Reversible CAPE in Tropical Cyclone Tornado Regimes

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Wednesday, 5 November 2014
Capitol Ballroom AB (Madison Concourse Hotel)
Roger Edwards, SPC/NWS/NOAA, Norman, OK; and R. L. Thompson
Manuscript (553.7 kB)

Tornadic supercells in tropical cyclones (TCs) climatologically occur in environments of large boundary-layer moisture content, beneath weak low–middle-tropospheric lapse rates, and often, high humidity aloft. As such, determining the most physically representative method of analyzing soundings in these environments is crucial, given that small adjustments in thermodynamic conditions can yield changes of 1–3 orders of magnitude in CAPE, introduce CAPE where there was none, or eliminate it altogether. Such environments are typically unsuitable for substantial water loss via evaporation. Furthermore, liquid water is abundant in the TC setting. These conditions call into doubt the assumption inherent in traditional pseudoadiabatic CAPE of complete and irreversible parcel loss of liquid water as a TC supercell processes its high-moisture inflow. Reversible CAPE (RCAPE), by contrast, assumes the opposite extreme: no evaporation and no loss of liquid water.

We analyze and compare CAPE and RCAPE using all available observational proximity soundings within ±2 h and 80 km of TC tornado reports from 1995–2013. This is done via two perspectives: tornado-centric (some TC tornadoes have multiple soundings) and sounding-centric (some soundings have multiple TC tornadoes), each containing ~100 samples.