000
AXPZ20 KNHC 170922
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC THU APR 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 
0900 UTC.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 02N78W 01N84W 11N115W 05N140W. 
NUMEROUS MODERATE TO STRONG CONVECTION FROM 06N TO 11N BETWEEN 
103W AND 111W. SCATTERED MODERATE CONVECTION WITHIN 60 NM OF 
AXIS BETWEEN 115W AND 120W. SCATTERED MODERATE CONVECTION FROM 
2N TO 5N BETWEEN 125W AND 128W.

...DISCUSSION...

E OF 120W...DIVERGENCE ALOFT ASSOCIATED WITH AN UPPER RIDGE AXIS 
EXTENDING EASTWARD ALONG ROUGHLY 10N IS ENHANCING CONVECTION 
ALONG THE ITCZ MAINLY W OF 100W. STRONG SUBSIDENCE E OF 100W IS 
SUPPRESSING CONVECTION...ALTHOUGH SMALL CLUSTERS ARE STILL 
EVIDENT DIRECTLY ALONG THE ITCZ...ESPECIALLY N OF THE GALAPAGOS. 
THE CONVECTION NOTED W OF 10OW IS BEING FED BY LOW LEVEL 
CONVERGENCE RESULTING FROM FRESH ELY FLOW BETWEEN 90W AND 
100W...AS NOTED ON QUIKSCAT AND ASCAT PASSES FROM THIS PAST 
EVENING. SPORADIC CONVECTIVE FLARE UPS WILL PERSIST OVER THE 
NEXT COUPLE OF DAYS OVER THE ITCZ BETWEEN 100W AND 110W OWING TO 
CONTINUED ANTICYCLONE DIVERGENCE ALOFT. GFS AND EURO MODEL SHOW 
A WEAK SURFACE TROUGH EMERGING OVER THE NEXT COUPLE OF DAYS. 
GIVEN THE STRENGTH OF THE CONVECTION NOW IN PLACE THIS IS 
PLAUSIBLE...ALTHOUGH THE FEATURE WILL REMAIN SHORT LIVED AS THE 
SUPPORTING UPPER RIDGE PIVOTS TO BECOME ORIENTED MORE N-S IN 
PHASE WITH AN UPPER RIDGE TO THE N. MEANWHILE SCATTEROMETER 
PASSES REVEALED MODERATE TO FRESH NWLY FLOW ALONG THE BAJA 
COAST...ON THE EDGE OF HIGH PRES OVER THE PACIFIC...AS WELL AS 
MODERATE TO FRESH FLOW THROUGH THE GULF OF PAPAGAYO. GFS 
INDICATES THE PAPAGAYO EVENT WILL CONTINUE OFF AND ON DUE TO 
ENHANCED TRADES IN THE CARIBBEAN. MEANWHILE ONLY LIGHT TO 
MODERATE WINDS ARE NOTED IN THE GULF OF TEHUANTEPEC 
HOWEVER...ENDING A LATE SEASON ROUND OF GAP WIND FLOW THAT BEGAN 
SEVERAL DAYS AGO. WW3 HINTS OF A 6 FT 16S SWELL MOVING 
NE...REACHING THE CENTRAL AMERICAN AND MEXICAN COASTS BY SAT.

W OF 120W...A PAIR OF WEAK UPPER CYCLONES...NEAR 33N135W AND 
25N137W ARE NEARLY STATIONARY AND MAKING VERY SLOW EWD PROGRESS. 
THIS IS DUE TO A BLOCKING UPPER RIDGE SITUATED ALONG THE 
CALIFORNIA COAST. THE UPPER PATTERN BECOMES MORE DEAMPLIFIED AND 
FLOW MORE ZONAL OVER THE NEXT COUPLE OF DAYS AS THE RIDGE 
WEAKENS AND THE UPPER TROUGH SHIFTS E TO NEAR 125W...AHEAD OF 
ANOTHER UPPER RIDGE BUILDING NEAR 145W. A SURFACE RIDGE N OF THE 
AREA WEAKENS SLIGHTLY AND SHIFTS FURTHER S...AHEAD OF A DEEP 
LAYER TROUGH DIGGING NW OF THE AREA. THIS WILL MAINTAIN FRESH 
TRADES TO THE S INTO THE WEEKEND. UPPER WLY FLOW S OF TROUGH 
SPLITS E OF 130W AS IT ENCOUNTERS THE WESTERN EXTENT OF AN UPPER 
RIDGE AXIS EXTENDING ALONG 10W TOWARD CENTRAL AMERICA. THE 
RESULTANT UPPER DIVERGENCE IS ENHANCING SOME MODEST CONVECTION 
NEAR THE ITCZ.
$$
CHRISTENSEN