000
AXPZ20 KNHC 152208
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC FRI AUG 15 2008

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 
2130 UTC.

...SPECIAL FEATURE...

TROPICAL STORM ISELLE STATIONARY AT 17.6N 111.2W 1004 MB AT 2100 
UTC. MAXIMUM SUSTAINED WIND 35 TO 45 KT. SCATTERED MODERATE TO 
ISOLATED STRONG CONVECTION IS WITHIN 210 NM OF W SEMICIRCLE. 
ISELLE IS FORECAST TO BECOME A TROPICAL DEPRESSION IN THE NEXT 
24 HOUR AS COOL SEA SURFACE TEMPERATURES CUT OFF ITS SOURCE OF 
HEAT AND MODERATE EASTERLY SHEAR TAKE ITS TOLL AGAINST THE DEEP 
CONVECTION. SEE THE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO 
HEADER MIATCMEP5/WTPZ25 KNHC FOR MORE DETAILS.

...TROPICAL LOW...

LOW PRES 15N120W 1011 MB MOVING N AT 5 KT OR LESS. MODERATE 
CONVECTION IS DISPLACED W OF THE LOW WITHIN 120 NM W OF 15N122W. 
DEVELOPMENT OF THIS SYSTEM IS NOT EXPECTED.

...TROPICAL WAVES...

TROPICAL WAVE ALONG 109W FROM 05N TO 14N MOVE W 15 KT. 
CONVECTION IS NOTED 210 NM W OF THE WAVE AXIS BETWEEN 13N AND 
16N. DEVELOPMENT OF THIS SYSTEM IS NOT EXPECTED.

TROPICAL WAVE ALONG 99W FROM 05N TO 15N MOVE W 12 KT. SCATTERED 
MODERATE TO ISOLATED STRONG CONVECTION CAN BE FOUND WITHIN 210 
NM W OF THE WAVE AXIS FROM 06N TO 13N AND WITHIN 330 NM E OF THE 
AXIS S OF 10N. DEVELOPMENT OF THIS SYSTEM IS NOT EXPECTED.

...ITCZ...

ITCZ AXIS IS ALONG 06N77W TO 05N87W TO 10N105W TO 10N110W TO 
09N116W TO 09N126W TO 13N140W. SCATTERED MODERATE ISOLATED 
STRONG CONVECTION IS WITHIN 180 NM N OF AXIS AND 120 S OF AXIS E 
OF 91W AND WITHIN 90 NM OF AXIS FROM 93W TO 105W. SCATTERED 
MODERATE CONVECTION IS WITHIN 90 NM OF AXIS FROM 106W TO 122W. 

...DISCUSSION...

THE UPPER LEVEL MEAN TROUGH OVER NW WATERS IS EXPECTED TO 
MAINTAIN ITSELF NEAR 130W AS REINFORCING SHORTWAVE ENERGY MOVES 
SW FROM THE N CENTRAL PACIFIC PASSING N OF THE AREA TOWARD THE 
MEAN TROUGH AXIS OVER THE NEXT 2 DAYS. THIS TROUGHING WILL HELP 
STEER THE LOW NEAR 14N121W N OF W AND INTO AN ENVIRONMENT OF 
INCREASING VERTICAL SHEAR AND COOLER SEA SURFACE TEMPERATURES 
OVER THE NEXT FEW DAYS.  

STRONG E UPPER LEVEL FLOW ON THE S EDGE OF THE UPPER ANTICYCLONE 
CENTERED OVER NW MEXICO CAN BE FOUND OVER MUCH OF THE REGION 
WITH THE MOST ABUNDANT TROPICAL MOISTURE E OF 120W BETWEEN 13N 
AND 20N. THE VERTICAL SHEAR INDUCED BY THESE STRONG UPPER LEVEL 
WINDS IS CONTRIBUTING TO THE WEAKENING OF T.S. ISELLE AS WELL AS 
INHIBITING CONVECTION WITH THE TROPICAL WAVES OVER THE REGION.  

THE MODERATE TO STRONG CONVECTION NOTED EARLIER NEAR THE MOUTH 
OF THE GULF OF CALIFORNIA HAS WEAKENED AND NOW LIES OVER THE 
BAJA S OF 25N. ELSEWHERE...AFTERNOON TSTMS CURRENTLY MOVING 
TOWARD THE MAINLAND MEXICO COAST BETWEEN 27N AND 30N ARE 
ASSOCIATED WITH A MID LEVEL SHORTWAVE SYSTEM TRIGGERING 
CONVECTION CURRENTLY PASSING JUST S OF THE UPPER LEVEL 
ANTICYCLONE CENTER IN A REGION OF LIGHTER VERTICAL SHEAR AND 
ABUNDANT MOISTURE IN PLACE DUE TO THE EARLIER SOUTHERLY LOW 
LEVEL FLOW E OF ISELLE. EXPECT CONVECTION TO DISSIPATE AS THE 
SYSTEM PASS W.

$$
SCHAUER CLARK