Observational Strategies for Detecting Rapid Changes in the Immediate Pre-tornadic Environment

It is generally acknowledged that variations in atmospheric moist static energy and vertical wind shear associated with the development of severe thunderstorms can display a variety of time scales prior to convective initiation. It will be demonstrated that extremely rapid, local changes in vertical wind shear, storm-relative helicity, and Convective Available Potential Energy (CAPE) can occur prior to the explosive development of supercell storms, with the most rapid changes occurring on a time scale of 1-2 h being superimposed on a more gradual tendency associated with synoptic-scale processes.  These conclusions are drawn from use of special ground-based remote sensing systems, mobile soundings, and very high-resolution analyses.  Yet, the broader question remains about how such observing systems might optimally be combined with satellite, Unmanned Aircraft Systems (UAS), and other observations.

Reports from the National Research Council and instrumentation workshops have generally recommended that networks of ground-based profiling systems (e.g., microwave and infrared radiometers, Doppler wind profilers and lidars, and water vapor lidars) be developed for monitoring rapid changes in the local severe convective environment.  However, these systems are not inexpensive, require frequent calibration, and are generally limited to cloud-free conditions in the lower troposphere.  Weather radars provide critical information about internal storm structure and processes.  Recent successes using advanced methods for assimilation of Doppler weather radar into convectively permitting numerical prediction models indicates the value of rapidly updated radar data – once storm echoes are present, since radars do not observe the storm environment.  The utility of GOES-R Advanced Baseline Imager and possible future geostationary advanced hyperspectral sounders using results from Observing System Simulation Experiments, as well as emerging UAS technologies using both mobile and fixed-site profiling UAS systems, also will be summarized briefly.  The presentation will conclude with a set of recommendations for systematic experiments that should be conducted.