4/7/2006 DISC: Midwest and South

[Greg Stumpf]

The typical stuff...height, extent, and intensity of reflectivity cores, etc. We've been using a chart put together by another office (their exact identity escapes me at the moment), that relates current freezing levels to the height of 50-55 dbz necessary for severe hail, and it has performed admirably for discriminating strong from severe, but that's just one tool, of course.

For the most part, we "calibrate" our size expectations with the first several hail reports we receive. I don't remember ever seeing anyone here look at the size estimations in SCAN, but then again, I don't remember seeing many people use SCAN. I don't want to slam the work you guys have done with the algorithms, far from it. The TVS algorithm performed very admirably during our 3/31 event, noticeably better than usual, in fact.
[/b]

Don't feel bad about knocking the algorithms, and we'll take all the constructive criticism we can use. As I said, these were initially developed over a decade ago, and we are continuously looking for ways to improve warning decision guidance. For example, what you describe above has been used to develop what we call our "intermediate hail diagnosis" products for WDSSII, and are available from NSSL's Google Earth WDSSII set-up. We're also pumping some of these multi-radar/ multi-sensor hail diagnostic grids into AWIPS at several WFOs (OUN, TSA, FWD), products like reflectivity on the 0C and -20C temperature altitudes, 50 dBZ Echo Top, and the difference in Height of the 50 dBZ Echo Top to the -20C level, along with gridded multi-radar POSH and MESH (same stuff available in GR2), and MESH swaths of various accumulation intervals. Temperature information is automatically updated from RUC 3D analysis grids.

More information and our thoughts on the topic are included in this paper.

 

[Joe Nield]

Don't feel bad about knocking the algorithms, and we'll take all the constructive criticism we can use. As I said, these were initially developed over a decade ago, and we are continuously looking for ways to improve warning decision guidance. For example, what you describe above has been used to develop what we call our "intermediate hail diagnosis" products for WDSSII, and are available from NSSL's Google Earth WDSSII set-up. We're also pumping some of these multi-radar/ multi-sensor hail diagnostic grids into AWIPS at several WFOs (OUN, TSA, FWD), products like reflectivity on the 0C and -20C temperature altitudes, 50 dBZ Echo Top, and the difference in Height of the 50 dBZ Echo Top to the -20C level, along with gridded multi-radar POSH and MESH (same stuff available in GR2), and MESH swaths of various accumulation intervals. Temperature information is automatically updated from RUC 3D analysis grids.

More information and our thoughts on the topic are included in this paper.
[/b]

Sounds promising. Thanks for passing that along.

 

[Dan Robinson]

I've got another radar grab request for anyone who happened to archive imagery from 4/7. We had a nice conversation with a homeowner in Goodlettsville who lost his roof. He asked us if we could find a radar image of the storm at the time it was in Goodlettsville, as the tornado was passing over or to the left of I-65. If anyone has something like this please send me a PM - it would be greatly appreciated!

 

[Jonathan Whitehead]

Im not an expert in radar so I dont know all the differences in one radar versus another but im trying to understand what all happened at NWSFOBNA (communications failure, radar failure, or combo of both). It seems from the posts in the thread that OHX failed. Now unfortunately as I mentioned in my first post in this thread that I had academic and family matters to attend to right before the time of failure but from an armchair chasers standpoint, first place I would go would be to local TV stations and their radars. Now I know a majority of this thread has focused on hail and hail algorithims as part of radar and how those algorithims would change with a TV stations radar i do not know, but its definately the next place I would go to look for mesos in the Nashville area. Now unfortunately a TV stations radar isnt archived or is accessible like that of NOAA's radars.

 

[Kurt Wayne]

So far, F3 maximum rating for the Tennessee tornadoes of 4/7/06.

 

[Bill Hark]

For the discussion about TV radar, here are some images from Channel 2 of the tornadic storm posted on a blog. One is visible and you can click on the link for a few more. Very nice hook.

http://www.nashvillewx.com

Bill Hark
http://www.harkphoto.com

 

[Mark Farnik]

Maybe this is just me, but it seems the NWS is refusing to give ANY of these tornadoes in this outbreak higher than an F3 rating. Based on the damage photos I saw from Gallatin, TN I'd say there was low to mid end F4 damage to several houses in the subdivision which took the hardest hit. Anymore the NWS seems to underrate the stronger tornadoes in these outbreaks and they seem very hesitant to issue any rating higher than F3. I'm confused as to why they suddenly have this near inability to give a tornado a violent rating even if the damage would justify that rating. :blink:
Any thoughts on this?

 

[Justin Turcotte]

Maybe this is just me, but it seems the NWS is refusing to give ANY of these tornadoes in this outbreak higher than an F3 rating. Based on the damage photos I saw from Gallatin, TN I'd say there was low to mid end F4 damage to several houses in the subdivision which took the hardest hit. Anymore the NWS seems to underrate the stronger tornadoes in these outbreaks and they seem very hesitant to issue any rating higher than F3. I'm confused as to why they suddenly have this near inability to give a tornado a violent rating even if the damage would justify that rating. :blink:
Any thoughts on this?
[/b]

There is plenty of discussion on this topic in the WC thread "Where have all the violent tornadoes gone".

I agree with you that the maximum damage looks very much like F4. A half million dollar home (anchored or not) crumbled into nothing more than a pile of rubble is worthy.

 

[AlDanks]

A coworker was driving N through AL on his way back to MI. At 11:00 AL time they spotted a lightning lit funnel in front of them on I65 at Cullman, AL. They stopped and then got blasted with strong winds, blinding rain, and softball sized hail. Their cars took a beating. He said they passed about 50 cars pulled off along the side of I65 - all smashed by the hail - before they exited at Cullman.

He said the tornado was a wide cone at the top, then curved and narrowed to more rope-like on the ground.