[ADEQ Forecasts] ADEQ Issues a Ozone Health Watch for the Phoenix Metro Area for Saturday and Sunday, August 1 - 2, 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 Friday, July 31: Unusually sensitive people should
consider limiting prolonged or heavy exertion outdoors.

Health message for Saturday, August 1: Unusually sensitive people should
consider limiting prolonged or heavy exertion outdoors.


Synopsis and Discussion

 High pressure is on the move... By late Saturday evening, high pressure
will be centered over central Arizona, reaching western New Mexico by
Sunday night.  This will affect the movement of locally generated ozone
this weekend.  With nearly calm winds and very little vertical movement
of the air on Saturday, ozone could pool closer to the Phoenix
metropolitan area with sites like North Phoenix, Central Phoenix, and
South Scottsdale recording the highest levels.  Winds turn out of the
east on Sunday, resisting the natural movement of the ozone plume to the
east.  This could put the target for highest concentrations in the
west-central part of the Valley (Phoenix Supersite, West Phoenix,
Glendale and North Phoenix again).  Both days could see levels approach
the health standard.  For this reason, we are issuing an Ozone Health
Watch for Saturday and Sunday (click here and here for ozone related
information and health effect).  

With high pressure getting into a more favorable Monsoon position,
models suggest a possible moisture surge from the Gulf of California
will take place early Monday morning.  However, they aren't translating
that into significant rainfall yet.  In fact, it may not be until the
second week of August that we see a return to daily thunderstorm
activity state-wide.  Increased moisture means somewhat lower
temperatures (thought it feels just as hot), but not necessarily lower
ozone.  The moisture could weigh down some suspended particulates, but
lack of cleansing rain means we can't expect PM-10 levels to stay in the
Good/low-Moderate range for long.  

Check back on Sunday for the latest ozone concentrations and what you
can expect weather and air quality-wise early next week.  Until then,
have a great weekend!

The Arizona Department of Environmental Quality
Office of Communications
1110 W Washington St, Phoenix, AZ 85007
(602) 771-2215
ms15@azdeq.gov


An Ozone Health Watch means concentrations are expected to approach the
health standard.

An Ozone High Pollution Advisory (HPA) means concentrations are expected
to exceed the health standard.

(Note: the term "Alert" is not used in Phoenix metro area air quality
forecasting)

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