The Motion and Predictability of Precipitation Lines

Boucher, Roland J.; Wexler, Raymond

doi:10.1175/1520-0469(1961)018<0160:tmapop>2.0.co;2

Cited by 13 publications

(5 citation statements)

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“…Recent storm-scale experiments have concentrated on the predictability of precipitation and the role that deep, moist convection plays in mesoscale predictability (Zhang et al 2003;Hohenegger and Schä r 2007). Some indirect investigations of MCS predictability consist of attempts to develop forecast aids for existing systems, whether simple extrapolations of the storm movement (Boucher and Wexler 1961) or prediction of system maintenance or decay based on environmental conditions ). Radar-based observational studies (Carbone et al 2002;Germann et al 2006) also suggest the possibility for enhanced predictability on the system scale, if not for individual elements within a convective system.…”

Section: Introductionmentioning

confidence: 99%

On the Predictability of Mesoscale Convective Systems: Three-Dimensional Simulations

Wandishin

Stensrud

Mullen

et al. 2010

Monthly Weather Review

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Mesoscale convective systems (MCSs) are a dominant climatological feature of the central United States and are responsible for a substantial fraction of warm-season rainfall. Yet very little is known about the predictability of MCSs. To help address this situation, a previous paper by the authors examined a series of ensemble MCS simulations using a two-dimensional version of a storm-scale (Dx 5 1 km) model. Ensemble member perturbations in the preconvective environment, namely, wind speed, relative humidity, and convective instability, are based on current 24-h forecast errors from the North American Model (NAM). That work is now extended using a full three-dimensional model.Results from the three-dimensional simulations of the present study resemble those found in two dimensions. The model successfully produces an MCS within 100 km of the location of the control run in around 70% of the ensemble runs using perturbations to the preconvective environment consistent with 24-h forecast errors, while reducing the preconvective environment uncertainty to the level of current analysis errors improves the success rate to nearly 85%. This magnitude of improvement in forecasts of environmental conditions would represent a radical advance in numerical weather prediction. The maximum updraft and surface wind forecast uncertainties are of similar magnitude to their two-dimensional counterparts. However, unlike the two-dimensional simulations, in three dimensions, the improvement in the forecast uncertainty of storm features requires the reduction of preconvective environmental uncertainty for all perturbed variables. The MCSs in many of the runs resemble bow echoes, but surface winds associated with these solutions, and the perturbation profiles that produce them, are nearly indistinguishable from the nonbowing solutions, making any conclusions about the bowlike systems difficult.

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Section: Introductionmentioning

confidence: 99%

On the Predictability of Mesoscale Convective Systems: Three-Dimensional Simulations

Wandishin

Stensrud

Mullen

et al. 2010

Monthly Weather Review

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“…In various observational and analytical studies (e.g., Harper and Beimers (1958), Boucher and Wexler (1961), Boucher (1961), Browning and Ludlam (1962), Yamada (1962), Tatehira and Fukatsu (1963), Tatehira (1964 and, Imakado and Tsutsumi (1966)), the relation between the (1971) and Matsumoto (1972) have revealed that a zone of intense rainfalls appears along the ageostrophic low-level jet stream*.…”

Section: Introductionmentioning

confidence: 99%

Band Structure of Mesoscale Echo Clusters Associated with Low-Level Jet Stream

Ninomiya¹,

Akiyama²

1974

Journal of the Meteorological Society of Japan

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A large echo band, whose length is about 1,000km, developed over the East China Sea adjacent to southwestern Japan on 7 July 1970. The three dimensional structure of the echo band is analyzed by using the data of the Experiment of Severe Rainstorms Research Project.The echo band is associated with strong precipitations and a remarkably developed ageostrophic low-level jet stream. The analyzed moisture field around the jet stream coincides well with the model of the low-level jet's circulation proposed by Matsumoto and Ninomiya (1971). It is inferred about the mechanism of the echo band that the convective mixing of the horizontal momentum in the echo band maintains the ageostrophic low-level jet. The unbalanced solenoidal field caused by the ageostrophic wind field accelerates the vertical circulation and thus maintains the convective activities of the echo band.It is also found that the echo band is not a zone of uniformly distributed echo cells but a row of mesoscale echo clusters whose spacing is about 150km.Two other cases of large-scale echo bands, one over the Pacific coastal area and another over the Midwest of U. S. A., are also presented as similar examples.

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“…Figure 2 shows the movement of the radar echo of the snow band. According to Boucher and Wexler (1961), the movement of a line-shaped precipitation radar echo can be represented by where C is the speed of the line echo, U E the speed of the individual convective echo elements of the line echo, α the angle between the direction of movement of the line echo and the direction of the movements of the echo elements, and C 0 the propagation speed due to the generation and dissipation of the echo elements. In the present case, U E = 54 km h −1 , α = 20°, C = 18 km h −1 , therefore C 0 = 0 km h −1 .…”

Section: Results Of Analysismentioning

confidence: 99%

A case study of snowstorm gusts and blowing/drifting snow

et al. 1993

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The mechanisms of strong winds associated with snow clouds, and the relationship between strong winds and blowing/drifting snow, were investigated. A snowstorm occurred with a typical L-mode snow band which was generated and organized longitudinally during a continental cold-air outbreak over the Sea of Japan. Doppler radar observations revealed that the snow band consisted of small echo cells arranged along the direction of the snow band. When one of the echo cells passed, blowing/drifting snow was generated and intensified by a snow cloud-induced gust, and the horizontal visibility near the ground surface was significantly decreased. Doppler radar and radiosonde data showed that the gust was due to the cold air outflow (CAO) from the snow clouds. The leading edge of the CAO was about 9 km ahead of the center of the snow cloud and the depth of the CAO was about 600 m near the forward flank of the snow cloud. The CAO was caused by a downdraft at the center of the snow cloud, which was initiated at a height of about 1.3 km and with a velocity in excess of 1 ms−1. The observed CAO speed was explained by the theory of the gravity current.

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The Motion and Predictability of Precipitation Lines

Cited by 13 publications

References 0 publications

On the Predictability of Mesoscale Convective Systems: Three-Dimensional Simulations

On the Predictability of Mesoscale Convective Systems: Three-Dimensional Simulations

Band Structure of Mesoscale Echo Clusters Associated with Low-Level Jet Stream

A case study of snowstorm gusts and blowing/drifting snow

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