Updraft: July 7, 2009 Archive

Good sleeping weather

Posted at 8:33 AM on July 7, 2009 by Paul Huttner (1 Comments)

My dad used to say it on nights like we've been having the past few weeks.

"Good sleeping weather."

Back in the day, there was no air conditioning at the young Huttner Weather Lab when I was a kid. The huge, old-school window fan roared to life every evening, sucking the hot air from the upstairs out the window and pulling cooler nighttime air in the other windows from outside. Of course, there was always the debate on which method was more effective, fan blowing in or out?

On hot nights we used to sleep in the hallway by the fan, so we sometimes liked to have it blowing on us. Ultimately I think dad was right, it cooled the house better to have the fan blowing out.

I remember the stories my parents used to tell about how people slept out by the lakes in Minneapolis during the heat waves of the 1930's dust bowl summers. Apparently hundreds of people brought blankets and pillows out to lakes like Calhoun, Harriet and Nokomis and slept outside on hot nights before AC was widespread. I can picture the scene of families sleeping by the lake, and how unusual that would seem today.

The past few weeks have been ideal for home comfort in most of Minnesota. In the Twin Cities you probably have not needed air conditioning since June 25th, our last 90 degree day. Hopefully you have not had to run the furnace since that unseasonable and unreasonable cool spell that ended June 8th with a high of 57 degrees.

We keep track of home heating and cooling needs in weather through degree days. Basically it works like this. If you assume the average home is comfortable at 65 degrees, then anything warmer or cooler requires additional energy to maintain home comfort. If the day's average temperature was 80 degrees, then it requires 15 degrees of cooling to keep your home comfortable. That would be 15 cooling degree days.

This month the Twin Cities has had no heating degree days. We've only racked up 31 cooling degree days. That's pretty close to the base average daily temperature of 65 degrees. It's also why you probably are saving money by not running the air conditioner.

The bottom line is it's pretty comfy these days in Minnesota. If you manage your windows right through the day, nature keeps your home comfortable. The only thing you have to do is decide which way is better. Fan blowing in, or fan blowing out?

PH

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Weather smorgasbord

Posted at 3:54 PM on July 7, 2009 by Paul Huttner (0 Comments)

GOES 1km visible satellite image this afternoon shows a variety of sky cover in Minnesota.

There's an old saying in Minnesota. "If you don't like the weather, just wait 15 minutes." We might modify that today to say; "If you don't like the weather just drive 15 miles."

Take a look at the visible satellite image above. Let's start near Lake Superior. You can see puffy cumulus clouds in much of northeast Minnesota and northwest Wisconsin. For the most part these are fair weather cumulus. This is a pretty typical July sky in the North Country. Temperatures are in the comfy 70s at places like Hibbing and Hayward.

Now look around the edges of Lake Superior. You can see cloud free skies over and around the lake. The lake breeze from Superior has pushed ashore. This relatively cooler air wipes out the heating that generates thermals over land to support cumulus development. So while it's in the 70s inland, it's only in the 50s near the lake in places like Grand Marais today.

In other parts of Minnesota you can see high cirrus clouds with no rain. There are sunny areas with relatively few clouds and a classic summer day in southern Minnesota. You can also see the tops of towering cumulus with showers in south central Minnesota. There are also thunderstorm clusters with cumulonimbus tops evident in South Dakota.

The best chance of severe weather is in the eastern Dakotas and southwest Minnesota today. A severe thunderstorm watch is posted for the area. Look for showers to approach the metro as we go thought the evening tonight.

And remember, if you don't like the weather today, just drive 15 miles!

PH

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