No thunder no lightning, you call that a severe thunderstorm?

[Jason Harris]

Just reflecting on the issue of warnings for the public and the lightning-less storms producing some tornadoes (allegedly) in CA today and the line currently moving through with no lightning (and thus no thunder), and it makes me wonder how often perhaps people have ignored storm warnings if they didn't at least hear thunder or see lightning. Like you're telling me there's severe thunderstorm warning and I don't even see any lightning? Must not be near me. Perhaps a throw-away question. I suppose just saying convective storm wouldn't work?

Also, today might not be a great example since I had just been glancing at wunderground NEXRAD but I see here there is lightning data coming in:
http://www.uspln.com/images/uspln_animated.gif

 

[rdale]

It's the best you can do without overly confusing the public. More urgent to get out than a High Wind Warning (nobody cares about those anyways.)

 

[Jeff Miller]

I can recall many events of lightning-less "thunderstorms" that prompted Severe Thunderstorm Warnings.

One in particular went through NW Ohio in the late 90s. A line of showers with high straightline winds in excess of 60 MPH went through the area and severe thunderstorm warnings were issued on a north to south line. There was absolutely no thunder whatsoever with this line - and the public comments I heard the next day were "they blew that one" for issuing severe thunderstorm warnings...without even the least bit of thunder - Just high winds and heavy rain with a thunderless squall line with that. Yet I suppose it was the correct warning format though technically it is true they were not thunderstorms - just rainshowers with a strong gust front.

I just don't think the public would take a "HEAVY SHOWER WITH STRONG WINDS" or "A RAINSHOWER CAPABLE OF PRODUCING A TORNADO" as seriously as "SEVERE THUNDERSTORM WARNING" and TORNADO WARNINGS with the "thunderstorm" wordings, and I think that's what Rob Dale was pointing out as well.
There was another incidence as well with "thunderless" warnings. Some activity just isn't electrical but still can create severe wind, straightline or rotating. I've seen this happen many times.

On a sidenote is the myth that thunder/lightning intensity and frequency in a thunderstorm in the public's mind corresponds with the chance of large hail, tornado, etc... this shatters that theory completely and thunder/electrical activity should never be a gauge for the dynamics that produce warnable severe weather, ie. large hail, damaging thunderstorm winds, and tornadoes. Constant CG lightning alone can't get a severe thunderstorm warning issued...but no lightning at all and good dynamics certainly can.

 

[Jeff Duda]

I've never really thought of that until now, but what is the definition of a thunderstorm? I found the NWS and AMS definitions:

Thunderstorm
A local storm produced by a cumulonimbus cloud and accompanied by lightning and thunder.

thunderstorm—(Sometimes called electrical storm.) In general, a local storm, invariably produced by a cumulonimbus cloud and always accompanied by lightning and thunder, usually with strong gusts of wind, heavy rain, and sometimes with hail.

I very much agree that dangerous weather can occur with events that contain no lightning or thunder and that a severe thunderstorm warning for high wind, for example, would probably be a very good idea, even if it is inaccurate or misleading. However, this causes me to question the definition of a thunderstorm. Certainly the above definitions are correct and sensible, but like Jason said, maybe "convective storm" is a better definition (even though I realize that would require an overthrowing of most people's knowledge base regarding thunderstorms). Still, it is interesting, since by definition, a high wind event, even if convectively produced, might not be technically considered a thunderstorm:

Severe Thunderstorm
A thunderstorm that produces a tornado, winds of at least 58 mph (50 knots), and/or hail at least 1" in diameter. Structural wind damage may imply the occurrence of a severe thunderstorm. A thunderstorm wind equal to or greater than 40 mph (35 knots) and/or hail of at least 1" is defined as approaching severe.

 

[Jeff Miller]

Speaking strictly technically: I agree with you that if the weather phenomenon does not have the ability to create lightning then, technically speaking, it's not a thunderstorm.

The public will never take seriously the fact that a heavy rainshower has created or can create a strong or violent tornado - or that a line of heavy rainshowers in squall line form can and occasionally does create straightline winds in excess of 58 MPH. Therefore, even though they aren't technically thunderstorms until we get that one flash or stroke of lightning - it's best to call them that so we don't minimize the severity of the approaching situation.

One other question, taking the squall line in consideration: If you have a 600 mile wide "lightningless" squall line - and one flash happens somewhere in the line - again, being annoyingly technical - does that one flash make the entire squall line a "thunderstorm" since it is all a solid line - or just that radius around the individual spark?

 

[Paul Knightley]

We quite frequently get events which produce severe winds from convection but don't have thunder (winter time especially). Some of these produce tornadoes too, without thunder.

Is it a big problem with SVR? How many people take note of severe thunderstorm warnings anyway?

 

[John Wetter]

With the numerous tornadoes in Eastern MN on August 19, 2009 (including the tornado in downtown Minneapolis) MSP never reported TS...

 

[Jason Foster]

Let's face the real fact here, it's California. Would anyone be paying attention to the NWS office anyway.

I think it is interesting how some terms just eventually get used as general terms and don't necessarily reflect the 'technical' element that was the root of the original word.

I'm not so hung up on wording of NWS messages as long as it points toward safety. When we can get folks (aka the general public) to have a greater knowledge of the difference between watches and warnings and what those really mean to them, that's when I'll start to even worry about technicalities.

 

[Larry J. Kosch]

Lightning and Thunder!

There was another thread on a related subject of why we see lightning before we get the rain.

http://www.stormtrack.org/forum/showthread.php?t=22788

This web site has good lightning questions:

http://www.usatoday.com/weather/resources/askjack/archives-lighting-science.htm

In the website, it was said that 80 percent of the storm's lightning is C-C (Cloud-Cloud), the rest is 20 percent C-G (Cloud-Ground). Most of the CC lightning rarely produces thunder. And we normally don't see the CC stuff unless it happens to be dark.

I suspect the storms coming in were not sufficiently uplifted to generate a charge potential between the cloud base and the ground to produce CG strokes. And perhaps the dewpoints and freezing levels were not where they need to be to produce the ice pellets and hail needed to create the electrical imbalance needed to make lightning.

I have seen rain on a widespread basis in my area where it fell with no CG lightning strikes. Sometimes in the passage of a cold front, you get gusty winds, then the heavy rain. And you catch the lightning on the backside of the storms. Some of the storms have what they call anvil crawlers, where they branch out from the storm core and "crawl" along the underside of the cloud anvil like spiders!!

 

[rdale]

. Most of the CC lightning rarely produces thunder.

Why would CC lightning not have thunder?

 

[Brandon Goforth]

Why would CC lightning not have thunder?

LOL! I saw that too and was like "wth?"...

 

[Larry J. Kosch]

Clouds Muffles the Thunder

Why would CC lightning not have thunder?

It's akin to a mobster putting a pillow over his gun before making his "hit". He doesn't want people to hear his gun go off when he execute his victim.

The cloud tends to muffle the thunder sounds and the C-C lightning strokes tends to occurs miles above ground in the thinner air layers. The C-G lightning stroke heats up the air below the cloud without the cloud muffling.

For a brief instant, the air expands around the lightning stroke faster than the speed of sound. This produces a "shock wave" that compresses the air around the lightning bolt and creates the thunder sound. Thunder heard close by or above you tends to sound like a BANG, where the thunder further away tends to be lower in volume and intensity. Also some thunder sounds have varying intensity due to the main stroke and the feeder strokes closing at different times.

Thus the rumbles you hear may not be your hungry stomach...

 

[Jeff Miller]

CC lightning and IC ligntning can and does produce thunder which is audible quite frequently at ground level in many thunderstorm events.

While it is true that in some instances the air profiles may "muffle" or "redirect" Cloud to Cloud thunders, as in winter snow events snow does, the thunder is in reality just as sonic as even CG thunder. In many instances, CC lightning and IC (intracloud) can cause the long, rolling, punching thunders associated with many mesoscale convective systems and complexes. Other times, the atmospheric profiles can be such that you can hear virtually every CC and CG charge in a storm producing what I call the "Thunders of Zeus" - a constant wall of roaring, unabating thunder.

Cloud to Cloud and Intracloud lightnings are also responsible for the unabating, long winded, never ending thunder rolls that I personally am a huge fan of.

I think it was innacurate to say that CC's (and IC's, since IC's are more common than CC's, actually) rarely produce thunder. All lightning produces thunder. Not all thunder reaches our ears, however, as intensely in some situations, as they do others.

 

[Larry J. Kosch]

"Thunder of Zeus" Tornado?

I'm wondering since it has been noted that severe thunderstorms going tornadic has a sudden increase in the frequency and intensity of lightning. both CC and CG. Could that contribute to eyewitness statements the tornado sounds like a loud frieght train/jet engine? When they may be hearing the continuous roar of thunder from the lightning? Or is it the sounds of the winds near the ground and the debris breakup making the tornado sounds??

 

[Jeff Miller]

The sounds within a tornado circulation vary widely - factors include wind speed and strength, debris within the funnel, debris being torn up around and inside the funnel, thunder due to lightning in and around the circulation, among other possible noise-making elements (transformers blowing, gas pipes leaking, etc etc etc).

Short answer to a complicated question.