US extreme heatwave for July 4: Heat bubbles, thunderstorms.
A sustained blast of heat is expected to bake much of the United States with hotter-than-usual temperatures this holiday weekend, and forecasts suggest that the heat and the humidity could linger for several weeks.
The extreme weather — the first major heat wave of the season — comes as many states are scrambling to contain the rampant spread of the coronavirus and resources are already strained. And though the pandemic presents some unique challenges this summer, experts say these extreme events will continue to pose public health risks because climate change is making heat waves around the world more frequent and more intense.
The upcoming heat is projected to affect huge swaths of the U.S., from eastern New Mexico and Colorado, across the central Plains and into the Northeast.
“The first half of July looks to have well-above-normal temperatures, at pretty high probabilities, beginning around the Fourth of July or slightly before,” said Jon Gottschalck, chief of the Operational Prediction Branch at the National Weather Service’s Climate Prediction Center.
Some places are already sweltering under record conditions. Miami recently had its hottest week ever recorded and posted its 11th consecutive day with a heat index over 103 degrees Fahrenheit, Brian McNoldy, a senior research associate at the University of Miami’s Rosenstiel School of Marine and Atmospheric Science, tweeted Thursday.
Gottschalck said it’s likely that several regions may see heat advisories and excessive heat watches, and he added that warm conditions may persist into the evenings, with little relief from the humidity.
The heat is being driven by the northward shift of the jet stream, which creates a “ridging effect” — a pocket of high pressure that allows for warm, dry conditions at the surface, according to Gottschalck. The impending blast of heat could also create a “ring of fire” weather pattern, in which storms ride along the periphery of the heat dome and trigger severe thunderstorms across the northern Plains, he said.
Current forecasts show that this dome of heat could stick around well into this month.
“Our models indicate that this is going to be somewhat persistent through the first two weeks of July, and potentially longer,” Gottschalck said.
He added that the Climate Prediction Center has been working closely with the Federal Emergency Management Agency (FEMA) and local agencies on how to manage heat waves and other extreme weather events during the coronavirus pandemic.
Some cities, for instance, may not be able to provide relief for vulnerable people in their communities because of social distancing guidelines.
“We’re dealing with such a unique situation, where even if some areas can open up cooling centers and things like that, they’re likely to have limited capacity,” said Julie Caron, a climate scientist at the National Center for Atmospheric Research in Boulder, Colorado. “So now, you could have a vulnerable population that has to make a choice to either stay home and risk the heat, or go to a cooling center and risk exposure to the virus.”
But even without the ongoing pandemic, she said these events are troubling when placed within the context of global warming.
“There’s a long-term warming trend, but we’re also seeing?? an increasing rate of change that’s notable since 2015,” Caron said. “What that means is we’re getting hotter and more frequent heat waves on top of each other.”
These changes can become magnified in the summer, particularly since July is typically when most locations in the contiguous U.S. experience their hottest day of the year.
“You’re exacerbating heat extremes in an already hot season,” Caron said. “That’s why it’s not just about heat waves, necessarily, it’s that we’re seeing hotter-than-normal seasons.”