Terrain Induced Gravity Waves, MN

[baroclinic_instability]

Thanks to NiuMetGF, he alerted me to a standing wave over northern MN. I am too lazy right now to delve into the dynamics, but what is particularly interesting with this is the co-existence of both vertically propagating and trapped lee waves. Note the trapped lee waves over Lake Superior and northern WI with the propagating wave tilted upstream over the arrowhead of MN.

In short, terrain induced gravity waves form due to statically stable flow over terrain as stable air is deflected by the terrain. That air oscillates due to gravity :

http://en.wikipedia.org/wiki/Brunt%E2%80%93V%C3%A4is%C3%A4l%C3%A4_frequency

Which can then take on both vertically propagating or trapped wave form. Sometimes, like in this case, they co-exist. Mountain wave dynamics are plain ugly and, in their purest form, are over my head.

Here is a topo map for those not familiar with the terrain.

[mnweather]

I have had a few flurries with this this morning. You can see all of the dark clouds out over the lake from where I live. It is interesting. This exact thing happened last February to me here on the north shore as it hugged the shore from Grand Marais down toward Duluth. There was very impressive snow with it as I picked up a quick 4" in about 3 hours. It is just a little too far off the shore right now for anything big here. The snow depth at the water front now is about a trace to 1" while inland areas are at a foot or more. Quite a contrast. Interesting weather in this part of the country.

[L.B. LaForce]

I'm curious as to where you got the terrain maps? Those are very nice, and I have been looking for some nice topo maps of the US that are fairly high resolution.

[baroclinic_instability]

I'm curious as to where you got the terrain maps? Those are very nice, and I have been looking for some nice topo maps of the US that are fairly high resolution.

This map I had found at a different time on WIki: http://en.wikipedia.org/wiki/Duluth_Complex

They have a larger map that the Univ. of MN helped make.

This site probably has the best maps per state: http://fermi.jhuapl.edu/states/

[baroclinic_instability]

A much better view here from MODIS of the existence of a dual wave mode over the Arrowhead of MN.

http://ge.ssec.wisc.edu/modis-today/index.php?satellite=a1&product=true_color&date=2010_12_01_335&overlay_sector=false&overlay_state=true&overlay_coastline=true&sector=USA3&resolution=1000m

http://ge.ssec.wisc.edu/modis-today/index.php?satellite=t1&product=true_color&date=2010_12_01_335&overlay_sector=false&overlay_state=true&overlay_coastline=true&sector=USA3&resolution=1000m