An unusual heat burst occurred shortly after 3 am on the morning April 25, 2012, across the Springfield area. The temperature jumped some 15 to 20 degrees in a matter of 15 to 30 minutes, rising from the middle 50s and low 60s to the middle and upper 70s. The sudden rise in the thermometer was accompanied by a downburst of winds that gusted to near 40 and 50 mph in some locations.
What is a Heat Burst?
Heat bursts are interesting, relatively rare, atmospheric nighttime events characterized by gusty winds, a rapid increase in surface temperature, and a decrease in surface dewpoint associated with a dissipating thunderstorm.
There are two main atmospheric ingredients that are necessary for a heat burst to occur. The first is a dissipating thunderstorm or shower. Second, the midlevel atmospheric environment must be hot and dry, combined with a shallow surface inversion. Thunderstorms develop when moist, unstable air is given a nudge upward. Moisture in the cloud condenses and later falls as precipitation. Once the thunderstorm loses its updraft, the thunderstorm is said to be downdraft dominated. When this occurs with a hot and dry atmospheric midlevel in place, the moisture associated with the downdraft evaporates and initially cools this layer, increasing its rate of descent toward the surface. However, the descending air will stop cooling once all the moisture has evaporated, therefore causing adiabatic (compressional) warming and mixing of the warm (inversion) layer. The heat burst will occur once the warm and dry air descends to the surface.
This is the Doppler radar image at 3:04 am showing rapidly decaying thunderstorms just west of the Springfield metro area.
This is the Doppler radar image showing the velocity or winds in the atmosphere at 3:04 am. The labeled areas in light blue show where winds are around 40 to 50 mph near the ground from these decaying thunderstorms.
A MESONET weather station located near Rogersville reported a temperature rise from 54 degrees to 75 degrees with a peak wind gust of 30 mph shortly after 3 am.
The ASOS weather reporting station located at the Springfield-Branson National Airport reported a temperature rise from 63 degrees to 75 degrees with a peak wind gustof 39 mph shortly after 3 am.
A MESONET weather station located in Battlefield reported a temperatures rise from 65 degrees to 74 degrees with a peak wind gust of 46 mph around 3 am.
A MODOT weather station located at the interchange of I-44 and Highway 65 on the northeast side of Springfield reported a rise in temperature from 66 degrees to 78 degrees with a peak wind gust of 38 mph between 3 am and 4 am.
This is a look at the upper air sounding or weather ballon data from the previous evening. It shows a warm and dry airmass up to 600 mb with an unstable atmosphere above the 600 mb level. This explains why there were high based thunderstorms last night which collasped into warm, dry air and causing a heat burst.