Going Visual

[Bob Hartig]

Let's say you're out in the field and all you've got to go by is your eyeballs and the experience you've gleaned as a chaser. No laptop computer, no numerical models, just your knowledge and your observational skills. What are some visual or perceptual clues you use to find the best storms?

I'm not talking about storm structure, such as overshooting tops or backsheared anvils. I'm talking about things that precede storm initiation or that affect storm development--e.g., how can you tell when the dewpoints are going to rise, or conversely, that the atmosphere is mixing out? How can you tell when a jet max is on the way? How do you know where the cap is more likely to break? How do you know when a storm is heading toward a better environment? That kind of thing.

What are your favorite tip-offs?

 

[Shane Adams]

how can you tell when the dewpoints are going to rise, or conversely, that the atmosphere is mixing out?

I've never been great with "sniffing" out moisture return/decline status, but if I'm in constant S/SE winds and my cu field isn't eroding, I'm confident my dewpoints are staying close to where I need them. Consequently, if my cu field gradually erodes over time, with flatter tops, higher bases, and even total disappearance, I am worrying about mixing out or full-on subsidence.

How can you tell when a jet max is on the way?

Often times a thin, wispy cirrus streak can be seen in the western sky, being carried along by the approaching jet max. Also, as the jet max 'rounds the southern/SErn part of the low, it can back surface winds as it pulls moisture towards the LOW circulation. So seeing cirrus to your west/southwest or a noticeable backing of surface winds can be signals of an approaching jet max.

How do you know where the cap is more likely to break?

Like I mentioned above, the cu field is the most telling sign of cap status/strength/potential. A vigorous cu field with tops that are "fighting" to push up but are continually suppressed is the best sign of a strong cap that is likely to break. A "fair weather" cu field is a sign of plentiful moisture but not enough "umph" to break through; the clouds are thick and numerous but they are showing no signs of vigorous vertical development - stout cap. The worst is a clear blue sky, which by 6'o clock usually means it's time to start deciding where you want to eat dinner.

How do you know when a storm is heading toward a better environment?

For me, I have to know the general surface environment/forecast before I leave; i.e. if I go to western OK knowing the dewpoints are slightly higher in central OK, I have a good idea that any storm that initiates in my area will be moving into better air. However there are some cases where you will have a collapsing storm ahead of your storm's track, or even a group of ongoing storms ahead of your storm, that can lay down boundaries (such was the case on the 6-12-04 Mulvane day). It's important to remember any other convection in the area of your storm can greatly influence your storm, be it for better or worse. Sometimes there is no fail-safe plan, you just gotta make a choice and roll the dice.

What are your favorite tip-offs?

Mine is a dryline bulge. You start to see a "clear arrow" of blue sky slowly moving in from the west on your cu field, eating away at it. To the north and south there's still clouds, but they're not as thick as earlier. Then you look back to the east and it's like cotton candy. The best example of this I can remember seeing was on May 12, 2004. We were in Woodward and had decided to move north, and after a few miles outside of town we noticed all the clouds were gone to the west, and were thinning in front of and behind us. Meanwhile, east of us it was thick with cu. We immediately backtracked, went east out of Woodward, and then turned north towards the thickest part of the cu field we could see. As we drove north, two towers emerged from the cu field, and the chase was on

 

[Bob Hartig]

Thanks! That's exactly the kind of info I'm looking for.

 

[Jon Miller]

With the great visability out in the plains, is there any easy way of visually (wo/ radar) guestimating how far away a supercell is ? ie if you see a supercell with a developing anvil off in the far horizon , how do you tell if it is 40 miles away or 200 miles ? I've wasted a a fair amount of time , in past years, trying to get to a storm that ends up being a lot farther away than I thought it was.

 

[Shane Adams]

With the great visability out in the plains, is there any easy way of visually (wo/ radar) guestimating how far away a supercell is ? ie if you see a supercell with a developing anvil off in the far horizon , how do you tell if it is 40 miles away or 200 miles ? I've wasted a a fair amount of time , in past years, trying to get to a storm that ends up being a lot farther away than I thought it was.

There's really no way to describe it, you just kinda get a knack for it after you see it enough times. I can usually guess (to within 10-20 miles) how far off a storm is, just by how big it looks in the sky. That's not real scientific, but it's just the "visual" way. Also helps to have a NOAA radio blasting warnings and mentioning the storm's location

Seriously though, if you have an open view of the horizon and can see the base at all, it's a good bet you're within 25-30 miles of the storm. If you can't make out anything underneath but can see good definition in the updraft (crispiness) it's more like 40-70 miles away. (However in some cases haze will play a major factor in whether or not you can see the base, even if the storm is in the 20-30 mile out range). Anything over 70-80 miles you usually only see the "schematic" shape of the storm, and details are sketchy. Beyond that distance, it's time to find a beer.

These aren't concrete rules, just advice from my own experiences.

 

[Tim Bond]

Can I add my thanks for your very informative post, Shane. From the point of view of someone new to the board here and very much in the chase novice camp, that was an extremely interesting answer to read!

Cheers

Tim

 

[Dave Gallaher]

With the great visability out in the plains, is there any easy way of visually (wo/ radar) guestimating how far away a supercell is ? ie if you see a supercell with a developing anvil off in the far horizon , how do you tell if it is 40 miles away or 200 miles ? I've wasted a a fair amount of time , in past years, trying to get to a storm that ends up being a lot farther away than I thought it was.

Non-severe convective days can offer a great opportunity to practice distance estimates. Even though my home area is hilly and forested, when storm towers rise I like to guess where they are, then come and check GRLevel3 to see the actual location. One season of doing this in one's locale will greatly enhance visual distance guessing.

BTW--Thanks, Shane--very informative post.

 

[Jon Miller]

Thanks for the good info Shane. Hope to put it to use this upcoming spring - time and especially finances permitting.

Jon Miller
KT8NDO