Heat burst

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Template:Weather In meteorology, a heat burst is a rare atmospheric phenomenon characterized by a sudden, localized increase in air temperature near the Earth's surface. Heat bursts typically occur during night-time and are associated with decaying thunderstorms.[1] They are also characterized by extremely dry air and are sometimes associated with very strong, even damaging, winds.

Although the phenomenon is not fully understood, the event is thought to occur 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, as informally known as "Satan's Storm", have reached well above Template:Convert, sometimes rising by Template:Convert or more within only a few minutes.

Characteristics

In general, heat bursts occur during the late spring and summer seasons. During these times, air-mass thunderstorms tend to generate due to daytime heating and lose their main energy during the evening hours.[4] Due to the potential temperature increase, heat bursts normally occur at night, though they have also been recorded during the daytime. Heat bursts can vary widely in duration, from a couple of minutes to several hours. The phenomenon is usually accompanied by strong gusty winds, extreme temperature changes, and an extreme decrease in humidity. They may occur near the end of a weakening thunderstorm cluster. Dry air and a low-level temperature inversion may also be present during the storm.[5]

Causes

Heat bursts are thought to be caused by a mechanism similar to that of downbursts. As the thunderstorm starts to dissipate, the layer of clouds starts to rise. After the clouds have risen, a rain-cooled layer remains. The cluster shoots a burst of unsaturated air down towards the ground. In doing so, the system loses all of its updraft-related fuel.[6] The raindrops begin to evaporate into dry air, which reinforces the effects of the heat burst (evaporation cools the air, increasing its density). As the unsaturated air descends into lower levels of the atmosphere, the air pressure increases. The descending air parcel warms at the dry adiabatic lapse rate of approximately 10 °C per 1000 meters (18 °F per 1000 feet) of descent. The warm air from the cluster replaces the cool air on the ground. The effect is similar to someone blowing down on a puddle of water.

On 4 March 1990, the National Weather Service in Goodland, Kansas, detected a system that had weakened, containing light rain showers and snow showers. It was followed by gusty winds and a temperature increase. The detection proved that heat bursts can occur in both summer months and winter months, and also that a weakening thunderstorm was not necessary for the development of a heat burst.

Microburst cross section

Forecasting

The first step in forecasting and preparing for heat bursts is recognizing the events that precede them. Rain from a high convection cloud falls below cloud level and evaporates, cooling the air. Air parcels that are cooler than the surrounding environment descend in altitude. Lastly, temperature conversion mixed with a downdraft momentum continues downward until the air reaches the ground. The air parcels then become warmer than their environment.

McPherson, Lane, Crawford, and McPherson Jr. researched the heat burst system at the Oklahoma Mesonet, which is owned by both the University of Oklahoma and Oklahoma State University. The purpose of their research was to discover any technological benefits and challenges in detecting heat bursts, to document the time of day and year at which heat bursts are most likely to occur, and to research the topography of where heat bursts are most likely to occur in Oklahoma.

Scientists and meteorologists use archived data to manually study data that detected 390 potential heat burst days during a fifteen-year period. In studying the archived data, they observed that 58% of the potential days had dry line passages, frontal passages, or a temperature change due to an increase in solar radiation in the hours of the morning or a daytime precipitation weather system.

By studying the archived data, scientists have the ability to determine the beginning, peak, and end of heat burst conditions. The peak of heat burst conditions is the maximum observed temperature. The beginning of a heat burst is the time during which the air temperature increases without decreasing until after the peak; the end of a heat burst is when the system ceases to affect the temperature and dew point of the area.

In addition to researching the life cycle and characteristics of heat bursts, a group of scientists concluded that the topography of Oklahoma coincided with the change in atmospheric moisture between northwest and southeast Oklahoma. An increase in convection normally occurs over the High Plains of the United States during the late spring and summer. They also concluded that a higher increase in convection develops if a mid-tropospheric lifting mechanism interacts with an elevated moist layer.[7]

Documented cases

Date Location Temperature

°F/°C (Initial)

Temperature

°F/°C (Final)

Difference

°F (Max)

Reference(s)
Template:Dts Schertz, Texas Template:Convert Template:Convert 20 °F [8]
Template:DTS Cherokee, Oklahoma Template:Convert Template:Convert 13 °F [9][10]
Template:Dts Georgetown, Texas Template:Convert Template:Convert 17 °F [11]
Template:DTS Durban, South Africa Template:Convert Template:Convert 12 °F [12]
Template:Dts Tracy, Minnesota Template:Convert Template:Convert 13 °F [13]
Template:Dts Beja, Portugal Template:Convert Template:Convert 18.9 °F [14]
Template:Dts Greenville, North Carolina Template:Convert Template:Convert 13 °F [15]
Template:Dts Littleton, Colorado Template:Convert Template:Convert 16 °F [16][17]
Template:Dts Friona, Texas Template:Convert Template:Convert 18.1 °F [18][19][20]
Template:DTS San Antonio, Texas Template:Convert Template:Convert 12 °F [21][22]
Template:DTS Travis AFB, California Template:Convert Template:Convert 20 °F [23]
Template:Dts Edmond, Oklahoma — Template:Convert — [24]
Template:Dts Donna Nook, Lincolnshire, England Template:Convert Template:Convert 18 °F [25]
Template:Dts Chicago, Illinois Template:Convert Template:Convert 7 °F [26][27][28]
Template:Dts Chicago, Illinois Template:Convert Template:Convert 8 °F
Template:DtsTemplate:Efn Hobart, Oklahoma Template:Convert Template:Convert 25.2 °F [29]
Template:Dts Calgary, Alberta Template:Convert Template:Convert 7 °F [30][31][32]
Template:Dts Melbourne, Victoria Template:Convert Template:Convert 16.2 °F [33][34][35]
Template:Convert Template:Convert 14.9 °F
Template:Convert Template:Convert 12.6 °F
Template:Convert Template:Convert 5 °F
Template:Dts Grand Island, Nebraska Template:Convert Template:Convert 19.5 °F [36]
Template:Dts Dane County, Wisconsin — — 10 °F [37]
Template:Dts South Dakota Template:Convert Template:Convert 21 °F [38]
Template:Dts Georgetown, South Carolina Template:Convert Template:Convert 11 °F [39]
Template:Dts Bussey, Iowa Template:Convert Template:Convert 11 °F [40][41]
Template:Dts Torcy, Seine-et-Marne, France Template:Convert Template:Convert 18.9 °F [42]
Template:Dts Atlantic, Iowa Template:Convert Template:Convert 14 °F [43][44][45]
Template:Dts Indianapolis, Indiana — — 15 °F [46]
Template:Dts Wichita, Kansas Template:Convert Template:Convert 17 °F [47]
Template:Dts Buenos Aires, Argentina Template:Convert Template:Convert 6.4 °F [48]
Template:Dts Delmarva Peninsula Template:Convert Template:Convert 19 °F [49]
Template:Dts Edmonton, Alberta Template:Convert Template:Convert 16 °F [50][51][52][53][54]
Template:Dts Sioux Falls, South Dakota Template:Convert Template:Convert 31 °F [55]
Template:Dts Cozad, Nebraska — — 20 °F [56]
Template:Dts Midland, Texas Template:Convert Template:Convert 26 °F [57][58]
Template:Dts Emporia, Kansas Template:Convert Template:Convert 20 °F [59]
Template:Dts Canby, Minnesota — Template:Convert — [60]
Template:Dts Hastings, Nebraska Template:Convert Template:Convert 19 °F [61][62]
Template:Dts Wichita Falls, Texas Template:Convert Template:Convert 11 °F [63][64]
Template:Dts Chickasha, Oklahoma Template:Convert Template:Convert 14.3 °F [65]
Template:Dts Ninnekah, Oklahoma Template:Convert Template:Convert 13.5 °F
Template:Dts Phoenix, Arizona Template:Convert Template:Convert 8 °F [66]
Template:Dts Barcelona, Spain — — 23 °F [67]
Template:Dts Barcelona, Spain — — 23 °F
Template:Dts Kopperl, Texas Template:Convert Template:Convert 65 °F Template:Efn[68]

See also

Notes

Template:Notelist

References

Template:Reflist

External links

  1. ↑ Script error: No such module "citation/CS1".
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  3. ↑ Script error: No such module "Citation/CS1".
  4. ↑ National Weather Service Albuquerque, NM Weather Forecast Office. "Heat Bursts". Retrieved from http://www.srh.noaa.gov/abq/?n=localfeatureheatburst
  5. ↑ Script error: No such module "citation/CS1".
  6. ↑ National Weather Service. Wilmington, North Carolina. "Georgetown Heat Burst." Retrieved from www.weather.gov/ilm/GeorgetownHeatBurst.
  7. ↑ Kenneth Crawford, Justin Lane, Renee McPherson, William McPherson Jr. "A Climatological Analysis of Heat Bursts in Oklahoma (1994-2009)." International Journal of Climatology. Volume 31. Issue 4. Pages 531-544. (10 Mar.).
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  29. ↑ Script error: No such module "citation/CS1".
  30. ↑ Script error: No such module "citation/CS1".
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  33. ↑ Script error: No such module "citation/CS1".
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  35. ↑ Script error: No such module "citation/CS1".
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  37. ↑ Script error: No such module "citation/CS1".
  38. ↑ Script error: No such module "citation/CS1".
  39. ↑ Script error: No such module "citation/CS1".
  40. ↑ Script error: No such module "citation/CS1". Template:Dead link
  41. ↑ Script error: No such module "citation/CS1".
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  47. ↑ http://www.kwch.com/kwch-jab-did-you-feel-this-mornings-heat-burst-20110609,0,5006130.story Template:Dead link
  48. ↑ Script error: No such module "citation/CS1".
  49. ↑ Heat burst erh.noaa.gov Template:Webarchive
  50. ↑ Script error: No such module "citation/CS1".
  51. ↑ Script error: No such module "citation/CS1".
  52. ↑ Script error: No such module "citation/CS1".
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  55. ↑ Script error: No such module "citation/CS1".
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  57. ↑ http://www.mywesttexas.com/articles/2008/06/17/news/top_stories/doc4857af7c54b33314052160.txt Template:Dead link
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  60. ↑ Script error: No such module "citation/CS1".
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  66. ↑ Script error: No such module "citation/CS1".
  67. ↑ ARÚS DUMENJO, J. (2001): "Reventones de tipo cálido en Cataluña", V Simposio nacional de predicción del Instituto Nacional de Meteorología, Ministerio de Medio Ambiente, Madrid, págs. 1-7 Repositorio Arcimís, http://repositorio.aemet.es/handle/20.500.11765/4699 (versión electrónica).[1] [2] [3] [4]
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