[ADEQ Forecasts] ADEQ ISSUES AIR POLLUTION HEALTH WATCH FOR THURSDAY, JUNE 19, 2008

[forecasts@lists.azdeq.gov]

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

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

Health message for Wednesday, June 18:   Unusually sensitive people
should consider reducing prolonged or heavy outdoor exertion. 

Health message for Thursday, June 19:  Unusually sensitive people should
consider reducing prolonged or heavy outdoor exertion. 

Synopsis and Discussion
AN OZONE HEALTH WATCH HAS BEEN ISSUED FOR THURSDAY JUNE 19
A familiar pattern has become established this week with regards to
local ozone formation.  In the absence of additional ozone/precursor
transport from California, Valley ozone concentrations have ramped up
quickly during the a.m. period, but then leveled off or decreased during
the afternoon.  This decrease tends to be coincident with the onset of
gusty southwest to westerly winds associated with daytime heating and
upslope flow, as well as westerly winds aloft approaching ground level
due to thermals and mixing depths near 15K'.  The source region for much
of these winds is the sparsely populated desert between Phoenix and
Yuma, where little if any precursor emission sources exist.  Subtle
changes can have major impacts;  surface wind speeds are advertised to
be noticeably less on Thursday, with perhaps a later onset as well.  In
addition, the flow aloft will become more conducive for transport from
California, where unhealthy ozone levels are predicted to occur today
and Thursday.  Since the potential exists for increasing production and
accumulation, an Ozone Health Watch has been issued; due to the
prevailing wind direction, locations in the northeast and east metro
area will have the highest risk for elevated ozone readings.  -Reith    

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