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Plains tornado threat Mon 5/27-Fri 5/31


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16 now. From the top article:

 

"The families were worried about the storm and were afraid of the tornadoes, especially after the EF5 tornado that struck May 20. The seven left home and sought shelter above a drainage canal, then were swept away when the high waters came, he said."

 I think that number is the total from the tornadoes and flooding combined. There are people still missing though. I know another one of those tips given is a get in a drainage ditch, but should be stressed that this is a last resort option. (i.e. caught in the open or in very unsafe structure like a mobile home with no other shelter). Often there is limited precip around the tornado itself so flooding isn't an issue, but obviously with the supercell motion and training anyone going into a ditch during this event was putting themselves in grave danger.

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There were at least two research teams out yesterday (DOWs and an OU team), pretty good chance there were more, hearing some crazy velocities were sampled (> 100 m/s).

NWS Norman tweeted about reviewing mobile Doppler data this morning, so they will apparently be using it to help rate this tornado.

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Hate to be that guy

But if any red tags or pro forecasters have any info on DOW recorded wind speeds during the El Reno tornado I would greatly appreciate it if you could PM me whatever you have at this point.

I'm in the middle of doing some research and obviously any info on early wind estimates would be welcomed.

Along these lines...

Is there an established conversion of g2g velocities to max wind speeds?

I imagine this must factor in distance of radar beam (height) as well as diameter of the couplet... just curious about the 290+ kt g2g couplet we all posted near El Rino... TIA

If you want to estimate the maximum tangential winds in a tornado, it's just the maximum inbound or outbound velocity in the circulation. Work done incorporating TIV data has found the difference in tornado wind speeds between the surface and the lowest 100 meters isn't as large as previously thought.

Gate-to-gate radial velocities are used because they can be used to estimate vertical vorticity if you assume you have an axisymmetric vortex (often a bad assumption). Vorticity is equal to twice the max velocity difference divided by the distance between the max outbound and inbound observations.

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DOW 110 m/s east of 81 and preliminary 115.5 m/s near I40.

Wow. What elevation? How does that compare to some of the other monsters that have been sampled?

Not totally sure, but I think it's 0.5 degrees at 13.5 km away, so approximate beam height of 120 m.

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Here's an animation of 1-minute data from the Phased Array Radar of the El Reno supercell, courtesy of Robin Tanamachi (@tornatrix). You can see the debris ball slingshot northward suddenly.

 

 

I was wondering if the PAR had captured any data from this. Great to see the improved temporal resolution.

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Assuming the 20% reduction is the standard, that would put winds at the surface between 195-210 mph. Definitely a violent EF4 or EF5 tornado. This peak was probably observed over a rural area, but it's strange to see how NWS Norman didn't see any evidence of tree debarking or ground scouring like you would think.

 

Yeah, it definitely doesn't add up.  I've always wondered how much an existing debris field plays in the tree-debarking and ground scouring.  Maybe, none....I don't know.  This tornado seemed to miss high density population areas so maybe that made a difference with less debris.  Have there been any studies on how existing debris within a tornado enhances the total damage?

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Yeah, it definitely doesn't add up.  I've always wondered how much an existing debris field plays in the tree-debarking and ground scouring.  Maybe, none....I don't know.  This tornado seemed to miss high density population areas so maybe that made a difference with less debris.  Have there been any studies on how existing debris within a tornado enhances the total damage?

 

Sort of.

 

http://journals.ametsoc.org/doi/abs/10.1175/2008JAS2686.1

 

I believe there have also been other papers that deal with the subject at least tangentially.

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Yeah, it definitely doesn't add up.  I've always wondered how much an existing debris field plays in the tree-debarking and ground scouring.  Maybe, none....I don't know.  This tornado seemed to miss high density population areas so maybe that made a difference with less debris.  Have there been any studies on how existing debris within a tornado enhances the total damage?

Also:

http://journals.ametsoc.org/doi/abs/10.1175/MWR2934.1

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Yeah, it definitely doesn't add up.  I've always wondered how much an existing debris field plays in the tree-debarking and ground scouring.  Maybe, none....I don't know.  This tornado seemed to miss high density population areas so maybe that made a difference with less debris.  Have there been any studies on how existing debris within a tornado enhances the total damage?

 

IMO a violent tornado moving through a city is going to have considerably greater intensity damage indicators than the same violent tornado moving over an open field with few trees for the sole reason of the amount of debris that gets swept up and turns into projectiles.  I don't know of any studies that would back my claim up, but debris has more momentum than air so when debris hits an object vs. only air, the object is going to suffer greater damage.  I'd call it the sandblaster effect.

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RaxPol data of the El Reno Tornado

 

Interesting. The bottom left panel has what looks like two areas of strong rotation in relative proximity of each other. Kinda obvious which one is the main circulation, though.

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Incredible images. For all its tragedy, it's great to see this storm was at least so well-sampled, as it appears a rather exceptional case in some regards that could add significant value to the existing body of data. The maximum path width may rival some of the largest known, most or all of which occurred after dark (e.g., Hallam and Greensburg).

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Howie Bluestein's RaXPol is absolutely INSANE. I saw it while I was out on the plains, it does a full (rotational) scan every 2 seconds (180°/s) and a full volume scan every 20 seconds. I watched a presentation in which Bluestein said that he figures that a air parcel comes in and goes out of a tornado in about 10 seconds on average and that same parcel can go up ~5km in about 100 seconds. So he got the funding for this monstrosity to measure parcels on such timescales. I feel as though it's the last of the mechanical breeds before everybody switches over to phased array.

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Incredible images. For all its tragedy, it's great to see this storm was at least so well-sampled, as it appears a rather exceptional case in some regards that could add significant value to the existing body of data. The maximum path width may rival some of the largest known, most or all of which occurred after dark (e.g., Hallam and Greensburg).

 

2.6 mi wide EF5.

 

http://kfor.com/2013/06/04/update-el-reno-union-city-tornado-widest-tornado-on-record/

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I'm assuming it's what KFOR is reporting. Just saw that - nothing official from OUN yet though.

 

Yeah, the Twitterverse is ablaze from some pretty credible people but I'll wait for the official announcement. Pretty incredible if true though. And continues the interesting debate of using radar measurements in ratings. 

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