Mesoanalysis of the Big Thompson Storm

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

doi:10.1175/1520-0493(1979)107<0001:motbts>2.0.co;2

Cited by 116 publications

(93 citation statements)

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“…Rainfall-induced flooding in the Rocky Mountain region of the United States has been well documented (e.g., Michaud et al 2001), including extreme events such as the Rapid City, South Dakota, flash flood of June 1972 that resulted in 220 fatalities, the Big Thompson flash flood of July 1976 (Caracena et al 1979;Maddox et al 1978) that resulted in 144 fatalities, and the Fort Collins flash flood of July 1997 (Petersen et al 1999) that resulted in 5 fatalities and $200 million in damage. Long-term historical data show an event similar to September 2013 took place in the same region in September 1938, though there is little information available on the hydrometeorological details surrounding that event (BASIN 2014).…”

Section: Hydrologic Processes and Impactsmentioning

confidence: 99%

The Great Colorado Flood of September 2013

Gochis

Schumacher

Friedrich

et al. 2015

Bulletin of the American Meteorological Society

198

177

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During the second week of September 2013, a seasonally uncharacteristic weather pattern stalled over the Rocky Mountain Front Range region of northern Colorado bringing with it copious amounts of moisture from the Gulf of Mexico, Caribbean Sea, and the tropical eastern Pacific Ocean. This feed of moisture was funneled toward the east-facing mountain slopes through a series of mesoscale circulation features, resulting in several days of unusually widespread heavy rainfall over steep mountainous terrain. Catastrophic flooding ensued within several Front Range river systems that washed away highways, destroyed towns, isolated communities, necessitated days of airborne evacuations, and resulted in eight fatalities. The impacts from heavy rainfall and flooding were felt over a broad region of northern Colorado leading to 18 counties being designated as federal disaster areas and resulting in damages exceeding $2 billion (U.S. dollars). This study explores the meteorological and hydrological ingredients that led to this extreme event. After providing a basic timeline of events, synoptic and mesoscale circulation features of the event are discussed. Particular focus is placed on documenting how circulation features, embedded within the larger synoptic flow, served to funnel moist inflow into the mountain front driving several days of sustained orographic precipitation. Operational and research networks of polarimetric radar and surface instrumentation were used to evaluate the cloud structures and dominant hydrometeor characteristics. The performance of several quantitative precipitation estimates, quantitative precipitation forecasts, and hydrological forecast products are also analyzed with the intention of identifying what monitoring and prediction tools worked and where further improvements are needed.

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Section: Hydrologic Processes and Impactsmentioning

confidence: 99%

The Great Colorado Flood of September 2013

Gochis

Schumacher

Friedrich

et al. 2015

Bulletin of the American Meteorological Society

198

177

View full text Add to dashboard Cite

show abstract

“…The height of the maximum echo intensity was below the 0°C level (∼3.5 km altitude), suggesting that coalescence was important in the orographic precipitation (Caracena et al, 1979;White et al, 2003). Medina and Houze (2003a) found that the vertical echo structure over the first peak of the terrain seen in IOP 2b was associated with the low-level jet rising abruptly over the peak.…”

Section: Precipitation Growth Processes Determined From the Map Sop Datamentioning

confidence: 99%

“…More highly convective orographic precipitation, of the type that sometimes produces severe convection and flash floods over mountainous terrain in the summer seaons (e.g. Maddox et al, 1978;Caracena et al, 1979) were relatively infrequent during MAP.…”

Section: Pre-sop Findingsmentioning

confidence: 99%

Lessons on orographic precipitation from the Mesoscale Alpine Programme

Rotunno

Houze

2007

Quart J Royal Meteoro Soc

259

279

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Although moisture-laden airflow towards a mountain is a necessary ingredient, the results from the Mesoscale Alpine Programme (MAP) demonstrate that detailed knowledge of the orographically modified flow is crucial for predicting the intensity, location and duration of orographic precipitation. Understanding the orographically modified flow as it occurs in the Alps is difficult since it depends on the static stability of the flow at low levels, which is heavily influenced by synoptic conditions, the complex effects of latent heating, and the mountain shape, which has important and complicated variations on scales ranging from a few to hundreds of kilometres. Central themes in all of the precipitation-related MAP studies are the ways in which the complex Alpine orography influences the moist, stratified airflow to produce the observed precipitation patterns, by determining the location and rate of upward air motion and triggering fine-scale motions and microphysical processes that locally enhance the growth and fallout of precipitation. In this paper we review the major findings from the MAP observations and describe some new research directions that have been stimulated by MAP results.

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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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Mesoanalysis of the Big Thompson Storm

Cited by 116 publications

References 0 publications

The Great Colorado Flood of September 2013

The Great Colorado Flood of September 2013

Lessons on orographic precipitation from the Mesoscale Alpine Programme

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

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