Lake Effect

[wolfriver]

What determines how much LES a area gets. Does wind speed or surface temp have any affect. I know that the lake moisture causes it by what determines how much. Some times I see it come down like crazy and the next day just a dusting. Please explain. Thanks

 

[jd]

There are a number of factors that lead to the development and intensity of lake effect snow.

Below I have listed (in order of importance) the factors needed for LES and then most of the factors that determine intensity.

Factors needed to make LES:
1) An open body of water that cold air can travel over to pick up heat and moisture from. In most cases, the air needs to travel over at least 35-40 miles of water to produce LES of significance.
2) A large enough temperature difference (delta T) between the waters surface and the air at around 5000 feet. This delta T needs to be at least 13 degrees Celsius.

Some factors the determine the intensity of the snow:
1) The stability of the atmosphere from the surface to 15,000 feet. The more unstable, the heavier the snow. Also the more moisture that is already in the air before it travels over the lake, the heavier the LES.
2) The fetch or distance the air travels over the water. The greater the fetch, the heavier the snow,
3) Changes in elevation once the LES clouds hit land. A larger increase in elevation leads to heavier snow than a more subtle increase in elevation.
4) Temperature. Contrary to belief, the colder the air is, does not necessarily produce heavier LES. As the air temp starts to drop below around 10 degrees, it becomes less favorable to producing heavy LES. Flake size is typically smaller when the air is very cold and leads to lower LES amounts.
5) Convergence of winds near the surface. Wind that converge near the surface will enhance the lifting of the air. That lifting of the air then can increase the intensity of the LES. These areas of heavier snow within a broader area of LES are called "convergence bands". Snowfall rates of 3-6" per hour are not unheard of in convergence bands.

Hope this helps!

-John

 

[wolfriver]

That clered it up thank you for the great response. And thank you for the great site.

 

[jmpsly]

John, I live in Saugatuck MI, just off Lake Michigan. There is a sand dune, supposedly highest in west MI. between town and lake Mt Baldy. Frequently on radar images of area this dune seems to split image of radar.. Is this possible or is it my imagination?

John P

 

[cobalt_502]

Jmpsly sorry to get off topic but are you familiar with "The White House Bistro"? Partied with the owner Einstein in Puerto Vallarta, he is a great guy!

 

[jmpsly]

It's the one place in town that keeps going in good times and bad with a good crowd. A fellow named Barton is a real go type person and takes part in many other town social activities. Food is also good.
JohnP

 

[jd]

I don't think that there is a sand dune tall enough to interfere with the radar signal. It would have to be at least 700 feet tall to do that.

-John

 

[meathead]

Jd les

there are a number of factors that lead to the development and intensity of lake effect snow.

Below i have listed (in order of importance) the factors needed for les and then most of the factors that determine intensity.

Factors needed to make les:
1) an open body of water that cold air can travel over to pick up heat and moisture from. In most cases, the air needs to travel over at least 35-40 miles of water to produce les of significance.
2) a large enough temperature difference (delta t) between the waters surface and the air at around 5000 feet. This delta t needs to be at least 13 degrees celsius.

Some factors the determine the intensity of the snow:
1) the stability of the atmosphere from the surface to 15,000 feet. The more unstable, the heavier the snow. Also the more moisture that is already in the air before it travels over the lake, the heavier the les.
2) the fetch or distance the air travels over the water. The greater the fetch, the heavier the snow,
3) changes in elevation once the les clouds hit land. A larger increase in elevation leads to heavier snow than a more subtle increase in elevation.
4) temperature. Contrary to belief, the colder the air is, does not necessarily produce heavier les. As the air temp starts to drop below around 10 degrees, it becomes less favorable to producing heavy les. Flake size is typically smaller when the air is very cold and leads to lower les amounts.
5) convergence of winds near the surface. Wind that converge near the surface will enhance the lifting of the air. That lifting of the air then can increase the intensity of the les. These areas of heavier snow within a broader area of les are called "convergence bands". Snowfall rates of 3-6" per hour are not unheard of in convergence bands.

Hope this helps!

-john

john i was actually able to follow your comments ... Wow we ca zoo we..after i retire from jewel can i come up and do weather stuff and ride too....lol...lol..jd thank you for this site and all of the help from the others ...merry christmas to all ...meathead