Downbursts from Innocuous Clouds: An Example

McNulty, Richard P.

doi:10.1175/1520-0434(1991)006<0148:dficae>2.0.co;2

Cited by 9 publications

(5 citation statements)

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“…Finally, McNulty (1991) described an incident that occurred on 4 March 1990 in Goodland, Kansas. The National Weather Service (NWS) Office at Goodland reported an apparent microburst at 1048 UTC when a wind gust of 18.3 m s −1 occurred.…”

Section: Historical Overview Of Heatburstsmentioning

confidence: 99%

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A climatological analysis of heatbursts in Oklahoma (1994–2009)

McPherson

Lane

Crawford

et al. 2011

Intl Journal of Climatology

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ABSTRACT:Heatbursts are characterized by a sudden and highly localized increase in air temperature, a simultaneous decrease in relative humidity and dewpoint temperature, and strong gusty winds, typically associated with decaying thunderstorms. The small spatial extent and short duration of most heatbursts makes detailed study of these events difficult using the standard federal observation network (e.g. hourly observations) established in most countries. Thus, many discussions of heatbursts note that they are 'rare' phenomena. However, observations from the Oklahoma Mesonet indicate that although heatbursts are meso-alpha scale phenomena, they are not rare. Using multi-criteria analysis, 207 heatburst events of various magnitudes, areal coverage and duration were identified between 1994 and 2009 across Oklahoma. Significantly more heatbursts were detected in the western two-thirds of the state as compared to the eastern third. Heatbursts were primarily nocturnal events, with 70% of heatburst events initiated between 0000 and 0800 UTC (i.e. between 6 p.m. and 2 a.m. Central Standard Time). With 62 of the 207 events, June was the most active month for heatbursts. At the other extreme, no heatbursts were detected during February and November, and only one was observed during January and December. Almost all of the heatbursts occurred underneath or adjacent to weak radar echoes at the time of the event. Four basic radar patterns were associated with the events: (1) radar echoes associated with rapidly weakening convection, (2) weak reflectivity not produced by or associated with deep moist convection, (3) weak radar echoes to the rear of a dissipating mesoscale convective system (MCS) and (4) weak reflectivity along the periphery of intense convection that did not appear to be weakening.

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Section: Historical Overview Of Heatburstsmentioning

confidence: 99%

“…Most of the documented heatbursts occurred in the Great Plains of the United States during the warm season, typically between 0000 and 1200 UTC, and were associated with weak or dissipating radar echoes (e.g. Cline, 1909; Sloan, 1966; Wood, 1966; Johnson et al , 1989; McNulty, 1991; Johnson, 2004; Trobec, 2008).…”

Section: Introductionmentioning

confidence: 99%

A climatological analysis of heatbursts in Oklahoma (1994–2009)

McPherson

Lane

Crawford

et al. 2011

Intl Journal of Climatology

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“…As the stratiform rain degenerated, this mesohigh rapidly transformed into a strong mesolow (see Johnson et al 1989, their Fig. The existence of unsaturated downdrafts driven by rainfall evaporation has been demonstrated in a well-known modeling study (Brown 1979), and is understood to be the mechanism for both microbursts (McNulty 1991) and heat bursts (Johnson 1983). This transformation was coincident with the appearance of a well-defined cyclonic vortex in visible satellite imagery.…”

Section: Introductionmentioning

confidence: 91%

Patterns of Precipitation and Mesolow Evolution in Midlatitude Mesoscale Convective Vortices

James

Johnson

2010

Monthly Weather Review

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Surface pressure manifestations of mesoscale convective vortices (MCVs) that traversed Oklahoma during the periods May-August 2002-05 are studied using the Weather Surveillance Radar-1988 Doppler (WSR-88D), the Oklahoma Mesonet, and the NOAA Profiler Network data. Forty-five MCVs that developed from mesoscale convective systems (MCSs) have been investigated, 28 (62%) of which exhibit mesolows detectable at the surface. Within this group, three distinct patterns of precipitation organization and associated mesolow evolution have been identified. The remaining 17 (38%) of the cases do not contain a surface mesolow. Two repeating patterns of precipitation organization are identified for the latter group.The three categories of MCVs possessing a surface mesolow are as follows. Nineteen are classified as ''rearinflow-jet MCVs,'' and tend to form within large and intense asymmetric MCSs. Rear inflow into the MCS, enhanced by the development of an MCV on the left-hand side relative to system motion, produces a rearinflow notch and a distinct surface wake low at the back edge of the stratiform region. Hence, the surface mesolow and MCV are displaced from one another. Eight are classified as ''collapsing-stratiform-region MCVs.'' These MCVs arise from small asymmetric MCSs. As the stratiform region of the MCS weakens, a large mesolow appears beneath its dissipating remnants due to broad subsidence warming, and at the same time the midlevel vortex spins up due to column stretching. One case, called a ''vertically coherent MCV,'' contains a well-defined surface mesolow and associated cyclonic circulation, apparently due to the strength of the midlevel warm core and the weakness of the low-level cold pool. In these latter two cases, the surface mesolow and MCV are approximately collocated.Within the group of MCVs without a surface mesolow, 14 are classified as ''remnant-circulation MCVs'' containing no significant precipitation or surface pressure effects. Finally, three are classified as ''cold-pooldominated MCVs;'' these cases contain significant precipitation but no discernible surface mesolow.This study represents the first systematic analysis of the surface mesolows associated with MCVs. The pattern of surface pressure and winds accompanying MCVs can affect subsequent convective development in such systems. Extension of the findings herein to tropical oceans may have implications regarding tropical cyclogenesis.

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“…The acceleration of these downdrafts is initiated and strengthened by negative buoyancy due to precipitation loading (e.g., Proctor 1988;Kingsmill and Wakimoto 1990), diabatic cooling processes including the melting of graupel and hail (e.g., Srivastava 1987;Straka and Anderson 1993), and evaporation of raindrops (e.g., Srivastava 1985;Wakimoto 1985), both of which are related to the amount of precipitation in a volume. The ambient environment is also an important control on the relative efficiency of the diabatic cooling processes generating negative buoyancy, which makes environmental information a crucial component of any conceptual model employed by forecasters to anticipate downbursts (e.g., Atkins and Wakimoto 1991;McNulty 1991).…”

Section: K Dp Cores and Scientific Conceptual Modelsmentioning

confidence: 99%

Using KDP Cores as a Downburst Precursor Signature

Kuster

Bowers

Carlin

et al. 2021

Weather and Forecasting

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Decades of research has investigated processes that contribute to downburst development, as well as identified precursor radar signatures that can accompany these events. These advancements have increased downburst predictability, but downbursts still pose a significant forecast challenge, especially in low-shear environments that produce short-lived single and multicell thunderstorms. Additional information provided by dual-polarization radar data may prove useful in anticipating downburst development. One such radar signature is the KDP core, which can indicate processes such as melting and precipitation loading that increase negative buoyancy and can result in downburst development. Therefore, KDP cores associated with 81 different downbursts across 10 states are examined to explore if this signature could provide forecasters with a reliable and useable downburst precursor signature. KDP core characteristics near the environmental melting layer, vertical gradients of KDP, and environmental conditions were quantified to identify any differences between downbursts of varying intensities. The analysis shows that 1) KDP cores near the environmental melting layer are a reliable signal that a downburst will develop, 2) while using KDP cores to anticipate an impending downburst’s intensity is challenging, larger KDP near the melting layer and larger vertical gradients of KDP are more commonly associated with strong downbursts than weak ones, 3) downbursts occurring in environments with less favorable conditions for downbursts are associated with higher magnitude KDP cores, and 4) KDP cores evolve relatively slowly (typically longer than 15 min), which makes them easily observable with the 5-min volumetric updates currently provided by operational radars.

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Downbursts from Innocuous Clouds: An Example

Cited by 9 publications

References 0 publications

A climatological analysis of heatbursts in Oklahoma (1994–2009)

A climatological analysis of heatbursts in Oklahoma (1994–2009)

Patterns of Precipitation and Mesolow Evolution in Midlatitude Mesoscale Convective Vortices

Using KDP Cores as a Downburst Precursor Signature

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