The relationship of surface pressure features to the precipitation and airflow structure of an intense midlatitude squall line

Abstract

During the formative stage, the pressure field to the rear of the squall line mesohigh is relatively flat with only weak stratiform precipitation present. As the squall line enters the developing-to-mature stages, a pronounced wake low appears at the back edge of the surface stratiform precipitation area. The squall line at this time is characterized by a strong rear-inflow jet, descending from the upper troposphere, as far as 500km behind the leading convective line, to the lower troposphere just behind the line. During the mature-to-dissipating stages, the trailing stratiform region splits into two segments, as does the wake low, with each low pressure center hugging the back edge of the stratiform segments. It is proposed that the wake low, which can be attributed to subsidence warming, is a surface manifestation of the descending rear-inflow jet and that the warming is maximized at the back edge of the trailing stratiform precipitation area where there is insufficient sublimation and evaporative cooling to offset adiabatic warming. -from Authors