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Tis the season for severe weather across the south, but it’s been extremely quiet so far?

Tornado and hurricane drought?
It’s no surprise that the recent lack of hurricane landfalls has drawn the attention of the insurance industry. The long-standing Florida hurricane drought ended with hurricane Hermine’s landfall on September 2, and of course, Matthew threatened to end the major U.S. hurricane drought as well. However, there is another drought quietly confounding the insurance industry. After 2011 and reports of a “new normal” for severe weather, several years have now passed with lower than normal tornado activity.
So far the 2016 U.S. tornado count is among the lowest of the last 11 years. As of Nov 27, 981 tornadoes touched down in the U.S., which is 303 less than the 17-year average for that time period.

Tornado counts are below the 17-year average in eight of 10 months so far this year. Most recently, tornadoes in September and October were well below average. This is despite hurricane Hermine, which spawned eight confirmed tornadoes and hurricane Matthew which spawned two confirmed tornadoes. Hurricanes can produce a significant number of tornadoes, but neither Hermine or Matthew produced very many.

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U.S. Inflation Adjusted Tornado Count from 1950. It shows that this year could take the record for the lowest inflation adjusted tornado count since 1950.

This year’s unusually dry tornado spell started in June, which produced only 86, the fewest in that month since 1988. The 17-year average number of tornadoes for June is 216. February, March and August are the only months that featured above-average tornado activity this year.

Had it not been for a concentrated outbreak of 35 tornadoes in Indiana and Ohio on August 24, August would have finished below its 20-year average as well. Though the tornado pace has been slow for the year as a whole, February was an exception. With 138 confirmed tornadoes during the month, it was the second most tornadic February since 1950. Only 2008 produced more February tornadoes: 146 total tornadoes, including the record “Super Tuesday” outbreak of 84 tornadoes.

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2016 Tornado touch down locations and daily total count which shows the lack of tornadoes since the end of September.

Through last Monday, November 21, zero tornadoes had been reported this month, which is highly unusual. With an average November tornado tally of 58 (1991-2010), we are in near-record low territory again this month. Only four other years since the 1950’s have witnessed comparably low tornado activity in November (according to NOAA Storm Prediction Center Data): zero tornadoes in 1976, two tornadoes in 1954, and three tornadoes each in 1980 and 2009.

Severe Weather Insured Losses

As one might expect, insured losses from severe weather are often a matter of luck, and although there were some powerful tornados this year, very few impacted large populated areas. Yet despite scant tornado activity, 2016 is already the second costliest severe weather year in recent years, totaling $16.6B in insured loss. This total is far behind the $28B of insured loss experienced in 2011 as a result of several deadly and damaging tornadoes across the southeast U.S. Large insured loss losses this year were likely driven by wind and hail events. In fact, over 80% of U.S. insured loss results from hail and wind events, but luck is an ever-present factor. This year, bad luck settled over the state of Texas. Several hail storms impacted large metropolitan area such as Dallas-Fort Worth, San Antonio and El Paso, and these storms have driven the large losses experienced in the U.S this year. In fact, almost half of the total loss of $7.9B so far this year occurred in Texas.

Louisiana was also hit hard by severe weather and flooding, and that bad luck could continue today with a new severe weather threat.

This week’s severe weather threat

Tornadoes happen all year, but climatologically two seasons exhibit peak activity. Spring is prime time for tornado activity. That’s when warm Gulf of Mexico air clashes with winter’s remnant cold as dry air masses spill over the Rockies. Another peak arrives in October and November, but tends to be more erratic throughout fall. In something of a reverse of the spring air migration, jet streams again traverse and target specific parts of the country as the calendar changes from summer to winter.
It’s been over seven weeks since the U.S. has had a day with over 50 severe weather reports, and today this trend may snap due to expected severe weather across the south-central U.S. The HRRR model is forecasting the formation of prefrontal super-cells by mid-day Monday across central and northern Louisiana.

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Today HRRR Forecasted Radar for 2 CST over the South Central U.S.

This severe weather threat will continue to move across the southeast U.S. over the next weeks, which in some cases will be welcome given the ongoing drought conditions that triggered recent wildfires.

So although it has been quiet and the U.S is at near near-record low tornado fatalities and low tornadoes counts, we shouldn’t forget what occurred in December of 2015. That December began with a record-low of 10 tornado deaths. Then waves of tornadoes struck the South and the yearly toll jumped to 36. With a more energetic weather pattern ahead, we should stay tuned and remember that droughts won’t last forever.

El Niño saves Florida from hurricane winds, but other severe weather could be costly this winter

The central and eastern Pacific experiences a lot of year-to-year variability in Sea Surface Temperatures (SST). Some years the water is much warmer (El Niño), and some years the water is much cooler (La Niña). The current phase of the El Niño/Southern Oscillation (ENSO) is approaching its peak warmth with near-record SST anomalies. This relatively predictable El Niño weather pattern should help the insurance industry prepare for weather patterns that could cause insured losses this winter.

Although the media often highlights the negative aspects of an El Niño weather pattern, there are many positives for the insurance industry: overall insurance loss data suggests that an El Niño weather pattern generally produces better financial results for the industry than a La Niña weather pattern.

Hurricanes, which are the largest cause of insured loss across the U.S., are a great example to show how El Niño has improved financial results. An El Niño weather pattern increases wind shear over the tropics, which significantly reduces the season’s Atlantic hurricane activity and therefore lowers the probability of a U.S. hurricane making landfall – ultimately leading to lower insured losses overall in El Niño years. However, as hurricane season ends and winter begins, El Niño may impact Florida weather, and consequently the insurance industry, in less financially favorable ways.

ElNino_Florida
Previous El Niño patterns suggest that the Gulf Coast will see cooler and wetter conditions this winter; not because of numerous arctic outbreaks, but because of the stronger influence of the subtropical jet stream. Storm tracks will then move farther south producing more clouds and rain. On the positive side, more precipitation reduces the risk of wildfires across region. On the negative side, these conditions can also lead to severe weather that includes hail and tornadoes.

Figure 1 shows a comparison of storm tracks during El Niño versus La Niña years.

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Figure 1. Winter storm tracks in El Niño versus La Niña years. (Source: NWS)

Figure 2 shows that the El Niño severe weather signal is most pronounced in central and south Florida and illustrates increased tornado reports from National Weather Service (NWS) local storm report data for the period, 1950-2014. El Niño years produce 77% more tornadoes than ENSO-neutral years and 53% more tornadoes than La Niña years. Further, it should be noted that Florida tornadoes typically occur in the evening hours which can increase fatalities.

FL_ENSO_Statistics

Figure 2. NWS severe weather local storm reports between November and March during Neutral, La Niña, and El Niño years for the period 1950 to 2014 in Central and South Florida (NWS Melbourne, Tampa and Miami Warning Areas).

Property Claims Services report that Florida insured wind and thunderstorm event losses vary drastically between El Niño and La Niña years: a whopping 152% difference between an El Niño year and La Niña year, and an even greater difference (188%) between an El Niño year and ENSO-neutral year. The higher loss levels are driven partly by specific large loss events that impacted Florida during El Niño years. The following tornado outbreaks are prime examples:

  • The 1998 February 22 – 23 “Kissimmee” outbreak continues to live in infamy as the deadliest tornado event in Florida history. In all, 12 tornadoes touched down across Central Florida. The strongest was rated EF3 and was one of the strongest tornadoes ever recorded in Florida.
  • The 2007 February 2 “Groundhog Day” outbreak was deadly and costly for Sumter, Volusia and Lake Counties and for the insurance industry: it caused over $100 million in insured losses and damaged or destroyed over 2,000 structure.

Tornadoes are highly correlated to the other perils that result from severe thunderstorms, and these other perils such as hail can result in high insured losses. In fact, one of the costliest severe weather events in Florida history was during the 1991-1992 El Niño winter which produced large hail storms that hit the Orlando metro area on March 25. Some locations reported hailstones the size of grapefruit; other locations reported that small hailstones piled up inches deep. At the time this event was the largest insured disaster in the state history; it even topped the notorious hurricane Donna in 1960. Unfortunately, the devastating hail storm was soon eclipsed when Andrew blew through southern Florida later that year.

Of course, global factors other than the ENSO cycle complicate seasonal forecasting. From soil moisture in the U.S. to winds way up in the stratosphere and early winter Eurasian snowpack, these other factors sometimes cancel each other out. However, as shown above, the data suggest that although Florida has not seen the wind blow as a result of a hurricane in over a decade, El Niño could cause the wind to blow from severe thunderstorms that ultimately lead to potentially higher-than-expected severe weather losses across the state.

50th Anniversary – Insurance Retrospective of May 6, 1965 MSP Tornadoes

50 years ago today, the upper Midwest was devastated by an outbreak of severe weather. A similar storm today would result in what might be one of the largest-ever severe thunderstorm losses to the insurance industry. For four consecutive days in May 1965, severe weather, including 37 significant tornadoes, of which at least nine were major tornadoes, affected much of the central United States. The most devastating part of the outbreak occurred when six tornadoes swept across the western and northern portions of Minneapolis/St. Paul. Of the six tornadoes that swept the seven-county region, four were rated F4, one was rated F3, and the other produced F2 damage.

ChanhassenTornado_Milligan

Shown is a photo of a tornado crossing to the west of the junction of highways 7 and 101 on May 6, 1965 (taken by Minnetonka resident. H. B. Milligan). It is believed that this was the tornado that touched down in Chanhassen at 6:27 p.m. and dissipated in Deephaven at 6:43 pm.

The outbreak was significant in several ways. First, it occurred just three weeks after the historic Palm Sunday tornado outbrea, which no doubt left local residents feeling a heightened sense of alarm about storms. Second, it was the first time in Minneapolis/St. Paul history that civil defense sirens, now used nation-wide, were used to warn people about severe weather. The U.S. Weather Bureau issued quick and successful warnings that were widely communicated by local radio and television stations. These significant new communication methods likely saved many lives, despite the fact that the storms killed 13 and injured 683. Finally, the tornadoes served as yet another example that helped dispel the myth that tornadoes won’t hit a city, a lake or a river.

Historical accounts have focused mostly on the tornadoes during the outbreak because of their remarkable pattern: at a single point in time three tornadoes were on the ground, and two tornadoes hit the same location just hours apart. Some of the hardest-hit cities included Chanhassen, Deephaven, Fridley, Mounds View and the Spring Lake Park suburbs, all of which have undergone tremendous growth since 1965. It is estimated that 600 homes were destroyed during the series of storms, and over a thousand more were damaged. Today, the affected suburbs have expanded from what was farmland 50 years ago, to what is now primarily residential.

The increased number of homes and the increased value of homes in Minneapolis/St. Paul suburbs also increase the potential for catastrophic damage from a similar future event. In some cities, the type of housing exposed to storm perils affects the potential loss severity. Two of the F4 tornadoes touched down in the west suburbs, and these suburbs have seen explosive growth since 1965. For example, one of the 1965 F4 tornadoes reportedly impacted 35 homes on Lotus Lake and 50 homes on Christmas Lake. This area now hosts many multi-million dollar lake homes. Home values in other nearby neighborhoods have grown significantly as well, including multi-million dollar homes that line the expansive shores of Lake Minnetonka. Fridley, Mounds View and Spring Lake Park were impacted by two F4 tornadoes that touched down just hours apart and crossed paths. Those cities may not include as many high-value homes, but the number of residential properties has grown, and now includes not only more residential properties, but high-value commercial properties as well. For example, one of the 1965 tornadoes tracked less than a mile from what is now the Medtronic world headquarters campus.

Despite the loss of life and property damage caused by the May, 1965 storms, it’s important to note that the historical data includes only limited reports of hail and damaging winds. These perils most likely also impacted the area 50 years ago, and arguably, including damage from these lesser-reported perils would increase the financial impact of the storms.

Although there are large uncertainties on exact track, width, and strength of all the tornadoes that occurred 50 years ago across the seven-county metro region, BMS Analytics digitized these historic tracks to create a deterministic scenario in an attempt to understand the potential impact of a similar storm today. The scenario suggests an insurance industry loss between $10 – $14 billion dollars. This is equivalent to a return period of 2,500 – 7,500 years according to various catastrophe models.

1965_TornadoTrack_Analysis

BMS Analytics digitized deterministic tornado scenarios with four perturbation to account for track uncertainty

Recently we have seen images of single tornadoes hitting cities like Tuscaloosa, AL; Joplin, MO; and Moore, OK and causing billions of dollars worth of insured damages ($6 Billion in total insured loss). Recalling the events of early May, 1965, is a reminder that several major tornadoes can hit a large metropolitan area such as Minneapolis/St. Paul on the same day. Although unlikely, a similar event would be extremely damaging due to the ongoing population and wealth growth described above. And if such an event occurred, it is likely a similar outbreak would have a large impact on the insurance industry.

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.