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.

[edit] 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).^[8]

[edit] External links

[edit] References

^ Oklahoma "heat burst" sends temperatures soaring. USA Today. Retrieved on 2007-05-09.
^ Johnson, Jeffrey (December 2003). "Examination of a Long-Lived Heat Burst Event in the Northern Plains". National Weather Digest 27: 27–34. National Weather Association.
^ Special Weather Statement. National Weather Service, Topeka, Kansas. Retrieved on 2008-05-25.
^ Late Night Heat Burst in Western Minnesota on July 16-17, 2006. National Weather Service, Twin Cities. Retrieved on 2007-05-09.
^ Cappella, Chris (1999-06-23). Heat burst captured by weather network. USA Today. Retrieved on 2007-05-09.
^ Heitkamp; Holmes. Tri State Area Heat Burst March 26, 1998. Retrieved on 2007-05-09.
^ Petricic, Dusan (2000). "It's Raining Eels: A Compendium of Weird Weather". Scientific American Presents: 54–55. ISSN: 1048-0943.
^ Freaks of the Storm, Randy Cerveny 2006, ISBN 1-56025-801-2