A Systematic Warning Approach for Quasi-Linear Convective System Mesovortices (48)

Jason Schaumann, NOAA/NWS, Springfield, MO

John Gagan, NOAA/NWS

Jacob Beitlich, NOAA/NWS

 

Abstract:

Quasi-linear convective systems (QLCSs) remain a formidable challenge to warning decision-makers (WDMs) for a variety of reasons. Mesovortex tornadoes spawned by QLCSs may present the greatest challenge to WDMs given their propensity to rapidly develop in seemingly random fashion. Additionally, QLCS structures and radar features are not well understood by many WDMs, especially those which signify an increased likelihood for mesovortex genesis and tornadoes. This is likely due to an overall lack of training on these topics. To further compound matters, differing opinions exist regarding the proper way to &ldquowarn&rdquo on QLCS tornadoes.

Research within the National Weather Service (NWS) Central Region (CR) has resulted in the development of a comprehensive warning system for QLCS mesovortices. This system features three foundational components:

1) Identifying portions of a QLCS where mesovortices are favored based on the shear/cold pool balance regime, 0 to 3 km line-normal bulk shear, and the presence of surges or bows

2) Identifying key mesoscale and radar signatures in favored mesovortex regions, known as confidence builders and nudgers, which indicate an increased likelihood for tornadoes

3) Issuing the appropriate warning product based on the number and quality of confidence builders and nudgers.

The goal of this approach is to place the odds in favor of WDMs to proactively issue warnings prior to mesovortex development instead of reactively warning for mesovortices after they develop. This warning system empowers WDMs to only issue a Tornado Warning when there is high confidence for mesovortex tornadoes. A Severe Thunderstorm Warning is used for lower confidence situations.

The understanding of the physical processes associated with QLCS hazards has improved over the last decade within the research community. This warning approach takes full advantage of these advancements and promotes the issuance of more accurate, timely, and consistent warnings for QLCS mesovortices.