Monitoring of concurrent, co-located tornado and flash flood (TORFF) warnings

Below is the most recent image showing overlapping tornado and flash flood warning polygons thus far in 2021. Warnings are shown if they overlap in space and are valid within 30 minutes of one another, calculated as described in Nielsen et al. (2015, Weather and Forecasting). The images are updated once per day at approximately 1045 UTC. The images are zoomed in on the region where overlapping TORFF warnings are most frequently observed.

Images last updated 1135 UTC Wednesday January 20 2021. (click image to embiggen)

The ten most recent TORFF overlapping warnings in 2020 are:

IND issued TOR warning at: 202010232110 and FF warning at: 202010232125
LIX issued TOR warning at: 202010090411 and FF warning at: 202010090357
JAN issued TOR warning at: 202009240304 and FF warning at: 202009240322
JAN issued TOR warning at: 202009240136 and FF warning at: 202009240110
LCH issued TOR warning at: 202009231958 and FF warning at: 202009231939
LCH issued TOR warning at: 202009231935 and FF warning at: 202009231939
LCH issued TOR warning at: 202009231917 and FF warning at: 202009231939
LCH issued TOR warning at: 202009231744 and FF warning at: 202009231725
ILM issued TOR warning at: 202009171917 and FF warning at: 202009171854
CAE issued TOR warning at: 202009171902 and FF warning at: 202009171919

Download the text file with the details of this year's overlapping warnings.

Maps of overlapping warnings from previous years:

Year: 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019

All TORFF Warning Intersections (n=4173) from 2008-2019:

Map of "Verified" TORFF Events from 2003-2018:

"Verified" TORFF events are identified by finding intersections between flash flood local storm reports (LSRs) and official tornado paths that were reported within three hours of one another, allowing for up to a 50 km spacing between the two. Five different spacing thresholds are tested from 10 km to 50 km, where the 10 km (50 km) spacing creates the most (least) conservative event totals. Between 25 and 75 "verified" TORFF events occur on average per year, depending on spatial threshold chosen. Discussion of the specific methods can be found in Nielsen (2019) and Henderson et al. (2020, Weather and Forecasting).

Select a Spatial Buffer:

10 km Buffer 20 km Buffer 30 km Buffer 40 km Buffer 50 km Buffer

TORFF Warning Intersections for Select U.S. Tropical Cyclones:

Select a Storm:

Ike (2008) Lee (2011) Isaac (2012) Matthew (2016) Harvey (2017) Irma (2017) Nate (2017) Florence (2018)

This research is sponsored by NOAA grant NA15OAR4590233, in support of the 2016 VORTEX-SE field campaign.