Introspect: 2014 Severe Convective Storm Season

The earth’s weather and climate is naturally variable on all time scales, and a number of factors can cause a sustained change to weather and climate. Referred to as “climate forcers,” these factors invoke the idea that they force or push the weather and climate towards a new state. These climate forcers have created a winter to remember over much of the U.S., but there is at least some (symbolic) hope for warmer weather in that the spring equinox has passed, which signals the end of astronomical winter in the northern hemisphere. But the official start of spring may have insurance companies wondering how the Severe Convective Storm (SCS) season might pan out. The latest BMS Introspect looks at the climate forcers that drive severe weather, and considers whether or to what extent they will influence the upcoming SCS season.

Are We Done with PCS Winter Storm Losses for 2014?

With February 28 marking the close of meteorological winter (December – February), a mountain of interesting stats are about to be released – so be prepared for media fact overload!

For the most part, these facts should show that points east of the Mississippi have experienced one of the coldest, snowiest winters since the late 1970s – and in some cases, depending on the area, the coldest, snowiest ever or at least since 1917. But, as last spring proved, the weather doesn’t pay close attention to the calendar. As a reminder, the north-central U.S. was cold and snowy with North Dakota having a record cold April and Duluth, MN having its snowiest month ever – helping to contribute to the fifth-largest April U.S. snow cover extent on record. Given the long-range forecasts, the extreme cold and some significant snow will continue in March, which will add to the records and likely create new ones.

The average U.S. temperature anomaly from Dec 1 – Feb 26 (shown below) clearly demonstrates the U.S. as a whole has been colder than the 30-year average. In fact, it would appear the U.S. has experienced 6 – 7 Polar Vortex episodes of cold air, when the nation’s average temperature anomaly dropped below -4 C (25 F). Interestingly, the nation as a whole was colder for a longer period of time during the first Polar Vortex outbreak during the second weekend in December than it was during the main event on January 5 – 8 – which the media dubbed the “Polar Vortex.”

Are we Done with PCS Winter Storm Losses for 2014?

Image Source: Weatherbell.com – Ryan Maue

To-date, PCS has estimated $1.5B in loss due to the media-dubbed “Polar Vortex.” This freezing, ice, snow and wind event brought blizzard-like conditions to some areas of the country, with cold air producing wind chills as low as -60 F and gusts of up to 45 miles per hour with white-out conditions. The cold temperatures often forced schools and businesses to close and caused water damage from frozen and burst pipes. The frontal system impacted many states as it moved south and east across the United States – including Mississippi and Georgia, which saw extensive damage from the wrath of this extreme event.

So far this meteorological winter season, five PCS Winter Storm events have contributed to $2.1B in loss – and $2B of that has come in 2014. Given that PCS digital records only go back to the 1950s and the PCS definition of a Winter Storm can be multifaceted (potentially including severe weather aspects such as tornadoes and hail) it is difficult to estimate the true Winter Storm component of PCS losses.

So… Have we seen the end of the Winter Storm losses for 2014?

Looking at the PCS Winter Storm data in January and February that include Winter Storm event perils such as snow, wind, ice, flooding and freezing – but exclude Severe Convective Storm  (SCS) event perils such as tornadoes and hail for states east of the Mississippi, the answer is essentially “yes” – with a projected 93% of the loss already incurred based on historical loss development. There are only five years on record when Winter Storm losses occurred in March, with the biggest impacts happening during the historic winter of 1976.

However, if you base the answer on the wider definition of Winter Storm perils, which include SCS events, we are not done yet. The U.S. could easily still experience a Winter Storm that creates severe weather such as tornadoes and hail across the southern states while producing Winter Storm-like perils across the north. A classic example of this type of PCS event is the March 12 – 14 1993 Storm of the Century, also known as the ’93 Superstorm (1993 PCS #46). The 1993 Superstorm still ranks as one of the costliest Winter Storm events of the 20th century, creating a PCS CPI adjusted loss of $2.8B. Based on the definition of Winter Storm that would include SCS perils, only 71% of losses have occurred thus far in 2014. With March roaring in like a lion and more cold, snow and severe weather forecasted for the eastern half of the nation over the next few weeks, we should anticipate adding yet more losses to the PCS Winter Storm total.

Hurricane Wilma’s 8th Anniversary

As we approach the end of the 2013 Atlantic hurricane season and take in the media attention around the anniversary of Superstorm Sandy, it is also important to mark the 8th anniversary of Hurricane Wilma’s landfall, which occurred October 24, 2005. This was the last major hurricane to make landfall on the U.S. coastline. It has now been 2,938 days without a major landfalling hurricane – remarkable given the changes scientists said might result from warmer sea-surface temperatures in the Atlantic Ocean. The U.S. landfalling hurricane event data set is one of the best meteorological records that exist in the U.S. In looking at the historical landfall record, the longest period without a major landfalling hurricane stands at 3,316 days (August 11, 1860 – September 8, 1869). If a major hurricane doesn’t make landfall in the U.S. next year, we will surpass the longest period without one.

Unless we are in some very unusual climate state that has not been discovered, there is a growing disconnect between overall Atlantic Basin activity and landfalling named storms. While the average overall Basin numbers are higher than normal since 2006, with every passing year since then the U.S. has seen only 19 named storms make landfall, and only six hurricanes – with no major hurricanes making landfall. This translates to a landfall rate of 0.75.

Using the landfall data from 1900, in a given year the expected landfall rate of a hurricane impacting the U.S. coastline is 1.5, with a 77% probability of at least one hurricane impacting the U.S. coastline. For major hurricanes the rate is 0.5 with a 40% probability – so the U.S. landfall rate is significantly below average.

Given this landfalling hurricane drought, the United States coastline has been lucky. Although insurance companies have been suffering losses of other types over it, the average annual hurricane loss during this drought has been just $4.9 billion, according to Property Claims Services. This is below the long-term average annual loss of $6.4 billion as calculated using the insured historical loss data from Dr. Pielke Jr., a database that attempts to normalize hurricane damages in the United States. Accounting for Superstorm Sandy in 2012, which was not a hurricane at landfall, this average annual loss since 2006 would increase to $7.7 billion.

With a below normal landfall rate of only 0.75 hurricanes since 2006, in the future the trend for more landfalls should correct back closer to the long-term rate if we assume that hurricane landfalls follow a poisson distribution and we are not in some unknown climate regime. After all, the probability of not having a major hurricane make landfall over a 9-year period is a very low 1%, meaning insurance companies should expect an increase in losses from hurricanes in the future. Something to ponder as we await next year’s forecast.

It’s a risky world

Over the last few weeks Travelers and Swiss Re released polls suggesting people perceive that the world is becoming a riskier place and many are under-insured.

The main driver for public opinion is that this is a perceived period of “more extreme weather”. Although many mention that it is a riskier world, many people don’t seem to be doing much about it. Generally, preparation for extreme events is poor and there often seems to be an overreaction or under-reaction of preparation to such events. This contrast highlights the subjective nature of individual risk perception.

It seems only urgent alarms of an impending “Frankenstorm” really inspire proactive preparation, sending people shopping for batteries and bottled water. All too often people assume that their flashlights, sandbags and backup generators will protect them from the fierceness of Mother Nature. Therefore, the more control over a risk you think you have, the less worried you might feel – no matter how false that sense of control might be.

We often view these risks in terms of probabilities, but many people are bad at understanding probabilities. It’s a good bet that most people who experienced a “once in a century” storm feel that such freakish weather is not likely to happen in the next few years or decades. Sorry, but Mother Nature does not work that way. There are probabilistic patterns for assessing the risk of natural disasters over the long-term. Managing risk is a real trick as the risks over the long-term are much larger than our very brief lifetimes have witnessed or can remember.

Our short memories often refer to past historical weather patterns that tend to get replaced by what we remember seeing more recently. As a meteorologist, I am not the only one guilty of consistently watching The Weather Channel when a major weather event is occurring. Some people would say many of us have become addicted and can’t stop watching television and scanning news sites and social media, far more than we actually require to stay informed.

That brings us to the transmitters of storm news – the media, both news and social. News coverage is far more likely to warn us that the sky is falling than to reassure us that it isn’t. “If it scares, it airs”, because anything that threatens us is more likely to grab our attention. If weather forecasts include days of Frankenstorm predictions, the future is going to feel frightening. To be fair, despite their breathless alarm-ism, the news media did make the public aware of Sandy, helping us prepare. The aftermath of Sandy demonstrated why we should worry.

Risk perception determines how prepared we are — or aren’t. It determines whether we follow government evacuation orders or make sure we have candles, working flashlights, and bottled water. When it comes to flood insurance, risk perception determines whether we buy insurance and polls suggest most people are confident that their home or dwelling are properly insured. However, flood insurance take-up rates are ridiculously low, suggesting the perception of flood risk is that flooding is not a high risk, yet time and time again high uninsured flood losses occur. Opinions of “it won’t happen to me” or “I’ve been through these storms before, it won’t happen again” do persist.

 

 

 

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Tropical Update: Approaching the Peak of the Hurricane Season

Historically, September 10 is the peak of the North Atlantic hurricane season, which typically sees 10 or 11 named tropical storms. This climatology number climatology number is usually represents the last 30 or 50 years, but the average since 1995 is higher – at 15 named storms, 8 hurricanes and 4 major hurricanes – and corresponds to the so-called active era in the North Atlantic, caused by warm Atlantic Multidecadal Oscillation. With the storm Erin just being named in the eastern Atlantic Main Development Region (MDR), the storm total for this year (through the second week of August) sits at 5. This is about two weeks ahead of climatology, which suggests the fifth named storm is often observed around August 31. The first hurricane is climatology-observed on August 10, so unless the current activity develops into a hurricane, the Accumulated Cyclone Energy will continue to fall behind the climatological norm.

In August, Sea Surface Temperatures (SST) in the MDR extending from the Lesser Antilles to the Cape Verdes Islands warm significantly, which is one reason why three storms have formed in the MDR so far this year. It’s also part of the reason seasonal forecasts are calling for a more active than normal hurricane season.

Figure 1 shows the SST in the MDR. Image Credit: www.weatherbell.com

SSTs are solidly 27°C off the African coast and rise slowly to 28°-29° as tropical waves approach the Caribbean islands.  But lately the main issue is the presence of Saharan dust in the MDR.

Figure 2 is a look at the graphics from the NASA GEOS-5 model, which shows the dust that continues to occur over the MDR. Image Credit: www.weatherbell.com

I am not quite sure what is considered to be normal in terms of dust occurrence. But as a proxy in lieu of actual dust measurements over the MDR, we can look at the at the 400-mb- specific humidity over the last dozen years to demonstrate how dry the MDR has been (Figure 3). This dry, dusty air is not conducive to tropical development and has been the main reason why Chantal, Dorian, and most likely Erin have stayed below hurricane status and could result in less overall named storm active compared to what has been forecasted.

Figure 3 is the 400 mb Specific Humidity since June 1, 2013 over the MDR. Image Credit: NOAA / Earth System Research Laboratory

Over the past week many media outlets have been hyping the upcoming few weeks of the hurricane season.  This is because the strong, opposing wind shear has weakened across the MDR. Furthermore, the dry, Saharan air off the African coast has begun to dissipate, compared to earlier this season. Thus, conditions in the Atlantic are quickly becoming more favorable  for hurricane development, which should come as no surprise since about 80% of the season’s hurricane activity is produced in mid- to late August and  September.

Updated Seasonal Impact Forecast:

A high impact for the U.S. is still expected, but the newest weather pattern forecasted for the next month suggests a shift centered at a corridor near Florida rather than in eastern Florida and up the east coast. The European Center for Medium Range Weather Forecasting (ECMWF) model September forecast appears to be much wetter in the Caribbean and eastern Gulf, which supports the idea of seeing storms track in that area at this time of year.

Florida, which just had its wettest July on record (with 12.38 inches of rainfall – 4.91 inches above average), is an example of the large amount of moisture that has been observed along the east coast this hurricane season.  Because wet soil can increase basement leakage and tree fall, these wet soil conditions should lead to increased losses if the area is impacted by a named storm.

Approaching the Peak of the Hurricane Season

Historically, September 10 is the peak of the North Atlantic hurricane season, which typically sees 10 or 11 named tropical storms. This climatology number  usually represents the last 30 or 50 years, but the average since 1995 is higher – at 15 named storms, 8 hurricanes and 4 major hurricanes – and corresponds to the so-called active era in the North Atlantic, caused by warm Atlantic Multidecadal Oscillation. With the storm Erin just being named in the eastern Atlantic Main Development Region (MDR), the storm total for this year (through to the second week of August) sits at 5. This is about two weeks ahead of climatology, which suggests the fifth named storm is often observed around August 31. The first hurricane is climatology-observed on August 10, so in terms of hurricane activity and the Accumulated Cyclone Energy will continue to fall behind the climatological norm.

In August, Sea Surface Temperatures (SST) in the MDR extending from the Lesser Antilles to the Cape Verde Islands warm significantly, which is one reason why three storms have formed in the MDR so far this year. It is also part of the reason seasonal forecasts are calling for a more active than normal hurricane season.

Figure 1 shows the SST in the MDR. Image Credit: www.weatherbell.com

SSTs are solidly 81°F off the African coast and rise slowly to 83°-84°F as tropical waves approach the Caribbean islands. However, lately the main issue is the presence of Saharan dust in the MDR.

Figure 2 is a look at the graphics from the NASA GEOS-5 model, which shows the dust that continues to occur over the MDR. Image Credit: www.weatherbell.com

I am not quite sure what is considered to be normal in terms of dust occurrence. But as a proxy in lieu of actual dust measurements over the MDR, we can look at the 400-mb- specific humidity over the last dozen years to demonstrate how dry the MDR has been (Figure 3). This dry, dusty air is not conducive to tropical development and has been the main reason why Chantal, Dorian, and most likely Erin have stayed below hurricane status and could result in less overall named storm active compared to what has been forecast for the season.

Figure 3 is the 400 mb Specific Humidity since June 1, 2013 over the MDR. Image Credit: NOAA / Earth System Research Laboratory

Over the past week many media outlets have been hyping the upcoming few weeks of the hurricane season. This is because the strong, opposing wind shear has weakened across the MDR. Furthermore, the dry, Saharan air off the African coast has begun to dissipate, compared to earlier this season. Thus, conditions in the Atlantic seem like they are quickly becoming more favorable for hurricane development, which should come as no surprise since about 80% of the season’s hurricane activity is produced in mid-to-late August and September.

Updated Seasonal Impact Forecast

A high impact for the U.S. is still expected with fewer named storms, but the newest weather pattern forecasted for the next month suggests a shift centered at a corridor near Florida rather than in eastern Florida and up the east coast. The European Center for Medium Range Weather Forecasting (ECMWF) model September forecast appears to be much wetter in the Caribbean and eastern Gulf, which supports the idea of seeing storms track in that area at this time of year.

Florida, which just had its wettest July on record (with 12.38 inches of rainfall – 4.91 inches above average), is an example of the large amount of moisture that has been observed along the east coast this hurricane season. Because wet soil can increase basement leakage and tree fall, these wet soil conditions should lead to increased losses if the area is impacted by a named storm.

Wet East Coast Increases Loss Concern this Hurricane Season

As we approach the peak of the 2013 Atlantic hurricane season (which peaks around September 10), the forecasts (for an active season) made back in April have partially panned out – if you consider the total number of named storms. Looking at the last 50 years (1976-2012), the average formation dates of the fourth named storm and first hurricane are August 19 and August 3. So in terms named tropical storms, the season is ahead of par with climatology, but slipping behind on the occurrence of the first hurricane for 2013. In terms of Accumulated Cyclone Energy (ACE), 2013 is essentially average for this date. We’re at 6.6 compared to the 1981-2010 average of 9 for this date.

With August being the month where typically the number of tropical systems ramps up and Colorado State University’s August forecast calling for an active landfalling season, the likelihood of the season’s wet soil conditions leading to increased losses from a landfalling named storm must be considered.

The Ohio Valley and East Coast were much wetter than average. June precipitation totals for 18 states – from Georgia to Maine – ranked among their 10 wettest in the historical record. The fact that this weather continued into July undoubtedly creates concern over a named stormed impacting these rain-soaked areas.

 

 

NOAA Advanced Hydrologic Prediction Service view of the past 60-day Percent of Normal Precipitation. Over the past 60 days, much of the East Coast has seen 150% – 350% of normal precipitation.

Research shows that past hurricanes have demonstrated the combined effects of subsequent excessive rainfall and a named-storm wind speed that can have a major impact on insured losses. These losses might not otherwise be represented if the subsequent seasonal rainfall was normal or below normal. This loss increase is primarily associated with increased basement leakage and tree fall. (When soil is saturated, the connection between the root plate of a tree and the soil is lessened, which can increase tree fall.) Research also shows that the average wind speed expected to snap a hard- or softwood tree trunk is a 90 mph gust. Therefore, while more intense winds wouldn’t necessarily increase the loss, lower wind speeds might – given the weakened condition of saturated soil.

Recent examples of events that might have seen increased losses due to higher soil moisture are hurricane Isabel 2003 and Irene 2011. With New Jersey and Delaware having had their wettest June on record and 18 other eastern states having had Junes ranking in their top 10 wettest, this August has seen some of the highest soil moisture levels ever recorded. And this could increase the risk of river and basement flooding as well as tree fall if a named storm were to impact the area.

 

2013 Half Year Review – U.S. Extreme Weather Events

Andy Siffert, BMS’ resident Meteorologist, reviews the first 6 months of 2013 in terms of U.S. extreme weather events and their impact on the industry.

As we round the corner into the second half of 2013 we can now put into perspective some of the U.S. extreme weather events that occurred during the first half of the year. With the tally of some of these disasters still being assessed, the U.S. insurance losses estimated by Property Claims Services (PCS) will continue to rise. As of July 1, 2013 the U.S. has seen $6.8 billion in PCS claimed losses from weather events across the U.S. Considering the expected upward adjustment of claimed weather events, losses reported thus far would fall below the five-year average for first- and second-quarter weather-related losses, which total $13.1 billion. This below-average loss is primarily connected to the current “Tornado Drought” that has been ongoing since the second half of 2012. Severe convective storm outbreaks in May 2013 produced major tornadoes causing widespread damage to properties in Texas, Oklahoma, and other states. But as of July 1, the tornado count is 42% below the five-year average, with a major portion of the tornado activity occurring in the lower Mississippi and Tennessee River valleys. Given that May is peak tornado season in the Central Plains, it should be no surprise that strong and violent tornadoes formed and caused damage there. In Tornado Alley this typically occurs during the second quarter of the year, but the number of tornadic weather events in the Central Plains and Midwest regions has been below normal again this year.

The overall lower PCS loss numbers could also be a result of fewer hail events, which, according to Storm Prediction Center (SPC) storm report data, are currently 21% below normal (with only 3,714 hail reports). With the main drivers of severe convective storm losses resulting from the May 20 tornado in Moore, OK and overall hail reports below the five-year normal trend, it seems that derecho or straight-line wind events are the likely driver of most U.S. weather-related losses to-date. These events appear to be trending with the five-year SPC severe wind reports, which as of July 1 stand at 7,360 vs the five-year mid-year average of 7,369 severe wind reports.

The Black Forest wildfire in Colorado appears to be one of the most destructive fires in Colorado’s history. Because of this, wildfires have been getting a lot of media attention lately and it might be interesting to put the current wildfire season into perspective.

According to the National Interagency Fire Center, the U.S. is about a million acres below the 10-year running mean of 2.4 million acres burned in the 22,050 wildfires that have been reported. This is also 15,000 fires fewer than the 10-year running mean. In fact, in 2013 there have been fewer fires than in any of the last 10 years, and the year stands next to last in terms of acres burned.

Like the tornado season, so far the fire season has been well below normal. The Black Forest wildfire in Colorado and the recent deaths of 19 fire fighters in the Yarnell Hill, Arizona wildfire are examples of fires that stick out like a sore thumb in a below-normal wildfire season – just like the two late-May tornadoes which were exceptions to the trend of the overall tornado season.

It is my understanding that in both the Black Forest and Yarnell wildfires, areas burned that had not burned in the previous 40 years – which has to be a major factor contributing to the wildfire catastrophe. The media would say the fires are due to dry conditions, which definitely exist and in some cases are extreme. But if it had been a wet spring, then more fuel would have been available as the summers always see drier conditions in the southwest. The old saying, “Pay me now or pay me later” applies here: If it’s wet, the resulting new growth will eventually dry out and die. And if it’s dry and dead, it will eventually burn.

Worldwide, recent catastrophes seem to be focused largely on flooding-related events, with the notable events originating from the remnants of Tropical Cyclone Oswald that triggered severe flooding in Queensland and New South Wales in Australia. More recently, flood losses that impacted a large area along the Elbe river basin in Europe will likely surpass the 2002 European flood losses. In North America, heavy rainfall provoked catastrophic flooding in southern Alberta, Canada – which will likely go down as the largest flood-related loss ever experienced in Canada. However, with the 7th-latest start to the typhoon season, few typhoons have resulted in flooding or the kind of disasters typically seen in Asia. In fact, global Accumulated Cyclone Energy (ACE) is still stuck in the lowest range – which began in 2007 and is similar to the 1980s. Before Super Typhoon Soulik was upgraded on July 10 to a major 96+ knots tropical cyclone, the last major tropical cyclone, Sandra hit just east of Australia on March 11. And the clock is still ticking on the 2,811 days since the U.S. was last hit by a Cat3+ hurricane – the longest such period since 1900, if not before.

Overall it would appear there is a silver lining – because extreme weather events could be worse based on past years, plus you can’t control nature. Most often, catastrophic events like the wildfires, tornadoes and floods of 2013 can be tied to events of similar magnitude that occurred in the past. We are building bigger towns in locations where catastrophic events have occurred in the past, and the understanding of changes in population, income and housing units can often explain the increase in loss.

Severe Weather in a Warming World

Andy Siffert, BMS’ resident Meteorologist, discusses Severe Weather in a Warming World

As we have all seen in the media it would appear that on May 15 Mother Nature has turned on the severe convective storm season, which to date had been historically quiet in terms of insurance losses and severe convective storm reports.

Since May 15 the preliminary tornado count stands at 305 tornadoes, but considering the nation is currently at the climatological peak of the severe convective storm season and the tornadoes are occurring precisely where historically they should occur, the impacts of the severe weather should be expected and can be easily explained by understanding the current weather pattern.

The reason we have seen the recent uptick in severe weather activity to more normal levels is the spring of 2013 has been climatologically cooler than normal over the eastern two-thirds of the country, which has kept instability levels low. This is most likely due to a weather pattern associated with the a negative phase of the Arctic Oscillation (AO), which has kept a low amplitude jet stream pattern in place over the eastern portion of the U.S., allowing cool air from Canada to spill southwards into the U.S. blocking warm moist air northward progression from the Gulf of Mexico.

Starting in mid May a shift in the jet stream winds resulted in a weather pattern that allowed for frequent weather systems to draw upon the warm moist air from the Gulf of Mexico to clash with the cooler, drier air moving east off the Rocky Mountains. This different weather pattern has provided the main ingredients necessary to produce what have been widespread multi-day severe weather events.

Understanding weather patterns can fluctuate explains the last three years of tornado activity, which have experienced both a record minimum and record maximum tornado count. These two extremes of recent tornado surplus (2011) and the current tornado drought are rare and considering they are back to back it makes the occurrence even more unusual. However, these patterns have resulted in several contradictory views on the impact a warming world might have on severe convective storms in the U.S. In a warming world should we experience more seasons like 2011 or fewer tornadoes like 2012? Are extreme tornadoes like Moore, OK, a result of this warming world?

In the latest BMS Introspect – Severe Weather in a Warming World and Its Impact to the Insurance Industry we attempt to answer these questions.