The Nomadic Nature of “Tornado Alley”

The deadly tornado outbreak across Alabama, Mississippi, Florida, Georgia, and South Carolina this past weekend was an abrupt and powerful announcement of the start of the 2019 tornado season. Although tornadoes can and do occur outside of the typical spring-through-summer tornado season (there have in fact been 14 tornado days since the beginning of this year), the majority of tornadoes in the United States do occur between April and July.

Tornado Climatology

Average Number of Tornadoes in the U.S. by Month. Source: NOAA National Centers for Environmental Information

An outbreak of violent tornadoes (EF4 or EF5) during the first week of March may seem a bit early, but according to the Storm Prediction Center it’s happened at least 7 times since 1980. Averaged over the course of a year, tornadoes are most likely exactly where you’d expect them: in the Great Plains, with a bulls-eye over central Oklahoma and northern Texas.

However, the majority of early-season tornadoes (January – March) spin up in the Southeast, where spring arrives early. In these areas, warm, moist air from the Gulf of Mexico creeps northward, bringing a taste of spring even as the rest of the country continues to hunker down in winter parkas. But even in the Southeast, that warmth doesn’t last this time of year. Inevitably, a storm system sags southward, ushering through a cold front and a return to winter. When the arctic air behind that cold front meets the warm, moist air ahead of it, severe and sometimes tornadic thunderstorms ignite.

Tornado Frequency in the U.S.

Per square mile, tornadoes are most common in the southern Great Plains, although other hotspots include Florida and the Southeast as well as the upper Midwest.

It is this clashing of air masses that fuels the majority of tornadic storms, and for that reason, “tornado alley” roams with the seasons.

By the time April and May roll around, people in the Southeast already have their air conditioners running and have shoved long-sleeved shirts and closed-toe shoes to the back of the closet. The meteorological action shifts north and west, towards Oklahoma, northern Texas, and Kansas – the heart of what has traditionally been labeled Tornado Alley and the birthing ground of many of the United States’ strongest and most devastating tornadoes.

In fact, the city most like to be hit by a tornado is Oklahoma City, which lies dead center in the state and has endured the impact of around 150 tornadoes since record-keeping began in 1890. The Oklahoma City metropolitan area was hit by violent EF4 and EF5 tornadoes in 1999, 2003, and 2013, with the paths of these tornadoes overlapping in several locations. The EF5 tornado that ravaged the suburb of Moore, OK on May 3, 1999 had wind speeds clocked at 318 mph – the strongest ever recorded.

ornado Probability throughout the Seasons

The hotspots of tornado activity shift with the seasons – starting out in the Southeast during early spring, shifting to the southern Great Plains during late spring, and then up to the northern Plains and upper Midwest during early to mid summer. By winter, the tornado threat has shifted back to the Southeast.

The unique geography of the southern Plains gives rise to its unique and tornado-prone climatology. Wedged between the cool, dry air that spills down the leeward side of the Rocky Mountains and the warm, humid air that’s pumped northward from the Gulf of Mexico, the Great Plains fields some of the most intense and violent air mass clashes in the world.

But by June and July, even the southern Plains have been given over to summer. Storm systems shift northward and focus the tornado threat in the northern Plains and Upper Midwest. By August, as the whole country settles in to the dog days of summer, the tornado threat retreats. Hot and humid air is in place across much of the country, and storm systems are weaker.

Paths of Three Violent Tornadoes in OKC

The paths of the three violent (EF4 and EF5) that impacted the southern Oklahoma City suburbs between 1999 and 2013. The paths overlapped in several places.

An exception is in central Florida, where afternoon thunderstorms are a daily occurrence during the height of summer and occasionally spawn tornadoes, especially when they interact with outflow or sea breeze boundaries. The tornadoes that form under these conditions are generally weak and short-lived, however.

As summer gives way to fall, the tornado risk shifts back to the southeast, where it remains, low but present, throughout the winter.

And in the spring, like a nomad, it starts roaming again.

Carbon Dioxide at 400 ppm: What Does It Mean?


What does a birthday mean? A major birthday – the type that warrants a card declaring your exact new age, possibly by spelling it out in macabre black balloons – what does it mean? Why do we care?

It’s not like you wake up on the morning of your birthday feeling dramatically older than when you went to bed. A decade’s worth of wrinkles don’t suddenly appear on your face. Yet you are older, and on your birthday, you are acutely aware of that fact.

A major birthday reminds you that life is short and you don’t have forever to act. It reminds you of all you’ve done and all you have left to do. Then it starts playing the Final Jeopardy countdown music in your ear. Time is ticking. Better get busy.

Carbon dioxide concentrations over the past 800,000 years. CO2 levels have not been as high as they are now for at least 3 million years. Source: NOAA NCDC

Carbon dioxide concentrations over the last 800,000 years. CO2 levels have not been as high as they are now for at least 3 millions years. Source: NOAA NCDC

Reaching a global average carbon dioxide (CO2) concentration of 400 ppm is that type of milestone, and we passed it in March. To put 400 ppm in perspective, consider that maximum pre-industrial CO2 levels were 280 ppm and that 350 ppm is widely considered the upper limit to avoid truly dramatic climate change. Consider that CO2 levels haven’t been as high as 400 ppm in several million years, when the world was much hotter and the oceans much higher than they are today.

Yet, besides the climate scientists who marked the passing of 400 ppm with a mixture of dismay, anger, and sad resignation, few others seem to have noticed (well, besides the United States military who consider climate change a national security risk and key business and insurance leaders who are already taking action to adapt). Nationally and internationally, we’re certainly not getting busy.

It’s as if we believe that if we don’t acknowledge what’s happening, it won’t happen. As if staying in bed with your eyes closed on your birthday somehow stays the hands of time.

Observed changes in average temperature across the United States for the period 1999-2012 as compared to 1901-1960 averages.

Observed changes in average temperature across the United States for the period 1999-2012 as compared to 1901-1960 averages.

But time doesn’t stand still just because we avoid clocks and mirrors – just as CO2 concentrations continue to increase whether we acknowledge it broadly and publicly or not. Of course, the critical difference between the inexorable forward march of time and the increasing concentration of greenhouse gases in Earth’s atmosphere is that we can actually do something about greenhouse gas concentrations.

We very likely can’t undo what we’ve already done (the technology just doesn’t exist to capture and indefinitely store vast quantities of atmospheric CO2). But we can slow down and eventually stop emitting new greenhouse gases, if only we muster the foresight to recognize and the willpower to address a large, costly, complex, global problem that will only get larger, more costly, and more complex with each year of procrastinated action.

Failing to even acknowledge the passage of the 400 ppm milestone doesn’t bode well, though.

So what does 400 ppm mean? What is this new world we’ve created for ourselves and our progeny?

Well, for one thing, 400 ppm means we’ve committed to major climate change – to what we’re already experiencing and more. The average residence time of carbon dioxide in Earth’s atmosphere is hundreds to thousands of years, so even if we stopped emitting CO2 tomorrow, our climate would continue to warm toward a 400 ppm equilibrium.

Surface temperature change under two different emissions scenarios -- rapid emissions reduction (blue) and business-as-usual (red). Source: IPCC 2014.

Surface temperature change under two different emissions scenarios — rapid emissions reduction (blue) and business-as-usual (red). Source: IPCC 2014.

Of course, we can’t put the brakes on instantaneously. If you’re traveling 100 mph down the highway and slam on the breaks, you keep traveling forward as you slow to a stop. A shift to renewable energy and carbon-neutral fuels, like stopping a speeding car, takes time, and the concentration of CO2 in the atmosphere will continue to increase during that shift.

Right now, though, we’re mashing on the accelerator rather than the brakes. With the exception of 1990-2000, each decade has seen an increase in the rate of CO2 emissions. Not only are we continuing to emit carbon dioxide – we’re emitting it faster and faster each year. If we continue along our current trajectory, we’re on pace for greater than 3° C warming, and that’s just the increase in average temperature. Extremes in both temperature and precipitation tend to increase more dramatically than their respective averages.

Such climatic changes would decrease crop yields and alter agricultural zones, decrease water availability while simultaneously increasing demand, inundate coastal areas with rising seas, extend the season and range of numerous pests and insect-borne diseases, increase heat stress and heat-related illness, and increase the frequency and intensity of flooding rainfall, among many other impacts.

Changes in average temperature for two different emissions scenarios - (B1) requires rapid and substantial emissions reduction, while (A2) is a continuation of our current emissions trajectory. Source: National Climate Assessment.

Changes in average temperature for two different emissions scenarios – (B1) requires rapid and substantial emissions reduction, while (A2) is a continuation of our current emissions trajectory. Source: National Climate Assessment.

400 ppm means that aspects of our environment that have been our touchstones for thousands of years – food and water availability, weather and climate – will shift in unprecedented ways. The ideal locations for cities, farmland, roads, factories, homes, and military assets will modify. Processes and procedures that have been reliable will become uncertain.

In short: the assumptions upon which we have built our societies may cease to be valid.

Although some progress toward mitigation (emissions reduction) and adaptation has been made on the local level both domestically and internationally, the sort of global-scale agreement and action required to alter our current emissions trajectory remains elusive. Emissions will therefore continue to rise, and the climate will continue to shift. Governments, industries, and individuals will be increasingly impacted by a variable and changing climate, and given the lack of coordinated effort to date, the unfortunate reality is that we must prepare to protect our own interests, assets, and welfare.

Businesses and insurers looking to take the long view of their investments, infrastructure, supply chains, and insured properties need to be aware of climatic changes that impact vulnerability. Blue Skies Meteorological Services is here to help these clients understand and mitigate their climate-related risk and exposure. Contact us at for more information.

Well, Hello There, Winter

Even Florida got in on this week’s pre-holiday winter chill, with Blue Skies’ home base of Gainesville, FL, breaking records for lowest maximum temperature (53 degrees on Nov 18) and lowest minimum temperature (24 degrees on Nov 20). (Yes, yes, the world’s tiniest violin is playing the world’s saddest song for the poor, shivering Floridians while upstate New Yorkers roll their eyes and stoically shovel out from 6+ feet of snow.)

car with snow cap

Car in Lancaster, New York, carrying a heavy load of snow. Credit: Gary Weipert/AP Photo

This fierce onset of winter caught many people across the country by surprise. After all, it’s not even Thanksgiving. Although temperatures will be moderating over the weekend for much of the US – bringing the risk of flooding to many affected by this week’s snowstorm in the northeast and a welcome and benign warm-up to many others – the annual rollercoaster of winter weather is just beginning.

If you’ve ever wondered why winter weather fluctuates so dramatically, you’re not alone. And you can place much of the blame on the location of the polar jet stream. Yeah, we know – it’s easier to blame the meteorologist messenger. But hear the messenger out on this one.

Jet Streams and Seasonal Weather

Jet streams are like fast-moving rivers of air in the upper troposphere, at approximately the same altitudes that commercial aircraft cruise. And just as rivers of water flow faster when the elevation change is dramatic and steep, jet streams become more vigorous during the winter, when the temperature difference (“gradient”) between the poles and the equator is more dramatic (it’s beach weather year round in Key West, but come January in Maine, you’re going to want to be wearing more than just a swimsuit).

Location of the polar jet stream in summer and in winter. Credit: COMET Program, UCAR

Location of the polar jet stream in summer and in winter. Credit: COMET Program, UCAR

As winter progresses, the pool of cold air at the poles expands and sinks southward. Since jet streams are found where the temperature gradient is largest – at the boundary between cold and warm air – the polar jet slides southward along with the expanding pool of cold air. Although in summer, the polar jet is typically pinned near the US-Canada border, in winter it can plunge as far south as Florida.

The polar jet isn’t straight, either, but rather meanders from north to south, bringing that characteristic wintertime rollercoaster of relatively warm and sunny weather (under ridges) followed by cold, dreary, and occasionally downright miserable weather (in troughs).

Where the jet stream ends up draping itself and how strong it is determines much about the winter’s weather. Certain large-scale factors (like the presence of an El Niño or La Niña), can exert a powerful influence on the average position of the jet stream and therefore on seasonal temperatures and precipitation.

What Will This Winter’s Weather Bring?

DJF Temperature Forecast

Temperature outlook for December, January, and February from the Climate Prediction Center

Despite indications this summer of a developing strong El Niño, it hasn’t materialized. Forecasters at the Climate Prediction Center are now calling for about a 60% chance of a weak El Niño developing this winter. This lack of a strong climate driver, like El Niño, makes seasonal forecasts somewhat less certain.

Although seasonal forecasts will never be able to predict daily high temperatures or the probability of afternoon precipitation months in advance, they can offer insight into general patterns and trends, like whether this winter is likely to be warmer or cooler than average. The strength of those patterns and trends, and therefore the skill of the seasonal forecast, is highest when strong, large-scale climate drivers dominate.

So, what about this winter’s weather? NOAA forecasters at the Climate Prediction Center are anticipating cooler than average temperatures across much of the Southeast and Southern Plains, with above average temperatures favored in the western US and throughout Alaska. Wetter than normal conditions are more likely throughout the southern US and along much of the East Coast, while drier than normal conditions are favored in the Northwest and Upper Midwest.

DJF Precip

Precipitation forecast for December, January, and February from the Climate Prediction Center.

Given the fairly weak El Niño signal this year, forecast confidence isn’t particularly high, but for those folks in the northeast still reeling from this week’s snowstorm, take heart. That winter pummeling isn’t likely to be the season’s norm. But for those of us in Florida, it might be worth picking up another couple of ugly holiday sweaters from the sale racks… you know, for layering.

Water Scarcity and Electricity Generation – Problems and New Solutions

world water1

Water Scarcity

Fresh water is among the earth’s most precious resources – we drink it, cook with it, bathe in it, farm with it, and use it in the generation of much of the world’s electricity. It is fundamental not only to life, but to our way of life.

Yet water availability is not assured for billions of people across the planet, and research has indicated that in the near future, an even larger percentage of people will likely face water scarcity.

The reasons behind the projected increase in water scarcity can be boiled down to supply and demand.


Source: World Water Development Report 4. World Water Assessment Programme (WWAP), March 2012

Source: World Water Development Report 4. World Water Assessment Programme (WWAP), March 2012

The supply of fresh water comes from precipitation and is stored in lakes, rivers, aquifers, and snowpack. Weather obviously affects the water supply from season to season and from year to year, but over the long term, climate is the main driver.

When the climate is in a relatively steady state (as it was for about the past 12,000 years as humanity developed agriculture, civilization, and technology), so too is water availability. Sure, droughts and very wet periods occur, but over decades and centuries, it tends to even out.

However, when the climate is rapidly changing (as it is now), water availability becomes less certain. Precipitation patterns shift and so too do the locations and levels of lakes and rivers, aquifers and snowpacks. The sources we have depended on for water become undependable.

That’s what we’re facing now. The supply of fresh water is shifting – increasing in some places and decreasing in others. Unfortunately for us, many of the regions that are expected to see a decrease in total water availability are also heavily populated.

Projected Changes in Water Withdrawals in the US with Climatic Changes. Source: National Climate Assessment 2014

Projected Changes in Water Withdrawals in the US with Climatic Changes. Source: National Climate Assessment 2014


And here is where supply predictably meets demand: people use water. Primarily, we use it to grow food and to produce electricity. In the US, these two uses account for over 75% of total water withdrawals.

As the global population grows and becomes more industrialized, we have more mouths to feed and more high-tech lifestyles to power. If we continue with business as usual, we could face a direct conflict between agriculture, electricity generation, and other water uses by 2040. We could literally use up all of the available water in the system.

Judicious and mindful use of water (i.e. not being blatantly wasteful) and adoption of more water-efficient farming practices can go a long way towards conserving water resources (demand side), while the energy sector offers opportunities for a “twofer” — both reducing water use (demand) as well as mitigating climatic changes that threaten to disrupt water availability (supply).

All thermoelectric power systems (like the combustion of coal or natural gas to produce steam that drives turbine generators) require inputs of water, both to create the steam and often to cool it. Meanwhile, if the power plant relies on a hydrocarbon fuel, it’s also emitting carbon dioxide and other greenhouse gases.


Solar and wind power are familiar and growing alternatives to traditional thermoelectric electricity generation methods, and they offer the twin benefits of significantly reduced water use and dramatically reduced greenhouse gas emissions. For people living in developed regions that can provide the supporting infrastructure and dependable maintenance that solar and wind systems typically require, these alternative energy solutions are very promising.

Air HES - water and electricity generation from clouds. Image: Andrew Kazantsev

Air HES – water and electricity generation from clouds. Image: Andrew Kazantsev

But for people living in less developed or simply less accessible regions, portable gasoline- or propane-powered generators are often their only option — although perhaps not for much longer. Andrew Kazantsev and his team of Russian scientists have reportedly developed a device that collects atmospheric moisture and channels it down to the ground where it can be used for both drinking water and electricity generation.

The device, called Air HES looks like a small dirigible (aerostat) with a fine mesh hanging below it. The aerostat rises to the mid-levels of the atmosphere, where water vapor and water droplets in clouds condense onto the mesh and are funneled to the ground. The water pressure from the descending stream of droplets can then be used to power a generator and create electricity.

Kazantsev reported that the prototype Air HES was able to create approximately 5 liters of fresh water per hour from low level clouds. If the technology scales successfully, it could provide not only portable clean electricity generation but also potable water to inaccessible and/or undeveloped regions where both are sorely needed.

Technology and the need for electrical power have inarguably propelled us into this water scarcity and climate change challenge, but with ingenuity and willpower, technology may well help us out of it as well.

Climate Change and Security

On February 16th of this year, Secretary of State John Kerry spoke in Jakarta, Indonesia, and issued a dire warning about the security risks posed by anthropogenic climate change (aka “global warming”). In his remarks, Sec. Kerry referred to climate change as a threat to national and international security on par with terrorism and weapons of mass destruction. For those remarks, he received swift and abundant political criticism.

Six weeks later, the IPCC released its updated report, “Climate Change 2014: Impacts, Adaptation, and Vulnerability,” which states, in no uncertain terms, that climate change is already occurring and that the world is not prepared to effectively deal with the impacts .


Despite the scientific consensus on the causes and the physical, economic, and societal consequences of climate change — further reinforced by the latest IPCC report — climate change remains a strongly politicized issue in the US, with large portions of the American public and their elected officials flat out denying that human activity is causing the Earth’s climate to shift in dangerous ways. The political response was not surprising.

What might be surprising to many people, however, is where the criticism over Mr. Kerry’s remarks and the latest IPCC report did not come from. It did not come from the US military – an organization intimately familiar with the sort of national and international security issues to which Sec. Kerry compared the threat from anthropogenic climate change (ACC). The reason for this lack of criticism is simple: John Kerry and the latest IPCC report did not say anything that the US military didn’t already know. For almost as long as politicians have been debating the reality of climate change, military leaders have been studying and preparing to deal with its consequences. The same is true for a growing but still grossly inadequate number of national and international business and industry leaders.


That is perhaps a bit surprising. The leaders in climate change adaptation and response are not the elected officials shouting so loudly in Washington DC, but rather the US military and a number of businesses that have been quietly but steadily making preparations for years. The fact that both of these communities – military and business – are traditionally considered quite conservative points to the fact that climate change is not fundamentally a political issue – it is not an argument about opinion, because decades of climate science have firmly established the basic facts. It is instead a practical issue, one that places in sharp relief the realization that, despite our tremendous technology, we human beings are still critically dependent on the weather and climate in which we live.

As far back as 2003 (and likely even earlier), the Department of Defense was considering the security implications of and adaptation strategies for anthropogenic climate change, including both abrupt and gradual change scenarios. The adaptation and mitigation strategies being considered and implemented include not only plans and contingencies for dealing with the political upheaval, famine, water shortages, mass refugee movements, and natural disasters that are expected to be induced by climate change but also plans for reducing the military’s non-renewable resource usage and greenhouse gas emissions.


While some uncertainty remains in the details of climate change impacts, the basic impacts like increases in extreme temperature and precipitation events, ecosystem shifts, disruptions to food production and water supply, and rising sea levels are well understood and known with high confidence. The uncertainty in the details can pose substantial challenges for effective adaptation planning, though. When you don’t know exactly how much, exactly when, and exactly where the impacts will be felt, estimation and bet-hedging are inevitable and necessary. Planning for the absolute worst is expensive and may not be necessary in the end, but simply hoping for the best could lead to a disaster of under-preparedness.

drought-07-Jay Janner

Of course, if we wait until all of the details become crystal clear and well constrained, it will be too late and far too expensive to effectively adapt. So smart players hedge their bets. They study their exposure and vulnerability to known and likely climate change impacts. They assess their risk. And they take action.

Some local and regional businesses may be understandably wary of spending money to prepare for something that “isn’t absolutely certain,” but keep in mind that we prepare for things that aren’t absolutely certain all the time.

Along the coast, we buy and keep plywood in our garages and stocks of canned food in our pantries for hurricane season, even though most of us won’t see more than a bit of tropical rain in any given season (and will end up eating lots of canned food to clear shelf space come October and November). In the Midwest, we build basements and safe-rooms to shelter us from tornadoes, even though most of us will never be hit by a twister. We buy insurance, and commodities futures, and keep money in the bank “just in case”.

We do this not because we’re certain that we’ll win the bet, but because it would be so much worse to lose the bet without hedging, without preparing. We seek security and resilience by acknowledging and adapting to risk.


So when the Department of Defense, Coca Cola, Levi Straus, Swiss Re, and other major players start creating and enacting climate change adaptation and mitigation plans, it’s time for the rest of us to take notice.

Climate change is real, it’s already happening, and it’s almost certainly going to get worse. How much worse is the trillion-dollar question and is largely within our control, should we choose to exercise it. We (as a species, as a collection of nations and communities) can choose how we adapt to the warming that’s already built into our climate system due to the past 150 years of industrial emissions, and we can choose how and by how much we reduce our greenhouse gas emissions to mitigate future climatic changes.

Despite the political overtones that stubbornly persist in the US, climate change is not a fundamentally political issue, and we treat it as such only at our peril. It is a practical, economic, and human issue for which pro-active planning, adaptation, and mitigation are the only reasonable responses. Ignoring climate change or denying it only amplifies the challenges that we face.

The first step toward building climate change resiliency is understanding the risks. Blue Skies Meteorological Services can help businesses identify their exposure and vulnerability to climate change impacts so that risks can be effectively targeted and reduced while resiliency is simultaneously built into operations.