Southerly Low-Level Jet in the Winter Cyclones of the Southwestern Great Plains

Abstract

On the basis of 20 cases in the winter half year, it is found that a southerly low-level jet (LLJ) is regularly associated with extratropical cyclones in the southwestern Great Plains. Only very weak and short-lived lows are not associated with an LLJ. A composite model is constructed that shows the typical sequence of events during the formation of the LLJ in the Texas-Colorado area. This jet is initially dry since it develops over the continent. Only in the advanced stage (1?2 days after its inception), and as it expands over a wide area, does the LLJ start drawing water vapor from the Gulf of Mexico.