000
AXPZ20 KNHC 182213
TWDEP 

TROPICAL WEATHER DISCUSSION     
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC SAT AUG 18 2007

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

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
2145 UTC.

...TROPICAL WAVES...

TROPICAL WAVE ALONG 86.5W HAS BEEN MOVING W AT 15 KT OVER THE 
PAST 24 HOURS. SCATTERED MODERATE ISOLATED STRONG CONVECTION IS 
ENHANCED IN THE E PAC WITHIN 30 NM OF THE WAVE AXIS AT 8N AND 
ALONG THE AXIS AT THE COAST OF COSTA RICA AND NICARAGUA. 

TROPICAL WAVE IS ESTIMATED ALONG 110.5W AND MOVING W AT 8 TO 10 
KT. A N TO S TROUGH IS ALSO IN THE AREA FROM 23N113W TO 17N107W. 
A SURFACE LOW IS NEAR 18N110.5W ESTIMATED AT 1007 MB. A LARGE 
AREA OF MODERATE CONVECTION WITH A FEW STRONG CELLS WITHIN 360 
NM EITHER SIDE OF LINE 6N99W 21N115W.

A TROPICAL WAVE ALONG 134.5W FROM 6N TO 16N HAS MOVED W AT 10 KT 
OVER THE PAST 24 HOURS. A WEAK CYCLONIC SWIRL IS NOTED WITHIN 
THE ITCZ WITH SCATTERED MODERATE CONVECTION ENHANCED AT 
10N137W.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 9N84W 9N93W 19N109W 12N113W 10N140W. 
SCATTERED MODERATE ISOLATED STRONG CONVECTION IS NOTED WITHIN 90 
NM EITHER SIDE OF LINE 5N81W 10N89W...WITHIN 60 NM OF 15N97W... 
AND WITHIN 360 NM EITHER SIDE OF LINE 6N99W 21N115W.

...DISCUSSION...

AN UPPER TROUGH DOMINATES THE E PAC EXTENDING S INTO THE 
DISCUSSION AREA FROM 32N127W TO 16N132W...SQUEEZED BETWEEN TWO 
UPPER RIDGES. AN UPPER ANTICYCLONE IS NEAR 24N146W WITH A RIDGE 
EXTENDING E TO A CREST NEAR 23N134W. AN UPPER ANTICYCLONE IS 
OVER OLD MEXICO NEAR 29N109W WITH A RIDGE EXTENDING SW TO A 
GENTLE CREST ALONG 14N117W 24N124W 32N120W. UPPER DIFFLUENCE 
FROM THIS RIDGE IS ENHANCING THE CONVECTION OVER THE PAC N OF 
THE ITCZ BETWEEN 100W AND 120W WITH THE RESULTANT DEBRIS 
MOISTURE MOSTLY N OF 7N BETWEEN 105W AND 120W...BUT SOME OF THE 
DEBRIS MOISTURE IS NOT ADVECTED SW TO THE EQUATOR BETWEEN 100W 
AND 120W. OTHERWISE...DRY UPPER AIR IS NOTED OVER THE DISCUSSION 
AREA N OF 12N W OF 123W. 

AN UPPER TROUGH EXTENDS S FROM A CYCLONE OVER THE EASTERN GULF 
OF MEXICO NEAR 25N83W TO ANOTHER SMALL UPPER CYCLONE AT 14N88W. 
THE UPPER FLOW IS NE OVER THE TROPICS E OF 105W.
 
ELSEWHERE AT THE LOW LEVELS A RIDGE EXTENDS ALONG 31N140W 
23N117W. 

$$
NELSON