Kinematic and moisture characteristics of a nonprecipitating cold front observed during IHOP. Part I: Across-front structures

A dryline was located to the southeast of the front, separating the hot, dry air mass from a warm, moist air mass composed of 10 m s⁻¹ southerly winds. Later in the afternoon, the warm, moister air moved farther to the northwest, approaching the cold front. The dryline was still well observed in the southwestern part of the observational domain while it vanished almost completely in the northeastern part.

Low-level convergence (~1 × 10⁻³ s⁻¹), vertical vorticity (~0.5 × 10⁻³ s⁻¹), and vertical velocity (~1 m s⁻¹) increased. The strong stable layer located at ~2.0 - 2.5 km MSL weakened in the course of the afternoon, providing a basis for the development of isolated thunderstorms. The applicability of gravity current theory to the cold front was studied.

There was evidence of certain gravity current characteristics, such as Froude numbers between 0.7 and 1.4, a pronounced feeder flow toward the leading edge, and a rotor circulation. Other characteristics, such as a sharp change in pressure and lobe and cleft structures, remain uncertain due to the temporally and spatially variable nature of the phenomenon and the coarse resolution of the measurements.