Revisiting the Texas Coastal Rainstorm of 17–21 September 1979

One of the unique aspects of Lance Bosart’s published studies on extreme rain events is how they highlight the multiscale interactions and rich complexities that act in concert to produce such notable events. His classic paper (Bosart 1984) on the extreme rainstorm along the Texas coast that occurred between 17 and 21 September 1979 represents one such study. In this case, rainfall approaching 500 mm fell over the region during the three-day period ending at 1200 UTC 20 September. Lance’s analysis showed that extreme rain fell in response to persistent coastal frontogenesis in the presence of an upper-level trough to the west, a remnant low-level baroclinic zone left behind by a previous synoptic-scale weather system, and a mesoscale circulation that formed on the southern end of this baroclinic zone that briefly reached tropical storm strength. Lance also pointed out that Tropical Storm Henri, which was located in the Bay of Campeche at the time, may have played an important role in supplying moisture for the Texas rain event.

As a tribute to Lance, the aim of this presentation is to re-examine the Texas coastal rainstorm case from a multi-scale perspective using modern datasets, numerical simulation, and conceptual models. Cursory examination of the Climate Forecast System Reanalysis dataset suggests that a southeasterly moisture plume that resembled an atmospheric river extended from Henri to the heavy rain region. This initial result suggests that this event may have been a predecessor rain event. We will also examine the spin-up of the mesoscale vortex on the southern end of the baroclinic zone in the context of modern views on tropical cyclogenesis in a baroclinic environment.