"Interesting" severe thunderstorm warnings

[Jeff Snyder]

What is the most interesting, unique, or "strange" warning you've ever seen? I think I can remember a few SVR warnings that mentioned >100 mph winds, which is certainly rare. I've also seen some ridiculously huge warnings before.

I started to think about this after seeing the SVR warning that was recently issued for southwestern Oklahoma. The nearest thunderstorm is >50 miles away, and there's no precipitation observed in the warning box. The latter point isn't that uncommon (strong outflow can cause severe-level winds outside of areas of precip), but I'm not sure I've seen such a large separation between the warning and the thunderstorm that's "causing" the elements for which the warning was issued.

 

[Jeff Duda]

Yeah that's somethin'. Radial velocity from KFDR certainly corroborates the presence of severe winds at/near the surface. Weirdest thing is there was no obvious dying storm in the vicinity to generate those winds. There was a storm that died as it was crossing from Knox County, TX into Foard County, TX, but that still leaves 35 nmi that the dying winds had to travel after the storm was kaput to prompt the warning, AND the dying storm's remnants would've had to have made a turn to the right slightly in order to get to where the warning is. The Grandfield mesonet site certainly shows some higher gusts (up to 50 mph), but there's no real signature of a heat burst or anything there.

Good catch, Jeff. I'd love to see this one explained.

EDIT: Well there goes the heat burst signature at the Grandfield site now in the last 20 minutes.

 

[Chris_Spannagle]

OUN was asked about this warning by media and an em in NWS Chat, their response was as follows: "The thunderstorms across Knox and Baylor counties are weakening rapidly. At this point we are more concerned about the potential for damaging winds associated with storm collapse. We've already seen evidence of this south of Frederick, OK as a well-defined heat burst has traveled northward from near Electra, TX to near Frederick, OK. We did receive a report of 60 mph wind gusts."

 

[brice.coffer]

At first I thought dry microburst out of the anvil of the dying storms to the SW. There was no precip and the Grandfield mesonet site didn't show any obvious signs of a heat burst. The velocity on the KFDR radar was impressive and the 00Z FWD sounding was quite dry between 700-850mb. Eventually though it was obvious a heart burst was underway. There's not much difference between the two phenomena anyways.

I've never seen a warning like this one, and I initially thought it should have been a high wind warning. I guess since it's from a dying thunderstorm is qualifies as a severe warning. A high wind warning might not set off any alarms for EMs so Norman issued a severe thunderstorm warning instead. That's pure speculation though.

 

[Patrick Marsh]

Ultimately, what's happening here is making the distinction between High Wind Warning or a Severe Thunderstorm Warning. In this case the forecasters went with the Severe Thunderstorm Warning. This morning the office went with a High Wind Warning.

Differences in warning philosophies exist even between forecasters...let alone WFOs.

 

[Matt Tottle]

Isn't that right within the "cone of silence"? Maybe there really was a discrete cell right there.. Do you have even any before/after data that might show the head or tail of a cell in that area?

Sent from my Samsung Galaxy SII using Tapatalk 2

 

[Joshua Nall]

Isn't that right within the "cone of silence"? Maybe there really was a discrete cell right there.. Do you have even any before/after data that might show the head or tail of a cell in that area?

The base reflectivity loop shortly after that warning was issued showed no precip within the warning box. If I understand it right the "cone of silence" is only the area above a tilt of 19.5 degrees. In other words a storm can't really hide near a radar site, unless the precip is evaporating before it reaches into the beam.

 

[Matt Tottle]

Believe me I'm not arguing, I'm very curious so don't take this wrong..

That polygon is (from my approximation) a maximum of 15NM from KFDR, and at minimum approx 1NM. From what I remember seeing while watching GR3 as storms approach me from SW KS and pass over KDDC, that seems to be right in the range where echoes disappear and you see the concentric rings around the site in the echo tops - with the 'totally blind' ring being about a 5NM radius.

It could've been something that blew up quickly and collapsed just as quickly - maybe those winds they detected were the resulting downburst?

 

[brice.coffer]

It was a heat burst from the rapidly decaying thunderstorms to the SW.

Good explanation of heat bursts can be found here:

http://www.theweatherprediction.com/habyhints/341/

Here is a 3D visualization of the cone of silence in GR.

It can still see precip at the ground, even right near the radar. However it can't see above the 19.5 degree tilt.

 

[Jeff Duda]

Isn't that right within the "cone of silence"? Maybe there really was a discrete cell right there.. Do you have even any before/after data that might show the head or tail of a cell in that area

It would be very difficult for that to have been the case. While an elevated storm that is no longer producing precipitation could certainly hide within the cone of silence from KFDR, it should show up on KTLX, KFWD or KDYX, as none of those radars are far enough from the region for the 0.5 degree beam to overshoot the storm (for example, the 0.5 degree beam from KTLX is at about 11,500 ft ARL, so perhaps 11,000 ft or so AGL at that spot, assuming standard refraction of course; even the 2.4 degree beam is at ~32 Kft AGL, which should be skirting the top part of any vigorous storm there). Surely one of those radars would've shown some high reflectivity values there, but none did (check them on the RAP site if you don't believe me...gotta do this within the next day or two, though, before the data is dropped from storage on that site).