Tomorrow's Moderate Risk

[BBauer]

I am considering chasing tomorrow's moderate risk. I'll be the first to admit I'm a newb chaser for sure. I have spent the last few years trying to learn as much as I can when I have not been attending to other obligations. With that said, I am far from producing a good forecast. I am limiting myself to east of the Missouri in Iowa. I wanted to come asking for a little help as far as initiation times with tomorrow's storms. I know things change hour by hour but I was curious about what some of you think when storms will enter or initiate in Iowa. The SPC forecast says by late afternoon/evening which is vague but maybe is the best they can put out right now? Another thing I am concerned about for my real first chase is storm motions and how fast they will be cruising along. So my inquiries summed up:

1. Thoughts on initiation times in general (or when storms will cross over into Iowa).
2. Thoughts on storm motion.

I'm trying to avoid going out and having to wait until dark until things cross over into Iowa. I don't want to chase at night. Also, I don't think fast storm motions would be good for a first chase. Would I be better off waiting for a good slight risk day? Thoughts? Thanks!

 

[Rob Wadsworth]

Statistics will tell you that initiation times in general occur between 4-7 PM. Usually whenever the 'cap' breaks. Daytime heating traps surface moist air that wants to rise, because warmer air aloft keeps it in check. But other elements come into play here too. It also depends on what means is triggering/forcing the storm - .eg. a cold front.

But I am pretty sure that some storms aren't going to necessarily cross over into Iowa, as they may well initiate in Iowa. How fast or how slow do storms move? Anywhere from 25kts to 40kts ground speed. Sometimes more; rarely less. They will probably travelling in a SW to NE direction. My best guess is that they won't be moving too fast since the cold front speed itself will regulate that. Maybe 35kts?

Been at this since 2008 and last year I had to leave early because of a family matter; so I and am by no means a seasoned chaser. I usually pick moderate to high risk days to chase. Because of the cost of gas and the certainty of success. Did manage to catch more than a dozen so far. Since I came away with only one last year near Spencer IA, my drive and game plan are on high this year - because of the moderate risk in my own back yard - so to speak..

I'm already in Storm Lake IA and will probably stay on this side of the Missouri River and wait until about 2PM until enough info can be gathered before the play is made. I'm sure - so long as the forecast doesn't change radically between now and then - that I really won't need to go very far to make a target. I will be looking for the area of the strongest 850mb surface inflow into the warm zone as near the triple point as I can get. Guessing Carrol IA at this time. But that is sure to change between this time and tomorrow afternoon . . .

 

[BBauer]

Appreciate the feedback. I hope storms will fire earlier than later as to have more daylight. I should have been a little more clear. My questions were in regards to tomorrow's specific initiation and storm speeds but maybe I'm wishing for too much specificity. I'll head west too but maybe stay near I-80 in case some storms fire in the southwest quadrant of the state, then I can ride them home toward Des Moines. Maybe the better play is NE Iowa though so I'll try and be flexible.

 

[jshields]

do you look/ are you familiar with the spc website? there will be mesoscale discussions that are issued usually as initiation is imminent within the next 1-2 hours. also, the rapid refresh website is a great tool for forecast radar images, which usually are somewhat accurate. if you are staying on the iowa side of the river i would target west central to nw iowa just to the east of the low near the triple point. make sure to get there early enough. it's always best to have to sit and wait for initiation rather than trying to run and catch up with it. i've had to do that too many times!! i would say be there by around 2 pm and then watch for md's and surface obs and adjust from there. i would say storms should fire around 4-5 pm based on current forecast timing first near the triple point and then fill in down the dryline/cold front as the evening progresses. the area near the triple pt will have the best chance of tornadoes, which according to the outlook could be strong tornadoes

 

[BBauer]

Great idea on the mesoscale discussion, yes I use the SPC site a lot. I also have a mesoscale discussion placefile on my GRlevel 3 so I'll watch for it to pop up tomorrow afternoon. Thanks for all the feedback guys, we'll see what tomorrow brings. Hope everyone has a great time out there!

 

[TJKLECKNER]

Yeah, I'm hoping for early initiation in western Iowa. I won't even guess where until morning/midday Monday and I concur but the Carrol IA area is looking pretty good for a sitting spot.

I'm here in Ames and I do alot of local chasing...I'm still in the process of getting a team going for the day.

 

[Jim Parsons]

Here are a couple good predictive sites to help you figure out an initiation time and location...
http://www.nssl.noaa.gov/wrf/
http://rapidrefresh.noaa.gov/hrrrconus/

 

[BBauer]

Any further insights into today's moderate? Thanks for those links. If I'm seeing correctly the model has storms firing in NE and does not have storms on the NE/IA border until around 7pm. Anyone agree or will it be sooner than that? Are storms initiating in Iowa around 5pm (as has been mentioned) still a possibility? I just hope I can be on a storm with quite a bit of daylight left. I don't have many opportunities to chase so I'm trying to maximize my chances. Thanks for helping the new guy!

Edit: If its more appropriate to sent me a PM with info then go ahead, thanks again.

 

[Rob Wadsworth]

For NW Iowa:
Right now, CAPE values are relatively high (~3000 J/kg). 'Capping'/inversion is almost non-existent. Temp/dew points are at 71/62 ATM. Winds are from the SE @ 10-15kts; with gusts up to 23kts. It appears theat the center of the low (now in C KS) is moving to the NE. Looks like most of the right ingredients are in place. Daytime heating with little/sparse cloud cover is supposed to get to 85 degrees! With so much return moisture available from close to 1 in of rain overnight; I'm betting the the dew points will increase accordingly. The warm front and triple point may arrive about/after 4 PM close to the Missouri River S of Sioux City IA and between Omaha NE. Helicity/wind shear is not where one would like to see it; but with the approach of the center of the low - I suspect this will be here on time as well.

So, it looks like I will change my original sight of Carroll IA for Ida Grove IA. Not too far from Mapleton - BTW. Or if it shifts farther NE, I may make a run for the Minnesota border. If it looks to be moving farther S; then Carroll IA and points to the NE will become my adjusted target . . .

Thoughts?

Edit: 300mb wind flow is over NW IA from the SW to the NE.

 

[BBauer]

Sorry for the spastic posting but from the wording of the SPC it seems like today's setup has fizzled a little bit. It seems large hail is likely, but the wording has changed to "a few tornadoes". It just does not seem as convincing. I'm debating waiting for tomorrow's slight risk. The SPC talks about organized multicell clusters and super cells tomorrow plus isolated tornadoes with many storms. Plus, initiation will be earlier it seems so there will be plenty of daylight. Putting yourself in my shoes what would you do? Again, PM me if needed. I don't want to hot spot. Also, I'm not trying to be a leech and just get the info I need. I'm working at understanding storms and forecasting I just have not put everything together at this point. Thanks again.

 

[BBauer]

For NW Iowa:
Right now, CAPE values are relatively high (~3000 J/kg). 'Capping'/inversion is almost non-existent. Temp/dew points are at 71/62 ATM. Winds are from the SE @ 10-15kts; with gusts up to 23kts. It appears theat the center of the low (now in C KS) is moving to the NE. Looks like most of the right ingredients are in place. Daytime heating with little/sparse cloud cover is supposed to get to 85 degrees! With so much return moisture available from close to 1 in of rain overnight; I'm betting the the dew points will increase accordingly. The warm front and triple point may arrive about/after 4 PM close to the Missouri River S of Sioux City IA and between Omaha NE. Helicity/wind shear is not where one would like to see it; but with the approach of the center of the low - I suspect this will be here on time as well.

So, it looks like I will change my original sight of Carroll IA for Ida Grove IA. Not too far from Mapleton - BTW. Or if it shifts farther NE, I may make a run for the Minnesota border. If it looks to be moving farther S; then Carroll IA and points to the NE will become my adjusted target . . .

Thoughts?

Interesting, everything does sound pretty good that you say. Jeff Duda in the Advanced forum mentioned that the hodos are not looking too favorable at this point. I'm beginning to understand how much chasing is a gamble sometimes. I don't know if I want to go for it today then miss out on some good storms close to home tomorrow. I can't chase both days. Its killing me. Such is chasing I guess.

Edit: Oh, just saw you did mention helicity/wind shear as not being the greatest. Still debating whether to hold off for tomorrow or not.

 

[Rob Wadsworth]

According to the SPC, the tornado threat for today's moderate level - has now shifted to the NE corner of NE. Man, I can still remember when the SPC made a prediction in the morning - and it was correct all day long. Hard to say what it will be like five hours from now at this rate. Feels more lke tornado hopscotch than chasing - IMO . . .

If it stays where it is; then I will have to cross the Missouri River @ Sioux City IA and go W on Hwy 20.
The SPC also said that 'Strong tornadoes' are possible.

Jeff Duda is probably right; I wonder if he is chasing this one?

 

[BBauer]

Ha ha, yes it does say strong tornadoes for now. They removed that wording I believe for the past update or two. It's looking more and more like I might sit this one out and wait and see what tomorrow brings as the tornado probability is being pushed farther away. I woke up last night to thunder and lightning and checked the SPC day 1 outlook and (unless I was dreaming) at one point they pushed the moderate risk almost completely out of Iowa and put it further west. Looks like its trending back that way now. I might keep an eye on things and bolt out west if any storms fire along the I-80 corridor out toward Omaha.

 

[Brett Nickeson]

I'm not a seasoned forecaster by any means, so take this for what it's worth...

The latest RUC runs are looking a bit more favorable towards Northeast and east-central NE due to the increased backing from the SE ahead of the surface low. It appears the low will create somewhat of a drier, stable slot to the south and west of Lincoln. Ahead of this, though, good deep layer shear of approx 50 kts, 70 degree dewpoints, and 3000+ CAPE should be very conducive to supercells once the cap burns off, which appears to be somewhere around 22:00. Now for the things I'm not a huge fan of. The 16:00 UTC RUC run shows a very narrow slot where the cap disintegrates, so I'm hoping that this doesn't turn into a cap bust. I don't think it will, especially near the triple point, but everyone has been surprised by it at one point or another. A second item is the upper level winds. I would much prefer to see them veering to at least the SW but all of the models have them straight from the south and even creating a pronounced S-shape in certain locations. The strong mid and upper level winds might try to makes storms go linear, but there should be at least a small period of time where large discrete supercells exist. Right now, I'm planning on targeting the Columbus area contingent on the model runs agreeing with me here in a couple hours. The RUC had been bouncing around the exact location of the low earlier but I think it should have a good handle on it now.

It's my guess that if you are going to stay on the Iowa side, the storms likely won't reach you until around dark or so. By that point they may be more messy and linear.

 

[Kevin Walters]

Obviously an open wave is preferred over a closing circulation however tornadoes are still possible in E NE and W IA. Wouldn't surprise me to see several tornadic supercells. No set up is perfect and this one is no exception, but I think the directional shear will be good enough to produce tornadoes.