Updraft: July 13, 2009 Archive

When lightning strikes

Posted at 11:56 AM on July 13, 2009 by Ken Paulman (0 Comments)

Paul Huttner's tied up (not literally) at the Weather Lab today, so I went traipsing off to the YouTube well in search of something fresh for the blog.

The above video was shot on Saturday by "cheliman1" of Hydetown, Pa. Nothing spectacular, really - a run-of-the-mill thunderstorm with some neat cloud formations. Then you hit about 3:15 into the video, and a bolt of lightning strikes maybe 20 or so feet away from the camera.

As a non-meteorologist, there were several things about this that I found fascinating:

• * It's been such a quiet summer in Minnesota that we have to look to Pennsylvania for storm footage
• * The lightning bolt looks really small up close
• * There is neither profanity nor loud proclamations of "WOOO!" when the lightning hits. Just a quiet "Did you get that?"

Also, note that the lightning bolt ignores the trees, power poles and an unknown number of golfers who may or may not be standing outside of the frame. The tallest structure near the strike is either the gazebo in which the storm-watchers are standing, or the nearby wooden fence. When I started watching the video, I expected the power pole across the street to bite the dust. You can't outsmart nature.

Since the last Updraft update on lightning safety a few weeks ago, at least eight more people have been killed by lightning strikes in the U.S., according to the National Weather Service. On average, fewer than one-third of those victims were standing under a tree.

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Unusual weather pattern: North Shore warmth

Posted at 3:45 PM on July 13, 2009 by Paul Huttner (1 Comments)

Web cam from Grand Marais today shows a warm scene on the North Shore.

Welcome to the Scandinavian Riviera.

It's not often Minnesota's North Shore is the warmest spot in the state. Today it's the place to be for summer temperatures.

An unusual weather pattern is causing temperatures along the North Shore this afternoon to be the warmest in Minnesota. As of 3pm Silver Bay is 82 degrees. Down by The Bay at Grand Marais, it's a toasty 83 degrees. That's pretty nice stuff for cities that are usually cloaked in forecast terms like "cooler by the lake."

Often in July we'd expect to see the warmest temps in the usual places like Wheaton in western Minnesota. It's 75 in Wheaton today. It's only 73 in Ortonville and Madison in western Minnesota.

So what's going on here?

There are two main weather factors at play today that are causing warmer readings along the North Shore.

First, the air mass over Minnesota is seasonably cool for mid-July. Average temperatures for this week are in the mid-80s in southern Minnesota. The current air mass features below average temperatures and is keeping readings on the cool side.

Secondly, there is a downslope wind on the North Shore. Winds today along the Shore are blowing from the northwest. Northwest winds cause air to rush down the hill toward Lake Superior. The elevation difference in places like Grand Marais is about 1,000 feet between the hilltop (1657 feet asl) and the surface of Lake Superior (610 feet asl).

As the air flows down the hill, it warms at the dry adiabatic lapse rate of about 5.5 degrees per 1,000 feet. Atmospheric lapse rates can vary, and today it is a full 10 degrees warmer at the Bay at Grand Marais than at Cook County Airport on top of the hill. The "urban" environment in Grand Marais may also be adding a couple of degrees today.

Today is an unusually enjoyable summer day along the North Shore. It's also on of those rare days we get to say, "warmer by the lake."

PH

Update 5:20pm:

What downslope giveth, the lake breeze taketh away. Winds turned off the lake in Grand Marais between 4 and 5pm. The temperature at The Bay at Grand Marais observing station dropped 24 degrees from 81 degrees to 57 degrees in under an hour. What's that old saying... if you don't like the weather just wait 15 minutes?

PH

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