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Heat burst

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In meteorology, a heat burst is a rare atmospheric phenomenon characterised by gusty winds and a rapid increase in temperature and decrease in dew point (moisture). Heat bursts typically occur during night-time and are associated with decaying thunderstorms.[1]

Although 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 denser than its surroundings.[2] The parcel descends rapidly, warming due to compression, overshoots its equilibrium level and reaches the surface, similar to a downburst.[3]

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.

Some documented cases

  • Salisbury, Maryland, April 26, 2009: Temperatures rose from 77°F to 87 with wind gusts to 52 mph. [4]
  • Sioux Falls, South Dakota, August 3, 2008: Temperatures rose rapidly from the lower 70s °F (21 °C) to 101 °F (38 °C) in a matter of minutes. Winds speeds also rose with gusts up to 50-60 mph (80-100 km/h).[5]
  • Cozad, Nebraska, June 26, 2008: Wind gusts reached 75 miles per hour (121 km/h), as the temperature rose 20 °F (11 °C) in a matter of minutes.[6]
  • Midland, Texas, June 16, 2008: At 11:25 pm a wind gust of 62 mph (100 km/h) occurred, and the temperature rose from 71 °F (22 °C) to 97 °F (36 °C) in minutes.[7] (These measurements were taken from miles away, and theories point to 80–100 mph (128–160 km/h) winds in a 2–3 block perimeter.)[8]
  • Emporia, Kansas, 25 May 2008: Reported temperature jumped from 71 °F (22 °C) to 91 °F (33 °C) between 4:44 am and 5:11 am (CDT)[9] as the result of wind activity from a slow moving thunderstorm some 40 miles (64 km) to the southwest.
  • Canby, Minnesota, 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.[10]
  • Hastings, Nebraska, 20 June, 2006: During the early morning the surface temperature abruptly increased from approximately 75 °F (24 °C) to 94 °F (34 °C).[11][12]
  • Texas Panhandle, June 3, 2002: Heat burst sends temperature from 77 °F (25 °C) to 91 °F (33 °C) at 3:21 am in Amarillo.[13]
  • 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.[14]
  • Oklahoma, May 22–May 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. [15]
  • Kopperl, Texas, 1960: A heat burst sent the air temperature to near 140 °F (60 °C), supposedly causing cotton crops to become desiccated and drying out vegetation.[16]
  • Portugal, July 6, 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 recognized on the Earth is 57.8 °C (136 °F) in Libya in 1922, and the former record has not been verified).[17]

See also

References

  1. ^ Glossary of Meteorology. American Meteorological Society. 2000. ISBN 1878220349.
  2. ^ "Oklahoma "heat burst" sends temperatures soaring". USA Today. Retrieved 2007-05-09. {{cite web}}: Text "1999-07-08" ignored (help)
  3. ^ Johnson, Jeffrey (2003). "Examination of a Long-Lived Heat Burst Event in the Northern Plains". National Weather Digest. 27. National Weather Association: 27–34. {{cite journal}}: Unknown parameter |month= ignored (help)
  4. ^ Heat Burst Strikes Salisbury, MD Saturday Night
  5. ^ Convective Heat Burst moves across Sioux Falls
  6. ^ NTV - KHGI/KWNB/WSWS-CA - Where your news comes first. - Grand Island, Kearney, Hastings, Lincoln | Cozad Witnesses Rare Weather
  7. ^ http://www.mywesttexas.com/articles/2008/06/17/news/top_stories/doc4857af7c54b33314052160.txt
  8. ^ Midland Heat Burst - Damage Survey
  9. ^ "Special Weather Statement". National Weather Service, Topeka, Kansas. Retrieved 2008-05-25.
  10. ^ "Late Night Heat Burst in Western Minnesota on July 16-17, 2006". National Weather Service, Twin Cities. Retrieved 2007-05-09.
  11. ^ History : Weather Underground
  12. ^ Heat Bursts Occur Across South-Central Nebraska Early Tuesday Morning, June 20th.
  13. ^ 03 June 2002 - Amarillo, Texas Heat Burst
  14. ^ Heitkamp. "Tri State Area Heat Burst March 26, 1998". Retrieved 2007-05-09. {{cite web}}: Unknown parameter |coauthors= ignored (|author= suggested) (help); Unknown parameter |publiisher= ignored (|publisher= suggested) (help)
  15. ^ Cappella, Chris (1999-06-23). "Heat burst captured by weather network". USA Today. Retrieved 2007-05-09.
  16. ^ Petricic, Dusan (2000). "It's Raining Eels: A Compendium of Weird Weather". Scientific American Presents: 54–55. ISSN: 1048-0943.
  17. ^ Freaks of the Storm, Randy Cerveny 2006, ISBN 1-56025-801-2
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