Intense Tropical Rainfall along Cold Fronts: Numerical Study of the Lesser Antilles Cases
Abstract
Cold fronts passing over the Lesser Antilles are broad oceanic frontal extensions generally centered over the eastern central Atlantic ocean. The southern part of these multiscale systems can bring heavy rainfall (producing more than 200 mm of rain accumulation per day) over the Lesser Antilles, which leads to high risk of flood occurring. Operational forecasters in the Caribbean are still challenged by the lack of model predictability of these high-impact weather phenomenon. That is, temporal and spatial bias in predictions on small scales often make difficult the implementation of an early warning system, and thus slow down responses of potential hazards by local authorities. Besides the difficulty to resolve large terrain changes over short distances in model simulations, confidence in predictions is partly weaken by a (mis)under-representation of physical mechanisms in models. In this study, we attempt to analyze the development of precipitation along cold fronts using high-resolution Weather Research and Forecasting (WRF) model and then investigate precipitation patterns and intensities over a small Caribbean island. Several cumulus parameterizations and surface layer schemes were utilized in order to improve forecast of these cold fronts, and to understand better the impact of atmospheric stability, orography and surface winds on the development of these flooding events over complex terrain islands. In the studied examples, local processes are similar to quasi-stationary cloud clusters. We also show the importance of trade winds, high level jet and stratospheric potential vorticity intrusions on the development of precipitating and non precipitating convection.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2017
- Bibcode:
- 2017AGUFM.A51C2085B
- Keywords:
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- 3307 Boundary layer processes;
- ATMOSPHERIC PROCESSES;
- 3322 Land/atmosphere interactions;
- ATMOSPHERIC PROCESSES;
- 0426 Biosphere/atmosphere interactions;
- BIOGEOSCIENCES;
- 1813 Eco-hydrology;
- HYDROLOGY