The Dryline

1. The Dryline Where will the thunderstorms develop? Some interesting facts and characteristics… Is found roughly 40% of the time over the Plains region during spring and early summer. (Rhea1966; Schaefer 1974; Peterson 1983 Typically, as a whole, advances eastward during the day while retreating west or north-westward during the early and mid evening hours. Commonly forms over the southern Great Plains and has been observed as far north as the Dakotas. (Schaefer 1986) During the day, some areas along the dryline, are often seen to ‘jump’ or advance faster than other areas. These are known as MesoscaleDryline Waves. In addition to terrain, factors such as dry bare ground vs fully vegetated fields, can help influence this behavior. Dryline events may also occur in the fall…where progressively cooler and drier continental air masses, come in contact with low level moisture from the Gulf of Mexico. Moisture depth heading east and southeast of the dryline, increases roughly in steps. The most shallow moisture layer, is along or just to the E and SE from the dryline boundary itself. On 70% of the days when a dryline is present, new radar echoes occur within 400km(216NM) of the dryline. (Rhea 1966)

2. L L Sfc U L very warm dry air moist unstable low level air 18KFT MSL (MID LEVEL) WINDS H