Michael O'Keeffe
The Stuttgart, AR tornado has been rated EF-3 which in my opinion is a bit much.
-
While Stormtrack has discontinued its hosting of SpotterNetwork support on the forums, keep in mind that support for SpotterNetwork issues is available by emailing [email protected].
Darrin Rasberry
At 1 PM after our AM chase of the elevated storm south of Tulsa was done, they had a line from the KS/OK border down south to just west of Tulsa, and further s/se of there, as the goal line, with Fabian using an extremely complex tool of a piece of paper folded a few inches across to measure a short distance from where he estimated the dryline to be (just east of 35) on a beat up old atlas. He said any cells that did become tornadic would do so quickly all down and over through the warning area, but I'm too much of a noob to recall the exact reasons. Their main pitch for selling it to me (to get me out of the terrible EC/SE OK geography) was the position, motion, and shape of the low.
Mikey - I'd love to see your list (yeah probably better to PM), especially if they have blogs and analysis online. Your blog is great as well. Fabian and Elton have been fantastic, but they don't have any place on the 'net where they blog it up. I figured the best thing for me to do is to look at all the great forecasters and see how their hunches play out.
---
As far as our Strang storm, I am pretty surprised I haven't seen any reports here on ST of anyone else being on this. It was issued one minute after the big one up north that hit Picher.
We got in view 3-4 min later to see nothing. Of course our road we wanted to take was blocked off, and our alternate route had the Budweiser Real Man of Genius Mr. Going 25 in a 45 Guy, with a train of 10 cars behind him (including us at the very end), but we got back on track on highway 20 and followed it the whole way to Bentonville. Even though we were a bit behind, we were still in excellent view of the "sweet spot" whenever we had clearing, and an hour later when we decided to quit on it at Bentonville because of the trees making us scream and pull our hair out - and of course the SPC verified it produced an EF1 briefly right where we were (just SW of Bentonville). Thanks for the view, Arkansas!
Last edited by a moderator:
Donald Giuliano
EF3
- Joined
- Apr 4, 2005
- Messages
- 226
Simon,
The WxScope ASOS data only include the hourly obs, which is why the 2243 ob you saw is missing. However, based on radar at that time the Joplin ASOS was deeply embedded within precipitation and appears to be have been very near or in the inflow region of the nothern meso, which may have contributed to the more backed wind at that observation time.
As far as the backed/stronger 850 mb winds are concerned, I would be very careful about using SGF, since they were on the north side of the front and there seems to have been large differences in hodograph structure over short distances in time and space based on the Tulsa VWP. The Neodesha, KS, profiler that was in the warm sector showed southwest winds at 500 m until it quit reporting due to the influences of nearby convection shortly after 2100 UTC, with no evidence of backing. That does not mean it's impossible that the 850 mb wind near the storm was significantly stronger/more backed at the time of the tube, but the data seem inconclusive.
Finally, you make a good point about backed surface winds not always improving the storm-relative helicity--although based on a cursory glance I'd say yesterday it would have increased it. And nice job pushing Jim & Mary to head north instead of staying for the graduation ceremony.
Good luck on catching some more tubes of your own soon.Darrin Rasberry
I would like to clarify a couple of things because this didn't come out of the cannon sounding like I wanted it to sound. I want to apologize to Fabian, Elton, and Craig for not being able to get my words together and represent exactly what I meant here. Let me see if I can balance it out right:
1. They had Tulsa as a potential target the day before, but were still willing to move just in case some things didn't verify. We certainly preferred the idea of Tulsa because the terrain is better up north of the Tulsa turnpike, and because it's closer to home.
The reason why the target was chosen was because of the previous night's runs, and it was cemented with assurance as we were driving south of Missouri and they were tracking the low, warm front, dry line, and many other parameters. We knew we wouldn't have to go south - maybe just a little west and even a bit north later in the day.
2. What I meant about the tornado potential was that we of course could have absolutely no idea where the tornadoes were going to be. Nobody on Earth could have a clue about that, as Mikey said, and I thought Mikey may have meant us when he wrote about some people knowing that big one would happen in Southern KS through Missou. Of course we didn't know - we ended up chasing the Tulsa cell instead, which had an identical "very dangerous tornado" report come up east of the city when it was simultaneously warned with the big monster. But I didn't mean to imply they didn't know about the tornado potential for the area as a whole - we knew it was there and bigger than the 2% mentioned by the SPC.
They certainly didn't purely wishcast some junk area, but at the same time they certainly didn't know 100% - nobody can know that, and luck ALWAYS plays some sort of a part no matter how good the parameters initially look like. We weren't dogging the southern area at all, but merely marrying greatest potential with convenience while still (before Tulsa was as assured as it could be for us) willing to change target if we had to.
Apologies to Mikey - I thought you may have meant me with your post about crystal ball forecasting, that was a pretty paranoid thing for me to assume. And apologies to all of my chasing team who did an excellent job forecasting a "sleeper area" that won out.
Mikey Gribble
EF5
Donald said...
"One thing to note regarding the backed surface winds discussion--I'm simply not seeing them. All surface wind observations ahead of the dryline in northeast OK/southeast KS were consistently veered to the SSW until you got on the north side of the warm front, where it was stable anyway (e.g., Springfield, MO, which had a mid-upper 50s dewpoint)."
I can't get your link to play for me, but I was watching surface stations very closely while I was chasing and I can assure that surface winds were backing ahead of the storms right as they went tornadic. There are those three stations in a N-S row over SE Kansas and I remember two of them showed a south wind and one was more southeasterly. I don't know the exact time on this, but you can get the time by watching radar and seeing what time it was when the rear storm collapsed. If you went west of there in the warm sector the surface winds were out of the SW. Transitioning from a southwest to a south to southeasterly surface winds would definitely increase SRH in this case. I don't know about 850 winds because I only had suface station data available to me while chasing (no profilers), but I can promise you the storms going tornadic coincided very well with when they hit the backed surface winds.
I agree that the environment was more stable (obviously) ahead of the warm front, but there should be a transition zone of favorable instability and low level shear. It's not like it's uncommon for storms to go tornadic when they encounter backed surface winds or a warm front (although I do agree you have to watch the winds from an SR perspective, but in this case the backed surface winds helped).
BTW Darrin I wasn't talking about you guys in my earlier posts. I was thinking of the Kansas guys (me included) where proximity comes into play when I wrote that.
"One thing to note regarding the backed surface winds discussion--I'm simply not seeing them. All surface wind observations ahead of the dryline in northeast OK/southeast KS were consistently veered to the SSW until you got on the north side of the warm front, where it was stable anyway (e.g., Springfield, MO, which had a mid-upper 50s dewpoint)."
I can't get your link to play for me, but I was watching surface stations very closely while I was chasing and I can assure that surface winds were backing ahead of the storms right as they went tornadic. There are those three stations in a N-S row over SE Kansas and I remember two of them showed a south wind and one was more southeasterly. I don't know the exact time on this, but you can get the time by watching radar and seeing what time it was when the rear storm collapsed. If you went west of there in the warm sector the surface winds were out of the SW. Transitioning from a southwest to a south to southeasterly surface winds would definitely increase SRH in this case. I don't know about 850 winds because I only had suface station data available to me while chasing (no profilers), but I can promise you the storms going tornadic coincided very well with when they hit the backed surface winds.
I agree that the environment was more stable (obviously) ahead of the warm front, but there should be a transition zone of favorable instability and low level shear. It's not like it's uncommon for storms to go tornadic when they encounter backed surface winds or a warm front (although I do agree you have to watch the winds from an SR perspective, but in this case the backed surface winds helped).
BTW Darrin I wasn't talking about you guys in my earlier posts. I was thinking of the Kansas guys (me included) where proximity comes into play when I wrote that.
Mike Peregrine
EF5
Jon Davies has blogged some notes on Saturday. Since he apparently hasn't gotten access to Stormtrack yet, here's the link.
Karen Politte
EF5
Donald Giuliano
EF3
- Joined
- Apr 4, 2005
- Messages
- 226
Mikey,
The file is a Quicktime file, so if you don't have Quicktime installed it may not play. It contains data synchronized to KINX BREF1, with the Mesonet data updating nearly every scan and the METAR data updating hourly. Below are hourly images from 2000-2300 UTC, which show that the surface winds ahead and to the right of the storms' motion were consistently west of south:
Mikey Gribble
EF5
The top image is probably about the time frame that I am talking about. Some where near the 4PM area. In southeast Kansas (the stations I was talking about earlier) two of the stations are southerly and one is southeasterly. Up until those storms got to this area surface winds were west-south-west. When the storms first moved into the backed winds (southerly instead of westerly) is when they went tornadic. I know that the winds were almost due westerly before that point too because I was standing there and I commented to Ryan several time sarcastically, "oh this is what you like to see", refering to veering surface winds. The storms fired in an area of badly veering surface winds just south of the low and until they tracked far enough east into the warm sector to get out out of the veering surface winds they did a whole lot of nothing. It was pretty clear to us watching the sensors that day that the winds backed right ahead of those three stations and I don't think it was a coincidence that the storms went tornadic as soon as they hit this area.
Mikey Gribble
EF5
Can you post the images from further West in the 2-4PM time frame. Kind of the Wichita to Chanute area. That will show the westerly surface winds the storm were in really well. In the last images you posted it looks like winds were almost due southerly the whole time, when if fact they were almost straight out of the West all the way up to the area where the left side of your graphic begins.
Mikey Gribble
EF5
Here is a good picture of it. This is from the NWS report on the event. There are two sensors just SW of the storms that show surface winds out of the west (slight southerly component) and then a little over one county ahead of that the next station shows southerly winds. The storms are located right in between these stations (radar is overlayed) and it is right before they went tornadic. SRH also starts to spike as the surface winds back. Anyways, it is the third image down on this page...
http://www.crh.noaa.gov/sgf/?n=may10,2008description
http://www.crh.noaa.gov/sgf/?n=may10,2008description
Donald Giuliano
EF3
- Joined
- Apr 4, 2005
- Messages
- 226
Well, the initial storms and particularly the rear one had more than just problems with veered surface winds, they were also dealing with poor dewpoints (below 60F in the case of the rear-most storm). The later storms fired on/just ahead of the dryline, and didn't have these problems. Perhaps I can resolve some of this ambiguity by simply noting that in a storm-relative sense the winds ahead of the dryline were strongly backed (as is typical for strong tornadoes), and that the fact the ground-relative winds were veered is not all that important or meaningful. Markowski and Richardson (2005) contains a solid discussion of the importance of looking only at storm-relative wind profiles when determining whether or not directional/speed shear exist:
http://ams.allenpress.com/perlserv/?request=res-loc&uri=urn:ap:pdf:doi:10.1175/WAF897.1
Donald Giuliano
EF3
- Joined
- Apr 4, 2005
- Messages
- 226
Nice, they sure got that event summary up fast. Thanks for the link!
Mikey Gribble
EF5
I understand that SR winds are always going to be different from environmental winds, especially when you have storm motions like we did on Saturday. A directional change in the surface winds is going to be felt all the same though. On Saturday the winds near the cold front/dryline were westerly and took away from SR lowlevel winds (since it was the same direction as storm motion it basically subtracted from the SR winds), but as winds backed further over the warm sector (to southerly) surface winds became perpendicular to storm motions (which were easterly), which increased SR winds. I know you understand that Donald, but I figured I'd cover it just in case somebody else reading this didn't. I know I didn't explain it very well. It gets pretty confusing when you start trying to think from a SR point of view and I'm not good at it.
That being said, I think it did matter that the surface winds were veering in the storms early environment and backing more as they approached far SE Kansas. You are totally right when you say that SR winds were backing (even where surface winds were veered) since storm motions were faster than the environmental surface flow, but once it hit the backing winds the environmental wind speeds weren't being subtracted from the SR winds any more since they were perpendicular to the storm motion at that point. Winds were out of the West at 15-20kts immediately ahead of the initiating boundary, so once the storms got into the southerly winds that is basically a 15kt increase in SR winds in the low levels (this is increased even further when the storm right turned and began heading more head on into the surface winds). I think that increase in in SR winds (from both the change in the direction of surface winds and the storm turning right) played a huge roll in that storm producing a strong tornado. If there would have been westerly surface winds across the entire warm sector I don't think we would have seen any tornadoes or at least not any strong ones. Just my two cents though.
I also agree that the rear storm had several problems. Unfortunately it's the only one I got a good view of that day lol. You know it's a rough chase when only two chasers (that I know of) witness an EF4 on a well publicized event. I think there were about 5 times that many chasers looking at the ass end of the storm with me.
That being said, I think it did matter that the surface winds were veering in the storms early environment and backing more as they approached far SE Kansas. You are totally right when you say that SR winds were backing (even where surface winds were veered) since storm motions were faster than the environmental surface flow, but once it hit the backing winds the environmental wind speeds weren't being subtracted from the SR winds any more since they were perpendicular to the storm motion at that point. Winds were out of the West at 15-20kts immediately ahead of the initiating boundary, so once the storms got into the southerly winds that is basically a 15kt increase in SR winds in the low levels (this is increased even further when the storm right turned and began heading more head on into the surface winds). I think that increase in in SR winds (from both the change in the direction of surface winds and the storm turning right) played a huge roll in that storm producing a strong tornado. If there would have been westerly surface winds across the entire warm sector I don't think we would have seen any tornadoes or at least not any strong ones. Just my two cents though.
I also agree that the rear storm had several problems. Unfortunately it's the only one I got a good view of that day lol. You know it's a rough chase when only two chasers (that I know of) witness an EF4 on a well publicized event. I think there were about 5 times that many chasers looking at the ass end of the storm with me.
Donald Giuliano
EF3
- Joined
- Apr 4, 2005
- Messages
- 226
Mikey,
Hey, no problem, I just love talking about storms. I certainly took no offense.
Anyway, no kidding about the fact the only a couple chasers actually saw the tornado, I've been thinking the same thing. My wife and I thought about going out Saturday, but given the terrain/storm motions/narrow time window as the cold front overtook the dryline decided it wasn't worth it and that there was too much stuff that needed to be done at home. Part of me is kicking myself for not heading out, but the other part knows the chances of actually seeing anything worthwhile were not very good, even if we were on one of the storms doing it.
I'm really looking for a decent setup where we can get slower-moving storms over better terrain, but so far this year is just not getting the job done. I have a feeling it's going to be big up in NE/IA/MN late in the season...good for the Northern Plains folks, but less than ideal for this Oklahoma chaser. But that's a topic for a whole different thread...
