Category: AzShear

THE 3 MARCH 2019 CASE FOR AZSHEAR – #2

Posted in AzShear, HWT on by Thea.

Looking at the 0-2km merged AzShear product, my attention was drawn to the line stretching to the SW of the KMXX radar. While I see utility in using this product more for SA, the SAILS artifact of not having the images lined up properly could lead to false interrogations of what’s actually occurring. In this first image (below), the wind field is apparent. In the second image, it looks like the wind field has separated. In the last image, it’s very clear that a slice being merged into the product shows the wind field significantly separated.

~Gritty

The 3 March 2019 Case for AzShear

Posted in AzShear, HWT on by Thea.

The single radar AzShear product made a rapidly developing tornado very apparent, forcing my attention to be pulled to it (first image, below). Additionally, it was very interesting to see the RFD so clearly (second image, below). However, as noted previously, I do have some reservations about the number of false alarms that it may be picking up, as seen in the last image (below). But, there is a lot of promise for this product to serve as an enhanced SA tool and/or increase confidence in the warning decision-making process.

~Gritty

Single Radar AzShear 3/03 Case

Posted in AzShear, HWT on by Thea.

A

Seconds into this simulation it’s apparent that an embedded supercell is about to wreak havoc. It’s incredible how well you can examine the anatomy of the thunderstorm using the Single Radar AzShear product. It’s still apparent in the merged products that there’s an area of concern, but you can’t quiet examine the anatomy of the thunderstorm like you can in single radar.

B

In B, the merged 0-2km  it’s clear where we should be paying attention, but trying to diagnose the structure of or the maturity of the thunderstorm is much more difficult.

 

-lakeeffect

Tornadic Supercell and AzShear and ProbTor Ramp-Up

Posted in AzShear, Live Blogs on by Kristin Calhoun.

The storm along the Milam/Burleson county line began to wrap up showing increasing Merged 0-2km AzShear and a stronger velocity signature. From 2204z – 2208z there was a brief couplet from this storm and the FWD and HGX offices, and the HWT forecasters all tornado warned this storm. You can see the Spectrum Width maxima at the point of the couplet and along the leading edge of the bowing segment to the south of the couplet. There is also an inflow notch as well all situation near the bookend vortex. The big thing to note is how the AzShear Merged product ramped up from 2154z to 2204z. This also impacted ProbTor. The trend went from:

  • 2149z: ProbTor 11%
  • 2154z: ProbTor 60%
  • 2159z-2206z: ProbTor 84%
  • 2208z-2212z: ProbTor 86% (2207z is when WFO FWD issued their warning)

ProbTor maxed out at 87% from 2216z-2218z while the couplet became less gate-to-gate. If you used a ProbTor threshhold of 60% that would have given 15 minute additional minutes of lead time, while a threshold of 80% would have given approximately 8 more minutes of lead time. As of writing this blog (2240z) there are no LSRs reporting anything in terms of damage or tornadoes with this storm.

-Alexander T.

 

Spike in Merged AzShear Product – Wed Apr 24

Posted in AzShear, HWT on by Michael Bowlan.

Noted a big jump in the merged 0-2km AZshear product – see below.  This caused a corresponding jump in ProbTor.  Also note the “double peak” likely caused by SAILS scans.  This is an a favorable location with > 30kts of 0-3km shear – so mesovortex formation is possible.  Will be interesting to see if anything develops….

 

Picking out the Little Circulations within the Bigger Lines

Posted in AzShear on by Thea.

Zoomed out from the single radar (KMXX) in this case there is a lot of convergence going on along the line of thunderstorms but in this view you might not notice that a small circulation has formed in the velocity data. There is no obvious reflectivity signature but there is a local max in the AzShear Data – in this cased the Merged AzShear 0-2km AGL data. Lets investigate that further. 

Zooming into the Merged Maxima you can now see a clear couplet in the SRM velocity data. And the pink tornado track line does confirm a tornado formed at this point. This is an example where on a broad scale the Merged Product (and the single radar as well) provided some Situational Awareness to a tornado that was not visible on the single KMXX velocity very readily.

Based on a rough guestimate a warning off of the Merged AzShear data would have given an additional 2-4 minute lead time to when the tornado formed in this case. An added bonus is that the Merged AzShear product decreased in intensity as the tornado dissipated just a few minutes later (see below). Going later in time the Merged AzShear does increase again, but the KMXX velocity couple remains rather diffuse and broad. The circulation does go onto later produce a tornado so the Merged AzShear product is at least indicating this is an area to keep monitoring. It is possible other local radars like KEOX, just to the south of this storm would have a better view of the couplet/storm.

-Alexander T.

 

AzShear False Alarm

Posted in AzShear on by Thea.

In this example, AzShear has highlighted a supercell that fails to produce a tornado. I suspect the cell merging from the south had a lot to do with the failed tornadogenesis, but this signal on other storms for this case was indicative of a tornado.Sandor Clegane