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

[Mike Smith]

Hi Lou, thank you for the comment here. There is nothing personal about you not being able to comment on my blog. It used to be open for comments but after spending an 1+hours/week deleting "make $7,000/week working for Amazon from home" and strip club ads, it just become too much work.

You may be correct as to how Mayfield got included in the warning. If that is the case, the WFO should have deleted it. Either the polygon is the official warning (per NWS regs) or it is not. Deviating only causes confusion which is never a good thing.

Thanks for the comment and for reading my blog.

In your blog (which I am not allowed to comment on directly, apparently) you note that the text of the early warning included Mayfield as one of the affected locations. It looks to me like part of the Mayfield ZIP Code was inside the polygon, even though Mayfield proper was not. I have seen the public get confused when ZIP Codes don't line up exactly with municipal boundaries ... so, I am guessing that the routine that picks affected locations maybe includes ZIP Code hits

 

[KenMcWatters]

I'm curious as to what has you so convinced that that stretch was not already surveyed for possible tornado damage. You seem to have a bias that there was in fact a tornado down in that gap and it's now up to CSI-type investigation to prove that the damage path was not continuous. Please justify.

Jeff, you're correct that I probably have a bias in my request for drone confirmation. If the path verifies it would be a historic tornado, at least for the number of states and possibly total length. Since the NWS surveys are already done, I was suggesting a private effort to confirm (or not) this 10 mile stretch. Couldn't these findings be submitted to the NWS for their consideration?

 

[rdale]

They could - but there’s nothing to indicate that it wasn’t done with drones.

 

[Lou Ruh]

Jeff, you're correct that I probably have a bias in my request for drone confirmation. If the path verifies it would be a historic tornado, at least for the number of states and possibly total length. Since the NWS surveys are already done, I was suggesting a private effort to confirm (or not) this 10 mile stretch. Couldn't these findings be submitted to the NWS for their consideration?

I don't know about any drone flights, but, the Civil Air Patrol did assist with the surveys ... Kentucky Wing Flying Post-Tornado Assessment Missions . I know that these have been very useful in my area (the Mount Holly ... a.k.a. Philadelphia CWA) especially for assessing heavily wooded areas like the Pine Barrens in NJ and the wooded areas in the Poconos.

 

[JamesCaruso]

Not to digress, but I have a question about the damage indicator that @Jeff Duda referenced above - FR12.html - how should I think about the concept of an Upper Bound? I am probably misunderstanding it, but it seems irrelevant. For example, Degree of Damage 3 - “broken glass in windows and doors,” is associated with an expected wind speed of 96 mph and a Lower Bound of 79 mph. So if I am interpreting this correctly, this damage is generally associated with 96 but could be as low as 79. But the Upper Bound of 114 seems irrelevant, as *any* wind speed greater than 96, including greater than 114, would produce that damage. I would think that everything would be stated in terms of “equal to or greater than…”

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?

 

[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.