A stifling summer heat wave will take over an unusually vast swath of the nation this week.
270 million people, representing 84% of the continental US population, will see peaks above 90 degrees for at least one day this week, and for most, it will be several days. At one point or another, around 150 million people will sweat through heat index numbers of over 100 degrees.
Although the heat wave will be expansive, it will not be very intense, at least at the beginning of the week. However, as the week progresses, the heat dome will focus and intensify, bringing the overall heat rates up from 105 to 115.
During the first half of the week, the core of the heat will be centered over the Great Lakes, the Ohio Valley and the Mid-Atlantic, with high temperatures between 90 and 90 degrees in cities like Detroit, Indianapolis and Washington DC. humidity, it seems that temperatures will reach 100 degrees. The heat during the day will certainly be high, but not many records will drop. This will last at least until Friday.
Meanwhile, the western extent of this heat wave, over the Lower Plain and Mississippi Valley states, will become dominant and develop later in the week through the weekend. Although there are still several days to go, in these areas, the heat wave can become quite severe.
By Thursday afternoon, the heat index values will begin to exceed 105 from Kansas south to Texas and east through Missouri, Arkansas and Louisiana. And it will only get more intense from there.
On Saturday, the heat index values in Oklahoma City, Dallas and Little Rock may approach 100-115 degrees.
This oppressive heat intensity can last a full week, or even longer. The National Weather Service points to a long-lasting period of heat and drought across much of the nation over the next 8 to 14 days, especially in the Southwest states and the plains.
NOAA
A study published a few days ago in Nature Communications shows that, since 1950, heat waves worldwide have become significantly more frequent, last longer, and produce more cumulative heat, making populations more vulnerable to stress from hot.
The figure below shows that the rate of heat wave days and the duration of heat waves, in most regions, is accelerating. The abbreviations on the right represent different regions such as CNA (Central North America), MED (Mediterranean) and Wor (the World).
SE Perkins-Kirkpatrick and SC Lewis 2020
The maps above show the different trends in each region. The map on the left indicates that the amount of heat on a given heat wave day (a day when the temperature exceeds the heat wave threshold) is increasing worldwide, generally by around 2+ degrees Celsius (4 degrees Fahrenheit) in the middle and high latitudes. The map on the right shows the trend by decade, which is increasing in most areas except, ironically, in Central North America.
The reasons for the lack of heat wave trend in the central US are not fully understood, but changes in the jet stream and the cooling impact of increased rainfall are supposed to explain part of it. Furthermore, the heat during the Dust Bowl years of the 1930s was so intense, due in part to damaging land use, that it has not yet been overshadowed, even with human-made climate change.
While these factors have led to few overall heat trends for the central US so far, research indicates that the severe heat waves that helped propel the Dust Bowl are now more than twice as likely. In fact, the next heat wave later this week through this weekend will focus on the Dust Bowl regions of the western lowlands.
This is an area that already faces a significant rainfall deficit. In the past three months, the area has seen less than half the normal amount of rain, and some places are in the middle of its driest stretch on record.
Due to arched terrain in Arizona, three of the state’s largest fires in modern history are burning simultaneously. Lack of rain has resulted in a large “extreme” drought area, with some pockets exceeding the “exceptional” threshold.
With an intense heat dome on the roof, no significant rain is forecast. Over the next ten days, much of the drought-affected area is not expected to receive more than a quarter of an inch of rain.
In a larger picture, this is all part of a long-term drought in the American West, which lasted for the past twenty years. In fact, in a recent studyThe researchers found that the area has now entered one of its worst Megadroughts in the past 1,200 years.
The researchers say that rising temperatures and increased evaporation due to human-caused climate change are responsible for about half the rate and severity of the current drought. With regional temperatures in the West expected to continue to rise, this trend is likely to continue.
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