4/10/08 DISC: AR/MO/IA

[Karen Politte]

To elaborate on Scott and Dennis' comments, on the way home this evening we pulled up some data from this afternoon - primarily the extra-curricular 18Z soundings that SPC requested from stations such as LZK and JAN (Jackson, MS). Here is Jackson's 18Z sounding:

A nice double-inversion seems to be evident on this sounding, which sure as heck didn't help us any today. This would at least go part way to explaining why our anemic little storms never truly tapped the potent conditions across the risk area today......they likely had just enough energy (just enough) to break through the first inversion, but that was all she wrote for the meager CAPE we could muster amongst the convective debris and zero direct insolation. Interesting.

KP

 

[Skip Talbot]

Any insight as to why the stuff to the north promptly started to fizzle before 0z? We had a good amount of sun left, and a nearby station was reporting 70/63 with 20 knot SE surface winds. Chad and I let some weak cells come to us across the Mississippi on I-72 in IL and I thought we would be game on. instead of taking off like the line to the north, the cells evaporated. Was it lack of instability across the river, dropping dewpoints, or that strengthening, double inversion that Karen pointed out?

 

[Mikey Gribble]

I made this post in the NOW thread the other day after people mentioned there was a "large and violent tornado reported in Iowa"...

"Keep in mind that they said the Breckenridge tornado yesterday was "large and violent" too. I think it is pretty much automatic for the NWS to say that when a tornado is confirmed and conditions may be able to support a decent/strong tornado."

The reports are in and the tornadoes were all EF0 and EF1. I wouldn't have mentioned this, but there were a couple posts questioning what I said. I have been on lots of tornadoes that were reported as large and violent (which is typically reserved for EF4-5) when the tornadoes were weak or nonexistant. My point was that you can't always buy into that. IMO the NWS forecasters do this some times when a tornado is confirmed and conditions could support strong tornadoes. I know I would if I was issuing the warnings at NWS. There is a time lag from reports until that information can be put out on the radio. If the environmental conditions could support a strong tornado you are better off reporting it as "large and violent" even if it may not be at the time. If you waited until it actually became large and violent to report that then odds are it is already too late for some people. Below is the survey information.
http://www.crh.noaa.gov/crnews/display_story.php?wfo=dmx&storyid=14109&source=0

 

[Scott Weberpal]

Just because it was rated EF0 or EF1 doesn't mean it didn't have the potential to do significant damage. We don't know if the struture(s) that were hit were directly hit or simply caught inflow winds near the tornado. The storm report doesn't give much detail the that effect.

The very large "wedge" tornado - the same one in the picture that has been circulating around stormtrack http://www.kcrg.com/younews/17509874.html?img=1&mg=t
was rated EF0 by DVN.

If I saw a tornado of that size that was moving at 50+ mph, I would call it in as a significant or violent tornado as well.

Where the heck is Breckenridge anyway?

 

[Mikey Gribble]

Breckenridge Texas. It was hit on the 9th.

Scott said...
"Just because it was rated EF0 or EF1 doesn't mean it didn't have the potential to do significant damage."

Did I say it didn't? I didn't say that, but IMO no an EF1 doesn't do "significant" damage. It is rated EF1 because of the damage that it did and "significant" typically isn't a word associated with EF1 damage. If you refer to EF1 damage as significant, then what words are you supposed to use for higher end tornadoes? It doesn't leave much room to go up. All I said was that you can't automatically validate a tornado as being "large and violent" just because the warning text says that. My point is that they say it all the time when the tornadoes weren't "large or violent". Violent is typically associated with high end tornadoes. EF0 and EF1 is not considered a violent tornado.

Scott said...
"If I saw a tornado of that size that was moving at 50+ mph, I would call it in as a significant or violent tornado as well."

You and everybody else can call it whatever they want. I couldn't care less about how they describe the tornado in the warning. All I was saying was that you can't take those descriptions in the warnings as fact because they are wrong more times than they are right.

 

[Scott Weberpal]

Breckenridge Texas. It was hit on the 9th.
.

Ok gotcha. I was looking around in Iowa thinking there was a Breckenridge somewhere there too, lol. I have no problem with your assertion that when a warning comes out with "large and violent tornado" it may be wrong the majority of time. I remember many tornado warning on the Limon, CO "mothership" supercell day (6-4-05?) coming across saying a large and violent tornado had been reported by spotter, when in fact there was not tornado at all!! I guess that's what happens when you have a beastly low hanging wall cloud and hill in the way

I can just think of so many instances where a violent tornado didn't hit a thing and ended up with an EF0 or EF1 rating when it could have easily ended up with an EF3 or 4 had it hit something.

 

[Mikey Gribble]

Scott said...
"I can just think of so many instances where a violent tornado didn't hit a thing and ended up with an EF0 or EF1 rating when it could have easily ended up with an EF3 or 4 had it hit something."

I totally agree. When there is an environment that is capable of supporting strong tornadoes and you have a confirmed tornado that has been on the ground for a few minutes, I think adding "large and violent" tornado" to the warning is most certainly the right thing to do. I remember the Attica tornado going from a dust whirl to an F3 in less than two minutes. IMO the NWS has to report what the tornado may be capable of, not what it actually was when the report was called in. I just think that's the prudent thing to do when you are responsible for warning the public. BTW I like your avatar a lot, but we're not allowed to talk about that lol.

 

[Jarrod Cook]

Any insight as to why the stuff to the north promptly started to fizzle before 0z? We had a good amount of sun left, and a nearby station was reporting 70/63 with 20 knot SE surface winds. Chad and I let some weak cells come to us across the Mississippi on I-72 in IL and I thought we would be game on. instead of taking off like the line to the north, the cells evaporated. Was it lack of instability across the river, dropping dewpoints, or that strengthening, double inversion that Karen pointed out?

Skip,

It was definitely the lack of instability to the east of the MS River. This was clearly evident on the SPC meso-anlysis page. CAPES in MO ranged from 500-1000 J/Kg. They dropped to nothing in IL. This is what kept me from leaving for W. IL earlier. However, we couldn't pass up the local chase to GBG when the line with embedded tornadoes was headed this way. With that much shear you just never know. However, just like we thought, the storms fizzled out.

ILX did not do an 18Z sounding like I had hoped, so not sure if there was any inversions this far north.

 

[Jesse Risley]

Skip,

It was definitely the lack of instability to the east of the MS River. This was clearly evident on the SPC meso-anlysis page. CAPES in MO ranged from 500-1000 J/Kg. They dropped to nothing in IL. This is what kept me from leaving for W. IL earlier. However, we couldn't pass up the local chase to GBG when the line with embedded tornadoes was headed this way. With that much shear you just never know. However, just like we thought, the storms fizzled out.

ILX did not do an 18Z sounding like I had hoped, so not sure if there was any inversions this far north.

While I wasn't able to chase, I would have to agree. Looking at forecast products in the early evening, CAPE values were ranging between 300-700 J/KG at best on the eastern side of the Mississippi. This is a far cry from the 1000+ values that were previously forecast.

 

[Chad Cowan]

Unfortunately due to the stacked nature of the low and the lack of progressive motion of the system, the deep convection that developed in the highly sheared and marginally unstable environment north of STL raced off to the northeast as the best lapse rates (and attendant instability) advected N and NW and didn't cross the MS river as the storms did.

ILX did not do an 18Z sounding like I had hoped, so not sure if there was any inversions this far north.

ILX did a 21z sounding but it's not showing up with a blue star on the SPC page (none of the 00z/11 soundings are working either):
21z ILX Sounding

 

[cstrunk]

You can read my storm report in the reports thread. I talked with EAX NWS office on Friday and was able to determine that I had indeed captured a few images of the wall cloud that produced the EF0 tornado in southern St. Joseph, MO.

Here is the link to their storm assessment that includes the picture of the wall cloud taken by myself south of St. Joseph:

http://www.crh.noaa.gov/crnews/display_story.php?wfo=eax&storyid=14100&source=0