000
AXPZ20 KNHC 121525
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC TUE AUG 12 2008

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

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1430 UTC.

...SPECIAL FEATURE...

TROPICAL STORM HERNAN IS CENTERED NEAR 18.3N 133.6W AT 1500 UTC 
MOVING W OR 260 DEG AT 08 KT. MAXIMUM SUSTAINED WINDS ARE 40 KT 
WITH GUSTS TO 50 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1002 
MB. SCATTERED MODERATE CONVECTION IS NOTED WITHIN 90 NM NE 
QUADRANT. HERNAN IS FORECAST TO GRADUALLY WEAKEN AS IT PASSES 
WEST-SOUTHWEST. SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO 
HEADER MIATCMEP4/WTPZ24 KNHC FOR MORE DETAILS.

...TROPICAL LOWS...

.LOW PRES IS ANALYZED NEAR 13N115W AND ESTIMATED AT 1008 MB. 
SCATTERED MODERATE ISOLATED STRONG CONVECTION IS NOTED FROM 14N 
TO 16N BETWEEN 115W AND 117W. THE LOW IS FORECAST TO MOVE 
WEST-SOUTHWEST THROUGH 48 HOURS. 

.BROAD LOW PRES OVER THE PACIFIC WATERS IS ANALYZED AS A SURFACE 
TROUGH FROM 12N102W TO 17N99W. SCATTERED MODERATE CONVECTION CAN 
BE FOUND N OF 15N TO THE MEXICAN COAST BETWEEN 99W AND 102W.  
WHILE THE SYSTEM IS EXPECTED TO PINCH OFF A CLOSED CIRCULATION 
AGAIN OVER THE NEXT 24 HOURS...ANY FURTHER DEVELOPMENT WITH THIS 
SYSTEM IS EXPECTED TO BE SLOW TO OCCUR AS IT MOVES 
WEST-NORTHWEST OVER THE NEXT 48 HOURS.

...TROPICAL WAVES... 

A TROPICAL WAVE IS ALONG 86W AT THE MOMENT AND HAS BEEN MOVING W 
AT ABOUT 16 KT THE PAST 24 HOURS. SCATTERED MODERATE ISOLATED 
STRONG CONVECTION IS NOTED W OF THE TROPICAL WAVE TO THE N OF 
04N BETWEEN 84W AND 89W.

...ITCZ...

THE ITCZ AXIS IS ALONG 09N84W TO 09N88W TO 12N102W TO 08N115W TO 
13N125W TO 09N140W. AS MENTIONED ABOVE ASSOCIATED WITH A 
TROPICAL WAVE...SCATTERED MODERATE CONVECTION CAN BE FOUND ALONG 
AND W OF THE TROPICAL WAVE WITHIN 180 NM N AND 270 NM S OF AXIS 
BETWEEN 87W AND 90W.

...DISCUSSION...

TROPICAL STORM HERNAN IS FORECAST TO MOVE WEST-SOUTHWEST OVER 
THE NEXT TWO DAYS...CROSSING 140W ON THU...AS IT PASSES S OF THE 
SURFACE HIGH PRESSURE NEAR 34N138W. AN UPPER TROUGH CURRENTLY 
SKIRTING THE FAR NW WATERS N OF HERNAN IS FORECAST TO WEAKEN AS 
IT LIFTS NE. THIS TROUGH SHOULD PUSH THE DEEP LAYERED RIDGE AXIS 
TO THE N OF HERNAN TO NEAR 20N115W SOUTHWARD OVER THE NEXT 48 
HOURS...YIELDING THE ANTICIPATED S OF W MOTION FOR HERNAN AS 
WELL AS THE SURFACE LOW PRESSURE SYSTEM NEAR 13N115W. THIS 
TROUGH SHOULD ALSO INFLUENCE THE UPPER LOW CURRENTLY NEAR 
22N120W N ALONG 120W WED AND THU.    

THE UPPER LEVEL ANTICYCLONE CURRENTLY CENTERED NEAR THE NW 
MEXICO/ARIZONA BORDER IS EXPECTED TO MIGRATE SE OVER THE NEXT 
TWO DAYS...SHIFTING THE DEEP LAYERED E FLOW S OF THE ANTICYCLONE 
FARTHER S OVER MEXICO. AT THE SAME TIME...THE TROPICAL WAVE 
CURRENTLY ALONG 86W WILL PASS S OF THE MEXICAN RIDGE. EXPECT AN 
INCREASE IN AVAILABLE MOISTURE AND MID LEVEL VORTICITY 
ASSOCIATED WITH THE TROPICAL WAVE TO MOVE NW THROUGH CENTRAL 
AMERICA...INCREASING THE CHANCE OF CONVECTION. THIS...COUPLED 
WITH E FLOW ON THE N EDGE OF THE TROPICAL WAVE...MAY ALLOW 
AFTERNOON TSTMS OVER LAND TO PUSH W OFFSHORE WED/THU. A SECOND 
TROPICAL WAVE...CURRENTLY ALONG 75W...WILL MOVE E INTO CENTRAL 
AMERICA OVER THE NEXT TWO DAYS.

$$
SCHAUER CLARK