Massive hail stones fall in tiny South Dakota town, challenge U.S. record

[mikegeukes]

Massive hail stones fall in tiny South Dakota town, challenge U.S. record

http://www.rapidcityjournal.com/news/article_2f011372-9902-11df-9314-001cc4c002e0.html

http://www.crh.noaa.gov/news/display_cmsstory.php?wfo=abr&storyid=55671&source=0

Mike

 

[Mike Hollingshead]

“I’ve got 19 holes in my roof. Three of them go all the way through my ceiling,â€￾ said Lisa Patrick, manager of the Coffee Cup in Vivian. “And it wasn’t just my house; it was every house in town.â€￾

That has to be something. Dodging hail in your living room.

That is an interesting article. Makes you wonder if a bigger beast will come out of there, while at the same time wonder if the town people melted them all too much showing people lol.

Sigh, pisses me off now since I had a damn cooler in my car too. But then I wondered....I wonder if the big ones would even fit in my small 6 can sized sorta cooler.

Sounds like something interesting will come out of this if several people were scouting out monsters and freezing them. Then again sounds like many probably didn't figure it was very important or interesting enough to really bother too much with.

 

[Jarrod Barnett]

Severe Studios I think it was put up a tweet about that on Sunday. I have them alerted straight to my phone. I clicked it and was like HOLY COW! lol

That is just freaking nuts!

 

[Robert Dewey]

That's 0.50 inches shy of volleyball diameter... although the circumference is off (volleyballs are 26.5 inches around) given that the hail isn't a perfect sphere.

 

[Marcus Hicks]

It's all over the news here. Interested to see if it does make the record. The stone being used weighed in at 1.9375 lbs.

 

[Jason Harris]

And apparently the fellow and his mother saw even bigger stones:

Scott picked up the hailstone because of its unusual “spider” legs, not because of its size. “If I knew it might be a record, I would have looked for a bigger one. There was lots bigger ones than the one I got,” he said. “My mother seen one as big as a football, she claims.”

http://www.rapidcityjournal.com/news/article_2f011372-9902-11df-9314-001cc4c002e0.html

 

[Mike Hollingshead]

The storm was changing quite quickly through that point so a couple caps won't show things well but here are a couple from that point around Vivian as the monsters were falling back there.

Wide angle still looking north at I90 and the long beaver tail/inflow band. Storm was riding the warm front so fairly easy to get crazy formations there just ahead of the thing on its boundary and the warm front.

Video capture panned more right/east from that same spot just moments later. Vivian is just west of here. Shot video before this too but this was the most telling point with that crazy band of convection above the beaver tail.

Going east on I90 moments later with a new base ahead of the main storm with its own curling inflow band, this happening just south of the main changing east-west inflow band/beaver tail to the main supercell.

Actually below is the only one I have when it was right on top of Vivian just before the above images....Vivian just over that small hill next to the interstate.

 

[Patrick Marsh]

And apparently the fellow and his mother saw even bigger stones:

http://www.rapidcityjournal.com/news/article_2f011372-9902-11df-9314-001cc4c002e0.html

I've seen some NWS documents from interviews indicating a resident claims hailstones were in the 11" range. I believe the hailstone discussed above (the one that was weighed) was allegedly quite a bit larger, but the finder lost power as a result of the storm and substantial melting occurred in his thawing freezer.

 

[Isaac Pato]

Stones weighing in close to 2lbs... makes me wonder just how strong that updraft was. Of course an 8-11" hailstone is going to have quite a bit of drag, but I'd assume that it would still require an updraft well in excess of 100mph to keep it up. Is there a reliable way to determine updraft speed by hail size?

 

[Jeff Duda]

Stones weighing in close to 2lbs... makes me wonder just how strong that updraft was. Of course an 8-11" hailstone is going to have quite a bit of drag, but I'd assume that it would still require an updraft well in excess of 100mph to keep it up. Is there a reliable way to determine updraft speed by hail size?

For spherical hail or hail of a regular known size (like a 30 deg angle cone, perfect cylinder etc), equations that relate terminal velocity to radius/weight/size could probably be derived. However, like most hailstones, this stone was rather irregularly shaped and it would be harder to determine a relationship of terminal velocity versus size for these type. An individual stone could be measured by putting it in some sort of tube and shooting high velocity air up at it enough to keep it in levitation, a la Mythbusters...

...that just gave me an idea *visits discovery.com/mythbusters to submit idea now*

 

[J Tyler]

This is one of those stories that if I had not just looked at the photos and saw where the NWS was reporting on this, I would have NEVER believed it. No way can hail get that big! Just a reminder to never say "never".

 

[Shane Adams]

I'm waiting for the tornado equivalent of that hailstone...the monster no one's ever seen before.

 

[Menno van der Haven]

Stones weighing in close to 2lbs... makes me wonder just how strong that updraft was. Of course an 8-11" hailstone is going to have quite a bit of drag, but I'd assume that it would still require an updraft well in excess of 100mph to keep it up. Is there a reliable way to determine updraft speed by hail size?

The formula for calculating the terminal velocity of a hailstone is:

V = SQRT { ( 4 * g * Ri * D ) / ( 3 * Cd * Ra ) }

from Chapter 6 in Severe Convective Storms by Knight and Knight, (Charles A. Doswell III, Editor)

where g = acceleration due to gravity
Ri = density of ice deposit
D = diameter of hailstone
Cd = drag coefficient
Ra = density of air

With g = 9,8 m/s
Ri = 900 kg/m3
D = 0,25 m (10 inch)
Cd = 0,55
Ra = 0,692 kg/m3 (ICAO Standard Atmosphere at 500 hPa)

the terminal velocity of a 10 inch hailstone is 88 m/s !

Ofcourse there are a lot of but's in this calculation. Was the hailstone spherical? Were there holes filled with air in the stone? Was it tumbling during it's fall etc. etc.
When a 10 inch hailstone made impact on the earth's surface it wasn't floating in the updraft anymore.
So, a rough guess of my is that maximum updraft speed was in the order of 60 m/s.

 

[Rob H]

An individual stone could be measured by putting it in some sort of tube and shooting high velocity air up at it enough to keep it in levitation, a la Mythbusters...

I would love to see a storm-centric episode of Mythbusters!

Back on topic, I've been doing some research on hail because at some point I'd like to take on some of the 2"-3" cores without losing windows. I've seen some terminal velocity equations but they are simplistic and don't agree well with real world experiments. A lot of the research that I've seen from weather organizations, roofing companies, and insurance companies suggests that the largest/fastest hail stones travel between 95-105 mph. Once the hail gets faster (and larger) than this, friction/drag starts to play a more important role and it almost looks like a limit - unfortunately, I don't think many scientists are trying to find velocities of 12"+ hail so we don't have an idea of the upper bounds.

Tumbling, melting from friction, wet accumulation on the descent, and a whole host of other things would complicate any sort of equation. Realistically, I think we'd have to make an accurate clone of the stone that was kept, figure out what happened on its final descent and adjust for that mass, and then shoot a stream of air at it like Jeff suggested.

Put my guess at 50 m/s (111mph) for the final falling velocity, which would make Menno's updraft guess plausible. However you look at it, this is a beast of a hailstone!

 

[Nick Nolte]

http://www.weather.com/outlook/videos/raw-biggest-hail-ever-17850&h=36a7b

Bettes posted this on facebook, some incredible video there showing the "craters" left by the stones and the damage to roofs as well as them handling it. Incredible stuff.