[ADEQ Forecasts] ADEQ AIR QUALITY FORECAST FOR WEDNESDAY, JANUARY 21, 2009

[forecasts@lists.azdeq.gov]

http://www.azdeq.gov/environ/air/ozone/ensemble.pdf

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

Health message for Tuesday January 20: Unusually sensitive people should
consider reducing prolonged or heavy exertion. 

Health message for Wednesday January 21: Unusually sensitive people
should consider reducing prolonged or heavy exertion. 
Synopsis and Discussion
Data from the most recent ACARS sounding for Phoenix indicates that the
best mixing depth today will be near 3700' and that dispersion will be
in the FAIR category.  Also, a strong (8-9 deg C) surface-based
radiation inversion that formed overnight reached to 2100' but has since
broken.  In response to the extant stagnant weather conditions, trapped
particle pollutant levels rose significantly this a.m.  Highest hourly
coarse particle (PM-10) concentrations included 198.2ug/m3 at the South
Phoenix monitoring site at 7:00 a.m., and 219.6ug/m3 at the West Forty
Third monitoring site & 208.9ug/m3 at Durango at 8:00 a.m.  Highest fine
particle (PM-2.5) levels reached 37.5ug/m3 at Durango at 8:00 a.m. and
27.2ug/m3 at West Phoenix at 9:00 a.m.  On Wednesday additional warming
aloft, mostly light winds, and considerable middle and high-level cloud
cover will likely contribute to the highest particle pollution levels of
the week.  On Thursday a weak upper level trough is forecast to move
rapidly by from west to east.  It now appears that this system will not
have much punch to it with just a modest increase in surface winds and
only light rainfall amounts expected.  However, it will be accompanied
by enough cooling aloft to improve dispersion and bring a temporary
reprieve from the current elevated pollution levels. Also of note is
that local ozone production has begun to increase in response to higher
sun angles and later sunset times.  The reading of 38 on the Air Quality
Index at Apache Junction on Monday was the highest since November 19
2008. -Reith  

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