Tag Archives: severe weather

Why are we having such bad weather?

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I think most people will agree that in North America (and other places) we’ve been having some bad weather. Some of the weather is not necessarily intrinsically bad … so what if it is a little cooler or a little warmer than you expect. Aridity? Deserts are nice! Extra rainfall? Great for the plants. But actually that sort of thing has its down side since important systems like agriculture, the water supply, and Spring Break work reasonably well because of expectations that might not be met if the weather is different.

Other weather is intrinsically bad. I’d mention tornadoes but at the moment climate and weather experts are not at all agreed on whether or not we are having more, worse, bigger, or otherwise badder tornadoes and if there are differences in tornadoes this decade compared to earlier decades, why that is the case. But other things can be pointed to. Superstorm Hurricane Sandy was the hurricane that should not have gone where it went, should not have been so strong, perhaps should not have been at all. Droughts. Widespread wildfires caused by droughts. Lots and lots and lots of rain causing widespread flooding. Heat waves and cold waves. As a category of things that can happen, these things are in the “bad weather” category, and it is reasonable to ask why they are happening so much “these days.”

It is possible that these changes in weather, or more exactly, these examples of rapidly changing weather that have come to be known as “Weather Whiplash,” are caused by global warming which in turn is caused by the unchecked release of large amounts of fossilized carbon into the atmosphere with the burning, by humans, of fossil fuels. But before I get to that argument (short answer: Weather Whiplash is caused by global warming, but hold on just a sec..) I want to point something else out that is very important.

I want to point out the problem of understanding shifting conditions. Let’s say you are a storekeeper and every day you make a certain amount of profit. How much you make each day varies a great deal owing to a large number of factors. I knew a guy who worked in a camera shop just off Wall Street. He would sell no cameras for days on end and then suddenly sell a gazillion cameras. That would be on a day that the stock market went way up and traders felt flush, and went and bought the expensive cameras and lenses they had been coveting for weeks. I know people who had businesses on Cape Cod and how much money they made on a given weekend depended on the weather forecast for “The Cape” shown to Boston area audiences on Friday (regardless of the actual weather itself, generally). But underlying all this is another set of factors that do not vary day to day or hour to hour (or week to week or even seasonally). One is the overall long term state of the economy (how much stuff do people buy, based on how free they feel with their cash). Another is the overall demand for your particular goods, which may vary little if you sell food but a lot if you sell some trendy widget.

In the absence of good information, how do you know if your business is about to either tank, because people stopped buying your goods, or take off, because people can’t get enough of your goods? If your sales shift a great deal in one day, is that enough information? No. If your sales shift for an entire week, does that tell you something? Maybe, probably not. Most likely, you can identify normal pseudo-cycles, ups and downs, that occur in your business and estimate their length. Some factors cause your business to go up and down over scales of weeks, some over scales of days. Perhaps you can estimate that if you get an average amount of business over six months, and that is higher or lower than the previous six months, then you can say that a basic shift has happened.

Weather has cycles and pseudo-cycles just like businesses do, and they run over the course of days, seasons, years, and somewhat longer cycles that have to do with the position and relationships of major high pressure systems that shift around over cycles of five to fifteen years, and a few other thigns.

Now think about what we expect from global warming.

A simple yet usable model is this: More CO2 in the atmosphere = more heat (energy) in the atmosphere = climate change. But the expected climate change is not linear. Models that seem to work together with direct observation show us that more CO2 has resulted in aridity and wildfires in certain areas. But if we go back in time to when there was even more CO2 in the atmosphere, it seems like everything was wetter, so the whole drought and wildfire thing may be something that gets worse and worse through the 21st century, but at some point is replaced by a whole different set of problems. With respect to sea level rise, which I think is one of the biggest problems we face, it is not likely that the continental glaciers will melt steadily. Most likely they will melt, once their melting really gets going, both steadily and in fits and starts, causing the occasional large rise in sea level.

In other ways, the climate system is likely to change rapidly from one state to another. We are seeing the melting of Arctic Sea Ice each year doing this now, going from one system where there was melting and re-freezing at a certain rate, and changing to a completely different system. Along with this we may be seeing a fundamental long term shift in the nature of Arctic air masses from one way of being to another.

It is like making ice cream, or butter, shaking catchup out of a bottle, or going steady. You work on it and work on it and work on it and all you have is cream and ice, or cream in the churn, or catchup stuck in the bottle, or a friend. Then, suddenly, you have ice cream, or butter, catchup spewing out all over the place, and a significant other. There are many things in life that work this way, where there is not a steady change over long periods of time, but rather, a lot of one thing followed by a sudden shift to a whole different kind of other thing.

So, here’s the problem. If cycles of normal climate change are in the order of a dozen years, but a particular true shift in the basic pattern of climate takes, say, five years and thereafter everything is different, how do you know it happened? How do you know that the “new normal” is a long term change rather than a temporary shift?

There are two ways to know this. One is to wait and see, but if you were thinking of doing something about it but only taking action after you are sure, this is foolish. The other is to use reason and science and stuff to figure out what is going on and then make your best estimate of the situation.

And this brings us back to Weather Whiplash, the New Normal, and the nature of the climate change we may very well be experiencing now. There is an explanation for Superstorm Hurricane Sandy, for Nemo and some of the other storms we’ve had over the last year or so, and for the strange spring and early summer we are experiencing now, and please don’t forget, the strange winters and summers we’ve been having for the last few years. This explanation applies mainly to the Northern Hemisphere and has to do with the Arctic and the Polar Jet Stream.

The Earth’s climate operates as a mechanism for moving excess heat form equatorial regions towards the poles in air and oceanic currents. In the atmosphere, part of this happens when warm tropical air rises and moves away from the equator, drops, and then flows back towards the equator. Farther from the equator, a separate cycling of air currents is thus set up, where air moves up then south at altitude, then drops along side that first cycle of air. Then, there is a third similar giant rotating donut of air closer to the poles. At those positions where the air is moving up, there tend to form high pressure systems, and where the air flows away from these high pressure ridges or mounds, low pressure systems develop. If you stand back and look at the Earth from a distance you can see bands of wet and bands of dry, and regions where certain kinds of storms (like hurricanes, for example) tend to be confined.

The jet streams form at the boundaries between these large scale systems, at altitude, near the top of the troposphere. The jet streams don’t really shape the larger scale systems; rather, they exist because the larger scale systems exist. But once they are in place, the jet streams can determine what happens in those systems.

One of the major jet streams is the Polar Jet Stream that separates temperate regions form more arctic regions. This boundary between two major air masses, defined by that jet stream, can be thought of as analogous to the partition that separates the freezer compartment in the top of a typical refrigerator from the fridge part down below. With this partition in place, the stuff in the freezer stays very cold, and the stuff in the refrigerator stays less cold. If you kept all the cooling coils in place but removed that partition, the difference between the freezer and refrigerator compartments of your Frigidair would be reduced significantly.

Another thing the Polar Jet Stream does is to generate the overall shape of the boundary between temperate and more northerly air masses. The jet stream can be straight, like a big ring around the earth, or it can be all wavy, with major undulations north and south. In the latter case, these undulations can move around the planet or they can sit in place. When they sit in place, they may cause an entire region to be habitually wet, or dry, or more importantly cool or warm, for a long period of time. (This is called “blocking.”) The shape and movement pattern of the Polar Jet Stream ultimately determines the overall pattern of weather everywhere in temperate and subarctic regions.

Now, remember that the position and shape, and movement pattern, of the Polar Jet Stream is determined by high pressure ridges and the low pressure systems they set up (more accurately, these things interact). High pressure systems are relative; A warmish region of the earth, warm relative to nearby cooler regions, will set up a high pressure system. So, during the summer, land masses tend to create high pressure relative to nearby oceans, but during the winter, the oceans may create stronger high pressure relative to land.

And at this point we can see how climate change caused by CO2 increases create Weather Whiplash and other effects.

Warming conditions have caused the Arctic sea to have much less sea ice on it for much longer periods of the summer. This, in turn, allows more sunlight to heat the arctic, because less sunlight is reflected away by shiny ice, and more sunlight provides heat to the sunlight absorbing open water. This changes the relationship between high and low pressure areas in the Northern Hemisphere. This, in turn, has caused the Polar Jet Stream to freak out. Sometimes it is very wavy, often it is blocked, and sometimes it is simply weakened to the point that it almost goes away and allows the freezer and refrigerator compartments to meld.

Cool weather in the United States is not really cool wether. It is the more even, less compartmentalized, distribution of heat across the region north to south. Everything is on average warmer (because of warming) but there is not a very stark boundary between the northern colder regions and the more southerly warmer regions. Last April when we were busy getting snowed on every few days in Minnesota, the Arctic was warmer (but still cold) than it normally would be. Last fall, the shape of these weather systems caused Superstorm Hurricane Sandy to be stronger, and to fail to do what these storms normally do: head north by northeast and dissipate. Instead, the storm turned left and blotto’ed New York, Connecticut and New Jersey.

Peter Sinclair of Climate Denial Crock of the Week, famous for his videos, in a post on Weather Whiplash, has produced a video that covers some of this very nicely:

So, lets get back to the original question. Why are we having such bad weather? Because the system that is usually in place, with a strong Polar Jet Stream that tends to be linear during the summer, has changed to a different system where the Arctic Oscillation … a high-low pressure system pattern … has shifted to a “negative” configuration because of warming of the Arctic sea. This different system has a number of effects that combine with other effects of global warming to produce strange weather. Those other effects include there being more energy in the atmosphere, and more moisture concentrated in more discrete dense patches, which therefore also means some very dry conditions. Blocking may have caused dry conditions to persist longer over selected areas than otherwise, and at the moment, blocking and added moisture seems to be causing the midsection of the United States to become the world’s largest water park. And, between storm fronts, the overall weather of the region is cool, yet the storm systems are very energetic.

Weather Whiplash. It makes sense because everything that is happening conforms to expectations based on what we know about climate and weather. Will this really be the “new normal?” Is a few years in a row of a strange acting Polar Jet Stream and that other stuff the result of a fundamental change in the way our climate system works, or is it just a typical variation that we can expect to happen now and then. Well, if this was a typical variation of the type we normally see on occasion, there would be less incredulity among climatologists, meteorologists, and forecasters. It makes more sense to explain Weather Whiplash as a new state that the climate has shifted to (mostly, expect some more back and forth, I assume) because of the unchecked release of fossil Carbon into the atmosphere by the burning of fossil fuels by humans.

How three storm chasers died, and what to do about it

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UPDATE (March 2017):

At the time that Samaras, his son, and his colleague, were crushed to death inside their tornado-chasing car, which was apparently rolled by the force of 200-300 mile an hour winds over a distance of a half mile or so, it was said by numerous news sources that this car had been trapped by a traffic jam caused by looky-loos who wanted to see the tornado and/or people sent out on the roads by a local weather reporter to “escape.” So, that apparent fact was part of the underpinning of the original post (below).

Later analysis of the situation indicates that there was indeed a traffic jam enhanced risk for several storm chasers, caused by the ill advised comments from local media (as described below) but that this happened after Samaras and his crew were killed, in a different location, and that this happened to not cause any deaths.

Here is what the tornado did: It grew from a big tornado to a bigger tornado, to what might be the largest tornado ever observed with instruments, in a matter of seconds, and it made a fast jog to the right, not an unusual thing for a tornado to do, but unanticipated by the storm chasers. Samaras’ car was perhaps too slow and too light, and the road was not amenable to fast driving. The tornado caught up with him and his crew and ended them.

Since I wrote this post, I’ve received many emails telling me that the premise is wrong, that traffic from too many storm chases did not contribute to the death of Samaras and others. At the same time, many helpful comments have been added to the post. I decided to let the comments speak for themselves, because, after all, this post was written three or four days after the event, and the comments reflect more recently available information and analysis.

I do regard some of the complaints I’ve gotten, especially some of the really nasty ones I’ve gotten by email, to be excuse making. Amateur chasers don’t want there to be strong evidence that what they do endangers themselves or others, so they want chaser-enhanced traffic jams to be taken out of the picture. They can’t have this, because the traffic is a factor, but yes, Samaras and his crew were not killed this way.

So, regarding the question of traffic: first, I know. I am hereby referring you and all readers to the comments. Also, read the wikipedia on Tim Samaras for more details, and watch this YouTube video (embedded below as well).

Second, the point is still valid. In the case of the El Reno tornado, traffic in combination with road bottlenecks (over a river) did in fact cause a number of storm chasers (and go watch the video to get an idea of how many storm chasers there were!) to get jammed up. They didn’t happen to be overrun by a killer tornado at the time.

Yes, lets get the facts straight, which the comments below and the information added here help do. I appreciate that, it is a good idea. But let us not let the fact that Samaras and his crew were killed in a manner that did not relate to traffic obviate further consideration of the “drive to the fire” problem. Look at that video. Skip Talbot makes this point. Pay attention to what he says.

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If you want to walk down Main Street, in downtown America, you can do that, because it is America. This is a free country and public space is public. But if the Acme Office Building, on Main Street, is on fire, broken glass is blowing out of windows and fire trucks and other emergency vehicles are trying to gain access to the building and nearby fire hydrants, and ambulances are trying to get in to pick up injured, and out to bring them to hospitals, you can’t walk down Main Street. The police can close off that street and nearby streets and as annoying or inconvenient as that may be, they are not taking away your rights. They are acting in the interests of public safety.

We’ll get back to that in a moment.

After a large and violent tornado went through Moore Oklahoma a few days ago, several people in various media outlets including CNN mentioned that given the (seemingly enigmatic) lack of good shelter in homes and public buildings in Oklahoma, that a good option to protect yourself in case a tornado comes your way is to drive away. In some but not all cases, this advice was qualified; If you know several hours in advance that there is a high probability that a tornado will come through your area, then it is a good idea to just go away and be somewhere else. This advice sounds reasonable, but it really isn’t. During the United States tornado season, it seems that we experience repeated tornadoes and other severe storms in a given area over several days. That area might include three or four of the several states that make up “Tornado Alley.” However, within that area, the exact location of a killer tornado isn’t predictable at the scale of several hours. So, if you live in Oklahoma City and figure there may be tornadoes coming later in the day, there is nothing to guarantee that driving north to Aunt Millie’s house in Enid, OK will not put you in the path of one of the tornadoes that happen to form that day. A tornado could hit Oklahoma City, or it could hit Enid.

So, the driving away several hours in advance isn’t really smart, because you don’t know that far in advance where “away” might be. Perhaps, the day before tornado-warned storms are expected, you could fly to France, but that is not really an option for most people.

The unqualified version of that advice is “If there is a tornado coming your way now, get in your car and drive away fast.” That is also bad advice. The reason that is bad advice is very simple. If you are directly hit by a strong tornado, ending up in the vortex, and you are in the bathtub of your home on the lower floor, you’ve got a pretty good chance of survival. Despite the horrible fact that some two dozen people died in the Moore tornado last week, there were tens of thousands of people directly in that tornado’s path, hiding out in low interior rooms within their homes or other buildings, who survived. Alliteratively, if you are in a car and hit by the vortex of an F3 or stronger tornado, your chances of survival are much lower. Roughly speaking, this is the equivalent of driving down the highway at several tens of miles an hour and suddenly flipping, three or four times. Or, perhaps, you are driving down the highway at 40 mph along with a dozen other cars also driving down the highway and suddenly you are all flipped. Then, when the car is done flipping, it gets flipped again. And again. And for several minutes you car is shoved around on the surface like you were a puck in a game of air hockey, with the car slamming into other cars and other cars slamming into you, and each car being turned over now and then. To make this point, here are photographs from major media of a handful of examples of cars that got hit with the vortex, most but not all from this latest tornado:

From www.chicagotribune.com
From www.chicagotribune.com
From www.wctrib.com
From www.wctrib.com
The Weather Channel's car; the people in it are OK.
The Weather Channel’s car; the people in it are OK.
Tim Samaras's Twistex vehicle; all three occupants were killed.
Tim Samaras’s Twistex vehicle; all three occupants were killed.

I admit that a flattened house may look pretty bad, may even look worse than a mushed up car, but generally speaking the interior lower floor room in a house that is badly messed up by a tornado is a survivable shelter, while there is no such shelter in your car.

So, let’s go back to the advice again. Say you are sitting in your home and you know there is a tornado coming and you are watching TV and the following breathless reporting is happening. Pay special attention to what the weather forecaster says starting at 4:35:

“… if you can drive south, anywhere around Whitewater Bay, State Fair Park, the Ballpark, downtown Oklahoma City, southwest Integres, US Grant District, Rose State college, Midwest City regional medical center, Midwest City, and Parts of Del city, you need to drive south now….” (approximate transcript)

The Oklahoma City metro district has about 1.3 million people. Of those areas mentioned in this quote, “Downtown OK city” has about 7,600 people living in it. Del City has 21,000 people in it. What this weather forecaster just did was to advice a couple/few tens of thousands of people in the path of a tornado to get in their cars and drive in the same direction.

That wasn’t the only broadcaster telling people to evacuate instead of hunker down.

The thing is, this tornado was heading roughly from west to east into a highly populated area. News casters were telling people in the direct line of the tornado do “drive south.” But then the tornado made a turn and headed straight for the “south” that people were being told to drive to. Here is a compilation of broadcasts and events documenting this:

I have no idea how many of the people in the viewing area of this station saw or heard this report and responded by driving into the path of the tornado. Of those who did I don’t know how many of them were primed to use “drive away” as a strategy by earlier chatter in major media outlets, and elsewhere such as twitter and other social media. I’m not sure how many people actually got in their cars and “drove south.” We do know, however, that the highways in the area became jammed with cars, and the vicinity around the intersection of I35 and I40 was described as a “parking lot.” One thing we do know is that many people who “drove south” to get away from the tornado in fact drove directly into its path, created a traffic jam, and most of the deaths associated with this tornado were among those people in those cars.

Three experienced tornado “chasers” … actual meteorological scientists … were killed when their truck (one of the vehicles depicted above, probably) was destroyed by the tornado. Other professional meteorologists, from The Weather Channel, were injured. As of this writing, the death toll stands at 13 with another 6 (though I’ve also heard 7) people still missing.

In his writeup of this event, meteorologist Paul Douglas made this point:

Every time I went down to Oklahoma [with storm chasers] I was struck by the number of people tagging along. Often scores, even hundreds of chasers would converge on the same cell by late afternoon. It’s a free country – you’re obviously free to drive when and where you want, and I certainly don’t want that to change, but something has to be done to avoid another tragedy like the one that killed 9 motorists Friday evening, including 3 professional tornado researchers Tim Samaras, his son, and intercept partner.

Paul is right. This is a free country, or at least we want it to be a free country, and being able to freely travel on public thoroughfares is part of that. If you want to walk down Main Street, in downtown America, you can do that, because it is America. But if the Acme Office Building, on Main Street, is on fire, broken glass is blowing out of windows and fire trucks and other emergency vehicles are trying to gain access to the building and nearby fire hydrants… you can’t walk down Main Street… you are not really free to walk or drive up and down Main Street to take pictures of the event. Public safety officials have the right and responsibility to restrict access to Main Street and areas nearby in order to save lives and property.

Until proven otherwise, I will assume that the special category of people known as “Professional Storm Chasers” like Tim Samaras and his crew as well as Reed Timmer, and others, are risking their own lives to make observations and collect data that help us understand tornadoes better, to make better predictions about storm behavior, and thus to make better predictions about unfolding storms. Also, their data helps us to better understand the dynamics of what happens in tornadoes which can help make safer structures. Reed Timmer and Sean Casey and their crews modified vehicles that successfully survived being in powerful tornados (for Mythbusters fans, you may have seen these two teams’ vehicles go head to head with a jet engine to see how they would survive tornado strength winds on the episode Storm Chasing Myths).

But the hundreds, or even thousands of non-professional “storm chasers” are probably not contributing to the science of tornadoes and tornado safety. Rather, they are jamming roads in the very places where a traffic jam can be deadly if a tornado happens to pass over the gaggle of cars stuck in place. If you watch the Discovery Channel’s Storm Chasers show, you will notice that as the seasons progress the professional storm chasers encounter more and more traffic as they try to move to the predicted path of oncoming tornadoes to drop data collecting probes or carry out direct intercepts (where the specially modified vehicles equipped with data collection devices are directly hit with a tornado).

There is a great irony to the deaths of the three storm chasers from Twistex. Tim Samaras’s strategy was never to get into the direct path of a tornado. Rather, his team would predict the path and drop machines on the ground designed to directly measure variables such as temperature, humidity, wind and so on, but with the team and their vehicles getting out of the way before the tornado comes. It is probably true that Samaras abandoned attempts at dropping probes more often then strictly necessary, cautiously avoiding rain-wrapped tornadoes where they would not have been able to see where the tornado was, in order to be extra safe. It is also true that the relatively cautious “drop and run” strategy meant that they missed getting their equipment in the direct path of a tornado more often than not. I can only assume that Tim Samaras had no intention of being in the path of the the tornado that killed him, his son, and his colleague, but was unable to get out of the way because of the traffic jam.

And that traffic jam was probably caused by the exodus of people following very bad advice, and possibly as well as non-professional storm chasers moving in on the likely path of the storm.

I suggest that law makers in tornado alley states consider legislation making it a violation to intentionally drive into or near the path of known or likely tornados. This is not an especially enforceable regulation but having such a thing on the books would probably encourage amateur storm chasers to think twice about putting others in danger by contributing to blocked roads. Such a law or regulation could be more general, specifying that police have the authority to direct people generally in relation to emergency disaster zones that have not happened yet. In other words, it is now probably legal and appropriate for police or fire departments to close off roads or direct traffic or tell people not to drive in a particular area where there is currently a major fire, explosion, storm devastation, and so on. A new law or regulation merely needs to specify that tornado-related disasters that have not happened yet (because the tornado hasn’t formed or has not yet arrived) can be considered in this public safety action. In fact, one could argue that a new law is not needed and this power is already available to police and emergency response agencies. That might be preferable because making a new law to address particularistic new circumstances that are already covered by existing law, regulation, and best practice is probably a bad thing. But a law or explicit regulation, or even a well publicized set of best practices in the interest of public safety, might make the point that needs to be made, thus discouraging people from making decisions that endanger others.

One might argue that if someone wants to drive their car into the path of a tornado they should be allowed to do so because it is a free country. But once your car is inside an F3 or F4 tornado, that is no longer your problem alone. Because of your action, your car has become a very large and dangerous projectile. You shouldn’t be allowed to do that.

Such a regulation or law would also require consideration of a certification of “professional” status for actual professional storm chasers. This, in turn, would require storm chasers to make their case that they are professionals that are doing something worthwhile, and that they take appropriate action related to their own safety and the safety of others. In fact, we probably need more professional storm chasers, and among storm chasers my feeling is that we need a better more comprehensive research design. For example, most storm chasers are individuals or small teams, and they benefit with direct contacts with actual tornadoes, and often fund their work this way as they sell their video to news outlets. But what about big storms that don’t drop tornadoes? It seems to me that we should be collecting equivalent data from storms that do and storms that do not drop tornadoes, because, after all, one of the things we want to know more about is the difference between those two types of storms.

What do you think?

Understanding Storms and Global Warming: A Quaint Parable

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A quaint New England rocky creek

Imagine standing next to Parable Creek, an imaginary rocky brook in New England. The water is rushing past you from left to right, around the rocks that emerge tall above the surface of the stream, mounding over the top of those that are lower down. The deepest parts of the steam are relatively flat but show ripples that belie the presence of other rocks and sunken branches that are well below the water line.

While you are observing a young boy of about 11 years old comes along, carrying his fishing pole. “Hey mister, how’s it going?” he says, as he steps into the stream. “I’m going fishing over there,” he says pointing in the direction of a mill pond a mile or so away. As he crosses the stream you notice that whenever he puts is foot down, some of the water mounds up on the upstream side as it rushes by him. He continues across the stream and climbs the opposite bank, running off to his destination. You wish him good luck with his fishing and return to your observations.

You can see large eddies here and there that seem to persist though they may change shape or grow or shrink a little. Smaller eddies, mini vortexes, form in certain parts of the stream, and rush down slope only to disappear as the water crashed into an obstruction. Every here and there there is a splash caused by the rushing water hitting a rock or branch just the right way.

Now, imagine that you are a compulsive data collecting scientist standing next to the rocky brook with nothing else to do for a while. So you start measuring things. Every where you see a mound of water built up in the current alongside a rock, that is a bit of kinetic energy (water moving) converted momentarily in to potential energy (water rising against gravity). So you estimate the number of mounds and their collective mass. This is a measurement of one form of energy in the stream.

You make a prediction. If the amount of water coming down this stream increases for a while, the total energy of the stream will increase, and this will be visible as an increase in total potential energy in the mounds you’ve been measuring.

Coincidentally it has been raining heavily upstream and just as you have formulated your hypothesis you see the water rising. Aha! A chance to test your prediction. At first, your hypothesis seems supported. As the water rises, the relative height of the mounds increases, and some new mounds form. You take some quick measurements, by eye, and note that the total potential energy stored in water mounds has increased, presumably as an effect of more overall energy in the stream. You gain confidence in your theory and congratulate yourself on your brilliance.

But then, as the water level continues to rise something different happens. More and more of the stream is now above the obstructing rocks. Therefore, there is less conversion of kinetic to potential energy. Most of the mounds disappear and the overall surface of the stream is much smoother. You take a new set of measurements and estimate that the total potential energy stored in water formed into mounds is an order of magnitude LOWER than your original measurement. Apparently, you think, something is wrong with this stream.

Just then a troop of Brownies comes along. The little girls want to cross the stream to take a short cut to their picnic grounds. They ask, “Hey, Mister, do you think it is safe to cross this stream?”

You had a nice theory linking total energy and a specific observation, which seemed to be confirmed by some of your research. The total energy of stream flow is linked to the total mound-i-ness of the stream’s surface. Now, the stream’s surface is smoother than it was before. Therefore, the total energy of the stream is at the low end of its known variation. A while back you saw a small boy cross the stream with no problem. Clearly, it is safe to cross now.

So, you say, “Actually, I’m sure it is quite safe. Go ahead and cross, and have a nice day!”

The brownies jump happily into the stream and start wade through the water. Half way across the stream, one by one but over just a few seconds of time of time, they are carried away by the water and drown.

“Hmmmm,” you think. “Maybe I had that wrong.”

Rivers Of Air

Air flowing over the surface of the land is a bit like water running down a stream or river. The air interacts with the ground (especially things like mountains). There are different layers, mounds, streams, and eddies of air that interact with each other. The overall form of movement is shaped by the spin of the earth, the tendency of warm air to form in certain areas (i.e., near the equator, or over water during winter and over land during summer, etc.) which causes the air to pile up and spill into nearby eddies. There are all sorts of ways in which batches of air interact, and when you thrown in differential amounts of moisture in different air masses, and things like night vs. day, and so on, you get the surface of Parable Creek. Metaphorically. In real life, we call the The Weather.

When the total energy in the system of air movement changes the way those crazy zany air masses move and what sorts of weather form can also change. For example, there is in total more energy on the hemisphere (north vs south) that is sticking its face towards the sun. It seems that one result of this is that the hemisphere with more energy (the summer end of the earth, as it were) has hurricanes, severe thunder storms, tornadoes, and so on while the hemisphere with less energy has less of that stuff.

However, a tornado is like a small eddy in the stream, and a hurricane like a large eddy, and a line of thunderstorms like the outer edge of one the mounds and the rainstorms are like the splashes at the edge of the log and so on and so forth. As Parable Creek’s level rises, exactly which phenomena are predominant changes, even as the total ability of the stream to wash away Brownies increases to the level where it can also wash away Girl Scouts and eventually Brawny Construction Workers and Bikers. Having said that, while a rocky stream converts to a large and deep river by adding a LOT of water, which may have a smooth surface despite the total energy of the river being orders of magnitude greater than Parable Creek’s energy, the system of air movement is not likely to become smoother owing to various limitations in the system.

Too Much Variability

You can’t measure the energy in the stream by only looking at one of the many phenomena that are the manifestations of that energy. In order to understand the relationship between global warming and storminess, it is minimally necessary to measure all of the storminess and find some way to combine it.

I remember when I first moved to Minnesota. That summer we had numerous straight line wind events of the sort never seen before. Maplewood, a community near where I lived famous for it’s tree lined streets lost almost all of its trees in one storm. That same storm also took out most of the stock of most of the new car companies in that town, famous for its numerous car lots. The cars were pitted with hail stones. Every single home for about three miles along a street right near where I lived had it’s vinyl or aluminum siding drilled with hundreds of holes and dents from large hail stones being driven by a 60–100 mile per hour wind. It was one of the worst weather years in Minnesota, with insurance companies practically going bankrupt.

There were only a few tornadoes in the area that year.

The next year there were hardly any straight line wind storms of the magnitude just described. But that is the year of the Saint Peter tornado. It was one of the largest tornado events ever; It was a twister that lifted and dropped a couple of times, so ‘nato-pedants divide it into multiple events, but that’s absurd. It was an F3 and F4 event, and it tracked for 67 miles and was up to one and a half mile wide.

There were a lot of tornadoes that year.

The atmosphere over central and southern Minnesota had a lot of energy those two years, for whatever reason. If we want to understand the total energy, and its effects on life and property, we would be doing a disservice to our pursuit of understanding if we failed to consider both straight line winds and tornadoes together (though obviously also separately).

The Big Picture

Weather comes in bands. The biggest and most obvious band is the Intertropical Convergence Zone, a band of thunderstorms that rings the entire planet and is pretty much always active. Another band is the arid band that rings the earth; actually there are two of them, one in the Northern Hemisphere and one in the Southern Hemisphere. Almost every major desert on the earth is in one of those bands. In fact, any desert that is not in one of those bands has to explain itself, and the excuse is usually a mountain rain shadow. Conversely, any wettish areas in those bands also have some ‘splainin to do. The southeastern US is in the Northern Hemisphere’s arid band, but the Gulf of Mexico keeps that region pretty wet much of the year.

Severe weather is also patterned in these bands, to some extent. Hurricanes form in the bands just north or south of the Intertropical Convergence Zone. Tornadoes tend to be confined to subtropical and southern temperate bands away from the equator. In a sense, one could say that most tornadoes that are not spinoffs from hurricanes occur in a certain band either north or south of the equator, and if we are going to count tornado activity, measure its total intensity, etc., we should be looking more globally at those zones, not just parts of those zones.

This of course applies to national borders as well. Tornadoes occur in the US but also in Canada, but the most easily available tornado data for North America is always presented as US tornadoes. Also, years are tricky. Events that span Jan 1st are hard to track if we count things by calendar years.

Some have been harping about the “tornado drought of 2012” as evidence that there is not an increase in tornadoes owing to global warming. Well, there are very few US tornadoes in January, but the January with the most tornadoes ever (in our records) was January 2012. Also, Canada had a lot of tornadoes in 2012. Has anyone looked to see what the combined US and Canadian count would be? And, how do you count a Canadian Tornado? The very fact that a tornado forms 1000 miles north from where most occur has something to do with the nature and distribution of atmospheric energy across the plant’s surface. I’m not making a specific claim about the distribution of tornadoes across time and space. I am saying, rather, that counting tornadoes within an arbitrary boundary in space (or time) can be misleading.

Then, there is the problem we have with all of these storm types, especially tornadoes and hurricanes, of how to actually measure them. Even using standard severity scales, tornadoes can be very different from each other in ways that are not counted in the usual statistics. An F3 tornado that is extra wide and stays on the ground for 100 miles involved significantly more energy than an F4 that formed momentarily and disappeared. Indeed, the different kinds of tornadoes (funnel vs. wedge, for example) really may be very different (but closely related) weather phenomena that should be examined separately at the very same time we combine vastly different storm types to measure and understand at a larger, global scale.

Tornadoes are not a good canary, in the canary in a coal mine sense. But they are obviously important. When we see people stating clearly and plainly that we need not be concerned about the frequency of tornadoes increasing with global warming, we should ask why they are saying that. We should be concerned with increasing storminess … there is almost no way that is not going to happen, and likely, it already has. If tornadoes are part of that increase storminess, we may want to get smart about it fast. For instance, we might want to take seriously the problem of schools and workplaces, where people tend to concentrate, having actual storm shelters instead of just hallways that some administrators says is a storm shelter, for protection when a big tornado comes along. Don’t you think?

See also this post which more directly addresses the question of tornadoes and global warming.

Photo Credit: Hamed Saber via Compfight cc

Welcome Spring Storm Season

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This picture, from a current (as of this writing) accuweather forecast page, is an excellent illustration of what happens here in the upper Midwest the spring.

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The overall pattern of movement of air masses at the continental scale is west to east, with extra moist and extra warm air secondarily moving north from the Gulf of Mexico, and cool and usually dry air coming form the Northwest (not shown here but note the “blizzard” part) and with dry Pacific/Rocky Mountain air coming from the west. The main energy flow to keep an eye on is that coming from the Gulf.

There is a rule of thumb you can apply here….

Continue reading Welcome Spring Storm Season →