Comparison of Meteorological Aspects of the Big Thompson and Rapid City Flash Floods

Maddox, Robert A.; Hoxit, Lee R.; Chappell, Charles F.; Caracena, F.

doi:10.1175/1520-0493(1978)106<0375:comaot>2.0.co;2

Cited by 114 publications

(100 citation statements)

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“…Since the vorticity and divergence are small in such a flow while the deformation is large, even in the absence of distinct temperature gradient, heavy precipitation can result from the confluence associated with the deformation, through the focusing effect on moisture. The richness of moisture in the confluence zone provides a favorable condition for moist convection, although the actual triggering of convection is usually provided by something else, such as upper-level lifting by a short-wave trough or weak but still present low-level convergence (Maddox et al, 1978;Hoxit et al, 1978;Caracena et al, 1979;Maddox et al, 1980a,b). These will be discussed in detail for two real precipitation cases in sections 4 and 5.…”

Section: An Idealized Flow Field Modelmentioning

confidence: 99%

Total deformation and its role in heavy precipitation events associated with deformation-dominant flow patterns

2008

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In this paper, it is elucidated that the total deformation (TD), defined as the square root of the sum of squared stretching deformation and squared shearing deformation, is an invariant independent of the coordinate system used. An idealized flow field is then constructed to demonstrate the confluence effect of a non-divergent and irrotational deformation field on moisture transport. To explore the characteristics and role of TD, two heavy rainfall cases associated with a front with shear-line, are analyzed using the WRF model output data. One of the cases occurred in the middle and lower reaches of the Yangtze River (MRYR) over China and the other occurred in north China. It is found that right before the occurrence of precipitation, the effect of the confluence induced by deformation on moisture transport provides a favorable condition for precipitation.During the precipitation, both location and orientation of the zone of large TD coincide with the confluent shear line. The rainbands are nearly parallel with, and located lightly to the south of the zones of large TD and the confluent shear line. The TD in the lower troposphere increases in value as precipitation persists. When TD approaches its maximal value, the next 6-hour precipitation reaches its peak correspondingly.A tendency equation for TD is derived. The analysis of linear correlation and RMS difference between individual terms in the total deformation equation and the sum of the terms shows that the pressure gradient plays a major role in determining the local change of total deformation.

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Section: An Idealized Flow Field Modelmentioning

confidence: 99%

Total deformation and its role in heavy precipitation events associated with deformation-dominant flow patterns

2008

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“…Deep and severe convective events occurring in the vicinity of mountainous regions leading to anomalous rainfall and subsequent flooding, have been the focus of research for a long time due to their often disastrous outcome for human settlements and ecosystems (Maddox et al, 1978;Caracena et al, 1979;Nair et al, 1997;Das et al, 2003Das et al, , 2006Houze et al, 2011;Webster et al, 2011;Rasmussen and Houze, 2012;Rasmussen et al, 2014). Houze et al (2011) identified the occurrence of a synoptic-scale channel of anomalously moist flow towards the mountain barrier in Pakistan (JulyÁ August 2010) to be responsible for the development of very wide precipitating mesoscale convective systems (MCS) producing huge runoff and flooding.…”

Section: Introductionmentioning

confidence: 99%

Improved understanding of an extreme rainfall event at the Himalayan foothills – a case study using COSMO

Shrestha

Dimri

Schomburg

et al. 2015

Tellus A: Dynamic Meteorology and Oceanography

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A B S T R A C TIn recent years, an increased occurrence of loss and damage of property and human casualties over the southern rim area of the Himalayas, caused by landslides following intense rainfall events, has been reported. An analysis of Tropical Rainfall Measuring Mission (TRMM)-gridded rainfall data shows that events with an exceedance probability of 1.6% for 200 mm/d rainfall are common over this region during the monsoon season. An improved understanding of the mechanisms, which lead to such events, is important for their prediction and to estimate the impact of climate change on their recurrence. In this study, we analyse such an extreme precipitation event, which hit the Uttarakhand region of the central Himalayas on 13 September 2012. We use the operational regional weather forecast model COSMO at a convection-permitting resolution of 2.8 km to simulate this event. The spatial pattern of daily-accumulated precipitation and atmospheric state profiles simulated by the model compared well with the TRMM-gridded data and radiosonde observations, which adds confidence to our model results. Our analysis suggests a three-step mechanism leading to this event:(1) development of an easterly low-level wind along the Gangetic Plain caused by a low pressure system over the central Gangetic Plain; (2) convergence of moisture over the north-western part of India, leading to an increase of potential instability of the air mass along the valley recesses, which is capped by an inversion located above the ridgeline; and (3) strengthening of the north-westerly flow above the ridges, which supports the lifting of the potentially unstable air over the protruding ridge of the foothills of the Himalayas and triggers shallow convection, which on passing through adjacent folds initiates deep convection.

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“…Several devastating flash floods in the 1970s (e.g., Rapid City, SD; Big Thompson Canyon, CO; Johnstown, PA) resulted in a needed research emphasis aimed at improved flash flood prediction (e.g., Hoxit et al 1978;Maddox et al 1978). The result of this emphasis has been a better understanding of the synoptic settings associated with excessive rainfall events (Maddox et al 1979). Although many lives have undoubtedly been saved with the improvements in forecasting of these events, flash flood forecasting remains a difficult challenge, and the number of annual fatalities remains high relative to tornadoes or hurricanes.…”

Section: Introductionmentioning

confidence: 99%

Eta Simulations of Three Extreme Precipitation Events: Sensitivity to Resolution and Convective Parameterization

Gallus

1999

Wea. Forecasting

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A versatile workstation version of the NCEP Eta Model is used to simulate three excessive precipitation episodes in the central United States. These events all resulted in damaging flash flooding and include 16-17 June 1996 in the upper Midwest, 17 July 1996 in western Iowa, and 27 May 1997 in Texas. The episodes reflect a wide range of meteorological situations: (i) a warm core cyclone in June 1996 generated a meso-Î²-scale region of excessive rainfall from echo training in its warm sector while producing excessive overrunning rainfall to the north of its warm front, (ii) a mesoscale convective complex in July 1996 produced excessive rainfall, and (iii) tornadic thunderstorms in May 1997 resulted in small-scale excessive rains. Model sensitivity to horizontal resolution is investigated using a range of horizontal resolutions comparable to those used in operational and quasi-operational forecasting models. Sensitivity tests are also performed using both the Betts-Miller-Janjic convective scheme (operational at NCEP in 1998) and the Kain-Fritsch scheme. Variations in predicted peak precipitation as resolution is refined are found to be highly case dependent, suggesting forecaster interpretation of increasingly higher resolution model quantitative precipitation forecast (QPF) information will not be straightforward. In addition, precipitation forecasts and QPF response to changing resolution are both found to vary significantly with choice of convective parameterization. ABSTRACT A versatile workstation version of the NCEP Eta Model is used to simulate three excessive precipitation episodes in the central United States. These events all resulted in damaging flash flooding and include 16-17 June 1996 in the upper Midwest, 17 July 1996 in western Iowa, and 27 May 1997 in Texas. The episodes reflect a wide range of meteorological situations: (i) a warm core cyclone in June 1996 generated a meso-␤-scale region of excessive rainfall from echo training in its warm sector while producing excessive overrunning rainfall to the north of its warm front, (ii) a mesoscale convective complex in July 1996 produced excessive rainfall, and (iii) tornadic thunderstorms in May 1997 resulted in small-scale excessive rains.Model sensitivity to horizontal resolution is investigated using a range of horizontal resolutions comparable to those used in operational and quasi-operational forecasting models. Sensitivity tests are also performed using both the Betts-Miller-Janjic convective scheme (operational at NCEP in 1998) and the Kain-Fritsch scheme. Variations in predicted peak precipitation as resolution is refined are found to be highly case dependent, suggesting forecaster interpretation of increasingly higher resolution model quantitative precipitation forecast (QPF) information will not be straightforward. In addition, precipitation forecasts and QPF response to changing resolution are both found to vary significantly with choice of convective parameterization.

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Comparison of Meteorological Aspects of the Big Thompson and Rapid City Flash Floods

Cited by 114 publications

References 0 publications

Total deformation and its role in heavy precipitation events associated with deformation-dominant flow patterns

Total deformation and its role in heavy precipitation events associated with deformation-dominant flow patterns

Improved understanding of an extreme rainfall event at the Himalayan foothills – a case study using COSMO

Eta Simulations of Three Extreme Precipitation Events: Sensitivity to Resolution and Convective Parameterization

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