The 24
August 2016 "Surprise" Tornado Outbreak: Part 1
Todd
Holsten,
National Weather Service Northern Indiana, Syracuse, IN
Jeff Logsdon, National Weather Service Northern Indiana
Amos Dodson, National Weather Service Northern Indiana
,
,
Abstract
During the afternoon and evening of 24 August 2016 an outbreak of
tornadoes occurred from central Indiana through northwestern Ohio. This outbreak produced 23 tornadoes,
including 11 in Indiana, 10 in Ohio, and 2 in southeastern Ontario. This was the largest single tornado event
ever to occur in August for both Indiana and Ohio.
An existing line of showers
and embedded thunderstorms, downstream of a mesoscale convective vortex over
Illinois during the morning of the 24th, devolved into isolated cyclic
supercells by afternoon across central and eastern Indiana. While this event
was poorly forecast- stemming from a lack of coherent numerical model guidance,
near-term forecasts and trends from high-resolution numerical guidance allowed
forecasters to rapidly shift focus and switch to an effective severe weather
operations mode.
Even though 14 tornadoes
occurred in the National Weather Service (NWS) Northern Indiana (IWX) county
warning area on August 24th, no fatalities and only one minor injury occurred.
Communication between emergency managers, trained spotters, media, public, and
the NWS was crucial to preventing a loss of life. A local volunteer served as a
virtual operations support team coordinator, monitoring reports from chasers in
the field and relaying relevant information to the office through NWSChat
(i.e., collaboration software). His timely relay of accurate storm information
to the office, along with pictures and video, allowed for real-time
verification and aided in effective warning decisions.
This presentation will focus
on a local threat assessment using numerical model guidance from the National
Centers for Environmental Prediction including near term trends of the High-
Resolution Rapid Refresh model.
Mesoscale processes and storm-scale evolution that occurred during this
event will also be examined. Finally, IWX warning operations will be reviewed,
including radar interrogation and warning decision making considerations that
lead to timely impact-based warnings.