000
AXPZ20 KNHC 180924
TWDEP 

TROPICAL WEATHER DISCUSSION     
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC SAT AUG 18 2007

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 
0845 UTC.

...TROPICAL WAVES...

TROPICAL WAVE ALONG 83W MOVING W AT 10 TO 15 KT. ISOLATED 
CONVECTION JUST OFF THE COSTA RICAN COAST.  

TROPICAL WAVE ALONG 110W N OF 6N MOVING W AT 10 TO 15 KT. LARGE 
CLUSTER OF STRONG CONVECTION NEAR THE MEXICAN COAST AT 23N107W. 
OTHER SCATTERED CONVECTION NEAR THE WAVE AXIS BUT NO 
ORGANIZATION. 

A TROPICAL WAVE ALONG 133W FROM 6N TO 16N MOVING W AT 15 KT. NO 
EVIDENCE OF THIS WAVE. 

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 10N83W 8N91W 16N108W 12N120W 11N131W 
11N140W. ISOLATED STRONG CONVECTION NEAR 5N80W. SCATTERED 
MODERATE WITHIN 45 NM EITHER SIDE OF A LINE FROM 9N86W TO 
10N103W. SCATTERED STRONG WITHIN 90 NM OF 12N112W. SCATTERED 
MODERATE NEAR 11N123W AND 11N137W. 

SCATTERED STRONG NEAR 14N92W AND WITHIN 60 NM OF 18N110W. 
CLUSTER OF STRONG CONVECTION CENTERED NEAR 23N107W.

...DISCUSSION...

LARGE MID LEVEL RIDGE OVER SRN CONUS TONIGHT EXTENDS W TO 115W. 
SECONDARY RIDGE CENTER OVER WRN PORTION OF AREA TONIGHT CENTERED 
NEAR 25N145W. IN BETWEEN THE TWO A WEAKNESS EXISTS IN THE PRES 
FIELD AND A STRONG TROUGH TO THE N CONTINUES TO WORK INTO THIS 
AREA ALONG 130W AND AN INVERTED TROUGH ALONG 122W CONTINUES TO 
DRIFT NW. ON THE SURFACE TONIGHT THE PACIFIC RIDGE EXTENDS SE 
OVER THE AREA TO 115W AND IS PRODUCING N AND NE TRADES TO 20 KT 
N OF 12N AND W OF 120W. WINDS ALONG THE BAJA COAST REMAIN LIGHT 
NWLY. A WEAK LOW WAS NEAR 15N109W MOVING SLOWLY NW. GAP WINDS 
REMAIN LIGHT WHILE CROSS EQUATORIAL SLY WINDS TO 20 KT ARE 
EVIDENT BETWEEN 105W AND 125W S OF 12N ACCORDING TO SSMI 
IMAGERY. 

LATER DAY 1 A SHORTWAVE TROUGH DROPS SE INTO THE BASE OF THE MID 
LEVEL TROUGH..LOWERING MID LEVEL HEIGHTS ALONG 128W. THE 
INVERTED TROUGH RESPONDS BY LIFTING NW SLIGHTLY. ANYWAY..IT 
SERVES TO MAINTAIN A WEAKNESS IN THE PRES FIELD BETWEEN 115W AND 
135W. ON THE SURFACE LATER DAY 1 LITTLE CHANGE TO THE PACIFIC 
RIDGE AND NE TRADES CHANGE LITTLE. THE WEAK LOW DRIFTS NW TO 
NEAR 19N121W CAUGHT UNDER THE INVERTED TROUGH ALOFT. WINDS OVER 
THE REGION REMAIN ABOUT THE SAME.

FOR DAY 2 NOT MUCH LEFT OF THE SHORTWAVE THAT DROPPED INTO THE 
BASE OF THE MID LEVEL TROUGH. GFS MODEL SHOWS IT CAPTURED BY THE 
INVERTED TROUGH WITH THE WHOLE SYSTEM CONTINUING WWD TO 130W. 
ANYWAY BOTH RIDGES REMAIN IN PLACE WITHE A WEAKNESS IN THE PRES 
FIELD CONTINUING BETWEEN 120W AND 137W. ON THE SURFACE DAY 2 THE 
PACIFIC RIDGE WEAKENS ABOUT 4 MB WITH NE TRADES DECREASING 
SLIGHTLY. THE WEAK LOW CONTINUES TO DRIFT NW TO NEAR 21N123W 
WITH MOSTLY LIGHT WINDS. GAP WINDS REMAIN LIGHT. CROSS 
EQUATORIAL SLY WINDS MOSTLY LESS THAN 20 KT BUT SLY SWELL TO 8 
FT WILL CONTINUE S OF 10N.

$$
RRG