No… it’s not the weather we’ve seen around here lately, although the name might lend itself to this unbearably hot and dry spell we’re currently enduring. A heat burst a phenomenon that happens on a much smaller scale.
If you’ve lived in Tornado Alley for any amount of time at all… you’ve probably heard your local meteorologist mention the term, downburst. It’s really a pretty common event associated with strong thunderstorms. The glossary of the National Weather Service defines a downburst as; “A strong downdraft current of air from a cumulonimbus cloud often associated with intense thunderstorms. Downdrafts may produce damaging winds at the surface.” Many thunderstorms produce these downburst winds, and they can reach severe level wind speeds upwards of 56 mph.
A similar phenomenon that it not as well known is the heat burst and the subject of this webstory.
Meteorologist Jeff Haby, a Geoscience and Meteorology instructor at Mississippi State University says there are two characteristics that separate a heat burst from a downburst. “…the air must start its descent from fairly high up and the environmental air aloft needs to be very dry. Precipitation falling into very dry air aloft will cause the air to cool through latent heat absorption. If the air is very high aloft and the air is much more dense than the surrounding air then it will accelerate toward the surface. In the case of a heat burst, all the precipitation that cooled the air aloft has been vaporized. Therefore, the precipitation can no longer absorb latent heat. As this dense air accelerates toward the surface it rapidly warms at a dry adiabatic lapse rate compression.”
In layman’s terms, a heat burst is a strong downburst of hot air often characterized by a sudden burst of strong, hot and dry wind. This can and does cause temperatures to rise suddenly. This typically occurs at night and many folks believe it to be a rare occurrence.
Operational Meteorologist Dr. David Arnold, an old professor of mine disagrees, asserting, “while the "observance" of heat bursts (i.e. measurable and therefore much easier to report) is relatively rare, their occurrence is likely more common than many people would think.”
Chief Meteorologist Steve Kersh has often observed heat bursts while watching severe weather from the Storm Command Center on several of our schoolnet sites.
“We’ve been able to see that these heat bursts are much more common than previously thought, thanks to our schoolnet site network. We’ve been able to detect and measure them much quicker than before.”
Though not all heat bursts are capable of this kind of impact, Haby says, “The worst heat bursts persist for a significant amount of time and have temperatures that go over 120° Farenheit, even in the middle of the night. This extremely hot and dry air can remain in place for several hours before temperatures return to normal.”
So while most of us will likely not experience one of these heat bursts, it is interesting to note their existence and give you yet another insight into, ‘The Wild, Wild, World of Weather.”
