The heavens declare the glory of God;
the skies proclaim the work of his hands.
-Psalm 19:1

Do you know that God controls the clouds and makes his lightning flash?
-Job 37:15



Thursday, June 18, 2009

What is heat lightning???

SKY WATCH FRIDAY time! I am busy busy with stimulus yuck, so I might not get a chance to say hi. Please don't take offense. Our hosts: Klaus Sandy Ivar Wren Louise Fishing Guy

Thanks, also,to Dot and Tom, who were instrumental in the success of this blogging event. You should definitely come fly with us!

In honor of our summertime-like thunderstorms, I give you cloud to cloud lightning at night.This morning, I awoke to flashes of lightning, no thunder, just bright flashes of light, lighting up the dawning morning sky. Just moments ago (6:40AM or so), the National Weather Service in Jacksonville issued a severe thunderstorm warning including the county to my east, indicating that hail and wind were a definite threat from the supercell that was pressing southward out of Fargo, Georgia. Yesterday evening, we had the same, severe warned in the county just east of me, and 1 3/4" hail was reported in Fargo with that powerful cell. Here... of course, nothing but brilliant flashes of light, which might have actually been on the outskirts of that storm which was 15-20 miles away. We didn't even have rain...

Lightning without sound is referred to as "heat lightning". My parents used to tell me that "heat lightning" was caused by extreme heat and it's harmless. Many people actually believe that heat lightning is a "safe lightning", not necessarily true. Well, it is called heat lightning, but that really is a misnomer. Heat lightning is lightning with no audible thunder. It's not because it has no sound, but because it is too far away or changes in densities in the air affect whether or not the sound of the thunder is able to refract to us, so we can hear it.

If a lightning strike is a sufficient distance from the observer, sound from the strike will not be heard. These "silent bolts" are called heat lightning.

The movement of sound in the atmosphere depends on the atmospheric properties of the air such as temperature and density. Because temperature and density change with height, the sound of thunder is refracted through the troposphere. This refraction results in spaces of volume in which the thunder does not propagate through. The sound of thunder often reflects off the earth's surface. The rumbling sound from thunder is partly due to reflections off the earth's surface. This reflection and refraction leaves voids where thunder can not be heard (click here for an applet of this by Tom Whittaker.) Therefore, the Earth's curvature also contributes to people far from the strike from not hearing it. Thunder is more likely to be bounced off the earth's surface before it reaches an observer far from the strike. The reflection and refraction in the troposphere determines who hears the strike and who doesn't.

The term "heat" in heat lighting has little to do with temperature. Since heat lightning is most likely to be seen in association with air mass thunderstorms in the warm season, the term "heat" may have been used because these flashes are often seen when surface temperatures are warm.
~Meteorologist, Jeff Haby
As I said though, it is possible for density and temperature to affect whether or not the sound of thunder travels through the air, so potentially dangerous nearby thunderstorms can go unheard (not too common). So, "if you hear thunder, you are close enough to be struck" AND if you see nearby lightning, get inside! Lightning is a real and serious threat, always. Lightning strikes can (and do) occur outside of the audible thunder zone. Click on the above image for lightning facts about strikes "out of the clear blue sky". Play it safe. If there is a thunderstorm anywhere nearby, get indoors.

Speaking of thunderstorms, looks like a major concern for hefty severe weather, including a heightened risk for tornadoes. The Storm Prediction Center is expecting the next two days to be among the most active of the year for severe weather.






Folks in the northern plains, including Wisconsin should be very aware of the weather, and take any warnings seriously, as tornadoes are a serious threat today.
SEVERAL ROUNDS OF SEVERE STORMS WILL LIKELY AFFECT THIS AREA... COUPLED WITH STRONG DAYTIME HEATING AND DEWPOINTS IN THE MID 70S WILL YIELD EXTREME INSTABILITY WITH MLCAPE VALUES APPROACHING 5000 J/KG AND LITTLE CAP. FORECAST SOUNDINGS OVER SOUTHERN MN AND NORTHERN IA INDICATE THE RISK OF INTENSE SUPERCELLS FORMING OVER THIS AREA CAPABLE OF VERY LARGE HAIL...DAMAGING WINDS...AND PERHAPS SIGNIFICANT TORNADOES.
Have a safe day... turn on your weather radios! (That includes you, sis!)

12:00pmEDT: Talk about Dewvoid... those watches might has well have been 1000 miles away... I am between them.Alas, the tornado probabilities have been redrawn...... and we are within an area with a chance of tornadoes...

Latest update: Apparently, I typed too loudly... Dewvoid, back in action.~Dewdrop

34 comments:

  1. That was a great light show last night! Sadly I had no camera. Shame on me..

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  2. How fascinating! So heat lightning, has nothing to do with heat!!! Amazing.

    I really apprecdiated this post. Thank you so much for sharing all this wonderful interesting information!

    I envy you your thunderstorms, but not the tornados!

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  3. fascinating and interesting post. to me lightning is lightning and I am frightened.

    enjoy the weekend.

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  4. I had no idea that if you can hear the thunder that you're close enough to be struck. That's scary!

    Last weekend I met a young woman who was struck by lightning while riding on a farm tractor. When she shakes hands she gives off sparks...so she says. I didn't test it. ;-)

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  5. I love that photo - the lighting appears as a steady, internal fire rather than a strike.

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  6. WOW, awesome post and photo's!!
    I love thunder and lightening!!
    Happy SWF

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  7. hello and happy thursday.
    we had some heat lightning before we left for california last week. i should have gotten up and snapped some shots but...didn't.
    lovely capture...
    have a wonderful evening.

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  8. Great photo. I really enjoy all of the great information you provide!

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  9. Another stunning lot of info here Dew.... we have had some storms again this week... but nothing like this.

    Tom
    My Sky Watch post are: Sky Views and Rainbows

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  10. How fascinating and interesting post!Great sky!
    Happy SWF and thank you for sharing!

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  11. Good evening. Wonderful lightening photograph you have shared with us today and the write up is always so helpful to me.Thank you.
    We had storms on Monday though there was to much rain and hail to get a picture.
    Have a good weekend.

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  12. Excellent skywatch post as always, I just love that night shot.

    Have a great weekend
    Guy
    Regina In Pictures

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  13. Awesome photo of a very powerful looking cloud for Sky Watch Friday, thanks for adding to the party.

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  14. That's an amazing shot !!

    I think we may have had some of that they other night. It was pretty noisy for a little while.

    Your posts are so informative... thank you !! :-)

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  15. Wonderful sky shot and as always a fascinating post.

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  16. Great post, not only your perfect dramatic picture, also your writings are superb, learned a lot from it!!!

    Have a nice Skywatch Friday.

    Greetings from NL

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  17. that sky looks scary and gloomy

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  18. looks like there is a heavy rain coming...

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  19. So interesting to learn about lightning. The photo is great. We need you in CO - much unsettled weather here lately!

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  20. Thanks for sharing this post and these images. That first photo is intimidating!

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  21. great post, exciting weather, outstanding photo.

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  22. You give us clouds and knowledge.
    Thanks.
    Luiz Ramos

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  23. I should get you and my mother together. She would never admit it, but everyone who knows her knows she's paranoid about severe weather. She watches the news just to see whether or not her panic attacks are justified. That's my conjecture, but I believe it to be true.

    In an scary sort of way, I wish I could get some of your enthusiasm and fascination with weather, more importantly your actual knowlegdge and understanding, to rub off on her. I've had nearly 55 years of watching her be terrified.

    Wow. Sorry. I guess I needed to vent a bit! Must be the humidity! :-D

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  24. I love your enthusiasm for storm chasing and the phenomena of the wonders of nature weather wise. I get the adrenalin rush and get you have a respect for it. Awesome images and always come away learning.

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  25. Beautiful shot of that night time lightning....great info about the silent bolts...so interesting...

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  26. Fierce skies indeed! Summer storm season has not hit us yet. So far no thunder storms and very quiet with little rain. I am sure nature is going to change that eventually :)

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  27. Great post...great info... awesome picture!
    I'm chicken when it comes to thunder & lightning...
    *A wonderful weekend to you* Maria

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  28. Beautiful, as alway Dew! Thanks for sharing!

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  29. a threatning sky to be frightend of????? great shot

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  30. Dew: That is a neat capture and we are having that same weather today. I can hear the thunder roll as I'm typing.

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  31. My sister in law was working in a potato field when a young girl was struck by lightning and died so I am scared of it but love to see it XXX Don

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Dew comment, please...