[ADEQ Forecasts] ADEQ AIR QUALITY FORECAST FOR THURSDAY, AUGUST 21, 2008

[forecasts@lists.azdeq.gov]

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

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

Health message for Wednesday, August 20:  Unusually sensitive people
should consider reducing prolonged or heavy outdoor exertion.
 
Health message for Thursday, August 21:  Unusually sensitive people
should consider reducing prolonged or heavy outdoor exertion. 

Synopsis and Discussion
The current synoptic weather pattern features a deep low and trough in
the mid-latitude storm track over the Pacific Northwest and northern
Rockies and a sub-tropical high off the central Baja coast.  The
resulting flow aloft over Arizona is dry west to northwesterly and
accounts for the very low-grade summer monsoon period now being
experienced.  Models are suggesting that the sub-tropical high will
become re-established near the Four Corners as early as Friday
afternoon, but the amount of moisture available for westward transport
is uncertain.  If local mid-level winds shift to easterly as indicated,
afternoon westerly surface winds would not be quite as prevalent.  A
5-10 mph decrease in said winds usually has a negative impact on the
degree of dispersion of the locally produced ozone plume, with higher
ozone concentrations to follow.  Also, Valley temperatures are expected
to peak near 110 degrees by Friday.  Thus, will continue to call for
highest east Valley ozone concentrations to rise back into the
mid-moderate range of the Air Quality Index.  -Reith

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