Question About Clouds/Rain/Lightning

[riverratmike]

I've been into the weather ever since I was little and always wanting to learn more about it. One thing I never could understand or for that fact, knew about is what causes lightning. Just two months ago here where I live (Lake Havasu City, AZ) we had some pretty intense lightning storms (even right over my home). What has got my wondering tonight is that it's been raining very hard here the last 4 hours and the dewpoint is over 60 degrees, outdoor temp 65, pressure 29.72 and falling and 85% humitiy, but not one lightning flash has been seen in this storm at my location. Two months ago had about the same amount of rain as tonight but right over my head was lightning flashing 2 twice a second up in the clouds for hours but nothing tonight. Why is that? Just wondering why there is no lightning in this storm tonight?

[Aslkahuna]

You are dealing with two different types of systems for starters. What you have now is a frontal system and upper level Trough that's coming in from CA. The lift that's occurring is large scale and not as rapid as it is during the convective storms of the monsoon. However, this does NOT mean that you couldn't get thunderstorms later as the stronger dynamics and cold air aloft move over your location. In fact, they are very likely tomorrow over much of AZ.

Steve

[riverratmike]

You are dealing with two different types of systems for starters. What you have now is a frontal system and upper level Trough that's coming in from CA. The lift that's occurring is large scale and not as rapid as it is during the convective storms of the monsoon. However, this does NOT mean that you couldn't get thunderstorms later as the stronger dynamics and cold air aloft move over your location. In fact, they are very likely tomorrow over much of AZ.

Steve

Thanks for the info Steve, did a little searching on NOAA this evening and this is what I found...





Why do some clouds produce lightning and not others?

How Powerful is Lightning?
Each spark of lightning can reach over five miles in length, soar to temperatures of approximately 50,000 degrees Fahrenheit, and contain 100 million electrical volts.
Lightning Is A Random, Chaotic And Dangerous Fact Of Nature
At any given moment, there are 1,800 thunderstorms in progress somewhere on the earth. This amounts to 16 million storms each year! Scientists that study lightning have a better understanding today of the process that produces lightning, but there is still more to learn about the role of solar flares on the upper atmosphere, the earth's electromagnetic field, and ice in storms. We know the cloud conditions needed to produce lightning, but cannot forecast the location or time of the next stroke of lightning. There are lightning detection systems in the United States and they monitor an average of 25 million strokes of lightning from the cloud to ground every year!

Lightning has been seen in volcanic eruptions, extremely intense forest fires, surface nuclear detonations, heavy snowstorms, and in large hurricanes, however, it is most often seen in thunderstorms. A thunderstorm forms in air that has three components: moisture, instability and something such as a cold front to cause the air to rise. Continued rising motions within the storm may build the cloud to a height of 35,000 to 60,000 feet (6 to 10 miles) above sea level. Temperatures higher in the atmosphere are colder; ice forms in the higher parts of the cloud.

Ice In The Cloud Is Critical To The Lightning Process
Ice in a cloud seems to be a key element in the development of lightning. Storms that fail to produce quantities of ice may also fail to produce lightning. In a storm, the ice particles vary in size from small ice crystals to larger hailstones, but in the rising and sinking motions within the storm there are a lot of collisions between the particles. This causes a separation of electrical charges. Positively charged ice crystals rise to the top of the thunderstorm, and negatively charged ice particles and hailstones drop to the middle and lower parts of the storm. Enormous charge differences (electrical differential) develops.

How Lightning Develops Between The Cloud And The Ground
A moving thunderstorm gathers another pool of positively charged particles along the ground that travel with the storm. As the differences in charges continue to increase, positively charged particles rise up taller objects such as trees, houses, and telephone poles. Have you ever been under a storm and had your hair stand up? Yes, the particles also can move up you! This is one of nature's warning signs that says you are in the wrong place, and you may be a lightning target!

The negatively charged area in the storm will send out a charge toward the ground called a stepped leader. It is invisible to the human eye, and moves in steps in less than a second toward the ground. When it gets close to the ground, it is attracted by all these positively charged objects, and a channel develops. You see the electrical transfer in this channel as lightning. There may be several return strokes of electricity within the established channel that you will see as flickering lightning.

Thunder
The lightning channel heats rapidly to 50,000 degrees. The rapid expansion of heated air causes the thunder. Since light travels faster than sound in the atmosphere, the sound will be heard after the lightning. If you see lightning and hear thunder at the same time, that lightning is in your neighborhood!

Negative Lightning And Positive Lightning
Not all lightning forms in the negatively charged area low in the thunderstorm cloud. Some lightning originates in the cirrus anvil at the top of the thunderstorm. This area carries a large positive charge. Lightning from this area is called positive lightning. This type is particularly dangerous for several reasons. It frequently strikes away from the rain core, either ahead or behind the thunderstorm. It can strike as far as 5 or 10 miles from the storm, in areas that most people do not consider to be a lightning risk area. The other problem with positive lightning is it typically has a longer duration, so fires are more easily ignited. Positive lightning usually carries a high peak electrical current, which increases the lightning risk to an individual.

[Aslkahuna]

You get ice in the clouds associated with the cool season storms in AZ as well but in general the vertical motions in the large scale ascent brought about by the dynamics associated with these systems are generally not strong enough to produce the necessary charge separation needed for lightning. However, we can get thunderstorms with cool season storms if the dynamics are unusually strong, the ULL is unusually cold aloft which results in strong instability or we get unstable tropical air into the system. By and large, Pacific air coming into AZ is usually not unstable in the Winter unless we get really cold air topside.

Steve

[riverratmike]

You get ice in the clouds associated with the cool season storms in AZ as well but in general the vertical motions in the large scale ascent brought about by the dynamics associated with these systems are generally not strong enough to produce the necessary charge separation needed for lightning. However, we can get thunderstorms with cool season storms if the dynamics are unusually strong, the ULL is unusually cold aloft which results in strong instability or we get unstable tropical air into the system. By and large, Pacific air coming into AZ is usually not unstable in the Winter unless we get really cold air topside.

Steve

Steve,
Well I we did get quite a lightning show in the sky tonight. About 30 miles east of LHC, AZ I saw a ton of cloud to cloud lightning, looked like it was out over the Bill Williams refuge area, and was flashing about once every 5 seconds. I'm working night shift and I came out on break at 9pm and was very surprised to see all the lightning. Sure wish I was at home I would have captured some incredible lightning images with my camera. That bummed me out I missed it!

[Aslkahuna]

The ULL came directly over you so you got the cold air aloft which meant you had the greatest instability and hence the thunderstorms.

Steve

[riverratmike]

The ULL came directly over you so you got the cold air aloft which meant you had the greatest instability and hence the thunderstorms.

Steve

What exactly is a ULL?

[Aslkahuna]

Upper Level Low

Steve

[riverratmike]

ah ok, well we have a departing storm here in LHC, AZ but don't know if we'll get that ULL