WX MODEL 7: CAA sinking


Low level Cold Air Advection (LL CAA) contributes to sinking air. This occurs because cold air is denser than warm air. When warmer lower tropospheric air is replaced with colder denser air, the rest of the troposphere has to sink down as a result. Sinking air contributes to stability. The cold air also will have less moisture which also helps lead to stability. The region of CAA will generally occur on the left side of a trough thus this regions tends to have cooler, drier and more stable weather.

The 700-mb model image below shows vertical velocity. The purple color over Illinois and adjacent regions indicates strong sinking air. Notice this region is on the left side of the trough. The left side of the longwave trough will tend to have lower precipitation chances and below normal temperatures.