Heat Dome Steams Much of U.S.

Over 177 million people in 34 states are talking about the heat dome that is parked over one million square miles of the U.S. and sending temperatures and heat indices into dangerous triple digit territory.

A heat dome is a common summertime occurrence when heating on land occurs faster than over the ocean. This year, drought conditions in Texas and Oklahoma created the perfect conditions for rapid heating and a large dome began forming a few weeks ago. The Jet Stream in the upper atmosphere which usually pushes these high pressure systems across the country within a few days has been stuck up north in Canada, unable to move the growing lid of heat.

Eli Jacks at the National Weather Service tells the Associated Press, “When a high pressure system develops in the upper atmosphere, the air below it sinks and compresses because there’s more weight on top, causing temperatures in the lower atmosphere to heat up.” He adds, “The dome of high pressure also pushes the jet stream and its drier, cooler air, farther north — it’s now well into Canada — while hot, humid air from the Gulf of Mexico circulates clockwise around the dome, traveling farther inland than normal.”

Underneath the lid, people from Kansas to Maine are shriveling as record temperatures fall like dominoes. To add insult to sweaty injury high humidity and almost no wind are making temperatures feel far hotter than they actually are. And on top of all of that misery, there is little relief at night. In fact, since the dome began super-heating the upper mid section of the country, 98 cities set record high nighttime temperatures in the last week while over 1,000 new high temps have been recorded.

Places like Dallas have been trapped under the immobilized high pressure system. There temperatures have been consistently over 100 degrees for 18 days. In Oklahoma City, residents have had only two days this month when temperatures didn’t reach 100. On those days they were 97 and 99.

A few days ago the stagnant mass of hot air began to slowly edge its way east, heating up urban areas in Chicago, Philadelphia, New York and Washington D.C. where high air-conditioner use could create power problems. Already Detroit has begun implementing rolling brown outs.

Over 20 people have been killed by the excessive heat while hundreds have been hospitalized or treated for heat wave related illnesses.

According to NOAA’s State of the Climate report, before this heat wave the first half of 2011 ranked as the 11th warmest January to June period on record. June was the 7th warmest June on record and the 316th consecutive month above the 20th Century average temperature. The last time the average monthly temperature dipped below the 20th Century average was in February 1985.

Extended forecasts show this heat dome shrinking to its northeastern corner offshore of New England by mid next week but then another high pressure system begins to reform in the west, possibly creating a repeat of this sticky situation.