This study analyzes aboveground thermodynamic observations in three tornadic supercells obtained via swarms of small balloon-borne sondes acting as pseudo-Lagrangian drifters; the storm-relative winds draw the sondes through the precipitation, outflow, and baroclinic zones, which are believed to play key roles in tornado formation. Three-dimensional thermodynamic analyses are produced from the in-situ observations. The coldest air is found at the lowest analysis levels, where virtual potential temperature deficits of 2–5 K are observed. Air parcels within the forward-flank outflow are inferred from their equivalent potential temperatures to have descended only a few hundred meters or less, whereas parcels within the rear-flank outflow are inferred to have downward excursions of 1–2 km. Additionally, the parcels following paths toward the low-level mesocyclone pass through horizontal buoyancy gradients that are strongest in the lowest 750 m and estimated to be capable of baroclinically generating horizontal vorticity having a magnitude of 6−10×10−3 s−1. A substantial component of the baroclinically generated vorticity is initially crosswise, though the vorticity subsequently could become streamwise given the leftward-bending of the air stream in which the vorticity is generated. The baroclinically generated vorticity could contribute to tornado formation upon being tilted upward and stretched near the surface beneath a strong, dynamically forced updraft.

Recent long‐term characterization of the Pacific Intertropical Convergence Zone (ITCZ) shows that the ITCZ has narrowed, which may be due to the enhanced transport of dry air layers from the subtropics. In this study, we examine the relationship between the frequency of midtropospheric dry layers and ITCZ width. European Centre for Medium‐Range Weather Forecasts Reanalysis Interim midtroposphere (400 to 600 hPa) relative humidity is used to create a 36‐year (1979–2014) dry layer climatology for the Pacific ITCZ region. Analysis shows an inverse relationship between ITCZ width and dry layer frequency, with ITCZ width decreasing as the frequency of dry layers increases. Moreover, findings show that the region of greatest long‐term increase in dry layer frequency occurs in the central Pacific, where the greatest narrowing of the ITCZ is also observed.