In today’s case, MRMS rotation tracks did a better job at showing where the most likely tornadic storms were in a QLCS compared to the 0-2 km merged AzShear, at least over the entire period which makes sense. I would never warn just based on rotation tracks, but I couldn’t find a better SA tool today. It was easy to step back in after working way too long on a previous blog post and get an idea of what happened while I was away. I still feel like the single-radar AzShear would have been extremely useful with today’s QLCS.

QLCS situation just outside of the HGX CWA where low-level combined AzShear spotted two areas of increased low-level shear entering Robertson County. The northern circulation eventually led to  downed trees east of Calvert 12 minutes later, and may have been a tornado, according to the LSR. This product would have given me more confidence to at least have a severe thunderstorm warning out, if not a tornado warning, and would most likely have led to a greater amount of lead time than I would have had otherwise.

ZDR_Arcophile

What if you’re on shift and convection has become more widespread or robust than what was currently forecast? What if that happened during a time where staffing levels at the office were not ideal (for whatever reason)?

-Convection is rapidly developing.
-Minimal people around to sectorize radar/warning operations
– Limited time to interrogate all the storms, especially with a potentially tornadic situation developing.

Taking a look at Single-Radar AzShear, there are very high values near a velocity couplet north of the radar site. This couplet becomes your primary area of concern to where you want to focus most of your attention and analysis. However, there is also some bowing in the reflectivity signature coincident with some bowing/enhancement in the Single-Radar Az Shear output well to the northeast of the radar site. The angle of the radar beam with the bowing storm makes you question the strength of the storm and you realize the velocity values may be too low.

Would you consider issuing a SVR based solely on the enhanced bowing segment of the Single-Radar AzShear data, so that you can focus your attention on the tornadic storm? Something to think about…

A tornadic debris signature was noted during this event with a loop (not shown) of low CC values, with depth,  coinciding with a strong velocity couplet and high Single-Radar AzShear values. Is there any correlation to a TDS signature with Single-Radar AzShear values? To be determined…

Place marker denotes the TDS location in this image.

As we move along through this case, east of the convective line exists a plethora of potentially potent supercells; each is producing high values of AzShear from multiple radars as well as in the merged products.  But what about further back west with the incoming convective line that is looking a little QLCS-ish?  Here is an example of how three products can be used together to help determine areas of increasing potential for rotation.

First, from KEOX:

A broken line of storms has an area of enhanced inbound velocities with a stronger storm in the line (just south and east of the target/bulls-eye/red and white marker).  The single-radar AzShear shows cyclonic shear all along the leading edge of the line but with an enhanced area of shear along a small bowing segment.

Now take a look at KMXX AzShear (with the velocity and reflectivity staying with KEOX):

Only 1 minute 30 seconds after the KEOX scan, this shows what will likely be an area of rotation higher up in the storm (2.5 km up from KMXX vs 1.2 km up from KEOX using the beam sampling tool) so there is something aloft as well.  O.K….thinking along the lines of mid-level rotation above a strengthening area of shear at the lowest tilt; interesting.

Finally, looking at the merged 0-2km AzShear (again with the velocity and reflectivity products remaining at KEOX):

Yup, there could be something there BUT the big caveat is that you don’t want to get caught thinking that this feature has a long “history” since that trail extends south and west from our area of interest.  Nope, that’s the shear along the leading edge of the convective line.  However, it does show that the strongest AzShear values are close to our marker/area of interest so id doe need to be watched for future potential strengthening…(post-note: nothing was reported/observed tornado track wise)

-Dusty

Let’s say your storm’s velocity data crosses into the dreaded “purple haze”. This  loss of velocity data also results in a loss of single-radar Az Shear data. So, what do you do if you’re on the warning desk? Do you scream and panic? No, that wouldn’t be ideal. Rather, take a look at the Merged-shear products. In this example, a strong storm moved into the “purple haze” of KMXX’s radar, thus losing reliable velocity and single-radar AZ Shear data. However, surrounding area radars are still getting a good reading on the storm, and thus the operational forecaster can utilize the Merged Shear products to calm their nerves as to whether the storm is still worthy of maintaining focus on it.

What happens if convection moves far enough from your radar to where the single-radar Az Shear becomes less reliable? The Merged shear products can then potentially be useful! In this example, the storms have moved to the edge of the useful range of the KMXX radar. The KMXX single-radar Az Shear (top right) values are much weaker/potentially less reliable and the KMXX velocity data (bottom right) also leads to uncertainty as to how much attention should still be given to the ongoing convection. Utilizing the Merged shear products (left) indicates that the convection is likely still strong (at a minimum) and warrants further investigation.