Updraft: July 22, 2009 Archive

When lightning strikes

Posted at 8:36 AM on July 22, 2009 by Paul Huttner (0 Comments)

Fourteen-year-old Taylor Zimmerman was under a tree in the front yard of her Stillwater home Tuesday when a lightning bolt struck. That tragic story is all too common in lightning fatalities. Trees are often the highest object in the landscape, and their roots conduct lightning currents into the ground.

Numbers tell the lightning story best:

24 people have died in the U.S. so far this year from lightning strikes.
7 of those fatalities have occurred near or under trees.
2 deaths have occurred in Minnesota this year. (A 42 year old man was killed in St. Cloud on May 6th while doing yard work.)
100% of all lightning deaths since 2007 have occurred outside.
Lightning strikes U.S. soil about 23 million times a year on average.
About 1 million of those strikes occur in the Upper Midwest.
Minnesota averages 386,131 cloud to ground lightning strikes per year.
About 400 people are struck by lightning in the U.S. each year.
55 to 60 of those are killed.

Cloud to ground lightning is most frequent in Florida and along the Gulf Coast states. Other high frequency areas include tornado alley and desert southwest. I have talked with Ron Holle many times who is a lightning expert with Vaisala Inc. in Tucson, Arizona. Vaisala runs the National Lightning Detection Network. The network uses an array of sensors to detect and pinpoint cloud to ground lightning. Ron has studied lighting for decades. He has seen documented images of lighting bolts travelling sideways for over 30 miles and striking ground far away from thunderstorms.

Ron and others helped develop the 30-30 rule for lightning safety. You should seek shelter indoors if there are under 30 seconds between a lightning flash and when you hear thunder. You should stay indoors for 30 minutes after the storm has passed to be safe. Most people are struck by lighting before storms arrive and after thunderstorms have passed. Use the 30-30 rule to be safe.

I remember working the day 5 people were struck by lightning during the U.S.Open in 1991 at Hazeltine. I was on the air broadcasting severe thunderstorm warnings about 30 minutes before the strike as storms moved up the Minnesota River Valley toward Chaska. All 5 were seeking shelter under a tree when the bolt hit.

Stay inside your home or car when lightning is near. It's the best way to stay safe.

PH

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Scattered storms, lightning, hail and funnel clouds today

Posted at 2:50 PM on July 22, 2009 by Paul Huttner (0 Comments)

Lumpy cumulus building over the Weather Lab today.

Here we go again.

The atmosphere over much of Minnesota is unstable and moist enough for scattered storms to develop in the heat of the afternoon again today. Some of the stronger storms will produce local downpours, hail and gusty winds. There is also enough rotation in a few of the storms to produce funnel clouds. There are reports of funnels this afternoon.

Storms will be scattered again today, covering about 30% to 40% of the area at any given time.

These storms today are what we call "popcorn" or "air mass" showers in the weather business. Storms are not focused on any weather feature like a warm of cold front. The air mass over Minnesota has just enough moisture and instability to support development. A nice sunny morning heats the air to what is called the "convective temperature." Once it gets warm enough, air parcels begin to rise and produce showers and a few storms. The trigger for these storms is the heat of the day. This is just like when you turn your stove on to boil water. After a few minutes, bubbles (convection currents) begin to boil in your pot.

Keep an eye out to the northwest today. And respect the lightning. Storms will move slowly toward the southeast. I'm pulling for a good downpour at the Weather Lab today.

PH

Storm reports today:

MPX: Bloomington [Hennepin Co, MN] trained spotter reports HAIL of nickel size (M0.88 INCH) at 04:56 PM CDT -- pea and nickel size hail.

MPX: 1 Sse Clayton [Polk Co, WI] trained spotter reports HAIL of quarter size (M1.00 INCH) at 04:04 PM CDT -- hail covered the ground. some leaves ripped off trees.

MPX: 4 Ne Henderson [Scott Co, MN] public reports HAIL of nickel size (E0.88 INCH) at 02:20 PM CDT -- three miles south of Blakeley.

MPX: 3 S Montrose [Wright Co, MN] law enforcement reports FUNNEL CLOUD at 01:30 PM CDT --

MPX: 2 E Stockholm [Wright Co, MN] law enforcement reports FUNNEL CLOUD at 01:27 PM CDT -- intersection of county road 30 and 3. possibly same funnel seen near winsted and silver lake.

MPX: Winsted [Mcleod Co, MN] trained spotter reports FUNNEL CLOUD at 01:30 PM CDT -- funnel cloud roping out, still half way to the ground.

MPX: Winsted [Mcleod Co, MN] trained spotter reports FUNNEL CLOUD at 01:25 PM CDT -- funnel half way to ground.

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Funnel cloud near Cokato

Posted at 3:04 PM on July 22, 2009 by Paul Huttner (0 Comments)

A funnel cloud dips from the cloud base near Cokato around 2pm today. (Photo by MPR listener Mary Huff)

Mary Huff was driving near Cokato around 2pm today when she saw this in the sky.

This is a funnel cloud. It is what we would call a rope funnel extending from the cloud base. This is not a supercell type storm or classic rotating wall cloud funnel. This is closer to what we call "cold air funnels" in the weather business. These funnels rarely touch down, but when they do they can cause minor EF0 to EF1 damage.

If you see one of these today, show enough respect and take appropriate action and get to cover if it is going to touch down nearby.

PH

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