Several investigators have documented the existence of two drylines (DLs) that developed during the afternoon of 3 May 1999. The purpose of this paper is to reexamine the evolution of the DLs. The existence of the DLs is not in question. However, the placement and evolution of the two DLs, as previously analyzed, is refined.

A primary DL extended across central Oklahoma while remaining nearly stationary throughout the day. Prior to an increase in the horizontal moisture differentials across the primary DL, a subtle eastward DL bulge developed over extreme southwestern Oklahoma. The westerly wind surge associated with the bulge appeared to result from isallobaric flow associated with a persistent surface pressure fall center located just east of the primary DL over southwestern Oklahoma. Additionally, the surge and subsequent DL bulge transpired 15-30 min prior to the initiation of "storm B". Of interest, between 2000 and 2300 UTC a DL wave moved north along the primary DL.

The western DL developed rapidly as surface moisture migrated westward out of portions of Oklahoma and the Texas panhandle, over the Texas Caprock, and across the northwestern corner of Oklahoma. In contrast to a previous study, the development of the western DL is believed to have been in response to surface pressure falls over southeastern Colorado and eastern New Mexico. By late afternoon, the western DL rapidly propagated eastward and eventually merged with the primary DL.