A NEW CONCEPTUAL-MODEL FOR CYCLONES GENERATED IN THE LEE OF THE ROCKY-MOUNTAINS

When a shortwave trough moves eastward over the Rocky Mountains and in to the central United States, the following important features may for m: a drytrough (i.e., a lee trough that also has the characteristics o f a dryline), an arctic front, a low-level jet, and two synoptic-scale rainbands (called the cold front aloft rainband and the pre-drytrough rainband) that can produce heavy precipitation and severe weather wel l. ahead of the drytrough. These features are incorporated into a new conceptual model for cyclones in the central United States. Use of thi s model can aid the inter pretation of observational data and numerica l model output, and it may also help to improve short-range forecastin g in the central United States.