The 4 June 1999 Derecho event: A particularly difficult challenge for numerical weather prediction

Date
2005-10-01
Authors
Gallus, William
Correia, James
Jankov, Isidora
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Abstract

Warm season convective system rainfall forecasts remain a particularly difficult forecast challenge. For these events, it is possible that ensemble forecasts would provide helpful information unavailable in a single deterministic forecast. In this study, an intense derecho event accompanied by a well-organized band of heavy rainfall is used to show that for some situations, the predictability of rainfall even within a 12-24-h period is so low that a wide range of simulations using different models, different physical parameterizations, and different initial conditions all fail to provide even a small signal that the event will occur. The failure of a wide range of models and parameterizations to depict the event might suggest inadequate representation of the initial conditions. However, a range of different initial conditions also failed to lead to a well-simulated event, suggesting that some events are unlikely to be predictable with the current observational network, and ensemble guidance for such cases may provide limited additional information useful to a forecaster.

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This article is from Weather and Forecasting 20 (2005): 705, doi: 10.1175/WAF883.1. Posted with permission.

Keywords
Agronomy, atmospheric thermodynamics, climate change, climatology, heat convection, mathermatical models, rain, numerical weather prediction, rainfall forecasts, warm season convective system, weather forecasting, ensemble forecasting, parameterization
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