The Vaison-La-Romaine Flash Flood: Mesoscale Analysis and Predictability Issues

Abstract On the morning and early afternoon of 22 September 1992, a flash flood (220 mm of rain in 3 h) occurred in the city of Vaison-La-Romaine, located in southeastern France, causing numerous casualties and considerable property damage. It was generated by a combination of several mesoscale convective systems ahead of a slow-moving cold front associated with a cutoff low. The large-scale setting and a mesoscale analysis of the case, together with estimates of radar-derived rain accumulations, are presented. The mesoscale analysis demonstrates the complexity of the case, which involved five precipitation systems. Orographic influences generated a cold pool and focused convective cell development in a confined area, enabling two precipitation systems to be quasi-stationary. Precipitation forecasts by different versions of two models (a fine mesh version of an operational limited area model, and an operational stretched global model) are summarized. They demonstrate the extent to which realistic rainfall...

[1]  C. Chappell,et al.  Synoptic and Meso-α Scale Aspects of Flash Flood Events1 , 1979 .

[2]  D. McCann.  The Enhanced-V: A Satellite Observable Severe Storm Signature , 1983 .

[3]  R. Maddox.  Meoscale Convective Complexes , 1980 .

[4]  C. Doswell,et al.  Flash Flood Forecasting: An Ingredients-Based Methodology , 1996 .

[5]  Peter Craven,et al.  Smoothing noisy data with spline functions , 1978 .

[6]  Alan R. Moller,et al.  The Operational Recognition of Supercell Thunderstorm Environments and Storm Structures , 1994 .

[7]  L. Battan.  Some Factors Governing Precipitation and Lightning from Convective Clouds , 1965 .

[8]  John A. McGinley,et al.  Validation of a Composite Convective Index as Defined by a Real-Time Local Analysis System , 1991 .

[9]  C. Chappell,et al.  Mesoanalysis of the Big Thompson Storm , 1979 .

[10]  J. Creutin,et al.  Mean K-R Relationships: Practical Results for Typical Weather Radar Wavelengths , 1991 .

[11]  C. Chappell,et al.  Comparison of Meteorological Aspects of the Big Thompson and Rapid City Flash Floods , 1978 .

[12]  C. Chappell.  Quasi-Stationary Convective Events , 1986 .

[13]  Joseph B. Klemp,et al.  Characteristics of Isolated Convective Storms , 1986 .

[14]  Martin A. Uman,et al.  A Gated, Wideband Magnetic Direction Finder for Lightning Return Strokes , 1976 .

[15]  Jean-Francois Geleyn.  On a Simple, Parameter-Free Partition between Moistening and Precipitation in the Kuo Scheme , 1985 .

[16]  Philippe Courtier,et al.  A global numerical weather prediction model with variable resolution: Application to the shallow‐water equations , 1988 .

[17]  R. C. Miller,et al.  A Method for Forecasting Hailstone Size at the Earth's Surface , 1953 .

[18]  P. Bougeault,et al.  A Simple Parameterization of the Large-Scale Effects of Cumulus Convection , 1985 .

[19]  P. Hobbs,et al.  Organization and Structure of Precipitating Cloud Systems , 1982 .

[20]  K. Browning,et al.  Structure and evolution of a mesoscale convective system near the British Isles , 1984 .

[21]  G. Kinzer.  Cloud-to-Ground Lightning Versus Radar Reflectivity in Oklahoma Thunderstorms , 1974 .

[22]  Véronique Ducrocq,et al.  Simulation of an Observed Squall Line with a Meso-Beta-Scale Hydrostatic Model , 1995 .

[23]  R. C. Srivastava,et al.  Doppler Radar Observations of Drop-Size Distributions in a Thunderstorm , 1971 .

[24]  E. Krider,et al.  Lightning and surface rainfall during Florida thunderstorms , 1982 .

[25]  M. Shapiro,et al.  A Review of the Structure and Dynamics of Upper-Level Frontal Zones , 1986 .