Reforecasting the November 1994 flooding of Piedmont with a convection-permitting model

TL;DR

This study evaluates a convection-permitting model's ability to simulate the 1994 Piedmont flooding, showing success in reconstructing precipitation structures but limited added value for subsequent rainfall predictions, while highlighting atmospheric moisture transport effects.

Contribution

It demonstrates the effectiveness of a convection-permitting model in reconstructing precipitation structures during a historical flood event and analyzes atmospheric moisture transport impacts.

Findings

Successful reconstruction of precipitation systems on 4th November

No significant added value for 5th November rainfall prediction

Identification of moist air transport influencing flow stability

Abstract

The Piedmont region in Italy was affected by a heavy rainfall event in November 1994. On the 4th convective cells involved the coastal mountains of the region. On the 5th and early 6th, there were abundant precipitations, related to orographic lift and low-level convergences, in the Alpine area. This study aims to evaluate whether a convection-permitting model provides more valuable information with respect to past numerical experiments. Results for the 4th of November show that the cloud-resolving model successfully reconstructs the structure of precipitation systems on the downstream side of the coastal mountains. As regards the precipitations of the 5th of November, no added value is found. However, we provide evidence of the anomalously intense transport of moist air from the tropical and subtropical Atlantic and postulate how such transport is responsible for reducing the stability of the flow impinging on the Alps.