Storm Chasing

Dixie Alley Lights Up

Severe storms have been pushing through Dixie Alley this afternoon and evening, fed by dewpoints in the mid 60s to lower 70s and propped by bulk shear in the 60-70kt range. The action has been largely in Louisiana, where tornado warnings have been ongoing for several hours and tornado damage has been reported northwest of Atlanta.

Typical of southeastern storms, these ones look pretty HP-ish, real drenchers. They’ve waned in intensity from earlier, but they’re still dangerous storms, and one of them in East Carroll County is presently tornado-warned.

Here’s a GR2AE volume scan from the Shreveport radar depicting storm-relative velocity at 2107Z. Click on the image to enlarge it. You can see a pronounced couplet, indicating strong base-level rotation. I believe this was in fact the storm responsible for the tornado report, although two others in the same region displayed potent mesocyclones. More tornado reports may turn up from that part of Louisiana before the night is through.

November 29, 2010 by Robert Hartig

Filed Under: Storm Chasing, Tornadoes, Weather Tagged With: Dixie Alley, GR2AE volume scan, HP-ish, Louisiana, potent mesocyclones, pronounced couplet, severe storms, southeastern storms, tornado reports, tornado-warned

Late-November Severe Weather Outbreak In Progress

Now here’s something you don’ see very often on November 22 in the Great Lakes: supercells cruising across northern Illinois. I’d be very happy to be on either the one northwest of Toulon or the one northwest of Princeton. The storms are extending along the cold front northeast on into Wisconsin.

Whoops! The one down by Toulon is now tornado-warned. Imagine that! Here are some radar grabs. Click on them to enlarge.

And with that, I’m signing off.

November 22, 2010 by Robert Hartig

Filed Under: Nature, Storm Chasing, Tornadoes, Uncategorized, Weather Tagged With: radar grabs, severe weather outbreak, storms, supercells, tornado-warned

Severe Weather Potential Monday in the Western Great Lakes

A couple days ago, Lisa informed me that Dr. Greg Forbes was forecasting severe storms Monday in eastern Iowa and northern Illinois. I thought, hmmm…a bit far out to be definitive, but maybe I ought to take a look. I’ve been following the models since, and after this morning’s 6Z runs, it looks like Forbes is onto something.

Both the NAM and GFS suggest that an area from far eastern Iowa through northern Illinois and southern Wisconsin may be under the gun in the afternoon or evening. Here are a couple of NAM maps that will give you an idea why (click on maps to enlarge). The bottom line is that a low pressure system is cranking unseasonably warm temperatures and dewpoints in the mid-50s or higher into the Great Lakes region. The potential exists for weak instability to coincide with stiff 850 and 500 mb jet cores.

The GFS paints a somewhat more aggressive picture than the NAM and wants to clip things along a few hours faster. If that pans out, then north-central Illinois and south-central Wisconsin may see the best play. But both models are calling for essentially the same thing. Note the bullseye of 500 SBCAPE and 75 J/kg 3km MLCAPE at Clinton, Iowa, coincident with a nose of Theta-E bulging into the area. The GFS depicts the same scenario, albeit at 18Z rather than 21Z.

Today, Sunday, temps are forecast to rise into the 50s here in Grand Rapids, and tomorrow they should make it into the low 60s along with a significant increase in moisture. We stand a chance for a few thunderstorms of our own, particularly when the cold front moves in Monday night. As the KGRR forecast discussion puts it, “GIVEN TEMPS IN THE LOWER 60S…IT MAY ACTUALLY FEEL A BIT HUMID MONDAY AFTERNOON. THE CURRENT MENTION OF SLGHT CHC TSRA STILL LOOKS GOOD.” The SPC day 2 outlook has even thrown in mention of isolated tornadoes from southern Michigan southward, but tomorrow’s models will give a better sense of whether that’s any real concern. Helicity should be adequate, but instability is weak, and a November night-time squall line in Michigan is not your typical tornado machine.

Right now, the bottom line looks like warmer-than-usual weather in our area today and especially tomorrow, with storms in the offing in northern Illinois and nearby areas. And behind that, setting the tone for Thanksgiving, colder weather. So enjoy this last spate of warmth, because winter is waiting in the wings.

November 21, 2010 by Robert Hartig

Filed Under: Life, Michigan, Outdoors, Storm Chasing, Tornadoes, Weather Tagged With: dewpoints, Dr. Greg Forbes, forecasting severe storms, isolated tornadoes, NAM and GFS, squall line, unseasonably warm temperatures

Late-Season Thunderstorms in Lower Michigan

Amazing as it seems on November 17, I just heard a rumble of thunder. It wasn’t the first today. Several hours ago, a small line of storms swept through southwest Michigan, dumping rain, producing occasional lightning, and prompting warnings of “strong storms in the area capable of producing pea-size hail.”

Taking the unexpected opportunity, I hopped in my Buick and headed down into Barry County, where the more intense cells were moving through. We’re not talking anything major here–tops maybe scraped up to 20,000 feet–but this time of year I’ll take whatever I can get in the way of convection. Not being aware of any lifting mechanism in lower Michigan, I’m a bit mystified what it is that has been firing off the storms. The RUC soundings for 20Zand prior shows weak CAPE in the neighborhood of 200 J/kg with light winds at all levels. With surface temps peaking at 52 degrees, maybe that minimal instability has been enough to support some modest updrafts.

Whatever the case, it has been nice to get these late-season popcorn cells. They’re dying off now that daytime heating is dwindling, but they’ve made for a bit of serendipitous fun throughout the afternoon. And now I suppose we return to our regularly scheduled program of November drabness. I’m looking forward to watching Storm Chasers tonight and reliving the wild drama of May 22 in South Dakota.

November 17, 2010 by Robert Hartig

Filed Under: Life, Michigan, Weather Tagged With: Barry County, late-season thunderstorms in Lower Michigan, minimal instability, modest updrafts, popcorn cells, rumble of thunder, strong storms, weak CAPE

Leave Your Car and Take Shelter in a Ditch? Not So Fast!

You’ve heard it repeated often over the years during tornado warnings: If a tornado approaches you while you’re driving, abandon your vehicle and seek shelter in a ditch. For several decades that instruction has been disseminated as if it were gospel truth. But is it a proven life-saver or, like, some other popular tornado safety myths (hide under an overpass, open the windows of your house, head for the southwest corner of the basement) bad advice that could get you hurt or killed?

In my opinion, it depends. While the National Weather Service has historically recommended the ditch, recently at least some weather stations have been modifying that advice, and a lot of experienced storm chasers disagree with it vehemently. Among the excellent reasons why they would prefer to take their chances in a vehicle rather than in a ditch, they cite the following:

◊ Flooding. A ditch is a poor escape option if it’s rapidly filling with water. There’s no point in surviving a tornado only to drown in a flash flood.

◊ Debris. All kinds of material can get pitched into a ditch with lethal force during a tornado. This is no idle concern; ditches regularly fill with tornado debris.

◊ Electrocution. There you are hiding in your nice, flooding ditch, and down comes a power line smack into the water. Fzzztttt! You’re a crispy critter.

◊ Snakes. Depending on where in the country you live, you could find yourself keeping company with rattlesnakes, copperheads, and water moccasins.

All of the above are reasons commonly given by chasers why they will never abandon their vehicles in favor of a ditch. I’ll add one of my own: Unless a ditch is sufficiently deep, chances are good that the wind will just scoop you right out of it and blow you away. Take a look at this photo of a rear-flank downdraft (a type of strong, straight-line wind from a severe thunderstorm) and note how the dust fills the shallow ditch on the right. The RFD jet was crossing the road about 100 feet in front of our car when I snapped the photo, and it was easy to see that the wind wasn’t merely blowing over the ditch–it was blowing into it. There’s no reason why tornado winds won’t do exactly the same thing, only a lot more intensely. (Note as well the rainwater in the ditch and the power lines hanging overhead.)

Still not convinced? Check out this up-close video of a small but intense tornado traveling along a roadside ditch in Minnesota and consider how you would have fared had you been taking shelter there.

And then there’s the obvious.

Why on earth would you want to abandon your best means of escaping the tornado altogether, not to mention the added protection your vehicle affords, in order to expose your soft, pink body fully to the elements?

Contrary to what you may believe, you can outmaneuver a tornado. Storm chasers do it all the time. Tornadoes move at roughly the same speed as their parent storm. True, some can rip along at 60 mph or more, particularly in the early spring. But most tornadoes move at a much slower rate, generally between 25-45 mph. Given a decent road grid, unless you’re in an an urban area where traffic is congested, or unless your view of the tornado is impeded by terrain or precipitation, your most commonsense survival tactic is to get out of harm’s way. If you can see a tornado, you should be able to escape it unless it is nearly on top of you.

How to outmaneuver a tornado: advice for the average Jane or Joe.

Those of you who are storm chasers can skip this section. You’re already quite familiar with approach and escape tactics, or at least, you should be. (Of course, you’re more than welcome to share your own wisdom in the comments section, and I hope you will.) The following is written for the saner 99.9 percent of the population who don’t go gallivanting across the vast American heartland in the hopes of encountering massive wind funnels filled with debris, but who would like to know what to do when they see one approaching while they’re out driving in their cars.

Let’s say you find yourself in just such a situation. Your most obvious first step is to determine whether the tornado is moving toward you. Chances are it will simply miss you. If you’re north of its path, you may want to park under a shelter, because if you’re not already getting clobbered by hail, you probably will be shortly. If you’re south of the tornado, you might want to head a little more south yet just to be on the safe side. Then pull of the road and enjoy the spectacle, because it’s not one you’ll see every day.

If the tornado is in fact heading your way–if it appears to be growing larger without apparently moving–then you need to take action. Assuming that it’s approaching from the west or southwest, as will be the case in most (though by no means all) situations, your best bet is to head south.

In the map to your right (click to enlarge), the tornado is moving northeast directly toward you. Note the location of the number 1. That’s the general direction you want to head in for reasons you can easily see. If south isn’t an immediate option, then drive east and bail south at your first opportunity. Depending on how near you are to the tornado as it passes north of you, you may get slammed with vicious straight-line winds wrapping in from the storm’s rear flank, but that’s better than getting munched by the tornado itself.

The overall point is to sidestep the tornado by moving at a right angle to its path. (Situation: You’re standing in the middle of a railroad track and a train is coming. What’s the smart thing to do? Answer: Right–step off the tracks!)

Heading north toward location 2 is also an option, but it’s one you’re better off avoiding if you can. While you’ll escape the tornado, you will very likely find yourself in the storm’s hail core. As a general rule, heading south will take you away from the big hail and blinding rain. Of course, if you think the tornado is likely to pass south of your location and you’re concerned about crossing its path, then use common sense and either stay where you are or else move north. Better to risk losing your windshield than your life.

Let’s say, though, that you’re in a worst-case scenario. There’s no fleeing. Many chasers, probably most, would still prefer to ride out a tornado in their vehicle rather than in a ditch. Granted, neither option is a good one. There’s no question that the more violent tornadoes can do horrible things to an automobile; pictures abound of cars and trucks crumpled into balls of metal, or wrapped around trees, or filled with lethal debris. But at least your vehicle provides a layer of protection that you wouldn’t have in a ditch.

So is a ditch ever a good option?

This is a good place to mention that the ideas shared in this article are my opinion. They are not the result of scientific research. Then again, neither is the decades-old advice to abandon your vehicle for a ditch. It started as someone’s reasonable-sounding idea that gained authority through repetition rather than actual proof. Still, it does make sense to get as low as possible during a tornado, and I personally think there are occasions when a ditch could offer viable protection.

It’s a matter of situational awareness. Is the ditch deep, deep enough that it could minimize your exposure to the wind? If it were me, that would be my first question. Assuming that the answer was yes, my next concern would be with my surroundings. I would feel much more hopeful about sheltering in a ditch in the open countryside, with little in the way of trees and other large debris to get chucked at me, than I would in an area full of structures all strung together with power lines. And what about vehicles? I would certainly want to get far enough away from my own car that it wouldn’t be likely to roll over on top of me.

Flash flooding? Snakes? Those issues are of greater concern in some parts of the country than others. The best I can say is, know the environmental hazards of your territory and make your choices accordingly.

Again, the best way to survive a tornado is to get out of its path. Since most tornadoes are only a few hundred feet wide, avoiding them in a vehicle is quite easy given decent visibility, good roads, and ample lead time. If you’re in your car and you spot a tornado approaching in the distance, don’t take the fatalistic view that you can’t outrun it. It’s probably not heading directly at you in the first place. Determine where it is heading and do what you need to in order to position yourself elsewhere.

However, if it appears to be growing larger without moving to either the right or left, then you need to either skedaddle or else find adequate shelter. Ditches rarely qualify. In most circumstances, you should consider a ditch as only a last-ditch option.

November 14, 2010 by Robert Hartig

Filed Under: Life, Tornado Safety, Tornadoes, Weather Tagged With: ditch can offer viable protection, environmental hazards, experienced storm chasers disagree, flash flood, how to outmaneuver a tornado, leave you car and take shelter in a ditch, rear flank downdraft, straight-line winds, surviving a tornado, tornado debris, tornado safety myths, tornado warnings

MetEd: A Fantastic Self-Educational Approach for Learning Weather Forecasting

When I first began turning my lifelong fascination with tornadoes into an active passion for storm chasing over 14 years ago, I started with the essentials of storm structure. Then I began learning such arcane terms as CAPE, shear, dewpoints, helicity, and so forth, over time piecing together how the different ingredients interact. Bit by bit, the alchemy of the atmosphere–depicted by surface maps, forecast models, skew-T/log-P diagrams, hodographs, station obs, satellite, radar, and other mystifying tools of the trade–began to make sense to me. Tremblingly, nervously, with a deep sense of my woeful lack of knowledge, I began to try my hand at forecasting–and darned if I didn’t start to make some good calls.

Slowly I learned, and I’m still learning. There’s so much to know, and I want to know as much as I can in order to more accurately determine whether there will be tornadoes, and where, and at what time, and whether a weather scenario will be significant enough to warrant the long drive from Michigan to wherever the storms will be firing.

I wish I’d had a mentor to help me learn this stuff. Thank goodness for the community on Stormtrack–for the many experienced chasers and meteorologists who have generously answered my questions and shared their knowledge over the years! Fortunately for new chasers, a wealth of educational resources exists today that can make the learning curve quicker and less frustrating.

And that brings me to MetEd

I just completed a MetEd satellite interpretation module on vorticity maximas and comma clouds. The material has both enlightened me and kicked my butt. I’ve learned enough to know that I’ve got a lot to learn, but also enough to make better use of water vapor imagery. Now I’m moving on to vorticity minimas, but after finishing the first module I had to just back away for the evening and take a breather. This stuff may seem simple to some, but it makes me want to find a nice hard surface and bonk my head against it. I get the concepts, but working them out in real-life case studies is something else. What gives me incentive is the payoff of becoming a better forecaster. MetEd offers some fantastic tools for pursuing that goal.

Short of a formal education in meteorology, MetEd online courses are probably the best thing going for those who want to acquire basic forecasting skills or expand the skills they’ve already got. I recommend them highly. A program of UCAR (University Corporation for Atmospheric Research), MetEd is no lightweight survey. It’s a constantly growing and evolving suite of vanguard educational products covering a broad sweep of meteorological topics, and it is used by scores of operational forecasters to help them sharpen their blades. Predictably, some of what it offers is well beyond the grasp of most lay persons. Yet a fair amount is accessible to the motivated self-educator, and well worth the time it takes to absorb the material.

The course I’m working on, Dynamic Feature Identification: The Satellite Palette, is a good example. Its interactive format lets you get your hands dirty with actual application as you learn about vort maxes, vort minimas, comma clouds, deformation zones, blocking patterns, and more. Once I’ve completed the full course, while I’ll assuredly be no expert at interpreting water vapor imagery, I’ll nevertheless have gained some knowledge that will serve me well–stuff I’ll be able to use next spring when Big Weather returns to the Great Plains.

If you want to bone up on weather forecasting of any kind, from severe thunderstorms to winter weather and more, you owe it to yourself to check out MetEd. Do it now and you can thank me later for sending you. MetEd is a great way to hone your skills during the long stretch between now and Storm Season 2011.

November 5, 2010 by Robert Hartig

Filed Under: Software & Technology, Storm Chasing, Tornadoes, Weather Tagged With: comma clouds, experienced chasers and meteorologists, learning weather forecasting, MetEd, satellite interpretation module, severe thunderstorms, Storm Chasing, Stormtrack, the satellite palette, Tornadoes, UCAR, vorticity maximas, water vapor imagery

Lightning Storm over Caledonia

The day after my October 23 chase out in northwest Missouri and southwest Iowa, thunderstorms blew across West Michigan. Watching the MCS move in on my radar, I decided to try my hand at a few lightning photographs. I had learned a few essential tips since my last attempt, and this looked like a fantastic opportunity to see what kind of a difference they made.

The photos shown here were shot from the balcony of my apartment in Caledonia. Click on them to enlarge them. They may not be National Geographic quality, but they’re not bad. Fact is, one of my photos that night was my best lightning shot ever. Unfortunately, I accidentally erased it only minutes after I took it. You could hear my screams of anguish and bonking of my head against the wall all the way to Sam’s Joint.

What you see on this page are just compensation prizes. They’ll do, though. They’re mementos of what was probably the last lightning any of us around here will see this until next spring. Snow is in the forecast a few days hence, and with two months before it officially starts, the long winter is already winding up the mainspring and getting set to unleash.

November 1, 2010 by Robert Hartig

Filed Under: Michigan, Nature, Outdoors, Photography, Weather Tagged With: lightning photographs, Lightning storm over Caledonia, thunderstorms, West Michigan

Between Idolatry and Joy: Some Thoughts on Life from a Jazz Saxophonist and Storm Chaser

There is an art to pursuing the things we’re most passionate about without letting them consume us. I certainly find this to be true of my own two interests, jazz saxophone and storm chasing, but the principle applies to all of us in whatever our preoccupations may be. Without fascination, energy, focus, and joy to drive us wholeheartedly in our pursuits, there’s no point to them; yet without restraint, self-awareness, and awareness of the broader world around us, it is easy to become a mile deep in our passions and an inch deep in life at large. Between these two realities, for me and I think for many of us, there lies a dynamic tension.

As a disciple of Jesus, I have to reckon with the issue of idolatry. In Old Testament times, an idol was easy to identify. It’s hard for us today to fathom people fashioning gold calves and graven images, both human and bestial, and then worshiping the things that they themselves had crafted. Yet that’s exactly what people did back then, both in pagan nations and in apostate Israel.

The funny thing is, we’re no different. We still bow down to the works of our hands, to things that are capable of becoming our gods if we let them. Things that blind us to truths bigger than ourselves and hinder our capacity to love God and others.

The problem with our modern idols, however, is that they’re not readily identifiable as such in the same manner as, say, a brazen bull or a figurine of Marduk. Anything in our lives can become an idol–our careers, our pursuits, significant relationships, the desire for love, our injuries and disappointments, our causes, our appetites, our emotions, our cars and other possessions, even our ministries and charitable occupations. Idolatry today is not usually something that is innate to the things in our lives, but is a matter of our attitude toward them and God. In ways subtle and not so subtle, it’s easy for us to invest ourselves in what we have and what we do in such a way that we allow it to define life and purpose for us. That’s a problem, because any of it can be taken away from us at any time, and sooner or later all of it is going to go. Then where do we find meaning; then where do we find life?

Moreover, we can become irresponsible and selfish in reaching for what we’ve defined as life, setting our pursuits above people we love and who love us. When we’re frustrated in those pursuits, we can become downright nasty, even destructive, toward persons who seem to inconvenience us, challenge us, or obstruct us. We’ll sacrifice others to our idols and justify ourselves in doing so rather than deal with our own hearts.

All this in the quest for life on our own terms.

Well do the words of Isaiah the prophet speak to us today: “[The idolater] feeds on ashes; a deluded heart misleads him. He cannot save himself or say, ‘Is not this thing in my right hand a lie?'”

Is there a flip side to this coin?

Of course there is. If God never intended for us to enshrine the things that we enjoy and love to do, neither does he want us to smother those things in sackcloth. In the Bible’s book of Genesis, in the Creation story, God from the beginning gave Adam and Eve something meaningful to do. They were gardeners, caring for the trees and flowers in Eden. Ironically, after they sinned, the man and woman’s immediate response was to hide from God behind the very things he had assigned them to cultivate and protect.

The problem lay not in the shrubs and trees and vines, but in Adam and Eve. The greenery in the garden was the same as the day when God first looked on it and called it good; it was the human heart that had changed. Ever since, in various ways, we’ve had a tendency to conceal ourselves from God and from each other behind the things we do.

Yet those same pursuits also have the potential to express the robust life of Jesus living in us untamed and unfettered. There’s nothing at all winsome about Christians who are so paranoid about idolatry that everything they do is constrained by a gray, lackluster religiosity. Many well-meaning believers confuse holiness with a boxed-in, sanctimonious, hermetically sealed existence that is about as invigorating as paper pulp. It hardly mirrors God’s exuberance in the act of creation, when with a decisive word he spun the visions of his heart into being–planets, suns, galaxies, luminous gas clouds, multiplied quintillions of celestial objects, all whirling across the velvet-black vastness; ocean tides pulsing and surf crashing against craggy shorelines; wildflowers waving in vivid, multi-hued pointillism in meadows and forests, knit together, unseen, by untold millions of miles of subterranean roots and rootlets.

Talk about a hobby! It was no dour, stuff-shirted God who created this fabulous world around us, this universe that awes and fascinates and humbles us; no, it was an eternal being who throughout the ages remains forever young–smarter than the most brilliant scientist, wiser than the wisest sage, yet passionately, perpetually, and unapologetically a child at heart.

God created us to live our lives as wholeheartedly, creatively, lovingly, generously, fearlessly, and beautifully as he lives his, in ways unique to each of us. Failure to do so is in itself a form of idolatry, a lack of trust that the One who hardwired us with our personal interests also supplies the grace and wisdom to express his life and fulfill his intentions through those interests.

The overarching principle is love–love of God and love of others. Love is ultimately what separates between idolatry–which is about pursuing our own independent way on our own terms–and the abundant, God-dependent life that Jesus offers. Christianity is not about good morals and rock-hard dogma; it is about nothing less than the life of Jesus himself living inside us, energizing us, guiding us in the pathway of his character. That is no weak, wan way of living. To be sure, it is a way that is often marked by self-sacrifice, pain, loneliness, misunderstanding, prayer, struggle, and self-control. But it is also a way infused with immense purpose, remarkable potential, endless fascination, and a joy that can be found in nothing else this life can offer.

In conclusion

Bringing all of the above to bear in a practical way for those of us who chase storms and/or play music: Whatever you do, do it with all your heart. God is not glorified by a timorous approach to the things you enjoy, nor does he want you to walk on eggshells for fear of offending him. Just keep in mind that there is more to life than your pursuits. Enjoy those pursuits, treasure them, but don’t grasp them so tightly that you can’t let go, and don’t let them give you tunnel vision so that you fail to see and participate in the broadness of life around you. Other people’s worlds are as rich and important as yours; to the best of your ability, enter into them, celebrate them, and let them expand you. Harness your interests in a way that makes your life bigger, not smaller–an expression of generosity, not selfishness, and of a Christlike perspective that values God and others most of all.

Behind the sound of a saxophone playing now tenderly, now exuberantly, always striving for creativity and beauty…behind the sublimity, the fascination, and the awe of a tornado churning across the open prairie…you can, if you choose, hear the song and see the face of God. If you submit your heart to him, he will in turn release his own magnificent heart in and through the things you love to do.

This, in part, is what life, true life, is about: allowing the things that are central to us to become the servants and the expressions of Someone far bigger than ourselves, and of a kingdom greater than our own.

October 30, 2010 by Robert Hartig

Filed Under: Christian Music, Christian Spirituality & Inspiration, Church Worship, Jazz, Life, Music, Saxophone, Storm Chasing Tagged With: Adam and Eve, Bible's book of Genesis, Christianity is not about good morals and rock-hard dogma, face of God, God, idol was easy to identify, idolatry and joy, immense purpose, Isaiah the prophet, jazz saxophone, jazz saxophonist, kingdom greater than your own, life on our own terms, love God and others, Old Testament times, play music, prayer, remarkable potential, robust life of Jesus, self-sacrifice, sound of a saxophone, storm chaser, Storm Chasing, the Creation story, tornado churning across the open prairie

Guest Post: Robert Edmonds on Multiple Vortices

The following is an unexpected and interesting guest post from fellow storm chaser and atmospheric modeler Robert Edmonds. Earlier this week I got a note from Robert, and, recalling some of his very cool vortex models that he had posted on Stormtrack, I invited him to submit a guest post. At my suggestion–because Stormhorn.com is written on a popular rather than a scientific level–Robert has taken a concept that I’m certain can be expanded upon to incredible complexity and offered some essential thoughts on it which I think just about anyone can understand.

A bit on Robert’s background. A weather modeler for Mars who works frequently with NASA, Robert possesses a BS in astrophysics and a minor in mathematics, and is currently pursuing a Ph.D. With nine years experience chasing storms, he operates his own business as a storm chasing tour guide.

Without further ado, I give you Robert Edmonds sharing his insights on

Multiple Vortices: Stable and Unstable Configurations

Bob Hartig recently wrote an article titled “Multiple Vortices: How Deep Do They Go?” Being both a storm chaser and an atmospheric modeler for Mars, I thought I might share some interesting insights about multiple vortices. There is a lot of fascinating physics going on inside multi-vortex tornadoes.

First, however, it might be good to understand the difference between vorticity and circulation. Imagine a boat in the ocean. Let’s say that in this ocean is a giant whirlpool. The boat is circulating about this whirlpool; however, the nose of the boat keeps pointing in the same direction–let’s say, north. Clearly there is circulation because the boat is going around and around the whirlpool, but in the water immediately surrounding the boat there is no vorticity.

Now let’s move the boat closer and closer to the center of the whirlpool while keeping the boat’s nose still pointed north. There is still no vorticity in the water immediately surrounding the boat.

Only when we find the nose of the boat turning is there vorticity in the water immediately surrounding the boat. The boat is now experiencing not only circulation, but also vorticity.

At the following link you will find an applet with two windows: https://stormchaseguide.com/blog.html. The black dots represent locations of concentrated vorticity (places where the boat’s nose would turn). You can think of these dots as multiple vortices within a larger tornadic circulation. What I want to show you is that certain vortex configurations are stable.

First, uncheck the two boxes next to “Running.” This will freeze the motions of the vortices. Next: In each window there are vortices in a circular configuration. Drag one black dot in each window at most half a mouse cursor length (click and hold). When you’re done, go ahead and click the boxes next to “Running.”

You should find that in the panel with six vortices, the shape or configuration of the dots remains generally the same. However, in the panel with seven vortices the configuration eventually breaks down. This is because circular, evenly spaced configurations with more than six vortices are unstable.

This little demonstration touches on many aspects of weather, not just multi-vortex tornadoes. The chaotic behavior in the panel with seven or more vortices demonstrates why no weather forecast will ever be perfect. The air around us can be thought of as composed of billions, even trillions, of little vortices, all interacting in seemingly random fashion. As you’ve just seen for yourself in the very simplified model, small changes in the atmosphere can produce drastic differences over time–true of both tornadoes and of the larger weather systems that spawn them.

October 28, 2010 by Robert Hartig

Filed Under: Guest Posts and Interviews, Storm Chasing, Tornadoes, Weather Tagged With: atmospheric modeler Robert Edmonds, chasing storms, difference between vorticity and circulation, multi-vortex tornadoes, multiple vorticity, vortex models, weather systems

Chasing the Great Lakes Superbomb of 2010

Until early yesterday morning, I was pretty certain that I wasn’t going to be chasing yesterday’s squall line associated with the record-breaking low pressure system that’s moving across the Great Lakes. With storms ripping along at 60 knots, what kind of chasing is a person going to do?

Then came the 7:00 a.m. phone call from my chase partner, Bill Oosterbaan, informing me that the Storm Prediction Center had issued a high risk for the area just across the border in Indiana and Ohio. With the rapidly advancing cold front still west of Chicago, we’d have ample time to position ourselves more optimally. This would be an early-day storm chase. It would also almost surely be our last chase for the next four or five months. What did we have to lose?

I hooked up with Bill at the gas station at 100th St. and US-131, and off we went. The storms had moved into Chicago by then, and as we dropped south, it became apparent that we would also need to break east and then stairstep down into Ohio, buying time in order to let the line develop with daytime heating. Satellite showed some clearing in Ohio,

suggesting a better chance for instability to build. Catching I-94 in Kalamazoo, we headed east toward I-75, with the Findlay area as our target.

Off to the northwest in Minnesota, the low was deepening toward an unprecedented sub-955 millibar level, sucking in winds from hundreds of miles around like the vortex in an enormous bathtub drain. Transverse rolls of stratocumulus streamed overhead toward the north, indicating substantial wind shear. (Click on image to enlarge.)

By the time we crossed the border into Ohio, tornado reports were already coming in from the west as the squall line intensified. Soon much of the line was tornado warned. However, while the warnings were no doubt a godsend for a few communities that sustained tornado damage yesterday, they weren’t much help to Bill and me. Chasing a squall line is different from chasing discrete supercells.

We had in fact hoped that a few discrete cells would fire ahead of the line. But the forecast CAPE never materialized to make that happen, and we were left with just the line. In that widely forced environment, tornadoes were likely to occur as quick, rain-wrapped spinups rather than as the products of long-lived mesocyclones. Even with GR3, the likelihood of our intercepting a tornado would require a high degree of luck. It was harder to identify areas of circulation with certainty; I found myself using base velocity as much as storm relative velocity on the radar, and comparing suspect areas not with easy-to-see hook echoes in the reflectivity mode, but with kinks in the line. It was pretty much a game of meteorological “Pin the Tail on the Donkey.”

North of Kenton, we headed west and got our first view of the squall line. For all the hooplah that had preceded the thing, it didn’t appear very impressive. Just your average storm front–much windier than most, but also a bit anemic-looking compared to some of the shelf clouds I’ve seen. Still, it was a lovely sight, watching those glowering clouds grope their way across the late-October farmlands.

Neither of us was quite ready to end the chase, so with the storm rapidly closing in, we scrambled back into the car and stairstepped to the southeast in the hope of intercepting a likely-looking reflectivity knot that had gone tornado-warned. It was fun playing tag with the storm, driving through swirls of leaves spun up by the outflow. But there really wasn’t much incentive for us to continue the game indefinitely. Eventually we turned back west and drove into the mouth of the beast.

For a few minutes, we got socked with torrential rain and some impressive blasts of wind (and, I should add, absolutely no lightning or thunder whatever). Then it was over. Time to head home.

In Kenton, we grabbed dinner at a small restaurant. Then we headed toward Cridersville, 28 miles straight to the west next to I-75, where there had been a report of “major structural damage” from a tornado. The report was accurate. A small but effective tornado had torn through the community, uprooting and snapping off large trees, taking off roofs, and demolishing at least one garage that I could see. Of course we couldn’t get into the heart of the damage path, but a few passing glimpses suggested that some of the damage may have been fairly severe.

As I said at the beginning, this chase will likely have been my last of the year. I never know for sure until the snows fly, but it seems like a pretty safe bet that I won’t be heading out again after storms until March or April. It’s hard to call this chase a bust since our expectations weren’t all that high to begin with. Plus, tornadoes or no tornadoes, it was an opportunity to engage with a historical weather system. Like other significant weather events such as the Armistice Day Storm and the 1974 Super Outbreak, this one will be given a name in the annals of meteorology. Me, I’m calling it the Great Lakes Superbomb of 2010. In a number of ways, it hasn’t proved to be as impactful as was forecast, but it’s not over yet. And regardless, I’m glad I got the chance to get out and enjoy a final taste of synoptic mayhem.

October 27, 2010 by Robert Hartig

Filed Under: Michigan, Nature, Storm Chasing, Tornadoes, Uncategorized, Weather Tagged With: cold front, Cridersville, discrete supercells, Great Lakes Superbomb of 2010, high risk, rain-wrapped spinups, record-breaking low pressure system, storm chase, substantial wind shear, tornado damage, tornado reports, transverse rolls, yesterday's squall line