Quad-State Supercell/Tornado Event (2021-12-10)

[Alex Elmore]

I propose it would be of historic interest to get drone footage to confirm the path, or lack thereof, along this 10 mile stretch.

Better yet, NWS personnel have access to hi-res satellite data through the Dept. of Homeland Security for this event. The entire path of that supercell received a scan, and this data is able to be displayed as a layer in the internal version of the Damage Assessment Toolkit - the software used to plot damage points.

This is not targeted at Ken, but just a general statement to all - There is much that goes on behind the scenes that many assume is not happening without bothering to ask or think that it might be. NWS meteorologists are just as involved and curious in this event as all the enthusiasts and chasers. While there are some tornadoes that could stand to be surveyed better IMO, I can assure everyone that this damage track has many eyes on it from the meteorological and engineering communities, and will continue to be thoroughly reviewed. Regardless of if the rating and path length stand as they currently are, this was still a historic event.

As I am writing this, I’m thinking maybe I have the answer to my own question… Is the idea to say, continuing to use the DoD 3 example, that if “broken glass in windows and doors” is the *worst* damage found, then the tornado is unlikely to have had winds greater than 114 mph?

Correct. And that is why it is so hard to get EF5 damage as Jeff said - most DIs do not have an UB that goes into that range, and if they do, it's the worst possible destruction of the best engineered structure. The ranges (LB-UB) are given to account for varying degrees of engineering, construction quality, the impacts of debris loading, etc.

 

[Jeff Duda]

EDIT: Sorry, Alex, to repeat your wording. I did not see your reply until I posted mine.

The bounds are meant to account for variability in construction or material quality. Not all glass windows are the same. Glass windows vary in size, single/double pane, exposure angle to winds/debris, what kind of debris hits it, at what angle it is hit, and the quality of the glass itself. All of these add up to a range of wind speed values that could have caused that damage. Since a surveyor (and likely also, the person to whom that window belonged) will never know the precise circumstances under which the break occurred, there will never be any way to be absolutely certain which wind speed caused it. The EF-scale accounts for this by using the range of wind speeds.

 

[John Robinson]

As a follow-up to comments above regarding what resources WFO Memphis might be using to check their damage paths in more rural areas, I noted an updated storm survey posted today that included the following remark...

UPDATE #2...SIGNIFICANTLY EXTENDED TRACK OF TORNADO IN DECATUR COUNTY
INTO BENTON COUNTY UPON EXAMINING SENTINEL SATELLITE DATA. AN INTERMITTENT
TREE DAMAGE SWATH WAS FOUND EXTENDING ALL THE WAY ACROSS DECATUR COUNTY
AND INTO EXTREME SOUTHERN BENTON COUNTY.

While this does not, of course, pertain to the long-track tornado, it does indicate that the office is using resources other than just ground surveys.

 

[John Farley]

In addition to what Jonn notes above, and in a similar vein, they have also posted a couple of Public Information Statements that included the following in relation to the long-track tornado:

PLEASE NOTE...The information regarding tornado #4 below, from
Craighead County to Obion County, is based on data from ground
surveys. We are continuing to evaluate data from UAS, aircraft, and
satellites regarding the storm`s evolution as it moved through
Obion County. If the data from the supplemental sources reveals
additional critical information, this statement will be updated.