Where Tornadoes are Deadliest – Probably Not Where You Think - Page 3 of 4 - Blue Skies Meteorological Services

Where Tornadoes are Deadliest – Probably Not Where You Think

Having grown up in Oklahoma, in the heart of Tornado Alley where annual violent twisters are just part of the springtime scenery, even I was initially a bit surprised when I heard of a new report out of the Southeast Regional Climate Center (SRCC) at the University of North Carolina. According to research by Charles Konrad II and his team at the University of North Carolina (UNC), the state in which tornadoes kill the most people per mile tracked on the ground is not Oklahoma or Kansas, not Texas or Arkansas or Mississippi – it’s Florida.

Now, Florida is no stranger to tornados. In fact, per square mile, Florida has more tornados than any other state in the country. But they’re usually not violent tornadoes – not like the EF5 monsters that ripped through Joplin, MO, in 2011 and through Moore, OK, in 1999 and 2013.

Moore, OK EF5 tornado damage, 2011. CNN.

Moore, OK EF5 tornado damage, 2011. CNN.

The vast majority of violent tornadoes are spawned by long-lived supercell thunderstorms, and weather patterns in Florida just don’t support those sorts of storms. Instead, Florida typically experiences weaker tornadoes, often spun up by interactions with the Gulf Coast and Atlantic sea breezes or by tropical cyclones. These tornadoes can cause substantial damage (e.g. roofs and siding removed, trees uprooted, cars flipped), but it’s not the sort of damage that one usually thinks of as causing widespread loss of life.

Joplin, MO, EF5 tornado damage to hospital. Time.

Joplin, MO, EF5 tornado damage to hospital. Time.

And therein lies the initial – but not necessarily warranted – surprise. When we think about risk, we tend to oversimplify the equation. We tend to assume that exposure = risk. We figure that the bigger, badder, and more frequent the hazard, the more people are likely to be harmed by it. By that reasoning, the southern Plains and the Deep South should have the deadliest tornadoes. Those are, after all, the regions of the country that experience the highest frequency of strong tornadoes. In other words, that’s where the greatest exposure per square mile is.

Climatology for all tornadoes (EF0 - EF5). Notice the relatively high number of total tornadoes that impact the central Florida peninsula.

Climatology for all tornadoes (EF0 – EF5). Notice the relatively high number of total tornadoes that impact the central Florida peninsula.


Climatology of strong to violent (EF3 - EF5) tornadoes. Notice that although Florida receives a relatively high number of total tornadoes, it receives relatively few strong to violent tornadoes.

Climatology of strong to violent (EF3 – EF5) tornadoes. Notice that although Florida receives a relatively high number of total tornadoes, it receives relatively few strong to violent tornadoes.



But that’s not where the highest density of tornado-related deaths occur. According to Konrad and his team, that dubious honor – greatest number of deaths per mile along the track of a tornado – goes to Florida.

To understand why, we have to look at the real risk equation.

Risk = Exposure x Vulnerability

Exposure per square mile is only part of the story. Sure, you have to have tornadoes on the ground for people to be killed by them – but you also have to have people in the path of the tornado who lack the appropriate resources to protect themselves.

To understand why Florida’s risk for tornado deaths is so high, we can compare it another state with almost exactly the same average number of tornadoes per square mile: Kansas.

According to the SRCC study, the number of deaths per mile along tornado tracks is nearly five times higher in Florida than in Kansas. Yet, while Florida and Kansas experience almost the same number of total tornadoes per square mile, tornadoes in Kansas are, on average, stronger than in Florida.

Average annual number of total tornadoes per state per 10,000 square miles. Notice that Florida and Kansas experience roughly the same number of total tornadoes per square mile.

Average annual number of total tornadoes per state per 10,000 square miles. Notice that Florida and Kansas experience roughly the same number of total tornadoes per square mile.


Average annual number of strong to violent (EF3 - EF5) tornadoes per state per 10,000 square miles. Notice that Kansas experiences on average 4x more strong tornadoes per square mile than Florida.

Average annual number of strong to violent (EF3 – EF5) tornadoes per state per 10,000 square miles. Notice that Kansas experiences on average 4x more strong tornadoes per square mile than Florida.



So, why isn’t Kansas at the top of the list? The answer has to do with population density and population vulnerability.

The number of people in the path of the tornado is maximized when tornadoes form and track over populated areas. In Florida, tornadoes tend to cluster along the populous Atlantic coast and along a stretch of Intersate-4 from Tampa to Orlando.

The population density in these regions ranges from about 300 – 1000+ people per square mile. By contrast, only one county in Kansas has a population density above 1000 people per square mile, and the vast majority of the state has a population density below 50 people per square mile. In fact, the average population density of Florida is more than ten times greater than that of Kansas.

Where tornadoes are most likely to occur in Florida, by type/strength. FSU.

Where tornadoes are most likely to occur in Florida, by type/strength. FSU.


US population density in 2000.

US population density in 2000.



So, when a tornado touches down in Florida, it’s much more likely to encounter people along its path.

There are also a number of demographic factors that make Floridians more vulnerable to tornados than Kansans.

  • Florida lives up to its reputation as a retiree paradise. Florida ranks first in the country in the percentage of its population over the age of 60. Kansas ranks 17th. Older people, especially those in poor health, tend to be injured more easily and more severely than younger, healthier individuals.
  • Poverty rates in the US.

    Poverty rates in the US.

  • The geographically adjusted poverty rate is also 8% higher in Florida than in Kansas (due, largely, to the higher cost of living in Florida) . People living in poverty often live in housing that is less sturdy and offers less tornado protection than their middle-class counterparts.
  • And finally, the climatology of Florida (and of the Southeast in general) results in a higher percentage of Florida tornadoes occurring at night, when tornadoes are harder to see and when people are less likely to receive warnings in time to take protective action.

This study out of UNC reminds us that risk assessment often has more to do with human systems and the built environment than with the natural hazards themselves. Risk exists in that intersection of exposure and vulnerability – exposure is largely a matter of where we live, while vulnerability is largely a matter of how we live. Effective risk mitigation requires understanding and addressing both.

Blue Skies Meteorological Services can help businesses identify their exposure and vulnerability to weather and climate impacts so that risks can be effectively targeted and reduced while resiliency is simultaneously built into operations.

Are We Really “Due” for a Major Hurricane Landfall This Year?

Hurricane Wilma, the last major hurricane to make landfall in the US.

Hurricane Wilma, the last major hurricane to make landfall in the US.

3150 days, give or take a few. That’s how long it’s been since a major hurricane, defined as a Category 3 or higher storm, has made landfall in the U.S. The previous record was about 2250 days, almost 2.5 years shorter. Although the time between major hurricane landfalls has varied significantly since 1900, it’s been about 500 days (or every 1-2 years) on average.

Credit: Roger Pielke, Jr.

Credit: Roger Pielke, Jr.

So, are we really due?

It’s hard not to think so. After all, if we flip a coin 8 times (for the last 8 years in which the US escaped a strike by a major hurricane) and all 8 come up heads, we start thinking, “It’s bound to come up tails next time.” But we’d be wrong (well, unless the coin was rigged). Statistics just don’t work that way. Each coin flip has the exact same 50/50 probability of heads/tails, regardless of the pattern of results that came before. So the fact that we did not suffer a major hurricane landfall last year or the year before does not in any way influence the probability of a landfall this year.

Number of hurricanes per year 1950-2000. Notice that the majority of El Nino (red) years have below-average hurricane activity, while the majority of La Nina years (blue) have above average hurricane activity. Credit NOAA.

Number of hurricanes per year 1950-2000. Notice that the majority of El Nino (red) years have below-average hurricane activity, while the majority of La Nina years (blue) have above average hurricane activity. Credit NOAA.

What does influence the probability of a landfall is the number of storms that form and the atmospheric steering flow that guides those storms toward or away from the US coastline. This year, an El Niño pattern is expected to form during the summer or early fall, bringing warmer waters to the eastern equatorial Pacific Ocean, and, among other things, stronger vertical wind shear, stronger trade winds, and greater atmospheric stability to the Carribean and tropical Atlantic Ocean. Strong vertical wind shear inhibits tropical cyclone development, as it tends to rip nascent storms apart before they have the opportunity to organize and develop, and enhanced atmospheric stability does just what it sounds like – stabilizes the atmosphere and hinders storm formation. For these reasons, moderate to strong El Niño years are often associated with below-average hurricane activity in the Atlantic basin.

NOAA's forecast for the 2014 hurricane season.

NOAA’s forecast for the 2014 hurricane season.

In addition to the predicted development of El Niño later this year, Atlantic sea surface temperatures (SSTs) in the main tropical cyclone development region are expected to remain slightly below average throughout the June 1 – November 30 hurricane season. Tropical storm systems draw their energy from the warm waters over which they develop – cooler water means less energy and, generally, fewer and less intense storms.

These two major factors – the expected development of El Niño and cooler sea surface temperatures in the tropical Atlantic – have led most hurricane forecasters, including NOAA, to predict an average to below-average hurricane season for 2014.

Damage from Hurricane Ike near Galveston, TX. Credit National Geographic.

Damage from Hurricane Ike near Galveston, TX. Credit National Geographic.

Given the lack of a major hurricane landfall in the US during the last 8 years and the below average 2014 Atlantic hurricane season forecast, the most dangerous part of this year’s hurricane season may be complacency. We would do well to remember that it only takes one storm to create devastation (like Hurricane Andrew in 1992 that struck during an otherwise quiet season) and that even non-major hurricanes can bring widespread destruction (Hurricane Ike in 2008 and Sandy in 2012 come immediately to mind).

Both Ike and Sandy go to show that the sustained wind speed of a tropical cyclone (and therefore its Saffir-Simpson category) does not solely determine its destructive potential. The physical size of the storm is also a critical determinant of its storm surge, and water kills far more people and destroys far more property than wind.

Cause of tropical cyclone deaths. Credit Rappaport, 2014.

Cause of tropical cyclone deaths in the United States. Credit Rappaport, 2014.

The danger that storm surge poses to life and property is often poorly understood outside of the meteorological community (despite the well-publicized tragedy and horror brought by Hurricane Katrina’s storm surge in 2005). To address this common knowledge gap, the National Weather Service will begin issuing experimental Potential Storm Surge Flooding Maps for the U.S. East Coast and Gulf Coast during the 2014 hurricane season. For each hurricane that is forecast to make landfall, the storm surge maps will show the geographical areas where storm surge could occur as well as how high above ground level the water could reach in those areas. The maps are intended to provide a reasonable estimate of the worst case scenario for flooding in those areas that could be impacted by an approaching storm.

Example Potential Storm Surge Flooding Map for Ft. Myers, FL. Credit NOAA.

Example Potential Storm Surge Flooding Map for Ft. Myers, FL. Credit NOAA.

Last week’s National Hurricane Preparedness Week, highlighted the many dangers associated with tropical cyclones, including storm surge, inland flooding, and wind. These hazards, especially inland flooding, wind, and severe thunderstorms, can affect locations hundreds of miles from the coast, so hurricane preparedness isn’t just for those folks lucky enough to live where most of us only vacation. Chances are, even if you don’t live near the coast, you have friends or family who do. Both the National Hurricane Center and Ready.gov offer excellent resources related to understanding and preparing for tropical cyclones.

Many coastal states, including Florida, Louisiana, and Virginia, offer sales tax holidays when you purchase hurricane preparedness supplies at the start of the hurricane season. For those of you in Florida, like us here at Blue Skies, that sales tax holiday runs through this upcoming Sunday, June 8.

We’re hoping for a season as quiet as the forecast, but even so, we’re gathering our storm supplies and reviewing our plan. We hope you’re doing the same!

Weather-Impacted Automobile Accidents

How many of us check the weather before hopping in our cars for our morning or evening commutes, before a road trip, or even before a quick trip to the grocery store? I’d hazard to say that many, if not most, of us do.

accident-in-rain- credit-ShopOnce Insurance

But why? Why do we care what the weather is doing outside when we’re safely ensconced in our climate-controlled vehicular bubble? Is it just so that we can decide whether to grab our jacket or umbrella? Or is there perhaps an even more important reason to check the weather before jumping behind the wheel – anticipation of risk?

Weather is a critically important factor in roadway conditions. Rain or snow-slicked roads reduce tire traction, dramatically increasing stopping distances. Fog and precipitation of any kind reduce visibility, limiting how far ahead we can see, and therefore how quickly we can react to danger. Wind can destabilize high-profile vehicles, and the low sun angles just after sunrise and just before sunset can lead to blinding sun glare.

fog3

According to the National Highway Traffic Safety Administration, atmospheric conditions are a critical factor in almost 25% of all motor vehicle accidents in the US: adverse weather has historically been a critical factor in 8.4% of collisions, with another 16.4% critically affected by sun glare. With an average of 10.5 million motor vehicle accidents annually in the US, atmospheric conditions are therefore a vital factor in over 2.6 million crashes each and every year.

One such weather-impacted accident occurred in January of 1998, when former Boston Red Sox player, Mo Vaughn, flipped his SUV while driving home from Rhode Island. Vaughn was originally arrested on suspicion of operating his vehicle under the influence, but a forensic meteorological analysis of the weather conditions on the evening of the crash revealed that dense ground fog blanketed the area in which the accident occurred, leading to extremely low visibility. Due in large part to forensic meteorological information about the hazardous weather conditions present at the time of the accident, Mo Vaughn was acquitted of the OUI charge.

With summer comes an increase in the number of afternoon thunderstorms and their accompanying hazards, especially here in Florida: blinding rain, slick roads, strong winds, even hail and tornadoes. These weather conditions can and do contribute to motor vehicle accidents and deaths.

So, check the weather before you drive, and not just to inform wardrobe decisions. Anticipate any weather-related risks and take appropriate precautions (like leaving a bit earlier than planned, driving more slowly, and leaving more distance between you and the car in front of you).

car-accident-on-highway-in-rain

In the unfortunate event that you or a client is involved in a weather-impacted accident that results in criminal charges or an insurance dispute, give Blue Skies Meteorological Services a call or send us an email. We will gladly provide a free initial consultation to determine how a forensic meteorological analysis could support your case by revealing the exact weather conditions in place at the time and location of the accident.

Weekend Tornadoes, Storm Damage, and Insurance Coverage

All good things must come to an end. After almost four months of relatively quiescent weather, the 2014 tornado season kicked off quickly and tragically over the weekend.

Vilonia, AR tornado damage (Danny Johnston/AP photo)

Vilonia, AR tornado damage (Danny Johnston/AP photo)

On Friday evening, the year’s first intense tornado (defined as an EF3 or stronger) touched down in Chowan County North Carolina, killing an 11-month old child who was trapped beneath the debris of his home. That storm brought to an end two record-breaking streaks of benign weather, marking both the latest calendar date for a year’s first EF3 tornado as well as the latest calendar date for a year’s first tornado death.

Only two days later, on Sunday, April 27th, an outbreak of severe storms spawned multiple tornadoes that killed 16 people in Oklahoma and Arkansas. The most substantial damage occurred in central Arkansas, where an 80-mile-long path of destruction swept through northern Little Rock, leaving damage reportedly indicative of an EF3 or stronger tornado. The same slow-moving severe weather system hammered Mississippi, Alabama, and Tennessee on Monday and is expected to continue bringing dangerous weather, including the possibility of strong tornadoes, to the southeastern US through at least Wednesday.

Storm Prediction Center convective outlook for 29 April 2014

Storm Prediction Center convective outlook for 29 April 2014

Although intense tornadoes are relatively rare, accounting for approximately 5% of all tornadoes nationally, they are responsible for a disproportionate 75% of all tornado fatalities (statistics for North Carolina). While each tornado fatality is tragic, tornado deaths have been generally declining in the US since the 1920’s, with an average of 80 people killed each year by tornado activity.

Tornado Fatalities 1875 - 2010 (credit NOAA)

Tornado Fatalities 1875 – 2010 (credit NOAA)

Although the majority of tornado damage and fatalities are attributable to rare intense tornadoes, even much more common weak tornadoes and severe straight-line winds can cause substantial damage to property, felling trees, removing shingles and siding from homes, and flinging debris into structures and vehicles. Most homeowners insurance covers storm damage, including damage caused by wind, hail, lightning, debris, and falling trees. One notable coverage exception found in almost all insurance policies, however, is storm-induced flooding, including street flooding, storm surge, and areal flooding due to rising rivers, streams, and creeks. For such coverage, a separate flood insurance policy is required.

In some cases, though, street flooding is caused not by an exceptional storm (i.e. an “act of God”) but rather by an insufficient storm water drainage system. In such instances, liability for damages may rest with the planning or maintenance authority responsible for the storm water system, rather than with the homeowner.

Storm water sewer overflow (photo bwsc.org)

Storm water sewer overflow (photo bwsc.org)

If a neighborhood or section of a neighborhood regularly floods, even during normal, everyday storms, the drainage system may be deficient. A forensic meteorological analysis (like this one from BSMS) of known storm events that led to street flooding, considered in the context of the local rainfall climatology, can reveal whether the drainage system was adequately designed and maintained to handle foreseeable events.

In addition to flood damage, homeowners insurance will not cover damage caused by a lack of proper maintenance. Occasionally, negligence may be suspected as a contributing factor to storm damage, leading to a denial of claim, even when it is not immediately clear whether damage would have still occurred with proper maintenance.

Storm damage

Storm damage

For instance, if a tree falls during a storm and is later found to be rotten, the insurer may deny the homeowner’s claim, insisting instead that negligence on the owner’s part (failing to remove a rotten tree) caused the tree to fall, rather than the storm. Such insurance disputes can lead to nasty legal battles. Investigation as to whether the homeowner knew or suspected that the tree was rotten (i.e. whether he or she was on notice), examination of other damage throughout the area (did healthy trees of a similar size fall nearby during the same storm?), as well as a forensic meteorological analysis (were wind speeds with the storm sufficient to fell a healthy tree of that size? did heavy rainfall and saturated soils reduce the root stability of the tree?) can greatly assist in determining the ultimate cause of the damage and thereby assist in settling such disputes.

So, the bottom line is this: storm season is here, and after a late start, it appears to be making up for lost time (at least at the moment). Extreme weather, which includes severe local storms as well as tropical cyclones, droughts, heat waves, areal flooding, wildfires, and winter storms, causes tens to hundreds of billions of dollars in damage annually in the US.

Extreme Weather Damage Costs - Smith and Katz 2013

Severe local storms are, on average, responsible for more than 10% of all damages, with tropical cyclones and droughts/heat waves responsible for nearly 50% and 25%, respectively. While severe local storms are not responsible for the largest percentage of damage costs, they do represent the most common/frequent type of extreme weather experienced in the United States, and almost everyone, at some point, will experience storm damage. Make sure you understand your property insurance policy, including any exceptions, and take care of any nagging maintenance issues (like rotten trees or loose roof shingles) that could jeopardize a storm-related insurance claim.

In the event that you do find yourself in a weather-related insurance or legal dispute, whether as the insured or the insurer, the plaintiff or the defendant, do not hesitate to contact Blue Skies Meteorological Services. We will gladly provide a complimentary consultation to discuss how a forensic meteorological analysis could determine the role that the weather played in your case and how such an analysis could facilitate an advantageous resolution of the dispute.

Next time: Weather-impacted automobile accidents

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 .

floyd_19990915_2015_hg

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.

wildfire

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.

Del399380

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.

Tornado

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.