Identifying the Physical Drivers and Radar Signatures of Fire-Generated Tornadic Vortices

Wildfires can generate their own severe weather, including tornados and thunderstorms embedded in the wildfire plume. These fire-generated extremes threaten fire-fighter and public safety yet are poorly understood and often unpredicted. To fill this knowledge gap, the investigators propose to understand fire-generated extreme weather by identifying the common factors contributing fire-generated tornados and thunderstorms from weather radar and satellite data.

The project will also engage the public in wildfire science such as developing middle-school in-class lessons focused on fire-generated weather and conducting a citizen-science social-media campaign to collect photographs of the ash and debris that “rain” down from wildfire plumes. The crowd-sourced data collected by the public will help improve our understanding of wildfire plumes for better documenting the size and shape of material lofted into the sky.

The proposed work is motivated by decades of success in using radar and satellite observations to issue life-saving warnings for convectional severe weather (e.g., severe thunderstorms). For fire-generated tornadic vortices (FGTV) and pyrocumulonimbus (pyroCb) these same tools show remarkable, yet incompletely realized potential. To fully realize this potential, new physical and conceptual models are required for interpreting radar and satellite observations of the wildfire environment.

To develop these models, the investigators will test a sequence of hypotheses designed to isolate the common characteristics of radar and satellite observed fire and plume processes linked to the FGTV development. These hypotheses are based on preliminary observations demonstrating FGTV producing fires often exhibit: (1) bent-over and bifurcating plumes with both embedded and shedding vortices, (2) asymmetries in flow splitting and flow reversal around the fire that favor one sense of vortex rotation (i.e., cyclonic vs. anticyclonic), and (3) pyroCb initiation concurrent with vortex intensification.

In isolating the common attributes and observed signatures of FGTV fires, the research team aims to produce conceptual models for FGTV formation. These conceptual models will facilitate life-saving warnings and enhance decision support for wildfire stakeholders, thereby providing an immediate societal benefit. Community engagement and education as part of this proposal will include: (a) social-media citizen-science campaign linking radar observations with photographic documentation of size and shape of ash falling from wildfire plumes, (b) in-classroom middle school learning experiences and curriculum coupled with an app-based data collection module, (c) graduate student mentoring and curriculum development, and (d) outreach to the public and wildfire stakeholders.

The citizen-science campaign is expected to reach 1000s of users annually, and the in-classroom program upwards of 500 students per year.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.