Storms without Lightning & Thunder?

[MikeD]

Such a term does not exist. Are you perhaps thinking of "mesoscale convective system" or "mesoscale convective vortex"? Try perusing the AMS glossary (http://glossary.ametsoc.org/wiki/Main_Page) to check some definitions.

You get the idea. Right?

Why are people so toxic now?

 

[Devin Pitts]

Why are people so toxic now?

I don't think he was being toxic? Or is correcting an error toxic now? From reading the article, I assume you meant large mesoscale "circulation". What I'm getting from the article is that rather than the bow echo overtaking the supercell, the two merged and ultimately created something like a miniature MCV with embedded mesocyclones producing tornadoes within the larger circulation.

 

[MikeD]

Ok. Thanks! Last thing(s). I promise! Where do tornadoes occur in bow echoes, and why didn’t the supercell just become embedded(not combined with the bow echo)?

 

[John Farley]

Usually tornadoes in bow echoes are associated with mesovortices that develop along the leading edge of the bow echo, usually from the apex of the bow echo northward. Sometimes these mesovortices form where the bow echo interacts with some kind of pre-existing boundary from another storm, such as an outflow boundary. Tornadoes can also occur with circulations that form at the northern end of the bow echo; these are sometimes referred to as bow-head tornadoes. And as discussed above, tornadoes can occur if a supercell that initially formed ahead of the line is absorbed into a bow echo or squall line. I am not exactly sure what you mean by the difference between becoming embedded in and combined with the bow echo; to me these terms refer to a similar process.

 

[Nick Dewhirst]

As rdale said, it seems like most of the time the supercell will become absorbed by the line or weaken/diminish prior to the line intercepting it. However, there are some cases where the interaction between the squall line and supercell will produce a tornado or bow echo/wind damage. One of the more well-known cases is the Hunstville, AL tornado on November 15, 1989. Also, if anyone wants to do some reading, squall line and supercell mergers have been formally researched here: http://journals.ametsoc.org/doi/abs/10.1175/WAF-D-11-00058.1

A very prominent case I’ve seen this was exhibited on July 19, 2019 in northern Wisconsin. Moderate risk was issued by SPC for both significant tornadoes and very significant wind damage. PDS severe thunderstorm watch was also issued for gusts up to 105 MPH.

A powerful supercell that had a history of producing tornadoes and very large hail, moving east-northeast around 35 MPH, merged with the main squall line that was moving east-southeast around 40-50 MPH. Once the supercell and the northern portion of the squall line, and pronounced bowing segment was observed northwest of Green Bay. A 60 mile long, up to 10 mile wide significant damage swath occurred. Nearly complete forest blowdowns were viewed in a large areas from NWS damage surveyors in helicopters. Wind gusts were estimated around 100 MPH.

Perhaps the RFD in the supercell enhanced the already very strong rear-inflow jet in this segment? I’m not completely sure if this is logical, but I think it’s very possible this occurs.

 

[Marshall Stoner]

A very prominent case I’ve seen this was exhibited on July 19, 2019 in northern Wisconsin. Moderate risk was issued by SPC for both significant tornadoes and very significant wind damage. PDS severe thunderstorm watch was also issued for gusts up to 105 MPH.

A powerful supercell that had a history of producing tornadoes and very large hail, moving east-northeast around 35 MPH, merged with the main squall line that was moving east-southeast around 40-50 MPH. Once the supercell and the northern portion of the squall line, and pronounced bowing segment was observed northwest of Green Bay. A 60 mile long, up to 10 mile wide significant damage swath occurred. Nearly complete forest blowdowns were viewed in a large areas from NWS damage surveyors in helicopters. Wind gusts were estimated around 100 MPH.

Perhaps the RFD in the supercell enhanced the already very strong rear-inflow jet in this segment? I’m not completely sure if this is logical, but I think it’s very possible this occurs.

I think this probably does happen. I think the resulting bookend-vortex can continue to gather vorticity by a mechanism very different from the tilting of horizontal vorticity mechinism that's fundamental in the initial development of supercell mesocyclones though. It's a bit analogous to the transition of a hurricane to an extratropical cyclone. Not in the literal physical sense of course, but in the sense that rotation persists throughout a transition period where the dynamic mechanism feeding/maintianing the system morphs into an entirely different mode.

 

[Todd England]

On Sunday night October 20th, 2019 at 9PM an EF3 tornado (16.5 mile X 1/4 mile track) plowed through northwest Dallas without any approaching rumble of thunder. At 8 PM I had seen the radar showing 2 supercells 60 miles west of Dallas, while being ahead of a cold front by several hours. At 9:00 PM my phone alerted of a local tornado, at 9:01 the sirens and power went off. My labs who normally get a little jumpy from thunder; continued to nap until we hurried for the crawl space. At about 9:03 I took one more look to the southwest and I could hear the roar of the tornado rapidly traveling south of us. We were about a half a mile north of the tornado and could clearly hear the roar of the tornado and the transmission lines vibrating noise as they shorted out. Because the tornado was traveling so fast, I could easily tell where it was headed in the darkness. The tornado traveled 7 miles in 7 minutes (Walnut Hill Lane and I-35 to Royal Lane and N. Dallas Tollroad) with still no thunder that I could hear. The parent storm was only slightly connected to the tornado and centered about 10 miles to the north of the tornado. There was not really rain at my house, but an occasional 3" glob of water impacting the ground as a warm 10mph northerly breeze blew into the tornado. At about 9:08, as the storm traveled further east of us; it slowed considerably and lightning and thunder were then continuous. 3 close families had their homes destroyed without any warning! Incredibly, there were no deaths or serious injuries. Very spooky how it snuck up on us so silently and quickly! A couple of links:

https://twitter.com/x/status/1186124549802414081

 

[Marshall Stoner]

On Sunday night October 20th, 2019 at 9PM an EF3 tornado (16.5 mile X 1/4 mile track) plowed through northwest Dallas without any approaching rumble of thunder. At 8 PM I had seen the radar showing 2 supercells 60 miles west of Dallas, while being ahead of a cold front by several hours. At 9:00 PM my phone alerted of a local tornado, at 9:01 the sirens and power went off. My labs who normally get a little jumpy from thunder; continued to nap until we hurried for the crawl space. At about 9:03 I took one more look to the southwest and I could hear the roar of the tornado rapidly traveling south of us. We were about a half a mile north of the tornado and could clearly hear the roar of the tornado and the transmission lines vibrating noise as they shorted out. Because the tornado was traveling so fast, I could easily tell where it was headed in the darkness. The tornado traveled 7 miles in 7 minutes (Walnut Hill Lane and I-35 to Royal Lane and N. Dallas Tollroad) with still no thunder that I could hear. The parent storm was only slightly connected to the tornado and centered about 10 miles to the north of the tornado. There was not really rain at my house, but an occasional 3" glob of water impacting the ground as a warm 10mph northerly breeze blew into the tornado. At about 9:08, as the storm traveled further east of us; it slowed considerably and lightning and thunder were then continuous. 3 close families had their homes destroyed without any warning! Incredibly, there were no deaths or serious injuries. Very spooky how it snuck up on us so silently and quickly! A couple of links:

Some supercells produce mostly high-altitude lightning with very soft thunder that can't be heard very well over the sound of traffic and/or wind. I think you sometimes can't see much intracloud lighting from the directly below updraft area because the cloud base is very low to the ground. If there isn't a lot of lightning in the lower part of the updraft tower (due to lack of ice crystals), the tower itself will absorb and/or scatter a lot of the light from higher up away, giving the false impression there is little lighting in the storm. Light pollution in an urban area will also mask a lot of the lightning. The lightning will often be more visible under the forward-flank and/or rear-flank downdraft because descending precip and downdrafts thin out a lot of the low cloud, but that won't be where the tornado is. You can't always count on being able to hear thunder or see lighting when there's a tornado approaching at night. I think that particular tornado was particularly difficult to photograph as lightning flashes bright enough to provide backlighting to the funnel were rather infrequent. Few chasers got good footage of the cone itself. Most just captured powerflashes within the tornado.

 

[Nick Dewhirst]

Some supercells produce mostly high-altitude lightning with very soft thunder that can't be heard very well over the sound of traffic and/or wind. I think you sometimes can't see much intracloud lighting from the directly below updraft area because the cloud base is very low to the ground. If there isn't a lot of lightning in the lower part of the updraft tower (due to lack of ice crystals), the tower itself will absorb and/or scatter a lot of the light from higher up away, giving the false impression there is little lighting in the storm. Light pollution in an urban area will also mask a lot of the lightning. The lightning will often be more visible under the forward-flank and/or rear-flank downdraft because descending precip and downdrafts thin out a lot of the low cloud, but that won't be where the tornado is. You can't always count on being able to hear thunder or see lighting when there's a tornado approaching at night. I think that particular tornado was particularly difficult to photograph as lightning flashes bright enough to provide backlighting to the funnel were rather infrequent. Few chasers got good footage of the cone itself. Most just captured powerflashes within the tornado.

These are very good reasons. I think it was probably a coincidence that neither you nor your dogs heard it. Maybe the roar/wind outside was enough to muffle any thunder and create an apparent white noise for that time.

 

[Todd England]

Thanks for the informative comments. Merry Christmas!