[ADEQ Forecasts] ADEQ Daily Air Quality Forecast for Wednesday, August 19, 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, August 18: Unusually sensitive people should
consider reducing prolonged or heavy exertion outdoors.
 
Health message for Wednesday, August 19: Unusually sensitive people
should consider reducing prolonged or heavy exertion outdoors.


Synopsis and Discussion
The summer monsoon sub-tropical high has again been suppressed well
south of its usual position by an anomalously active mid-latitude storm
track.  Deep moisture exists over Mexico but is only slowly working its
way north once more.  It now appears that there will be no local outflow
boundaries/blowing dust episodes until Thursday evening at the earliest,
so particle pollution levels will remain mostly in the good range of the
Air Quality Index.  As the high center ostensibly moves farther north
this week, a deeper easterly wind regime aloft may become established.
One forecast model shows that this will occur in the 10-20K' layer as
early as Friday morning.  The closer to ground level this happens the
higher the risk for unhealthy ozone levels due to afternoon ozone
accumulation.  In the meantime, westerly winds in the 5-10K' layer are
expected to peak on Wednesday then weaken some on Thursday, and this
cycle of forecast ozone levels have taken this into account.  Latest Sky
Harbor Airport AMDAR soundings show that although winds near ground
level are relatively light, in the 5-15K' layer they are south to
southwesterly in the 10-20 mph range.  With today's mixing depth around
12K', it should be another breezy afternoon and highest ozone readings
should again tend to congregate in downwind locations.

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) 771-2215
ms15@azdeq.gov      

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