GLOBAL MODELS IN GOOD AGREEMENT 
SHOWING STRONGER HIGH PRESSURE BUILDING OVER THE NORTHEAST 
PACIFIC AND INCREASING THE GRADIENT...PROMPTING STRONG NORTHERLY 
FLOW ALONG THE CALIFORNIA COAST. THESE STRONGER WINDS AND 
ASSOCIATED SWELL WILL PUSH DOWN THE BAJA COAST BY WED. 
NOGAPS...EURO...AND UKMET ALSO SHOW CYCLONIC CIRCULATION FORMING 
NEAR 10N105W AND SHIFT IT NE...ALTHOUGH THERE IS CONSIDERABLE 
UNCERTAINTY CONCERNING THIS FEATURE IN TERMS OF TIMING AND 
STRENGTH.

$$
CHRISTENSEN