[ADEQ Forecasts] ADEQ AIR QUALITY FORECAST FOR TUESDAY, MAY 19, 2009

[forecasts@lists.azdeq.gov]

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

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

Health message for Monday, May 18: Unusually sensitive people should
consider reducing prolonged or heavy outdoor exertion outdoors. 
Health message for Tuesday, May 19: Unusually sensitive people should
consider reducing prolonged or heavy outdoor exertion outdoors. 
 
Synopsis and Discussion
AN OZONE HEALTH WATCH REMAINS IN EFFECT TODAY
Sunday was another prime example of how a deep easterly wind regime can
impact local ozone concentrations.  Due to a summer monsoon-like weather
pattern featuring an upper level high situated near the Four Corners,
clockwise rotation is producing wind flow from the east & southeast from
the surface all the way to 25K'.  On Sunday winds were mostly light or
calm all day until a dust-bearing outflow boundary from distant
thunderstorms arrived from the south around 8:00 p.m.  This situation
tends to keep the Valley air mass and its pollution constituents in a
near-static environment with above average ozone accumulation, as
evidenced by the clustering of highest ozone levels over the central
metro area.  Meanwhile, mostly clear skies and near-record afternoon
temperatures contributed to above average ozone production.   This
synoptic weather pattern has changed very little, and hourly ozone
levels at 10:00 a.m. today already ranged from 50-64 parts per billion;
thus, today's Ozone Health Watch will remain in effect.  A south to
southwesterly wind component is forecast to become established by
Tuesday afternoon as a weak trough approaches from the west.  This,
along with an increase in cloud cover both Tuesday and Wednesday, should
suppress both ozone production and accumulation with highest readings
shifting to areas northeast and east of the city center.  There will
continue to be a risk for strong thunderstorm outflow winds and areas of
blowing dust thru at least Wednesday.  -Reith  

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