EAGER: Opportunistic Soundings to Advance the Understanding of High-Shear Low-CAPE (Convective Available Potential Energy) Convective Environments

Severe convective storms within environments characterized by large vertical wind shear and marginal convective available potential energy (so-called 'high-shear, low-CAPE', or 'HSLC' environments) present a substantial threat to society, and yet they remain poorly understood. Recent studies indicate that a substantial fraction of all severe weather reports, including significant tornadoes (EF2 or greater on the enhanced Fujita scale), occur within HSLC environments. HSLC conditions occur nationwide and throughout the year, but are particularly common during the cool season and overnight, when public awareness of the severe weather threat is low. Storms within HSLC environments also tend to be poorly sampled by radar due to their comparatively small spatial dimensions compared to higher-CAPE convection, with typical echo tops of 4-6 km AGL, and mesocyclones having widths and depths of only 2-4 km. Taken altogether, HSLC storms are a significant concern due to their potential severity, their typical occurrence during non-traditional times of the day and year, and the difficulties they present to radar-based warning operations. The gap in our knowledge base is manifested in terms of the relatively low skill of severe weather watches and warnings for HSLC storms. At the most basic level, HSLC forecasts are hindered because we have very little understanding of the fundamental processes governing HSLC storms and their interactions with the ambient environment. Without targeted observations of HSLC environments, our understanding of HSLC storms is unlikely to improve.

The goal of this application is to undertake a program of local sounding measurements in HSLC environments at high temporal resolution. Operations will exploit the existing North Carolina State University (NCSU) sounding system, which will enable the research team to quickly coordinate launches and to target evolving cases at very low cost. The research team will use the collected data to quantify the environmental variability in HSLC regimes and identify the strengths and weaknesses of other proxy datasets that have heretofore been used for HSLC research.

Intellectual Merit:

HSLC severe weather is an important societal concern that requires further research. Unfortunately, a full basic research project addressing this problem is not likely until a baseline of quality observations has been made. HSLC environments are present for many hours each year, yet their conditional probability of producing severe weather on any given day is relatively low. Thus, rather than mounting an extended field campaign (which would no doubt have an unacceptable amount of 'down time'), the research team will conduct an exploratory work that is inexpensive and is able to opportunistically target the most promising days within a region where HSLC convection is common. The project period will include two distinct cold seasons, maximizing the likelihood of sampling a diversity of HSLC environments during a short grant. This work is potentially transformative because it will produce the first set of temporally dense measurements ever made in HSLC environments, thereby serving as a foundation for future basic science.

Broader Impacts:

All sounding launches will be performed by NCSU students. In addition to incorporating graduate students from the research team, the PI serves as co-advisor for the student-run soundings club at NCSU. These students gain hands-on experience in preparing and launching soundings, as well as analyzing the data collected. Their current funding model only allows them to launch 2-4 soundings per year. The research team will invite the soundings club to participate in all launches, which will greatly enhance the number of available launch opportunities, and will provide educational data from interesting days with severe weather potential. The PI also will incorporate the data (often in near-real time) into his course on Mesoscale Meteorology.