BBauer
EF2
Man, as I started to doubt the day I see something like this and get pumped...
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Tomorrow's Moderate Risk
- Thread starter BBauer
- Start date
rdale
EF5
1:18pm CT is not the time to doubt a day 
Heating is only beginning to kick in at that point.
Heating is only beginning to kick in at that point.
Andy Wehrle
EF5
I was surprised SPC went with a PDS watch, given the uncertainties about intense tornado potential today.
rdale
EF5
The forecast doesn't have much uncertainty:
PROB OF 2 OR MORE TORNADOES : 90%
PROB OF 1 OR MORE STRONG /F2-F5/ TORNADOES : 60%
Also remember that the SPC isn't a entity - the watches come out from individual forecasters. It's always good to learn their names and recognize them on the SEL product.
PROB OF 2 OR MORE TORNADOES : 90%
PROB OF 1 OR MORE STRONG /F2-F5/ TORNADOES : 60%
Also remember that the SPC isn't a entity - the watches come out from individual forecasters. It's always good to learn their names and recognize them on the SEL product.
Andy Wehrle
EF5
So, are they not as concerned about backed mid-level flow as much as some people on here? Or do recent observations indicate that such is not taking place as previously thought?
BBauer
EF2
Wow, that is impressive. I'm not going to make into Nebraska today. If things progress/initiate into Iowa fast enough I will head out. But I can't get out of here (Des Moines) for another few hours. I'm hoping some cells might move up from the SSW into SW Iowa, that would be ideal for me, then I could chase them back home.
rdale
EF5
It's not a "they" but a "he" - and given those percentages, apparently Mr Hales has no concern at all.
Rob Wadsworth
EF5
Looks like the golden play will be between Sioux City and Omaha ATM. But conditions have been changing hourly - so it seems. The SPC said yesterday, that there would be large tornadoes between I-70 and I-80 from CO to the NE corner of KS. None of what was said materialized. There were but a few touchdowns of very weak tornadoes. That is a gross indication of lack of updating the danger these situations possibly provide.
Not saying they are wrong today; but I will say that it gives me pause.
The 300mb seems to be pushing the low practically due N. I think that anything long the W side of Iowa and the E side of Nebraska may be in play after 'rigorous initiation' takes place in the next two hours. Still within 3 hours drive time .
Not saying they are wrong today; but I will say that it gives me pause.
The 300mb seems to be pushing the low practically due N. I think that anything long the W side of Iowa and the E side of Nebraska may be in play after 'rigorous initiation' takes place in the next two hours. Still within 3 hours drive time .
rdale
EF5
Of course those were two completely different forecasters, so the comparison is not really valid to begin with. And then I checked all the DY1s and none had >10% tornado, and none had a hatched area, and none refer to large tornadoes? And none of the watch probabilities had > 40% chance of EF2 or higher.
TJKLECKNER
EF4
Yeah, they cried "wolf" a bit on this one....for having sig risk areas and only one or two decent tornados...boo
I disagree. I was on the Aurora/York/Columbus supercell and it produced at least 3 tornadoes and given the motion two of them had, I'd be willing to bed two of them were EF2+. SPC definitely toned down the wording of the intensity of the event today and the convective outlook probs also portrayed that. I don't think they overforecasted at all. Rather I'd say they nailed the tornado forecast.
rdale
EF5
I think the PDS SVR watches were clearly not working out well (however my note above about recognizing names helped interpret) but with nearly 300 reports and the night still young -- I struggle to follow how they "cried wolf"
Since I saw my name mentioned a few times in this thread, I'll chime in on my day and my thinking.
As you can guess from my post above, I did chase today, mostly because I see this as the last serious chase for me this season and, although it had some hidden potential, during the morning I thought one would have to make very accurate and precise forecasts and maneuver just as well to see anything.
I'd say SPC's 10% small hatched tornado threat verified. There most likely were a few sig tors in SC/E NE today, but pretty much all of the tornadoes were spawned by 3 or 4 somewhat longer tracked cyclic supercells. However, I was quite surprised to see the PDS tornado watch. The high instability was there, but I didn't see any dangerously high levels of low-level shear that would seem to indicate an enhanced threat for strong tornadoes.
When I left Ames at about 11 AM this morning my initial target was Sioux City - the warm front/triple point area. I thought low-level winds would be most favorable for tornadoes in that area. However, it became pretty apparent that the warm front was not lifting north fast at all. This has been a trend over the last 2 weeks or so with warm fronts - they have not been making it as far north as progged. Thus our target shifted south towards the Denison-Blair corridor. As time continued, the whole system appeared to slow to a halt, thus all of the relevant forcing mechanisms were going to be farther west than progged. Thus we continued west into Fremont, NE. Once we got there we saw a N-S oriented band of mid level cumulus/stratus. Those clouds were right along the edge of the 700 mb cap and were moving east farther into the capped region. Due to the reduced diabatic heating under those clouds, we figured storms would not fire under that band of clouds. That band expanded as it moved east, so we got west of it. Once we saw a strongly visible radar fine line on KUEX arcing from W-E-SE-SSE, we knew that was the dryline/cold front. Given the lack of obvious development over us or along the trough extending northeastward from the sfc low through C NE, it became pretty obvious that we needed to be on that boundary, especially since it had a history of spawning supercells. Another thing that made the decision easier was that the deep layer shear vector was nearly perpendicular to the boundary, which implied a cellular storm mode. The moral here is that our target shifted dramatically over the course of the day due to changing conditions. Some chasers like to pick a target the night before or the day of and make a note to go to that target first before re-evaluating and moving from there. That can pay off, but I've always had more luck when I constantly analyze new data as it comes in. I switch my target all the time. That can lead to some back and forth chasing paths, but if you're quick to decide and commit, it can be beneficial, too.
Also, regarding my talk about the hodographs. In the model forecasts I saw a lot of southerly 500 mb winds in the target area. Coupled with the southwesterly 700 mb winds that would result in a hodograph that has an S-shape - cyclonically curved in the lowest 1-2 km but anticyclonically curved between about 3-6 km AGL. Although I can't recall off the top of my head any research that specifically says S-shaped hodographs favor a non-supercellular storm mode, what bothers me about S-shaped hodographs is that 1) you get less positive storm-relative helicity above 2 km or so and 2) the mean wind (and thus a first order approximation to the storm motion vector) tends to lay very near the hodograph. That means storms would have less storm relative helicity period to work with unless they turn hard right. However, it seems that there were some SW or SSW 500 mb winds in Nebraska today. Thus the hodographs were probably not so S-shaped.
As you can guess from my post above, I did chase today, mostly because I see this as the last serious chase for me this season and, although it had some hidden potential, during the morning I thought one would have to make very accurate and precise forecasts and maneuver just as well to see anything.
I'd say SPC's 10% small hatched tornado threat verified. There most likely were a few sig tors in SC/E NE today, but pretty much all of the tornadoes were spawned by 3 or 4 somewhat longer tracked cyclic supercells. However, I was quite surprised to see the PDS tornado watch. The high instability was there, but I didn't see any dangerously high levels of low-level shear that would seem to indicate an enhanced threat for strong tornadoes.
When I left Ames at about 11 AM this morning my initial target was Sioux City - the warm front/triple point area. I thought low-level winds would be most favorable for tornadoes in that area. However, it became pretty apparent that the warm front was not lifting north fast at all. This has been a trend over the last 2 weeks or so with warm fronts - they have not been making it as far north as progged. Thus our target shifted south towards the Denison-Blair corridor. As time continued, the whole system appeared to slow to a halt, thus all of the relevant forcing mechanisms were going to be farther west than progged. Thus we continued west into Fremont, NE. Once we got there we saw a N-S oriented band of mid level cumulus/stratus. Those clouds were right along the edge of the 700 mb cap and were moving east farther into the capped region. Due to the reduced diabatic heating under those clouds, we figured storms would not fire under that band of clouds. That band expanded as it moved east, so we got west of it. Once we saw a strongly visible radar fine line on KUEX arcing from W-E-SE-SSE, we knew that was the dryline/cold front. Given the lack of obvious development over us or along the trough extending northeastward from the sfc low through C NE, it became pretty obvious that we needed to be on that boundary, especially since it had a history of spawning supercells. Another thing that made the decision easier was that the deep layer shear vector was nearly perpendicular to the boundary, which implied a cellular storm mode. The moral here is that our target shifted dramatically over the course of the day due to changing conditions. Some chasers like to pick a target the night before or the day of and make a note to go to that target first before re-evaluating and moving from there. That can pay off, but I've always had more luck when I constantly analyze new data as it comes in. I switch my target all the time. That can lead to some back and forth chasing paths, but if you're quick to decide and commit, it can be beneficial, too.
Also, regarding my talk about the hodographs. In the model forecasts I saw a lot of southerly 500 mb winds in the target area. Coupled with the southwesterly 700 mb winds that would result in a hodograph that has an S-shape - cyclonically curved in the lowest 1-2 km but anticyclonically curved between about 3-6 km AGL. Although I can't recall off the top of my head any research that specifically says S-shaped hodographs favor a non-supercellular storm mode, what bothers me about S-shaped hodographs is that 1) you get less positive storm-relative helicity above 2 km or so and 2) the mean wind (and thus a first order approximation to the storm motion vector) tends to lay very near the hodograph. That means storms would have less storm relative helicity period to work with unless they turn hard right. However, it seems that there were some SW or SSW 500 mb winds in Nebraska today. Thus the hodographs were probably not so S-shaped.
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Ryan Pfeifer
EF0
- Joined
- May 22, 2007
- Messages
- 41
The sig risk area was pretty small too if remember right. The position obviously off a bit in the 1st Day 1 outlook issued, but in addition to the York supercell, some damage reports from the cell near Elm Creek suggest that tornado could have been decently strong. As for tornadoes in general, I experienced a moment where they were coming down left and right, literally. I was following the building cell just east of the Elm Creek one and got a little behind it zigzagging on country roads to get a across the Loup River. Turned out it merged w/ the Elm Creek cell almost immediately on forming and was quite a mess compared to the textbook supercell I was hoping for, but the mess of updraft bases on the back were very vigorous and lowered and had frequent funnel clouds. One of the smaller ones had the most insane twisting motion I've seen in an updraft. Anyways, in a span of about 5 minutes we saw 3 tornadoes all in completely different locations. One was just a brief dust spin up, but the other two had condensation funnels all the way to the ground. They all lasted less than a minute that we saw, but the 2 fully condensed funnels we didn't noticed until they were already fully formed, one on the left and then one on the right (none of the tornadoes came from the lowered up draft bases, they seemed to come from the regular LCL height, they were all probably 5+ miles away). Weirdest part is the wind was out of the south. Only explanation I can think of for this would be outflow from the supercell that came out of Kansas and then died as the Elm Creek cell popped up. Everything got pretty boring after those first 5 minutes though and we stuck around slightly too long as we only got to see the last minute of the tornado west of Osceola. That thing left like a foot deep pile of mud across the highway though.
BBauer
EF2
I didn't end up chasing yesterday. I decided to wait and see if the system would progress fast enough eastward which it did not for my purposes. My parameters were to chase east of the Missouri. By the time the line of storms were crossing into Iowa it was just a linear mess with severe winds. June has been very quiet by Iowa's standards. I didn't chase the two good early season systems in Iowa so I hope we can get a few more tornadic storms around here.
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