EWP Blog

First thing I realized when analyzing AzShear side bye side with Velocity is that the AzShear feature catches the eye much better than a weaker rotation signature in Velocity. Here is an example: If a forecaster was looking at a lot of activity going on around the CWA, a weaker velocity signature can be missed, but AzShear jumps out with the high (white) values. This circulation went on to strengthen quickly and to me the AzShear did a better job at showing that earlier in the tornadoes life.

Another example, also involving TORP: Focusing on the weaker circulation in the following images, which is outlined by the TORP circle that is farther southwest. 0.5 Velocity again shows a weaker rotation that could be overlooked. That same scan though, AzShear is lit up along with TORP of 48%. This allowed me to look closer at that feature and I found a weak echo region and a higher reflectivity core aloft. Once again showing AzShear and TORP are good for situational awareness.

-Gary

So far, I am finding this tool very helpful. However, I am wondering where I will put this on my typical setup. Add it to my 9 panel? Or make a whole new procedure? I think it may be repetitive to flip across procedures when I have SRM, ZDR, etc suggesting a TOR. Not sure it would be helpful enough to make a whole new procedure for.

Interested to see how it handles weaker tornadoes as well.

Just giving an initial test of a potential optimal layout. Using All-Tilts Z, SRM, AzShear/DvShear toggle, and CC for debris detection. Will refine later, but I like this as an initial start.
-dryadiabat

Green next to red = bad. Tornado warning issued.

-Lumbergh

Right off the bat, I notice that the icons for TORP, even when loaded with maximum line thickness, can easily get lost if the brightness of your loaded radar reflectivity is too high (top image below). By reducing the brightness to 75%, the TORP icons became more noticeable (bottom image below).

It was reassuring to see TORP perform well with the knockout cases. I would have been concerned if it missed a tornado signature this prominent. This increased my confidence in using it at the very least as a situational awareness tool. An example below:

It’s evident that TORP maintained very high probabilities the entire track of this confirmed violent tornado (>99%).

However, the limitations were still glaringly apparent at times, with a >20% probability for a tornado being shown in an area of noise (below)

– Mr. Peanut

Here are some interesting examples from the perspective of northwest KS on April 25, 2024. This first example shows two boundaries southwest of the radar. The east-west oriented boundary shows up in DivShear, while the SW-NE oriented boundary does not really show up in DivShear. Radar velocity (not pictured) was showing 50-70 knots north of the northern boundary, while the velocity was not as strong on either side of the SW-NE oriented boundary.

This circulation spun up quickly, but the TORP probs seemed to respond in kind, showing a sharp increase to near 70%. The circulation weakened briefly in subsequent scans (not pictured) before tightening again. A storm chaser reported there was “almost a tornado touchdown” north of Colby, KS around 0015z. Mesoanalysis (not pictured) seemed to suggest that this storm may have been north of a boundary, and perhaps lacked sufficient low-level instability for tornadogenesis.

At 0017z, there appeared to be two circulations – shown below in both velocity products and AzShear:

Here is an example that caught my eye where beam blockage was significantly impacting the velocity field (not pictured) and resulting in sharp columns of alternating AzShear minima/maxima. However, TORP was NOT creating detections along these areas, even after turning off all of the auto filters.

Here is a look at how the DivShear field appeared along a line of storms which had a tightening reflectivity gradient. Images were from 0057z on Apr 26 2024:

-Orange Lightning

Observed a drastic change in TORP probabilities from one scan to the next. AzShear is quite blocky, which seems to be due to velocity sidelobing. -Sidney Crosby

At 0005 UTC a weak velocity signature was evident on base velocity and DivShear showed a convergent signal.

Two minutes later at 0007 UTC, the velocity looked a little better but remained weak while the DivShear began showing a much better signal while AzShear began showing a signal but not as strong as the DivShear.

Another two minutes later at 0009 UTC, a weak velocity couplet developed while DivShear was beginning to develop that “cloverleaf” look and AzShear continued to increase.

By 0011 UTC, a stronger velocity couplet was evident with near gate to gate values, and both DivShear and AzShear showed very nice signatures. These are all factors indicating the potential for tornadic development and the AzShear and to a greater degree DivShear (picking up on the development a bit earlier) did a good job in this example despite relatively weak velocity couplet.

The Torp during this time frame also showed a significant increase from below 25% to up to 82% during this 5 min period.

Given all of this information, one would feel pretty confident in going with a tornado warning with the DivShear and AzShear products adding confidence. However, looking at the environment, a backdoor cold front pushed southeastward through this area about an hour earlier and surface temps dropped into the 50s with northeast winds stabilized the near surface layer and prevented anything from happening with this storm, although there was a storm report mentioning an almost tornado touchdown in this area.  So this brings the question about whether this was a Torp false alarm or not. It appeared to work as expected and likely would have been correct if the front hadn’t moved through.  It does give confidence that these new products bring value to the warning forecaster and would be beneficial to operations.

Flash