Surveying Damage

[Lori]

I have a pretty good idea what goes into surveying damage to determine a tornado rating.
However, after driving around viewing the damage, especially the damage from the tornado that damaged the town I live, my question is when the track of a tornado is determined does the tornado have to literally touch down the whole time (I’m assuming tree tops are touch down criteria) or can some skipping back up and down be counted?
Also, I could not find a crossing for the Pelham tornado on I-65 or even damage before or after it crossed I-65.

 

[warneagle]

I have a pretty good idea what goes into surveying damage to determine a tornado rating.
However, after driving around viewing the damage, especially the damage from the tornado that damaged the town I live, my question is when the track of a tornado is determined does the tornado have to literally touch down the whole time (I’m assuming tree tops are touch down criteria) or can some skipping back up and down be counted?
Also, I could not find a crossing for the Pelham tornado on I-65 or even damage before or after it crossed I-65.

If it lifts and then touches down again, it's counted as a separate tornado. It's sort of arbitrary, especially in cases where a storm is cycling rapidly, but that's the official definition.

 

[Equus]

Sometimes it's really borderline and subjective honestly, usually any break at all designates a separate tornado but occasionally a meso handoff can occur so fast and the path between be obscured by RFD winds that it's hard to tell.

Case in point the 4/27/11 Cordova tornado; Brian Peters was chasing it and says he saw the tornado lift and quickly be replaced by a new tornado that intensified rapidly into Cordova, and survey only found low end EF0 tree damage where the change in tornadoes would've occurred; it's listed as one tornado but due to the vaugeness of the damage in that area we honestly will probably never know

In older texts sometimes they'll list a long track tornado along a 'skipping' path but nowadays surveyors will look for explicit breaks in the path and designate it a separate tornado; I assume it's definitely possible though for a tornado to weaken to the point it's causing little to no damage at certain points (perhaps 50-60mph?) and that can make it unclear whether it lifted or just weakened significantly... sometimes TDS features can probably help with that

 

[eric11]

Sometimes it's really borderline and subjective honestly, usually any break at all designates a separate tornado but occasionally a meso handoff can occur so fast and the path between be obscured by RFD winds that it's hard to tell.

Case in point the 4/27/11 Cordova tornado; Brian Peters was chasing it and says he saw the tornado lift and quickly be replaced by a new tornado that intensified rapidly into Cordova, and survey only found low end EF0 tree damage where the change in tornadoes would've occurred; it's listed as one tornado but due to the vaugeness of the damage in that area we honestly will probably never know

In older texts sometimes they'll list a long track tornado along a 'skipping' path but nowadays surveyors will look for explicit breaks in the path and designate it a separate tornado; I assume it's definitely possible though for a tornado to weaken to the point it's causing little to no damage at certain points (perhaps 50-60mph?) and that can make it unclear whether it lifted or just weakened significantly... sometimes TDS features can probably help with that

Maybe this pic?

 

[Lori]

Sometimes it's really borderline and subjective honestly, usually any break at all designates a separate tornado but occasionally a meso handoff can occur so fast and the path between be obscured by RFD winds that it's hard to tell.

Case in point the 4/27/11 Cordova tornado; Brian Peters was chasing it and says he saw the tornado lift and quickly be replaced by a new tornado that intensified rapidly into Cordova, and survey only found low end EF0 tree damage where the change in tornadoes would've occurred; it's listed as one tornado but due to the vaugeness of the damage in that area we honestly will probably never know

In older texts sometimes they'll list a long track tornado along a 'skipping' path but nowadays surveyors will look for explicit breaks in the path and designate it a separate tornado; I assume it's definitely possible though for a tornado to weaken to the point it's causing little to no damage at certain points (perhaps 50-60mph?) and that can make it unclear whether it lifted or just weakened significantly... sometimes TDS features can probably help with that

I think this was the case in the two Shelby Co tornado damages that I saw. And explains how the Pelham was coming toward my house but then a or the tornado went slightly north from my location.
The same seemed to happen during the tornadoes 8 days before. Every indication showed the tornado on the ground as it headed near Sylacauga where I was located at that time but it went south a few blocks away and there was no continuous damage path.
I had a met friend say that the Correlation Coefficient can show damage that is still flying/rotating but it can be debris that was lifted not necessarily being pulled from the ground.

I love the science of this!! But ready for Dixie Alley to get a break. However, there’s still April and May..

 

[Equus]

Yeah I'd not be surprised if it lifted in a small area then came back down shortly. Pretty hard to tell when it's flanked by weaker damage and usually just gets connected as one path. I can imagine even CC could miss a brief lifting if debris stays lofted up at beam height; I don't envy the job of surveyors haha