EWP Blog

As the northern portion of this QLCS becomes oriented more north/south and perpendicular to the 0-3 km shear out of the SW, I would expect mesovortex genesis to become more likely. AzShear does a nice job of highlighting this zone several scans before tornado touchdown (pink line)Sandor Clegane

In the image above you can see that the AzShear and the Velocity product from the single radar have the circulation now lost in the infamous ‘purple haze’. One of the benefits of any MRMS product and in this case the Merged AzShear product is visibility in times like this. Neighboring radars (either individually or in the Merged Product) would still show the ongoing circulation. So lets take a look!

In the merged product you can indeed still see the circulation going strong in the Merged AzShear product, continuing to follow the pink tornado track, while the velocity couplet remains hidden (we are also getting far from the radar so we are looking well aloft in the storm). BUT the one noticeable feature of the Merged AzShear is the triple maxima in this case due to the SAILS cuts making their way into the Merged AzShear product.

Again this triple maxima is an artifact that training and experience would negate, but does show some of the good and the bad in terms of the Merged AzShear.

-Alexander T.

Later in the life of the storm, AzShear remains relatively high, even as the couplet in SRM is less obvious (though still there). This would boost confidence to keep a tornado warning going.However, toward the end of the tornado track both velocity and AzShear wash out before the tornado ceases (pink line).Sandor Clegane

While not at an ideal angle to view storm top divergence, AzShear very nicely highlights strong storm top divergence on this tornadic supercell.Sandor Clegane

One usefulness of the upper tilts in the Single Radar AzShear product is to be able to check and dismiss any erroneous data in the 0.5 degree tilt. In the image below you can see some speckled erroneous data in the 0.5 degree tilt ahead of the main line of storms. It could appear at a quick glance to be small spin ups in the AzShear data, but just quickly looking at the Velocity or Reflectivity shows that this is erroneous data.

Another check is just doing a quick check of the 0.9 degree tilt. Those local max in the AzShear are not present even just one tilt above. If these were to be real circulations you would expect depth in the circulation.

It is worth noting that these errors to at times make their way into the Merged AzShear product at least at the lower 0.2km AGL product. You can see that example below of the brighter reds below the large maxima in the center of the AzShear product. Even after only 2 days of looking at the AzShear products the large maxima keeps all of my attention, but someone looking at this product for the first time may see the brighter reds to the south and wonder about those.

-Alexander T.

In the first image below, there is clearly a strong supercell that undoubtedly warrants a severe thunderstorm warning. Without having a full picture of what the environment looks like, and without looking at additional radar products, I can’t say for certain whether or not it should have tornado warning, given the strong convergant but non-rotational signature.In this next image, a couple of AzShear features stand out to me. 1) Positive values of AzShear have begun spiking on the north side of the convergant zone. 2) I believe that you’ve seeing the RFD start to kick downstream. Shortly thereafter, the storm develops a very clear couplet and it is clear this storm deserves a tornado warning. The tornado survey revealed that the tornado began when the second image in this post was captured. AzShear did a nice job highlighting important features on this storm, and may have lead to additional lead time on a tornado warning.Sandor Clegane