7.a.1 Tropical Cyclone Tornadoes – a Research and Forecasting Overview. Part 1: Climatologies, Distribution and Forecast Concepts

Tropical cyclone (TC) tornadoes represent a relatively small subset of total tornado reports, but garner specialized attention in applied research and operational forecasting because of their distinctive origin within the envelope of either a landfalling or remnant TC. As with midlatitude weather systems, the predominant vehicle for tornadogenesis in TCs appears to be the supercell, particularly with regard to significant events. From a framework of ingredients-based forecasting of severe local storms (e.g., Doswell 1987, Johns and Doswell 1992), supercells in TCs share with their midlatitude relatives the fundamental environmental elements of sufficient moisture, instability, lift and vertical wind shear. Many of the same processes – including those involving baroclinicity at various scales – appear to contribute to tornado production in both tropical and midlatitude supercells. TCs do diverge somewhat from extratropical perturbations in supporting tornadic supercell potential, not in the necessity of the aforementioned basic ingredients inasmuch as in their relative magnitudes and spatial juxtaposition.