Discussing Lightning and Thunder

Lightning bolt! (Photo credit: Wikipedia)

With all the storms in the weekend forecast, why not talk about lightning and thunder?  Local WCCO-TV news ran a story on this yesterday, but in my humble opinion, it didn’t tell us much.  Some of it even missed the mark.  So here we go!

The question was asked:  Why does thunder crack and sometimes roll?

Many reasons determine the sound of thunder.  Distance is a key component.  As the sound waves from thunder travel toward you, they travel through different densities of air, different temperatures, and fade.  Lower tones travel the farthest.  You tend to hear the low rumble of distant thunder, therefore.

Also the length of a lightning bolt affects the sound you hear.  All thunder is the result of lightning and some lightning can travel over 60 miles.  You literally hear different parts of the lightning bolt at different times.  This can also give thunder and rumbling, rolling sound.  Different parts of the sound travels through different densities of air, for example.

Where you are in the storm matters, too.  Generally we hear the first strikes of thunder the loudest and clearest, especially if the thunder precedes any rainfall.  Without rain impeding the sound waves, the thunder tends to be more sharp and clear.

And if you happen to be right next to a strike, you get the loud crack that sounds instantaneous because the sound has very little distant to travel and distort.  You hear the loud crack.  If you still have your wits about you, you can often still hear the thunder roll away in the distance, too.

Two errors in the WCCO story.  One minor and the other a bit more signficant.

First, lightning and thunder rarely occurs in the winter not because there isn’t as much moisture in the air, but because there isn’t as much static electricity in the air.  The turbulent rising and falling of rain and especially ice in thunderstorms creates a charge (usually a negative charge) in the cloud that is discharged against a positive charge elsewhere, even in another cloud.   It is a matter of turbulent storm dynamics, not moisture, that causes lightning and thus thunder.  It does happen in the winter, but rarely, because the storm dynamics are not right.

May Storm Over Linden Hills

(I heard someone once say that lightning is rare in hurricanes, too.  Is that true?  I was told hurricanes expend energy in circulating winds that inhibit tall thunderstorm development.  I don’t know if this is true.  Does anyone from Florida or Louisiana read this post?  My dear friend Sandy can answer this for me.  I’ll get back to you.)

The second and more silly error is how the difference in time between a lightning strike and the sound of thunder was explained.  They explained that every five seconds counted after seeing a lightning flash and hearing thunder counted for a mile of distance, which is essentially accurate.  If you can count thirty seconds, for example, the storm is about 6 miles away.   The meteorologist said this was true because light travels five times faster than sound.  This is incorrect.   (Sorry, Mike Augustyniak…but it is ok.)

Light travels at a speed of 186,000 miles per second or almost 700 million miles an hour.  (We learned this in school, right?)  Sound travels about 768 miles per hour, right?  I’m not a math wiz, but light travels many millions times faster than sound.  And if you think about it, it doesn’t matter anyway.  If light travels “five times” faster than sound, how would counting to five measure that.  Where is the constant?  If I counted really slowly and only got to three, would that mean light traveled three times faster than sound?  Nope.  The logic behind the incorrect answer is incorrect as well.

So there you have it, my little brush up on lightning and thunder.  Please reply with all corrections kindly.

Related articles

• Why are we getting thunder and lightning? (metofficenews.wordpress.com)
• Flash Facts About Lightning (nationalgeographic.com)
• Frequently Asked Questions About Lightning (nssl.noaa.gov)

Pictures I Didn’t Take

Several opportunities for good photos came and went today.  They would have captured some of the more interesting people a guy can meet on a gig like mine…if I had taken the pictures.  I’ll tell you about them and explain briefly why I didn’t take the photos, if that is necessary.  This will be brief post.  (You should be scrolling down to an older post and reading something better, but bear with me anyway.)

The first opportunity for a photo I didn’t take presented itself when I pulled over to send an email to Pat Kessler at WCCO TV in Minneapolis.  I had just heard Michele Bachmann make another one of her reckless and misleading statements, this time about taxes and jobs, and Pat Kessler is an excellent journalist here who takes time to call out politicians when they make reckless and misleading statements.  Needless to say, Mr. Kessler is very busy.  And I’m frequently pulling over to fire off an email to someone or other.  You can’t drive a country mile without hearing something asinine on the radio.

These stops are something like an old school cake walk.  When the music stops you need to find a place to sit.  The difference is when I hear something stupid, I need to pull over.  You get the idea.

Today I stopped in a typical midwestern neighborhood in Stillwater, MN.  I pulled up in front of a 70s era one-storey house.  I’m not sure what you call the style.  Shoebox is how I would describe it, and within the shoebox are rooms are laid out like more shoeboxes…kitchen, dining, living, and three bedrooms and a bath.

It’s about 1:00 in the afternoon and I notice the light above the front door come on.  It is cloudy, but hardly dark.  Soon I see a young twenty-something disheveled woman go out the back and run to an old Oldsmobile.  We have thousands of those here in Minnesota and quite a few Oldsmobiles, too.  Nothing unusual. 

I was in the middle of my poorly written email to Pat Kessler when a young skinny guy comes out the front door and skips down to a car parked in front of me.  He rummage through something and I start to worry that he might be rummaging for a gun.  He had the look.  Perhaps he was in the high school production of West Side Story, but I don’t think so. 

No gun that I could see.  Just a pack of something then he starts back to the house.  When he gets to the door he stops, looks back at me, and comes running across the snow crusted yard in his stocking feet.  I roll down my window.

“Can I help you with something?” he asks me in a sarcastic voice straining to be polite.

“No, I’m ok.”

“What are you doing here?”

“Working.”

Now this might have been the wrong answer.  I imagine he figured that part out.  He thinks, perhaps, that I am the Barney Fife of the FBI sent to stake out his place and don’t have enough sense to park around the corner.  I am there in front of his house in a plain suit and I even wore a fedora.  Add to that my computer, phone, and the fact that I am watching him and his girlfriend and I suppose I look like an incompetent stake out.

Barney Fife. Not Me.

“What kind of work do you do?”

“I sell advertising.”  I say it almost with pride and nod at the pile of phone directories and newspapers spilling all over my front seat. 

“Here?”  He asks. 

“Yes, I stopped to do some work and send an email.”

“Here??”

I notice he has what appears to be a joint in his right hand.  Either he knows I’m not a cop or it is not a joint or he’s just recklessly curious. 

“Yes, I just happened to be here when I decided to stop and work.” 

The Oldsmobile is speeding off now.  He watches it careen around the corner and disappear.  Then he looks back at me.  Then back at the corner.  Back at me…then skyward, shaking his head muttering something…

This is the picture I wish I could have captured.  He seems to realize that he jumped at a false alarm, but it is unfolding to him slowly.  His brain is in no hurry to sort it out for him.  And I’m sitting there like a dork with my computer in my lap.  I was a dork.  If I had worn plaid pants I couldn’t have done any better. 

His shoulders sink, then he shrugs, and I say “Have a good day.”  He wants to kill me, but hasn’t the heart.  Now is not a time to ask for photo.  He trots back into the house, closes the door, and turns off the front light.