An Operational Technique of Forecasting Thunderstorms Along the Lee Slopes of a Mountain Range

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  • 1 Dept. of Atmospheric Science, Colorado State University, Fort Collins 80521
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Abstract

The lee slopes of the Rocky Mountains from Montana to New Mexico have long been recognized as prime breeding grounds for lee slope thunderstorms. A simple forecast technique is introduced which models the formation of these thunderstorms. It provides the operational meteorologist with an accurate short range forecast tool. Three forecast parameters are used to model thunderstorm development. The Mountain Layer Stability (MLS) measures the stability of the mountain thermal bubbles as they are lifted in the valley breeze circulation. The Max Heating Index (MHI) measures the thermal energy on the plains to trigger lee slopes cumulus into thunderstorms at the time of maximum heating. The Filter Index is used to separate borderline occurrences into a distinct forecast.

Abstract

The lee slopes of the Rocky Mountains from Montana to New Mexico have long been recognized as prime breeding grounds for lee slope thunderstorms. A simple forecast technique is introduced which models the formation of these thunderstorms. It provides the operational meteorologist with an accurate short range forecast tool. Three forecast parameters are used to model thunderstorm development. The Mountain Layer Stability (MLS) measures the stability of the mountain thermal bubbles as they are lifted in the valley breeze circulation. The Max Heating Index (MHI) measures the thermal energy on the plains to trigger lee slopes cumulus into thunderstorms at the time of maximum heating. The Filter Index is used to separate borderline occurrences into a distinct forecast.

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