[ADEQ Forecasts] ADEQ AIR QUALITY FORECAST FOR WEDNESDAY, OCTOBER 1, 2008

[forecasts@lists.azdeq.gov]

http://www.azdeq.gov/ensemble.pdf

For transportation alternatives:
http://www.valleymetro.org

Health message for Tuesday, September 30:  Unusually Sensitive People
should consider limiting prolonged exertion outdoors.
 
Health message for Wednesday, October 1:  Unusually Sensitive People
should consider limiting prolonged exertion outdoors.
 
Synopsis and Discussion
    Though it's been 19 days since our last rain (a trace on Sept. 10 at
Sky Harbor), the official Monsoon Season comes to an end today.  It was
the 10th wettest season (June 15-Sept. 30) on record for Phoenix, with
5.70 inches.  August was the best month with 3.55.  The amazing thing is
that this was all at Sky Harbor, which typically gets much less than
other local areas.  The Four Corners high will break down on Thursday,
paving the way for a trough of low pressure to move into the region over
the weekend.  Winds will shift out of the southwest by Friday.  Clouds
could increase a bit on Saturday, but it's not likely that we'll see any
wet stuff this weekend.  Afternoon desert temperatures will drop into
the low to mid 90s by Sunday.
   In the meantime, winds continue to be out of the east.  With the
desert surface drying out rapidly, dust has become an issue.  Though
local Valley PM-10 concentrations were only in the "Moderate" range on
Monday, some areas in Pinal County exceeded the standard.  Further
drying means that we can expect these concentrations to increase over
the next several days here in the Phoenix forecast area.  September 30
also marks the final day of the Ozone Forecast Season (EPA's Ozone
monitoring season runs through the end of October), where the attention
shifts from ozone to particulates.  Over the last six months, we have
seen 44 Ozone Health Watches issued, 11 High Pollution Advisories, and
28 days where at least one monitor exceeded the new Ozone health
standard of 0.075 parts per million (0.076 ppm is an exceedance).  On
these 28 days, 19 different monitors registered 107 exceedances of that
standard.  Had the standard not changed, remaining at 0.084 ppm (0.085
ppm exceeding), we would have only had one exceedance this year!  This
just shows how similar the 2008 forecast season was compared to 2007
where there were no exceedances of the old standard.  
   So what's the next few days look like air quality-wise?  Ozone should
remain in the upper part of the "Good" range while PM-10 increase into
the mid part of the "Moderate" category.  It will be interesting to see
what the shift in winds will do to Particulates this weekend.  We'll
keep an eye on that and more.  Check back tomorrow for the latest.  Have
a good day!  -J.Paul

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