What Gets You Out There?

[Danny Neal]

In an effort to forget it is snowing outside and to break away from my business page I thought it would be nice to talk some chasing strategy! I pose this question: What gets you out to chase? This isn't what fuels your chasing as I am sure we are all passionate about it. This is more of a "when you look at a set up" question. More so than just time off work or away from family, but specific set ups or parameters. Whether you are an SPC chaser, amateur forecaster, or scholarly meteorologist I pose the question...."What gets you out there?"

Obviously a negatively tilted trough with southerly 850's, 5,000 j/kg, and 400+m2/s2 are some of the most common answers. Anything that you look at that you feel unique for? Any tricks to the trade? For those who don't look at any model data, how do you determine where to chase?

 

[Marc R. O'Leary]

For me it's simple:

Lightning.

Edit: should have read DNeal's OP more closely. As for setups that get me out during the day, honestly, I'm really a short distance chaser, so I'll try just about any setup, but when I hear about Denver cyclone events it really gets me motivated. Close proximity drylines and upslope flow are my triggers.

Also, my wife thinks I'm nuts when I say "smells like a storm day" but around here its true. Added moisture to an arid environment is noticeable with the nose. And fronts coming from the N smell like cattle farms.

I'm still learning how to forecast, so im not usually ready for a target days ahead...more of a "how's today look" type.

 

[Dan Robinson]

For local chasing (within the STL metro): a rumble of thunder.

For Midwest chasing: any type of "spinny thing" (surface low, MCV, upper low) that entrains even the smallest amounts of surface-based instability will get me out the door looking for tornadoes within a 3-hour drive. A lot of these are general t-storm days on SPC outlooks (I've seen tornadoes in IL on days completely outside of the outlooked areas). Same thing for any day with greater than 1000 sbCAPE and greater than 30 knots of flow at 500mb, particularly if there is a boundary available (warm front, outflow boundary). The Midwest is a lot like the Caprock in that "magic" can happen with those setups.

For the Plains, I'm looking for greater than 40kts of anything westerly to south of westerly at 500mb, at least 2000 sbCAPE, an either: a.) surface low triple point b.) warm front or c.) dryline bulge. That mostly corresponds to Moderate Risks with at least a 5% to 10% tornado probabilites. That said, in May, I tend to follow Tim Marshall's adage "when it's May, you chase". If there's any midlevel flow above 30kts and decent instability, I'll probably hit the road especially if I haven't embarked on a worthy setup yet in the season.

 

[Jason Boggs]

Lots of things do it, but road network/terrain a lot of times gets me out there, or keeps me at home. Great road network/terrain, and I'm willing to gamble even if the parameters are lackluster. Great parameters in crappy road network/terrain, and I'll likely stay home.

As far as parameter wise, First thing I ALWAYS look at is the Td forecast. If model trends have a crappy outlook for Td values, it kills it for me.

By the way, very interesting post Danny.

 

[Danny Neal]

Interesting replies, thank you for that. I had a couple of motives behind this post. There is still plentiful information to be passed along from generation to generation. There is also a lot that I can still learn from reading these replies. I wholeheartedly agree with your Midwest synopsis Dan. Especially an early day MCV across C. IL. Jason, Td are obviously vital.... most of the time I don't even bother with model data as I do with surface charts. Especially inside 72 hours.

 

[JustinPhillips]

Probly in a small minority here, but even though I look at the models, I dont really chase off them per say. I usually check the SPC outlook in the morning and then go by surface maps/vis sat/mesoanalysis the rest of the day. For local days it doesnt take much to get me out, for non local chases, the thing that really decides if I am going to chase is the 850 winds.

 

[Adam Lucio]

Really any setup that lines up well logistically. I dont have a set criteria of parameters really, but I do focus a lot more on shear than anything. The speed and directional shear has to be there for me to really believe in a setup. Anything above 30kts and I start to give it consideration. 3500+ CAPE means nothing to me if youve got zero shear (outflow boundaries dont count in this case because you cant really predict those far enough ahead of time.) But you can have only 750 CAPE with 60kts of shear and stuff will still go down.

 

[John Farley]

I'm probably a lot like Dan, though I chase a smaller percentage in any of those situations than he does. (Now my local base is southern CO/northern NM rather than the STL area as in the past, but the principles are the same). Two other things I would add: 1) In local setups, even if the setup does not initially lead me to chase, I will tend to watch the radar to see if a good looking storm appears that offers an easy intercept. If that happens and I can, I will head out for a local intercept, even if the parameters are unimpressive. (Maybe this corresponds to Dan's "thunder" category!) Often this has gotten me interesting storms in setups that looked uninteresting, and last September, it even got me a rare tornado west of the Continental Divide in northern NM. 2) If I am going farther than a 3-4 hour drive, I tend to favor multi-day setups. I don't mind a long drive to a target area if there is a potential for 2 or 3 days of chasing in the same general area, so the potential for multiple chase days is a real motivator for me if I am going to a target area more than 3 or 4 hours away (which where I live now, is usually the case).

 

[Brian G]

I'm like Adam. I'm usually more focused on the wind shear. When I first started learning about supercells I would often use the ingredients based indices like EHI, SCP, STP, etc.. I still look at them, but I don't rely on them like I once did. So any range of CAPE will do as long there is a decent balance with the shear so I do use the BRN number. And if there's not at least 40 kts of bulk shear and strong indicators that the cells will be at least semi-discrete I'm probably not that interested. If it's something local and I can leave work early then I may be more inclined to chase slight risk style setups. In general though, I'm pretty picky especially if it means I have to drive more than a couple of hours to the target area. Because of my high threshold this usually means I don't venture out more than a few times a year at most. I still consider myself a novice so there is still lot I have to learn. One technique I'm hoping to apply or learn more about this season is the critical angle method on the hodograph. I'm not sure if it will have much value in my personal chasing decisions, but I'm hoping to find out!

 

[Wesley Luginbyhl]

I dont stick to this by any means, but 65 dew points is a big one I look at. Almost every day I have seen a tornado has landed at or above that level. I break that rule all the time, but quality moisture sure increases the odds of seeing something good. If it is within the 100 mile range from home, I will go out for about anything. Especially when it is out of the main chase season.

Misaligned low level jet (core 850mb winds 100+ miles off the dryline) or southwest 850s will get me to stay home just about everytime. I think the older/wiser/cheaper I get, it is not about what gets me out there, but more about what keeps me home.

 

[Royce Sheibal]

For long term 3-10 day planning on whether on not i'll chase, generally a good SBCAPE is all I care about up here in Nebraska, the shear is too hard to forecast that far out so I wait for high res to start paying attention. As for short term 1-3 day what gets me out the door is a good EHI/STP. I've been chasing for 10 years and I've gone out many marginal days and got squat, but days with high EHI/STP I've always gotten a little action, outside of 1 capped bust. I've got 2 jobs and grad school, so getting a day off to chase now is pretty rough. You can get tornadoes up here with ~1000SBCAPE, but the key there is SB. Storms this far north need to start and stay surface based, as they tend to gust out quickly once bases rise a hair, and gust fronts here tend to be destructive to the entire environment, as opposed to helpful as they can be further south.

Short story: Planned on chasing a slight risk day a few years back just south of Omaha, capped in the warm sector. Bummed about our cap-luck I went to buffalo wild wings with my uncle (now my chasing driver). Had a guiness and as we're sitting outside we see a huge tower go up to our west, hail reported. We pop in the truck, head toward Eagle, NE, met up with a tour group from... New Zealand? Got my uncle his first tornado sighting. Towers to my SW will always get me out the door in the late afternoon.

 

[Shane Adams]

I'm a huge fan of instability. I understand the importance of shear, but high instability can do wonders for overcoming lackluster shear, especially into the later parts of the Plains/Midwest season. I usually won't bite on an early season setup these days, unless it's a slamdunk type of event where the only question is "Will I see the tornadoes?" My situation doesn't allow me to take as many early season gambles as I did in years past, so I tend to tread more cautiously when picking setups between the first of the year through April. Though we do use technology on the road, we are still very "minimalist" compared to most chasers in 2015, so the long range chases can be a bit difficult for us when we're forced to make crucual decisions a day or so ahead of time.

Once "thermo" season kicks in, where most days are pre-set with instability and wind shear determines whether or not we pull the trigger, I'm much more apt to take chances on longshot type of setups. It's easier to have "accidents" within several days of high instability and marginal shear IMO, so we'll chase much more aggressively later in the year. My taste for instability-driven situations is most likely because I cut my teeth in the southern Plains, where CAPE usually plays a huge part in making setups successful. I've tried the rocket-speed, shear-driven events that typically happen early or late in the year further north and east, but have had little luck with them.

 

[Sean Ramsey]

I'll head out for most events that are within a couple of hours but shear is what makes it a go for me on long distances. Another consideration for me on whether I go out or not is if there is a lack of a cap, because big rainy messes aren't really a joy for me and trying to catch a storm in the first 30 minutes before it congeals may not be worth the effort.

 

[Ben Holcomb]

It's a combination of everything. Distance to the chase and what I think the likelihood of a tornado is.

The big things that are killer for me are sub 60-degree dewpoints. I really just refuse to chase anything less than 60 at this point. Just in time moisture really never pans out.

500mb winds. This is really the big one I look at now. If it's not going to be 5000+ CAPE I better have at least 35kts and I'm much happier with 50kts.

Being here in Norman, it's sometimes easy to judge in the morning what will be good and what won't just by looking up at the low level jet. If it's screaming north and bringing a lot of moisture, the day has a tendency to do well.

Terrain and Road Network is a huge one too like Jason stated. It may be a great outbreak, but if it's in Southern Indiana (March 2, 2012) I will likely pass.

 

[Michael Gavan]

This is certainly an easier question to answer if you aren't a "chasecationer." Neither my location nor career favor this hobby at all. I'm a full days drive away from getting into the southern plains. That means waiting for multiple good chase days and west of the jungles to be worth while. I hate turning down 5% type tornado days but unless there's days of them in a row expected in roughly the same area of the country and at least one guaranteed tornado day I have to turn it down. But there could be any combination of things to make it more enticing....Specific things I look for are possibilities for slow movers, LP's and structure, obvious tornado days, great terrain. Often, I'm allowed to pick only two of those at a time! Seeing some EHI is a good starting point....If it's good terrain I peak at Storm motion, PWAT, 9-11 km winds, etc those numbers may make or break it for me. I avoid HP and gorilla hail days if I can.

Either I get lucky and can work in a day off on a Friday, or I take a week or two vacation planned months in advance and hope I'm lucky. Luck. Luck, some skill, and then Luck.

So, that translates to seeing both the Rozel and Wichita tornadoes in 2013, or spending 8 days meandering from Omaha to Denver to Roswell to San Angelo last year for that cut off low during my 'chasecation' that amounted to LOTS of storms but no big prize. So in that case, I got out because of days and days of marginal setups, where the previous year was a two day weekend with near obvious tornado parameters. Separate from Rozel, my "chasecation" of 2013 got me a blue sky bust in Texas, a power flash from a 5 second long EF0 in Lawton, and a long early drive home in 40 degree crashing cold front.

I've decided this year to stop taking vacations for chasing. I'm now a little free-er this spring to get out more hopefully that translates to getting out there more and not a miserable bust like 2014 was.

The one parameter I never ignore though... Central IL. nearly 100% paved grid, flat, nearly treeless.