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 Action Day
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Air Quality Index (AQI)
observed at 12:00 MST
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Health Message: Unusually sensitive people should consider reducing prolonged or heavy exertion. |
Note: Values above 500 are considered Beyond the AQI. Follow recommendations for the Hazardous category. Additional information on reducing exposure to extremely high levels of particle pollution is available here. |
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Unhealthy for Sensitive Groups |
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Health Message: Active children and adults, and people with lung disease, such as asthma, should reduce prolonged or heavy exertion outdoors. |
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ACTION DAY |
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Moderate |
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Health Message: Unusually sensitive people should consider reducing prolonged or heavy exertion outdoors. |
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Forecast Discussion: [View the ADEQ Hourly Forecast for Phoenix]
Another near ozone exceedance! Tonto National Monument monitor was again the highest at 69 parts per billion (ppb). Second highest was Pinnacle Peak at 66 ppb.
Revisiting the "battlefield" between trough and ridge influence on the Desert Southwest, troughing has been slow to retreat northward, at least for the time being. Winds blowing between 5,000 and 10,000 feet have been breezy and persistent from the west and southwest. This nuance is certainly having a helping hand preventing a buildup of ozone over the metropolitan that would otherwise be available for mixing down during the daytime. Signaling this effect is Humboldt Mountain (that rural high elevation site north of Phoenix). Up on the mountain, higher ozone readings have not been sustaining into the overnight and morning hours. This is good news.
Closer to the surface, though, winds are light and variable until afternoon westerlies kick in. The late morning - early afternoon window of light dispersion in the Valley has given new ozone formation the chance to approach the 70 ppb EPA standard on a daily basis.
The Ozone High Pollution Advisory stands today, however, the forecast takes ozone down below Advisory thresholds tomorrow and going forward. Peak concentrations are kept within Health Watch territory (90-100 AQI). Okay, that covers ozone.
One more thing, it is still monsoon season! There is blowing dust to mention for Thursday afternoon and early evening. Ingredients are coming together for thunderstorms to get close to the city from the south and send gusty outflows our way. Storms in central and southern Arizona can fire up again on Friday. Our latest moment for storm chances is narrow. High pressure is quick to migrate out of the East Pacific this weekend, centering itself over Nevada.
Stay tuned!
J. Malloy
http://azdeq.gov/phoenix/forecast
Last Update: Wednesday, August 21, 2019, 9:24 AM |
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AQI: Good (0 - 50)
AQI: Moderate (51 - 100)
AQI: Unhealthy for Sensitive Groups (101 - 150) 
AQI: Unhealthy (151 - 200) 
AQI: Very Unhealthy (201 - 300)
AQI: Hazardous (301 - 500)
Tribal Boundaries
