Cross Section Velocity

[wxdudemike]

Hey all! We experienced a series of fairly strong downbursts the other night on the order of 50-60mph that I think was associated with the collapse of a fairly weak storm over my house. I thought I remember being told in the past that when you can see the stronger velocity returns extending from the lowest level up higher into the storm, that is a good signature for potential damaging winds at the surface. Is this true? Here is a screen shot from the other night that I'm talking about:

Note the brighter blue (indicates 45kts+ on my color table) which is near the base and extends up into the storm. I was just wondering if anyone here knows whether or not that is a true signature to look out for. Thanks!

[Hoosier]

I don't think there's any question that it's "better" to have those winds closer to the ground. After all, the closer they are to the ground, the more likely that they will actually reach the ground.

[wxdudemike]

I don't think there's any question that it's "better" to have those winds closer to the ground. After all, the closer they are to the ground, the more likely that they will actually reach the ground.

True, I was wondering if the fact that it kind of "noses" up into the storm is anything significant.

[OceanStWx]

True, I was wondering if the fact that it kind of "noses" up into the storm is anything significant.

Generally speaking, having a large area of high wind speeds throughout a storm gives you a better chance of convectively mixing that wind to the surface. Of course you can still generate a lot of wind at the surface without a lot of wind aloft through precip loading when conditions are right.

Probably the most famous of velocity signatures that you can look at with a cross section is the MARC (Midaltitude Radial Convergence). It's a radial feature, so it is important that you cut your cross section down radial and that the storm(s) in question are nearly perpendicular to the radar beam. But strong radial convergence in the mid levels of a storm can lead intense surface downdraft winds by up to 30 minutes. Since you want to look at convergence going on within a storm, you'll also want to view storm relative velocities, to avoid contamination by the storm's speed and direction.

Ron Pryzbylinski of LSX had done a ton of work on this if you are curious for more information.

http://www.crh.noaa.gov/lmk/soo/presentations/MARCSignature2.pdf

http://www.crh.noaa.gov/lsx/?n=marc_signature

I'm looking at your image and it appears to me that the radar is located "into the page" if you will. So if you cut a cross section the opposite way you might be able to see this feature.

[wxdudemike]

Generally speaking, having a large area of high wind speeds throughout a storm gives you a better chance of convectively mixing that wind to the surface. Of course you can still generate a lot of wind at the surface without a lot of wind aloft through precip loading when conditions are right.

Probably the most famous of velocity signatures that you can look at with a cross section is the MARC (Midaltitude Radial Convergence). It's a radial feature, so it is important that you cut your cross section down radial and that the storm(s) in question are nearly perpendicular to the radar beam. But strong radial convergence in the mid levels of a storm can lead intense surface downdraft winds by up to 30 minutes. Since you want to look at convergence going on within a storm, you'll also want to view storm relative velocities, to avoid contamination by the storm's speed and direction.

Ron Pryzbylinski of LSX had done a ton of work on this if you are curious for more information.

http://www.crh.noaa....CSignature2.pdf

http://www.crh.noaa....=marc_signature

I'm looking at your image and it appears to me that the radar is located "into the page" if you will. So if you cut a cross section the opposite way you might be able to see this feature.

Thanks for the response! I'll look into that.