Dryline convergence and the initiation of deep moist convection

For many years it has been known that the enhanced convergence of winds in the boundary layer near the dryline is important for the initiation of deep moist convection in the southern Plains. As a result, any precipitation forecast made relies heavily on whether or not the dryline will be able to provide enough convergence in order to overcome any inhibition present. This paper will attempt to quantify the relationship between the amounts of convective inhibition (CIN) present in an environment and the amount of convergence in the surface winds required to overcome it in order to initiate deep moist convection.

This study looked at days where a dryline was present in western Texas during the spring months of 2004 and 2005. Data from the 45 West Texas Mesonet (Texas Tech University) stations were used to locate the dryline and calculate the convergence along it. A combination of observed and model-forecasted upper air soundings were used to determine how much CIN was present in the dryline environment on a case-by-case basis. Satellite and radar data were then analyzed to relate the above calculations to the success or failure of deep moist convective initiation.

This paper will first show results from two cases, one with deep convection and one without, in order to demonstrate the methodology used. The combined results of the study will then be presented, highlighting relationships that were found between the dryline convergence, CIN, and convective initiation.