[ADEQ Forecasts] ADEQ Extends Todays Ozone Health Watch for the Phoenix Metro Area through Wednesday, August 03, 2011

Tue Aug 2 13:04:49 MST 2011

Health message for Tuesday, August 02:  Unusually sensitive people
should consider reducing prolonged or heavy exertion outdoors.
Health message for Wednesday, August 03:  Unusually sensitive people
should consider reducing prolonged or heavy exertion outdoors. 

Synopsis and Discussion
Another near-exceedance of the 8-hour average ozone standard occurred at
the Queen Valley monitoring site on Monday.  This indicates that
afternoon winds have begun to take on a westerly component although
several central city locations had uncomfortably high ozone
concentrations as well.  Believe that locations over the east Valley
will remain most at risk for near-to-unhealthy ozone levels today and
tomorrow due to day-to-day carry-over as well as an increasing afternoon
westerly surface wind component; as a result, the existing Ozone Health
Watch has been extended thru Wednesday.  As of 11:00 a.m. six monitoring
sites had hourly ozone concentrations of 70 parts per billion or higher.
An eventual downward trend in ozone concentrations is still expected
once afternoon westerly winds increase into the 15-20+ mph range since
this situation tends to keep the Valley ozone plume from lingering over
the metro area and usually prevents high accumulation episodes.  
PARTICLES:  A prolonged break in the summer monsoon circulation pattern
will begin on Wednesday for the Phoenix metro area as dry southwesterly
flow aloft returns due to an encroaching upper level trough from the
west.  This means that no local thunderstorm activity or
outflow-boundary generated dust is expected.  In the meantime, low-level
gradients will support breezy to gusty westerly winds each afternoon.

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

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