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July 11, 2011

Today's air unhealthy for everyone

Planning to head out for a jog today? Better skip it. Air pollution levels in the Baltimore region Monday are forecast to reach levels considered unhealthy for everyone, not just vulnerable groups such as children, ther elderly and the sick.

The Maryland Department of the Environment has issued a CODE RED Air Pollution Alert for Carroll, Baltimore, Harford, Howard, Cecil and Anne Arundel Counties, as well as Baltimore City. All Baltimore Haze Camresidents are urged to avoid strenuous activity or exercise outdoors today.

In addition, Clean Air Partners, a consortium of regional governments, private sector and advocacy groups, advises Marylanders to turn off lights and electronics when not in use to reduce electric power demand that contributes to air pollution from power plants; avoid lawn mowing; telecommute or use public transit; avoid using chemicals in your lawn or garden.

UPDATE, 1:50 p.m.: This is the first Code Red prediction from the MDE this year, although pollution levels have reached Code Red threshholds on five previous dates (June 8-10, and July 2 and 5). That's fewer Code Orange-or-worse days than last year at this time, but MDE spokesman Randy Mosier said "this yerar's been a little more intense," with more Code Red violations than last year.

Aircraft flown by the University of Maryland over the weekend detected high ozone levels aloft over Virginia. "With a south southwest flow of air, they know that stuff's coming our way," Mosier said.

Today's Code Red forecast was also spurred by a prediction that the development of a bay breeze today would bring a wall of wind up from the southeast, trapping pollutants along the I-95 corridor, in Harford County in particular. Unless a thunderstorm develops, or cloud cover thickens, "I don't think there's much indication we won't hit those [Code Red] levels," Mosier said.

Earlier post resumes:

A Code Orange Pollution Alert has been posted for Frederick, Montgomery, Prince George's, Charles, St. Mary's and Calvert counties. On the Eastern Shore, the Code Orange alert is extended to Kent. Queen Anne's, Talbot, Caroline, Dorchester, Worcester Wicomico, Somerset and the Maryland beaches.

A Code Orange Alert means the air is unhealthy for vulnerable populations, such as children, the elderly and those with cardiovascular illnesses.

The National Weather Service is predicting high temperatures around 94 degrees Monday at BWI-Marshall Airport. The high could reach 95 degrees in downtown Baltimore. And these forecasts  frequently prove to be too low on hot summer days in Baltimore. Relief coming

In response to the hot-weather forecast, the Baltimore City Health Department has issued a Code Red Heat Alert, opening cooling shelters across the city and sending outreach workers into the community to check on vulnerable residents.

The city has recorded two heat-related deaths so far this season. "Poor air quality combined with high heat and humidity can lead to respiratory distress. It is vitally important that all residents, but especially the elderly, stay cool, drink plenty of clear liquids, avoid alcohol and take it slow if you need to be outside," said Baltimore Health Commissioner Dr. Oxiris Barbot. For more information: 

Tuesday is expected to be even hotter, with highs forecast to reach 97 degrees at BWI and downtown. But the forecast discussion from Sterling this morning says the forecast models are in broad disagreement about that. So there's some chance we could see triple digit temperatures Tuesday afternoon at BWI. 

The record high temperature for Baltimore on a July 12 is 97 degrees, set in 1908. It's relatively low-hanging fruit - the coolest Baltimore record high for any date in July.

At the very least, we run the risk of triple-digit heat index readings as dew points near 70 degrees drive up the humidity side of the equation. That could get us into Heat Index numbers of 105 degrees or more.

Relief (map above) comes in the form of a cold front due to cross the region Tuesday night. That would drop the humidity level as drier air moves in from the northwest. Temperatures would drop a bit, into the mid-to-upper 80s for the balance of the week.

Posted by Frank Roylance at 10:43 AM | | Comments (4)
Categories: Forecasts


Just curious: Why the emphasis on dew points in the forecasts these days? They seem to have taken on more importance than the humidity reading; in some weather broadcasts, they give the dew point and nto always the humidity lately. What's the difference & does one matter more than the other?

FR: Relative humidity is a tricky number to use if you are trying to communicate how sticky the air feels in hot weather. That's because the atmosphere holds more water vapor at higher tempertaures, so RH percentages can mean much more uncomfortable weather, even at numbers that seem fairly low - in the 50 or 60 percent range). Dew points are more useful in hot weather because anything over 70 degrees (some would argue anything over 65 degrees) will always feel very uncomfortable.

Call me old fashioned, or better adept at science, but since I know warmer air can hold more water, the RH readings mean a lot more to me than dew points.

In my opinion, if people can't learn about warmer air having more capacity to hold more moisture, and the more moisture in the air the warmer it feels, it doesn't matter if you give them dew points or RH - they'll tell you "It's all Greek to me."

What does this mean? Immediate danger or cancer in 10 years? Is the air poison? Can you work out outdoors if you have an oxygen tank? Is the polution worse now that in the peak of the industrial revolution on a hot summer's day? Is that why people had shorter life spans? Code Red poses more questions than it answers.

FR: This may help:

Remember that cars and trucks contribute a LOT to bad air. Since there is a strenuous exercise warning, take it easy, but try to:

Walk, ride a bike, take transit, or drive an EV:

Do the right thing by the air.


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About Frank Roylance
This site is the Maryland Weather archive. The current Maryland Weather blog can be found here.
Frank Roylance is a reporter for The Baltimore Sun. He came to Baltimore from New Bedford, Mass. in 1980 to join the old Evening Sun. He moved to the morning Sun when the papers merged in 1992, and has spent most of his time since covering science, including astronomy and the weather. One of The Baltimore Sun's first online Web logs, the Weather Blog debuted in October 2004. In June 2006 Frank also began writing comments on local weather and stargazing for The Baltimore Sun's print Weather Page. Frank also answers readers’ weather queries for the newspaper and the blog. Frank Roylance retired in October 2011. Maryland Weather is now being updated by members of The Baltimore Sun staff

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