Shelby Co. Health Department issues first-ever "Code Purple" air quality alert

Memphis metro residents got an air quality wake-up call that seemed to come out of nowhere today.  A Code Orange Air Quality Alert that has become the norm under hot and stagnant air conditions was raised to Code Red about 4:30pm as ozone levels climbed, then raised again to uncharted territory - a Code Purple alert - two hours later.

Though the unprecedented Code Purple only lasted for about 90 minutes until the sun set, it still seemed to catch many metro residents by surprise.  The overwhelming comment on MWN's Facebook post relaying the information was "wow!"

EPA color-coded air quality forecasts and their health concern level

Shelby County Health Department air pollution meteorologist Mike Goldstein indicated that this was the first ever Code Purple issued for the metro, which includes Shelby County, as well as Crittenden County in east AR and DeSoto County in northwest MS. "Our numbers are ...as high as I’ve seen in many years," Goldstein said.

A Code Purple, which is the second highest of the color-coded air pollution levels, means that the general population, not just those who are in the "sensitive groups" category, could be affected. Ground-level ozone is different from upper-level ozone that people generally think of when referencing a hole in the ozone layer. Low-level ozone is formed when pollutants emitted by cars, power plants, industrial boilers, refineries, chemical plants, and other sources react chemically in the presence of sunlight. Ozone at ground level is a harmful air pollutant.  At Code Purple levels, ozone can cause serious and lasting damage to the lungs.

Diagram courtesy AirNow.gov.

As long as hot high pressure remains over the Mid-South, MWN expects at least Code Orange alerts to be issued daily.  If the right conditions come together, we could see more Code Red days, though hopefully not Code Purple.  You can keep up with the current and forecast air quality levels, as well as tips to help reduce air pollution on the MWN Air Quality page or at AirNow.gov.

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Hazy and hot will be joined by humid - and it's only the beginning of June!

The Mid-South is in the throes of weather normally reserved for August as the 3 H's (heat, haze, and humidity) are combining to make things miserable across the region. The heat began last Saturday as we started a streak of 90-degree days that right now seems to have no end. With a week of 90-degree weather and persistent high pressure aloft sitting directly over the Mid-South, hazy conditions have also joined in.

Humidity has also been on the rise each day, but until today has dropped enough in the afternoons to keep the heat index near or below 100. As the humidity starts to climb though, heat indices will reach 105+ today through the weekend (at least).  This has prompted the issuance of a Heat Advisory through 10pm tonight and we will likely see advisories continue through the weekend as high temperatures remain in the upper 90s into next week.

Interestingly, the earliest 100-degree reading ever seen at Memphis International Airport was on June 6 in 1977.  Though 100 is not in the forecast, there is a small chance we could touch the century mark this weekend.  If we do that, it'll be the earliest 100 degree temperature ever in Memphis.

The hazy part of the 3H formula can be seen in the snapshot from FOX-13's downtown SkyFox cam shown above and is due to increasing levels of ozone and pollution trapped in the lower atmosphere under sinking air created by persistent high pressure overhead.  Without much wind, the pollution sits in place rather than being dispersed. Ozone is chemically created from pollutants from cars, factories, and other industry reacting in the presence of sunlight and heat. It then becomes a pollutant (more on ozone basics).

For today, the level of ozone is forecast by the Shelby County Health Department Air Quality Improvement Branch is high enough that a Code Orange Ozone Advisory has been issued.  Code Orange means that the air is "Unhealthy for Sensitive Groups," including those with respiratory problems under normal circumstances (asthma, lung disease, etc.) and active adults and children and the elderly.  The Health Department urges everyone to reduce time spent outside and limit prolonged exertion, reduce trips and carpool, and schedule outdoor activities in the morning and evening, avoiding the hottest part of the day.

For more information on ozone and air quality, visit the following links:

• MWN's Air Quality Forecast page
• Shelby County Health Department Air Quality Improvement Branch
• AirNow.gov - excellent resource
• EnviroFlash - air quality notifications
• Environmental Protection Agency

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Code Orange Ozone Forecast for Tuesday

AIR QUALITY ALERT MESSAGE
MEMPHIS AND SHELBY COUNTY HEALTH DEPARTMENT
RELAYED BY NATIONAL WEATHER SERVICE MEMPHIS TN
417 PM CDT MON APR 12 2010

...CODE ORANGE OZONE FORECAST FOR TUESDAY...

THE MEMPHIS AND SHELBY COUNTY HEALTH DEPARTMENT HAS ISSUED A CODE ORANGE OZONE FORECAST EFFECTIVE FOR SHELBY COUNTY TENNESSEE... CRITTENDEN COUNTY ARKANSAS... AND DESOTO COUNTY MISSISSIPPI... INCLUDING THE CITY OF MEMPHIS FOR TUESDAY. THIS OZONE FORECAST IS DUE TO FORECASTED OZONE VALUES THAT WILL BE UNHEALTHY FOR SENSITIVE GROUPS. THESE VALUES WILL EXCEED THE ENVIRONMENTAL PROTECTION AGENCYS FEDERAL SAFE HEALTH STANDARD.

THE MEMPHIS AND SHELBY COUNTY HEALTH DEPARTMENT RECOMMENDS THAT SENSITIVE GROUPS WHICH INCLUDE ACTIVE CHILDREN AND ADULTS... AND PEOPLE WITH RESPIRATORY DISEASE... SUCH AS ASTHMA... LIMIT PROLONGED OUTDOOR EXERTION. PLEASE CONTINUE TO CHECK THE LATEST AIR QUALITY FORECASTS AND UPDATES UNTIL MONITORED VALUES RETURN TO SAFE LEVELS. FOR MORE INFORMATION GO TO WWW.SHELBYCOUNTYTN.GOV.

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Additional information regarding this alert can be found at AirNow.gov, as well as from the Memphis/Shelby County Health Department - Pollution Control Division. Air quality forecasts are also available daily at MemphisWeather.net.

Code Orange Ozone Forecast

AIR QUALITY ALERT MESSAGE
MEMPHIS AND SHELBY COUNTY HEALTH DEPARTMENT
RELAYED BY NATIONAL WEATHER SERVICE MEMPHIS TN
338 PM CDT TUE JUL 15 2008

...CODE ORANGE OZONE FORECAST FOR WEDNESDAY...

THE MEMPHIS AND SHELBY COUNTY HEALTH DEPARTMENT HAS
ISSUED A CODE ORANGE OZONE FORECAST EFFECTIVE FOR
SHELBY COUNTY TENNESSEE...CRITTENDEN COUNTY ARKANSAS...
AND DESOTO COUNTY MISSISSIPPI...INCLUDING THE CITY OF
MEMPHIS FOR WEDNESDAY THIS OZONE FORECAST IS DUE TO
FORECASTED OZONE VALUES THAT WILL BE UNHEALTHY FOR
SENSITIVE GROUPS. THESE VALUES WILL EXCEED THE
ENVIRONMENTAL PROTECTION AGENCYS FEDERAL SAFE HEALTH
STANDARD. THE MEMPHIS AND SHELBY COUNTY HEALTH
DEPARTMENT RECOMMENDS THAT SENSITIVE GROUPS WHICH
INCLUDE ACTIVE CHILDREN AND ADULTS...AND PEOPLE
WITH RESPIRATORY DISEASE...SUCH AS ASTHMA...LIMIT
PROLONGED OUTDOOR EXERTION. PLEASE CONTINUE TO
CHECK THE LATEST AIR QUALITY FORECASTS AND UPDATES
UNTIL MONITORED VALUES RETURN TO SAFE LEVELS.
FOR MORE INFORMATION GO TO WWW.SHELBYCOUNTYTN.GOV.