000
AXPZ20 KNHC 170956
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC SAT MAY 17 2008

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.

...TROPICAL WAVES...

A TROPICAL WAVE EXTENDS FROM 03N TO 12N ALONG 78W AND HAS BEEN 
MOVING W AT AN ESTIMATED 15 KT. CYCLONIC TURNING IS NOTED AT 7N 
ALONG THE WAVE WITH SCATTERED MODERATE AND ISOLATED STRONG 
CONVECTION NOTED WITHIN 30 NM EITHER SIDE OF THE WAVE IN THE E 
PACIFIC.

...ITCZ...

ITCZ AXIS IS ALONG 08N78W TO 08N87W TO 06N100W 09N112W TO 
04N131W TO 05N140W. SCATTERED MODERATE ISOLATED STRONG 
CONVECTION IS OBSERVED FROM 09N TO 12N BETWEEN 94W AND 130W.


...DISCUSSION...

A QUASI STATIONARY UPPER LEVEL CYCLONE IS CENTERED AT 24N138W 
WITH ITS ENVELOPE OF CYCLONIC FLOW DOMINATING THE DISCUSSION 
AREA N OF 5N W OF 130W. A BAND OF DRY UPPER AIR CIRCLES THE 
CYCLONE WITHIN ABOUT 240 NM OF THE CENTER. AN UPPER LONGWAVE 
TROUGH DISSECTS N AMERICA FROM NE TO SW ENTERING THE DISCUSSION 
AREA THROUGH A SMALL UPPER CYCLONE NEAR 30N107W WITH UPPER 
TROUGH CONTINUING S TO A BASE NEAR 21N109W. A BAND OF DRY UPPER 
AIR IS NOTED WITHIN THE W PORTION OF THE UPPER TROUGH...ROUGHLY 
WITHIN 240 NM EITHER SIDE OF LINE FROM 20N107W TO WELL BEYOND 
32N122W.

A BROAD UPPER RIDGE EXTENDS E TO W ALONG 10N AND IS DOMINATING 
THE TROPICS E OF 125W. A NARROW UPPER RIDGE ALSO EXTENDS N ALONG 
12N115W TO A SHARP CREST AT 23N122W AND EFFECTIVELY SEPARATES 
THE UPPER CYCLONES. UPPER DIFFLUENCE IS ENHANCING CONVECTION 
ALONG THE ITCZ E OF 130W. THE RESULTANT DEBRIS MOISTURE SPREADS 
N BETWEEN 125W AND 132W IN RESPONSE TO THE UPPER CYCLONE AT 
24N138W.  CONVECTION ALONG THE ITCZ E OF 122W IS ADVECTED NE 
ACROSS CENTRAL AMERICA BETWEEN 90W AND 105W AND CONTINUES NE 
ACROSS THE CENTRAL GULF OF MEXICO AND EVENTUALLY TURNS E ACROSS 
NORTHERN FLORIDA. DEBRIS MOISTURE OVER CENTRAL AMERICA E OF 90W 
APPEARS TO EVAPORATE IN VERY DRY AIR ALOFT OVER THE W CARIBBEAN.

AT THE SURFACE HIGH PRESSURE IS MEANDERING NEAR 30N140W WITH A 
RIDGE SE TO NEAR 18N110W. THE LOW LEVEL EASTERLY TRADES SW OF 
THE RIDGE ARE BEGINNING TO INCREASE TO 20 KT NEAR 10N138W AND 
THESE CONDITIONS ARE EXPECTED TO SPREAD NE AND COVER THE TROPICS 
N OF THE ITCZ W OF 125W BY MON. SOUTHERLY SWELL TO 8 FT HAS BEEN 
CROSSING THE EQUATOR OVER THE WATERS W OF 90W BUT SHOULD 
DIMINISH SOME THROUGH THE WEEKEND.   

$$
NELSON