Biggest Hail Climatology/Best Hail Video

[Jeff Duda]

Jared pretty much covered it well, so I'll summarize in different wording and add my nominee for best giant hail video.

You want giant hail? You need:
-High CAPE - the higher, the better (for strong updrafts)
-Strong deep-layer shear (for storm organization...rotating supercell has vertical perturbation pressure gradients which can enhance updraft speed)
-Low freezing level and wet-bulb-zero level (generally cooler and moister atmosphere to limit melting and sublimation as stones fall from origin region)

The problem usually is that these three ingredients don't occur in the same environment. In fact, in general, high CAPE and cold environments (at least below cloud base) are nearly mutually exclusive.

I suspect that CCN concentration may also play a role in cloud microphysics controlling hail growth, but I have no data or publications on hand to support that statement.

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One of the more impressive large hail videos I've seen was from Wichita in September 2010. The sporadic nature of them so that it's quiet aside from the big "BANG!"s makes it all the better.

 

[Bram]

I find these two very impressive in terms of hail intensity and vegetatation damage. The first is from the St. Louis storm from April 28, 2012 and the second is from the Oklahoma City storm from May 16, 2010:

 

[jaredleighton]

Jeff Duda picked a video from that Sept 10, 2010 mega-hail producer. If you want to see some pretty impressive hail videos watch any of the plethora of videos on YouTube from that day in Wichita. This one by Dick McGowan is one of the most impressive hail videos I've ever seen, with volley balls falling out of the sky.

What struck me the most on this survey were the number of houses that had hail go through the roof, through the ceiling and into the garage or living room. One guy had a large dent in the hood of his car, that was parked in the garage. Ouch!

 

[StephenHenry]

@jaredleighton Thanks for those two papers! I thought this was very interesting from the Blair paper:
"Maximum reflectivity within the radar volume, TBSS signatures [hail spikes], and VIL-based products showed little to no skill in discriminating giant-hail sizes."

Also curious about this:
"The results from the radar analysis successfully identified operational signals that distinguished storms more favorable for generating giant hail:
• Approximately 99% of the convection was classified as supercellular, with a BWER structure frequently present.
•The peak Vr magnitude of the mid-level mesocyclone typically was 20–29 m/s (39–56 kt), with a median of 24 m/s (47 kt).
•The maximum STD magnitude frequently was 60–88 m/s (117–171 kt), with a median of 72 m/s (140 kt)"

Does GRLevel3 have a nice analog for Vr or STD? Would Vr be close to the AVGDV in GRLevel3?

 

[Adam Adkins]

A lot of great information and videos! Those May 10 Oklahoma and September 10 Wichita stones are incredible.

Jared, the information you posted was extremely interesting! Hail in general is so fascinating to me. I feel like I would be as excited to see giant hail as I would to see a tornado. Maybe I'll be a hail chaser.

What's interesting is when you look at THIS map of only 4.5" or larger reports, the vast majority are over the great plains. Obviously, based on Jared's information, this does not truly reflect where giant hail falls most often. My question is, do you think that the reason there are more of these big reports in the great plans is because of all the chasers? That in reality, where big hail falls should be spread out more evenly across the great plains and east to IA, MO, IL, WI, MN, MI, and IN? Perhaps this map is misleading because of chaser convergence around the great plains?

 

[Jeff Duda]

Giant hail occurs more frequently in the plains because that's where the parent entities that produce them - supercell thunderstorms - occur most frequently. This is because environments favoring supercell modes - strong deep-layer shear and high CAPE - are more common there than elsewhere in the CONUS. This is where things like EML, GoM moisture and etc come into play regarding climatology.

 

[jaredleighton]

Yeah, perhaps I should clarify a previous comment. When I said, "I'm not sure there is a really strong geographic signal for giant hail." I was more referring to the idea that within the Plains, and maybe even the southeast that there isn't a great geographic signal. I was not implying that California, Arizona, or Maine have conditions favorable to giant hail. I'm not sure if that comment was taken that way, but I still wanted to clear it up.

@StephenHenry... Yes, the Vr (max) described in the paper is basically an average of the two maximum magnitudes of the shear... meaning,

( |inbound max| + |outbound max| ) / 2 = Vr (max)

As far as GR3 goes, using the SRM values would probably suffice to try to determine the Vr values. Just be sure you're properly sampling the mid levels of the storm. With only 4 volume slices you might not be able to get high enough in the storm to properly interrogate it.

But one thing to always keep in mind, regardless of the reflectivity or velocity signatures, this particular line from the paper... "Well-organized supercell storm structure, in combination with a moderate to strong mesocyclone, strong storm-top divergence, and high reflectivity values throughout and above the hail-growth zone, should be expected to be present in a storm capable of producing giant hailstones." Meaning, the thresholds suggested in the paper give a nice quantitative guideline for detecting large hail, however there is still a qualitative component to it, in the sense that these thresholds might become inadequate for determining the presence of large hail if the storm doesn't demonstrate the proper structure.

@Adam Atkins... As Jeff said, and as I tried to clear up above, there is clearly a stronger signal to large hail in the Great Plains, compared to other geographic areas of the US, such as the West Coast or the Northeast. When I disputed the geographic signal, I was more referring to the sub-geographic regions within the Great Plains, such as "Eastern Colorado" or "Southern Plains." As Jeff said, when you get to an area that has big CAPE, deep shear and an EML in conjunction with each other you have the ingredients for large-hail producing storms. Those ingredients show up much more frequently on the plains than they do in the coasts or desert regions.