[ADEQ Forecasts] ADEQ Issues Air Pollution Health Watch For Wednesday, April 22, 2009

[forecasts@lists.azdeq.gov]

For more information, please visit our Web page:
http://www.azdeq.gov/ensemble.pdf

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


Health message for Tuesday, April 21: Active children and adults and people with respiratory disease, such as asthma, should limit prolonged outdoor exertion.  

Health message for Wednesday, April 22: Unusually sensitive people should consider reducing prolonged or heavy outdoor exertion outdoors.  

Synopsis and Discussion

*AN OZONE HIGH POLLUTION ADVISORY REMAINS IN EFFECT FOR TUESDAY, APRIL 21, 2009,
AND AN OZONE HEALTH WATCH HAS BEEN ISSUED FOR WEDNESDAY, APRIL 22, 2009*

Near triple digit heat will continue Tuesday and Wednesday, with several Valley hotspots likely breaking that century mark Tuesday afternoon.  The unusually warm temperatures (normal high is only 86°F) due to a strong ridge of high pressure, in combination with an increasing sun angle will lead to elevated ozone concentrations across the Phoenix forecast area Tuesday.  The center of the high will continue to slide east through the day, and by evening, the general flow across the region will start to switch out of the southwest rather than the east.  This rebound effect may lead to some higher local ozone concentrations occurring later Tuesday evening after the sun goes down rather than the typical early afternoon spike.  Thus, an Ozone High Pollution Advisory remains in effect for Tuesday.  

The shift in wind flow out of the southwest will allow some of this trapped ozone and precursors to naturally disperse to the east over the next few days.  Thus we should see a downward trend in ozone concentrations through Thursday.  A brief spike may occur Friday ahead of a trough of low pressure that will brush northern Arizona late Friday through Saturday.  No further HPAs or Health Watches are being issued at this time, but a potential transport scenario could change that later this week.  Check back on Wednesday for the latest.  Until then, have a good day!

If you have any questions or comments regarding this forecast please contact:
The Arizona Department of Environmental Quality
Office of Communications
1110 W Washington St, Phoenix, AZ 85007
(602) 771-4583 
communications@azdeq.gov


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