The science behind the heat dome — ‘a mosh pit’ of molecules

This story was originally published by Grist Sign up for Grist s weekly newsletter here From Texas clear to Georgia from the Gulf Coast on up to the Canadian perimeter a mass of dangerous heat has started spreading like an atmospheric plague In the days and perhaps even weeks ahead a high-pressure system known as a heat dome will drive temperatures over degrees Fahrenheit in selected places impacting chosen million Americans Extra-high humidity will make that weather even more perilous while the thermometer may read it might really feel more like So what exactly is a heat dome and why does it last so long And what gives with all the extra moisture A heat dome is a self-reinforcing machine of misery It s a system of high-pressure air which sinks from a inadequate thousand feet up and compresses as it gets closer to the ground When molecules in the air have less space they bump into each other and heat up I think about it like a mosh pit explained Shel Winkley the weather and situation engagement specialist at the research group Atmosphere Central Everybody s moving around and bumping into each other and it gets hotter But these soaring temperatures aren t happening on their own with this heat dome The high pressure also discourages the formation of clouds which typically need rising air There s going to be very little in the way of cloudiness so it ll be a lot of sunshine which in turn will warm the atmosphere even more commented AccuWeather senior meteorologist Tom Kines You re just kind of trapping that hot air over one part of the country In the beginning a heat dome evaporates moisture in the soil which provides a bit of cooling But then the evaporation will significantly raise humidity A major contributor during this month s heat dome will be the swaths of corn crops across the central U S which could help raise humidity in states like Minnesota Iowa and Indiana above that of Florida This sort of high pressure system also grabs moisture from the Atlantic Ocean and Gulf of Mexico which evaporate more water the hotter they get And generally speaking the warmer the atmosphere becomes the more moisture it can hold Once that moisture in the landscape is all gone more heat accumulates and more and more A heat dome then essentially feeds off itself potentially for weeks a sort of giant blow drier pointed at the landscape Related Drought is draining water supplies and driving up food costs where you d least expect On their own temperatures soaring over are bad enough for human soundness Such high humidity makes it even harder for the human body to cool itself because it s harder for sweat to evaporate Hence degrees on the thermometer feeling more like The elderly and very young can t cool their bodies as efficiently putting them at higher vulnerability Those with heart conditions are also vulnerable because the human body tries to cool itself by pumping more blood And those with outdoor jobs construction workers garbage collectors delivery drivers on bikes or scooters have little choice but to toil in the heat with vanishingly limited laws to protect them Read Next After deadly flash floods a Texas town takes halting painful approaches toward recovery Naveena Sadasivam The humidity effect is especially pronounced in areas whose soils are soaked with newest rainfall like central Texas which earlier this month suffered catastrophic flooding There s the probable for compound disasters here relief efforts in inundated areas like Kerr County now have to reckon with soaring temperatures as well The Gulf of Mexico provided the moisture that made the flooding so bad and now it s providing additional humidity during the heat dome A heat dome gets all the more dangerous the longer it stagnates on the landscape And unfortunately situation change is making these sorts of heat waves longer and more intense According to State Central situation change made this heat dome at least five times more likely These temperatures aren t necessarily impossible but they d be very hard to happen without a fingerprint of context change Winkley declared Summer nights are warming almost twice as fast as summer days Winkley adds which makes heat waves all the more dangerous As this heat dome takes hold nighttime low temperatures may go up degrees above average For those without air conditioning or who can t afford to run it even if they have AC their homes will swelter through the night the time when temperatures are supposed to come down and give respite Without that the stress builds and builds especially for those vulnerable groups When you look at this heat wave yes it is going to be uncomfortable during the day Winkley announced But it s especially those nighttime temperatures that are the big blinking red light that this is a state change-boosted event Grist has a comprehensive guide to help you stay ready and informed before during and after a tragedy Explore the full Tragedy pool guide for more on your rights and options when accident hits Are you affected by the flooding in Texas Learn how to deal with tragedy relief and response Get prepared Learn how to be ready for a catastrophe before you re affected This article originally appeared in Grist at https grist org extreme-heat the-science-behind-the-heat-dome-a-mosh-pit-of-molecules Grist is a nonprofit independent media organization dedicated to telling stories of weather solutions and a just future Learn more at Grist org The post The science behind the heat dome a mosh pit of molecules appeared first on MinnPost