Heat burst
From Wikipedia, the free encyclopedia
A heat burst is a rare atmospheric phenomenon characterised by gusty winds and a rapid increase in temperature and decrease in dew point. Heat bursts typically occur during night-time and are associated with decaying thunderstorms. While this phenomenon is not fully understood, it is theorized that the event is caused when rain evaporates (virga) into a parcel of cold dry air high in the atmosphere making the air more dense than its surroundings.[1] The parcel descends rapidly, warming due to compression, overshoots its equilibrium level and reaches the surface, similar to a downburst.[2] Recorded temperatures during heat bursts have reached well above 90 °F (32 °C), sometimes rising by 20 °F (11 °C) or more within only a few minutes. More extreme events have also been documented, where temperatures have been reported to exceed 130 °F (54 °C), although such extreme events have never been officially verified. Heat bursts are also characterised by extremely dry air and are sometimes associated with very strong, even damaging, winds.
Documented Cases
Emporia, Kansas saw its reported temperature jump from 71 °F (22 °C) to 91 °F (33 °C) between 4:44am and 5:11am (CDT) on 25 May 2008[3] as the result of wind activity from a slow moving thunderstorm some 40 miles to the southwest.
On 16 July 2006, a heat burst formed in Western Minnesota, pushing Canby's temperature to 100 °F (38 °C), and causing a wind gust of 63 mph (55 kn/101 km/h). The dew point fell from 70 °F (21 °C) to 32 °F (0 °C) over the course of one hour.[4]
Hastings, Nebraska experienced a heat burst during the early morning of 20 June 2006 when surface temperatures abruptly increased from approximately 75 °F (24 °C) to 94 °F (34 °C).[citation needed]
Oklahoma, May 22-23, 1996: The temperature in the towns of Chickasha rose from 87.6 °F (31 °C) to 101.9 °F (39 °C) in just 25 minutes, while the temperature at Ninnekah rose from 87.9 °F (31 °C) to 101.4 °F (39 °C) in 40 minutes. In addition, wind damage was reported as winds gusted to 95 mph (83 kn/153 km/h) in Lawton, 67 mph (58 kn/108 km/h) in Ninnekah, and 63 mph (55 kn/101 km/h) in Chickasha. [5]
Minnesota and South Dakota, March 26, 1998: A temperature increase of 10-20 °F (6-11 °C) was reported in the towns of Marshall, Minnesota, Sioux Falls, South Dakota, Brookings, South Dakota, and Montrose, South Dakota during a two-hour period.[6]
In 1960, the town of Kopperl, Texas, experienced a heat burst sending the air temperature to near 140 °F (60 °C), supposedly causing cotton crops to become desiccated and drying out vegetation.[7]
In Portugal in July 1949, a heat burst reportedly drove the air temperature from 38 °C (100 °F) to 70 °C (158 °F) two minutes later (note that the highest temperature formally recognised on the Earth was 57.8 °C (136 °F) in Libya in 1922, and the former record has not been verified).[