000
AXPZ20 KNHC 122156
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC TUE AUG 12 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 
2100 UTC.

...SPECIAL FEATURE...

TROPICAL STORM HERNAN IS CENTERED NEAR 18.4N 134.1W AT 2100 UTC 
MOVING W OR 260 DEG AT 08 KT. MAXIMUM SUSTAINED WINDS ARE 35 KT 
WITH GUSTS TO 45 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1005 
MB. SCATTERED MODERATE CONVECTION IS NOTED WITHIN 180 NM NE 
QUADRANT. HERNAN IS RAPIDLY WEAKENING 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 14N116W AND ESTIMATED AT 1008 MB. 
SCATTERED MODERATE ISOLATED STRONG CONVECTION IS NOTED WITHIN 
210 NM NW QUADRANT. THE LOW IS FORECAST TO MOVE WEST-SOUTHWEST 
THROUGH 48 HOURS. 

.LOW PRES IS ANALYZED NEAR 16N102W. SCATTERED MODERATE 
CONVECTION CAN BE FOUND N OF 10N TO THE MEXICAN COAST BETWEEN 
97W AND 108W.  THE SYSTEM IS EXPECTED TO MOVE WEST-NORTHWEST 
OVER THE NEXT 48 HOURS.

...TROPICAL WAVES... 

A TROPICAL WAVE IS ALONG 88W 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 BETWEEN 04N 
AND 13N BETWEEN 86W AND 99W.

...ITCZ...

THE ITCZ AXIS IS ALONG 10N85W TO 12N100W TO 12N102W TO 09N110W 
TO 12N130W TO 10N140W. ASIDE FROM THE CONVECTION MENTIONED ABOVE 
ASSOCIATED WITH A TROPICAL WAVE...SCATTERED MODERATE CONVECTION 
CAN BE FOUND ALONG AND W OF THE TROPICAL WAVE WITHIN 90 NM OF 
AXIS BETWEEN 103W AND 114W.

...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 14N116W. 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 88W 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 77W...WILL MOVE E INTO CENTRAL 
AMERICA OVER THE NEXT TWO DAYS.

$$
SCHAUER CLARK