A case study of convective initiation along a retrograding dryline

The study of dryline motion and role in convective initiation (CI) has been studied on numerous occasions. Parsons et al (1991) provided a detailed study of the structure of a retrograding dryline using lidar measurements. Research has shown drylines to be a source for CI as they provide a source for moisture convergence in the hot environment of the Southern Great Plains. However, most of the previous studies have analyzed either dryline motion or CI associated with the eastward movement of the dryline. This study presents a case from the International H2O Project (IHOP_2002) in which a retrograding dryline produced isolated storms near the Kansas- Colorado border.

As found in Parsons et al (1991), a dryline retrograding in the late afternoon can have the characteristics of a density current such as a cold front. Storms that initiate from a retrograding dryline form in the dry air to the west and move up and over the boundary, which overruns the moist air to the east. Karan and Knupp (2005, summitted) performed a preliminary kinematic and thermodynamic analysis of this event and found this dryline to have similar characteristics to that of a density current. This study further analyzes the characteristics of the 18 Jun 2002 retrograding dryline and will give potential reasons for CI west of the dryline. Cai (2005, summitted) also studied a retrograding dryline from IHOP_2002, and analyzed why the dryline from that day did not produce CI. This study will compare the dryline from 18 Jun to the dryline studied in Cai et al (2005, summitted) to find any differences that could have produced CI.