Significant Tornado Events

[MNTornadoGuy]

Next tornado in the May 6, 1965 series: the first Fridley tornado. This tornado touched down near the Northern Ordnance plant in Fridley (which would be hit by all three tornadoes during the outbreak) and moved NNE through the commercial district of Fridley. The tornado only produced F0-F1 in the Fridley but rapidly intensified as entered the Fridley suburb called Spring Lake Park. Here it leveled multiple homes at F3 intensity with wind-rowing being evident on aerial imagery. The tornado then turned to the NE and impacted the Anoka Airport where it damaged a hangar and threw planes hundreds of yards. After this point, the tornado dissipated.

 

[andyhb]

Some Damage Photos from Wilburton

That's a pretty impressive damage path, well deserving of the F4 rating.

 

[Nightking2021]

That's a pretty impressive damage path, well deserving of the F4 rating.

Of course it does. It says you are a research assistant going for a PhD. Are you going to end up doing damage surveys to determine a tornadoes strength or something like it?

 

[andyhb]

Someday, perhaps.

 

[MNTornadoGuy]

Some other notable New Zealand tornadoes:

8/15/2004 Waitara F3
This intense tornado swept away a poorly anchored farmhouse scattering debris in a 400-m by 50-m area. Four concrete power poles were snapped and numerous trees were uprooted. 2 people were killed in the farmhouse.

4/28/1929 Kaimai F?
A manure shed made of 2-inch thick slabs and corrugated iron was swept away. Posts were torn out of the ground and a 50-gallon water barrel was carried 220 yards.

6/14/1917 Huntly F?
Lofted a large wagon 50 ft into the air, smashed fifteen headstones "into atoms" and picked up a house, carried it 100-200 yards, and smashed it into "matchwood." A sulky and spring cart was carried 200 yards.

 

[WIL9287]

Dr. Forbes survey said it was destroying 33,000 trees a minute and considering it was on the ground for an hour and 55 minutes.

Dr. Forbes' survey did state it was destroying 33,000 trees per minute. His survey is not publicly available but I was able to see some of his survey material from May 31, 1985. And from the research, I've done, the 88,000 number that is widely published occurred just in Clearfield County.

 

[buckeye05]

Something interesting I noticed from LZK. Remember how I was mentioning that some surveyors "break the rules" and use vehicles as DIs? Well NWS Little Rock did just that, and rated the 03/25/21 Monticello, AR an EF2 based entirely on vehicles being lofted and thrown into a field. This is especially surprising considering this is the same office that rated Vilonia EF4. However, the person who is largely responsible for that has since retired. This, combined with the surprisingly liberal FFC survey of the Newnan tornado, makes me wonder if either attitudes about always playing it conservative have changed, or if newer and younger employees at the NWS are less inclined to lowball ratings. Whatever the case is, I'm fine with it.

 

[Nightking2021]

Something interesting I noticed from LZK. Remember how I was mentioning that some surveyors "break the rules" and use vehicles as DIs? Well NWS Little Rock did just that, and rated the 03/25/21 Monticello, AR an EF2 based entirely on vehicles being lofted and thrown into a field. This is especially surprising considering this is the same office that rated Vilonia EF4. However, the person who is largely responsible for that has since retired. This, combined with the surprisingly liberal FFC survey of the Newnan tornado, makes me wonder if either attitudes about always playing it conservative have changed, or if newer and younger employees at the NWS are less inclined to lowball ratings. Whatever the case is, I'm fine with it.

Here is a house in Newnan that received an EF4. It has hard to tell how adequate the anchoring is but it looks like it is there. It looks like some tree debarking in the background.

 

[MNTornadoGuy]

Here is a house in Newnan that received an EF4. It has hard to tell how adequate the anchoring is but it looks like it is there. It looks like some tree debarking in the background. View attachment 8400

Notice how the car wasn't shifted much and how the house just slid off its foundation and collapsed. Debris wasn't blown very far and significant sections of the walls are still intact. Also it looks like those trees were snapped but not severely debarked.

 

[buckeye05]

Here is a house in Newnan that received an EF4. It has hard to tell how adequate the anchoring is but it looks like it is there. It looks like some tree debarking in the background. View attachment 8400

Those trees definitely aren't debarked, and there's no way to make any inferences about anchoring without close up views of the foundation perimeter, which isn't even visible here. Other photos of homes in this neighborhood did show a distinct lack of anchor bolting though. If it were somehow up to me, I think I honestly would have called this high-end EF3, but low-end EF4 works fine too.

 

[MNTornadoGuy]

Most offices would probably give this damage a low-end to a mid-end EF3 rating.

 

[MNTornadoGuy]

Other examples from the Newnan tornado survey. These are listed as an 152 mph EF3 DI in DAT when the damage looks more like EF1-EF2 damage.

 

[Nightking2021]

Those trees definitely aren't debarked, and there's no way to make any inferences about anchoring without close up views of the foundation perimeter, which isn't even visible here. Other photos of homes in this neighborhood did show a distinct lack of anchor bolting though. If it were somehow up to me, I think I honestly would have called this high-end EF3, but low-end EF4 works fine too.

It is a matter of opinion for even a tornado getting a high-end EF3 rating is still quite rare. It seems you have a really good eye for this because it can be really hard for me to tell.

 

[buckeye05]

EF3 for deroofed homes is something I've seen before in Dixie, and I think I've mentioned it too. I believe it has something to do with homes that have hurricane ties or other above-and-beyond roof attachments, but I never see estimates higher than low-end EF3 for that type of thing.

 

[WIL9287]

Here's an EF-4 rated house from Newnan from the DAT. Note the roof is still largely intact, the trees are not debarked, the car did not move, and there is very poor anchoring.

 

[Nightking2021]

Other examples from the Newnan tornado survey. These are listed as an 152 mph EF3 DI in DAT when the damage looks more like EF1-EF2 damage.

I would say mid to high-end EF2(125-135 mph) would be more appropriate but if they want to be more lenient that is on them.

 

[MNTornadoGuy]

EF3 for deroofed homes is something I've seen before in Dixie, and I think I've mentioned it too. I believe it has something to do with homes that have hurricane ties or other above-and-beyond roof attachments, but I never see estimates higher than low-end EF3 for that type of thing.

For the second photo only a small section of the roof is missing which is not mid-end EF3 damage.

This house is also a 170 mph EF4 DI. This should probably be EF3 as large sections of the roof and walls are still intact, it is a slider home. Also, notice how the pine trees directly behind the home still have foliage and small branches.

 

[buckeye05]

It is a matter of opinion for even a tornado getting a high-end EF3 rating is still quite rare. It seems you have a really good eye for this because it can be really hard for me to tell.

When it comes to anchoring, it mostly comes down to looking at the edge of the foundation for bolts, straps, nails, or nothing at all. There's some nuance to it but it's not super complex or difficult. Roughly speaking, bolts suggest solid anchoring, nails suggest weak anchoring, and nothing suggests well...a completely unanchored house. The foundation isn't visible in the first photo you posted, so nothing about anchoring can be determined from it. There's other factors too including methods of wall stud connection (straight vs toe-nails), and poured concrete (stronger) vs cinder-block foundations (weaker).

Have a look at the photo WIL9287 posted. Here, the edge of the foundation can be seen. Note how there are no bolts and only some nails sticking out of the sill plate (the plank that is attached to the edge of the foundation). This, combined with that car sitting there undamaged, suggests that this was a poorly anchored house. Does that make sense? In any case, I can DM you with more examples if you want to know more.

 

[Nightking2021]

For the second photo only a small section of the roof is missing which is not mid-end EF3 damage.

This house is also a 170 mph EF4 DI. This should probably be EF3 as large sections of the roof and walls are still intact, it is a slider home. Also, notice how the pine trees directly behind the home still have foliage and small branches.

So this is probably high-end EF2 to maybe low-end EF3 damage?

 

[buckeye05]

So this is probably high-end EF2 to maybe low-end EF3 damage?

Realistically speaking, the context is not consistent with a violent tornado, and the debris pattern isn't either, so one can argue that it shouldn't have been rated so highly.