Updraft: April 20, 2010 Archive

Volcanic lightning explained

Posted at 8:43 AM on April 20, 2010 by Paul Huttner (4 Comments)
Filed under: Severe weather, Volcanoes

Spectacular lightning flashes over Iceland's Eyjafjallajokull volcano. (Photo Credit: Marco, Fulle, Stromboli Online.)

The images are spectacular.

While volcanic lightning is not fully understood, it may give us some clues as to the mysteries of lightning within thunderstorms.

The basic idea when it comes to understanding lightning is electrical charge separation. When electrical charges separate enough to overcome the resistance of the air in between, an electrical discharge occurs. In our home we call this a "door knob shock." In the atmosphere we call it lightning.

It appears that you need rapidly moving rain and solid objects to create sufficient electric charge separation to produce lightning in thunderstorms. In thunderstorms, this is achieved by hailstones rapidly moving and colliding in violent thunderstorm updrafts which can exceed 100 mph.

In volcanoes such as Iceland's Eyjafjallajokull volcano, it appears to be caused by solid debris being ejected by the volcanic plume. Positive and negatively charged particles separate, and lightning is the result. In this case; really, really SPECTACULAR lightning.

Dr. Greg Forbes of The Weather Channel does a nice explanation here.

Severe weather awareness week:

This is severe weather awareness week in Minnesota and Wisconsin. Though our weather is blissfully quiet for now, it's a good time to brush up on terms, and to check you weather radios for the storms to come. If you have a weather radio that has SAME technology, you can program it to sound alerts only for your county. This is a great value at home or the cabin. You can find a list of SAME county codes here.

Enjoy the sun and low 70s today, as our stretch of May weather continues in April. There is some chance of rain this weekend as a weather system tracks to the south.

Stay tuned.

PH

(4 Comments)

Forecasting the ash plume

Posted at 2:50 PM on April 20, 2010 by Paul Huttner
Filed under: Volcanoes

NASA satellite image of Iceland's Eyjafjallajokull eruption on April 17, 2010. (Photo: NASA Earth Observatory.)

Be glad you're not a meteorologist with the UK Met Office these days.

Forecasting volcanic ash clouds as air traffic in your country and much of Europe is shut down can be a trifle stressful to say the least.

There is some good news in the ash forecast over Europe today. The volume of ash seems to be declining as the volcano transitions to a more lava based event. Many are hoping it stays quest. If it does, the ash plume may have a chance to disperse over the next few days.

UK Met Office volcanic ash forecast

The latest eruption appears to have belched out an ash plume that is mostly below 20,000 feet. That is good news for high altitude jet traffic that can fly over the plume, but not so good for descending though the plume to find a place to land.

Here is the latest from the UK Met Office today.

•Met Office and NERC aircraft have observed volcanic ash in UK airspace at varying heights.
•Multiple land observations have recorded ash in the skies across the UK, including across southern Britain.
•Balloon observations have shown a 600 m deep ash cloud at an altitude of 4 km across parts of the UK

NASA satellite image of volcano plume track on April 19th.

"Plume Dispersion" is an entire area of meteorology that deals with how emissions sources such as smoke stacks, power plants, and yes, even volcanic plumes disperse in the atmosphere. In a previous life, I used to issue a wind forecast for a nuclear power plant in Zion, Illinois. That forecast would have been used to create a plume dispersion model in the event of a nuclear accident that released a radioactive plume in the Chicago area. At the time, I lived 8 miles from the plant. It goes without saying that my heart was into that forecast 100%.

Here are some resources to track the Icelandic ash plume.

-UK Met Office ash plume forecasts
-UK Met Office lightning data
-UK Met Office Volcano page
-Satellite animation of initial eruption plume
-NASA satellite images

PH