Severe WX April 19-20, 2020 Severe Weather Threat

[Gail]

Per Jackson NWS regarding the Purvis tornado:

 

[andyhb]

JAN has gone liberal again. We're back to pre-2014 ratings it seems. This is good news. Though to be fair, nothing really liberal about that rating. An anchor-bolted home was leveled and partially swept away. Any time that happens, an EF4 rating should always be applied, given contextual support of course.

They're using the EF-scale in the way it was intended to be used, not inventing stupid reasons for tornadoes to not be rated the way they should be.

 

[andyhb]

What is the deal with these ridiculously wide tornadoes?

Lots of moisture -> low LCL heights. Also several of these supercells (and some of the QLCS circulations on 4/12) have had very large mesocyclones. Adding those two together = large tornadoes.

MS is often a hot spot for these, especially central and southern parts of the state. Yazoo City in 2010 being another good example.

 

[buckeye05]

They're using the EF-scale in the way it was intended to be used, not inventing stupid reasons for tornadoes to not be rated the way they should be.

I guess that's what I'm trying to say. Some may interpret it as "liberal", when in reality it's just correct use of the scale.

 

[Equus]

Most offices are overly conservative and seem to try to hold to lower bound, so I'd say sadly enough that proper use IS a pretty liberal use these days. It's pretty amazing still how that tornado produced that one tiny area of high end damage (and EF4 does seem the right call despite the tiny area, scary getting used to bent anchor bolts this month) and then barely above EF2 the rest of its extensive path... which extended FAR longer than the radar made it seem. Southern Mississippi is absolutely KING of long track tornadoes in the US, no contest.

 

[Shakespeare2016]

Low to mid EF4 looks about right for that house. It doesn't seem overly conservative or liberal to me.

 

[Equus]

Using the EF scale as it was originally intended, it is about right; I can think of some offices where this would've wound up mid to high EF3 though, which is definitely lower than such damage should wind up given contextual factors.

 

[Shakespeare2016]

Using the EF scale as it was originally intended, it is about right; I can think of some offices where this would've wound up mid to high EF3 though, which is definitely lower than such damage should wind up given contextual factors.

Anchorage bolts ripped off the foundation of a decently built home I would think indicate violent damage.

 

[Equus]

We've seen way more of that this month than I'm comfortable with really

 

[Shakespeare2016]

We've seen way more of that this month than I'm comfortable with really

Had this occured 20 to 30 years ago anchor bolts being ripped off the foundation of a decently constructed home likely would have been rated F5 on the original F scale.

 

[buckeye05]

Hard to see, but here's some video of the Sandy Hook tornado where you can actually see the wedge:

 

[bwalk]

Here is an excellent detailed post-analysis of the EF4 in S. Miss Sunday night. Very educational.

 

[Brice]

Would you guys consider this event a "Forecasted Convective Amplification Deficiency' even though we did have one strong, long track tornado?

 

[KoD]

Would you guys consider this event a "Forecasted Convective Amplification Deficiency' even though we did have one strong, long track tornado?

I don't think it was a Forecasted Convective Amplification Deficiency if you're judging the general prognosis made by many contributing members here. Seems like the expectation that there was a credible threat but not as substantial as Easter was pretty spot on.
I don't know if the stats line up with moderate risk SPC category but I do think moderate issuance was acceptable. It would be even more appropriate had Easter been a high risk.

 

[Brice]

I don't think it was a Forecasted Convective Amplification Deficiency if you're judging the general prognosis made by many contributing members here. Seems like the expectation that there was a credible threat but not as substantial as Easter was pretty spot on.
I don't know if the stats line up with moderate risk SPC category but I do think moderate issuance was acceptable. It would be even more appropriate had Easter been a high risk.

IF we expected what happened on Easter, High Risk would be near certain. If there wasn't any messy convection in the morning I think they would've went High Risk and the outbreak could've been worse. I think it was more under-performed than anything else now that I'm really thinking about it.(mini outbreak with the EF4.

 

[ARCC]

Just to show how small the world is and how quickly life can change, this is my parents Camper at Wind Creek. The second picture is their bed where my mom was sleeping a few minutes before the storm. The area is smashed and Kellyton has the worst non tornadic wind damage I’ve ever seen in person. Another example to take even STW seriously.