A rare event known as a "heat burst" caused temperatures in Russell, Kansas last night to soar from 85° to 93° in less than an hour. To the east, Salina hit 95° at 1:00 AM. These phenomena usually occur in unpopulated areas, so not many people have heard of them. So, what is a heat burst, anyway?
A heat burst occurs in the dying stages of a thunderstorm as the storm's updraft — the wind blowing up into the storm to feed it moisture and instability — weakens and the storm begins to collapse.
Sometimes, if there is a dry pocket in the middle of the thunderstorm, precipitation will fall into the dry air and quickly evaporate, which makes this dry air cooler than the air around it. Since cool air is more dense than warm air, it starts to sink towards the ground.
This descending pocket of air speeds up as it enters what is essentially free fall. The pocket of air heats up through compression heating — the pocket is falling into higher atmospheric pressure, so it starts to compress and rapidly warm up — the faster it falls towards the surface.
Eventually, this pocket of hot air hits the ground and spreads out in all directions, creating extremely strong winds and a rapid spike in temperatures that lasts for several hours before returning to where they were before the heat burst.
Last night's heat burst occurred just after 10:00 PM CDT, with the temperature going from 84° at 9:53 PM to 92° at 10:35 PM. As wind gusts exceeded 50 MPH, the temperature continued to climb to a high of 93° at 11:21 PM before starting to fall off. The heat burst actually set the daytime high temperature for June 3 in Russell, which would have been 92° if the event hadn't occurred.
Today's high in Salina, Kansas is only forecast to reach 90°, but its official high will sit at 95° thanks to the heat burst that hit at 1:00 AM.
Several prominent heat burst events have occurred in the past couple of years, including one in Wichita that sent temperatures soaring to 103° just before 1:00 AM on a stormy July night in 2011. Wikipedia has a list of a couple of extreme heat burst events that reportedly caused temperatures to soar to unimaginable levels, including one in Texas in 1960 that drove temperatures up to near 140°.
[Images via Google Maps / FAA / author]