Base Velocity Radar Question

[Michael Wilkinson]

https://www.facebook.com/video.php?v=10215602024073490

https://www.facebook.com/video.php?v=10215602023633479

https://www.facebook.com/video.php?v=10215602023833484

I'm very inexperienced. My education level is Skywarn Spotter, and currently working my way through the courses at Tornado Titans. I listen to the few podcasts I've been able to find, and have listened to many Chasercon lectures on YouTube. I know my weather education level is low. I'm working on becoming a beginner.

I need help interpreting Base Velocity radar. I've attached three series of images from March 10 in Arkansas when I was watching a storm.

The radar location is not obvious in the first series (SuperRes Reflectivity). It's just above the "Mc" in McAlmont, right side of the screen near the middle. The storm seems to be moving Northeast. It's located Northwest of the radar location, and looks to me to be maintaining about the same distance from the radar as it moves towards the radar (eastward) and away from the radar (northward).

Because of the nature of this movement relative to the radar, when looking at the second series of images (Base Velocity) I would expect a grayish color. Instead, there is a dominant red color that seems to say that the storm is moving overwhelmingly away from the radar. In that same series of images (Base Velocity), it seems odd to me that there is also such a strong green color to the East of the radar location and even a little green South of the radar. I think that the Base Velocity images makes it look like the movement of the system is from Southeast to Northwest.

I thought that maybe there was some kind of rotation causing the colors to be the way they are, but in the third series of images (Storm Relative Velocity) the colors look to be arranged nearly identical to the way they are in Base Velocity. To me, that seems like that there is no rotation in the storm, and that the interior of the storm is basically stationary relative to itself and is moving as a single unit in one direction.

My questions are, can someone point out the errors in my conclusions? What is the radar actually showing?

If my understandings are wholly flawed, I understand that an answer to correct me may be extensive. If that is the case, can someone point to a resource that I can read, watch, or listen to that will help put me on the right track of understanding Velocity Radar.

Thank you.

 

[Randy Jennings]

We where all beginners at some time - so happy to help, as others helped me when I was a beginner. So first things first - base velocity shows wind speed blowing towards or away from a radar. As you noted, radar can't "see" wind that is blowing perpendicular to the radar (which is where you get the grey isodop line). Even when you look at a velocity product on a non-storm day you will see the reds and greens. So in the images you posted the winds (at the 5 degree tilt) are from southeast to northwest. In your case this is a non-severe storm and isn't really producing much wind.

As or storm motion, you can't typically determinate that from the 0.5 degree tilt. Storm motion is typically more closely related to faster winds higher up in the storm. Speaking of storm motion, the storm relative velocity product subtracts out the mean storm motion from the velocity product, making it easier to see things like rotation in many cases.

I good tutorial on radar is the one at MetEd: https://www.meted.ucar.edu/training_module.php?id=960 . It is free, but you do have to create an account.

 

[Michael Wilkinson]

Thank you, Randy. I took my spotter training with MetEd, but I haven't taken that particular radar course. I think it will be helpful.

Thanl you also for the information about the importance of tilt. Of course it makes sense. I hope to keep a safe distance from storms in southern Arkansas tomorrow as I go on a practice run. Each time I go out, I try to incorporate something new that I've learned.