Jump in Sea Level Pressure at 25S 67.5W
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Question: Why is there a jump in MSLP in the Andes (25S, 67.5W) starting 
late 1998?

Answer: Starting late 1998, Reanalysis had to start using a new snow
product as the old (weekly) analyses were being discontinued.  The
new snow-cover analyses included, for the first time, a Southern
hemisphere analysis.  (Previously Reanalysis used climatological snow
for the Southern hemisphere.) For the point in question, the point went 
from snow-free to mostly snow-covered.  The 2m temperature dropped and the
sea-level pressure increased.  Obviously the climatological snow fields 
left something to be desired.  But to be fair, the climatologies were 
computed before the NESDIS snow analyses were available.


See andes.tmp