Category Archives: Windstorm

The Challenges Around Modeling European Windstorm Clustering for the (Re)insurance Industry

In December I wrote about Lothar and Daria, a cluster of windstorms that emphasized the significance of ‘location’ when assessing windstorm risk. This month we have the 25th anniversary of the most damaging cluster of European windstorms on record—Daria, Herta, Wiebke, and Vivan.

This cluster of storms highlighted the need for better understanding the potential impact of clustering for insurance industry.

At the time of the events the industry was poorly prepared to deal with the cluster of four extreme windstorms that struck in rapid succession over a very short timeframe. However, since then we have not seen such a clustering again of such significance, so how important is this phenomena really over the long term?

There has been plenty of discourse over what makes a cluster of storms significant, the definition of clustering and how clustering should be modeled in recent years.

Today the industry accepts the need to consider the impact of clustering on the risk, and assess its importance when making decisions on underwriting and capital management. However, identifying and modeling a simple process to describe cyclone clustering is still proving to be a challenge for the modeling community due to the complexity and variety of mechanisms that govern fronts and cyclones.

What is a cluster of storms?

Broadly, a cluster can be defined as a group of cyclones that occur close in time.

But the insurance industry is mostly concerned with severity of the storms. Thus, how do we define a severe cluster? Are we talking about severe storms, such as those in 1990 and 1999, which had very extended and strong wind footprints. Or is it storms like those in the winter 2013/2014 season, that were not extremely windy but instead very wet and generated flooding in the U.K.? There are actually multiple descriptions of storm clustering, in terms of storm severity or spatial hazard variability.

Without a clearly identified precedence of these features, defining a unique modeled view for clustering has been complicated and brings uncertainty in the modelled results. This issue also exists in other aspects of wind catastrophe modeling, but in the case of clustering, the limited amount of calibration data available makes the problem particularly challenging.

Moreover, the frequency of storms is impacted by climate variability and as a result there are different valid assumptions that could be applied for modeling, depending on the activity time frame replicated in the model. For example, the 1980s and 1990s were more active than the most recent decade. A model that is calibrated against an active period will produce higher losses than one calibrated against a period of lower activity.

Due to the underlying uncertainty in the model impact, the industry should be cautious of only assessing either a clustered or non-clustered view of risk until future research has demonstrated that one view of clustering is superior to others.

How does RMS help?

RMS offers clustering as an optional view that reflects well-defined and transparent assumptions. By having different views of risk model available to them, users can better deepen their understanding of how clustering will impact a particular book of business, and explore the impact of the uncertainty around this topic, helping them make more informed decisions.

This transparent approach to modeling is very important in the context of Solvency II and helping (re)insurers better understand their tail risk.

Right now there are still many unknowns surrounding clustering but ongoing investigation, both in academia and industry, will help modelers to better understand the clustering mechanisms and dynamics, and the impacts on model components to further reduce the prevalent uncertainty that surrounds windstorm hazard in Europe.

 

Lessons Hidden In A Quiet Windstorm Season

Wind gusts in excess of 100mph hit remote parts of Scotland earlier this month as a strong jet stream brought windstorms Elon and Felix to Europe. The storms are some of the strongest so far this winter; however, widespread severe damage is not expected because the winds struck mainly remote areas.

These storms are characteristic of what has largely been an unspectacular 2014/15 Europe windstorm season. In fact the most chaotic thing to cross the North Atlantic this winter and impact our shores has probably been the Black Friday sales.

This absence of a significantly damaging windstorm in Europe follows on from what was an active winter in 2013/14, but which contained no individual standout events. More detail of the characteristics of that season are outlined in RMS’ 2013-2014 Winter Storms in Europe report.

There’s a temptation to say there is nothing to learn from this year’s winter storm season. Look closer, however, and there are lessons that can help the industry prepare for more extreme seasons.

What have we learnt?

This season was unusual in that a series of wind, flood, and surge events accumulated to drive losses. This contrasts to previous seasons when losses have generally been dominated by a single peril—either a knockout windstorm or inland flood.

This combination of loss drivers poses a challenge for the (re)insurance industry, as it can be difficult to break out the source of claims and distinguish wind from flood losses, which can complicate claim payments, particularly if flood is excluded or sub-limited.

The clustering of heavy rainfall that led to persistent flooding put a focus on the terms and conditions of reinsurance contracts, in particular the hours clause: the time period over which losses can be counted as a single event.

The season also brought home the challenges of understanding loss correlation across perils, as well as the need to have high-resolution inland flood modeling tools. (Re)insurers need to understand flood risk consistently at a high resolution across Europe, while understanding loss correlation across river basins and the impact of flood specific financial terms, such as the hours clause.

Unremarkable as it was, the season has highlighted many challenges that the industry needs to be able to evaluate before the next “extreme” season comes our way.

Location, Location, Location: What Makes a Windstorm Memorable?

While wind speed can indicate a storm’s damageability, two storms with similar peak wind speeds can cause vastly different levels of damage if they pass over locations with different concentrations of exposure.

This month marks the 15th anniversary of Lothar and Martin. Two powerful storms that tracked violently across Europe on December 26-28, 1999.

The combined European loss of both storms is in excess of $11 billion (2013 values). Since the storms occurred within days of each other it’s difficult to calculate the exact split of damage, however a 70:30 ratio is commonly accepted, ranking Lothar as the second largest Europe windstorm loss on record after Daria (1990).

France was hit hardest by the stormsparticularly Paris, which was right in the bullseye of Lothar’s most extreme physical characteristics. The recorded wind speeds in the low-lying regions of Paris were above 160 km/h and as high as 200 km/h at the top of the Eiffel Tower.

An exceptional storm

While Lothar’s wind speeds are comparable to other historical Europe windstorms, it’s considered an exceptional event for the insurance industry because of its track and the timing of its maximum intensification over Paris. Today, Lothar is a key benchmark used by the industry to understand the potential magnitude of Europe windstorm losses.

Lothar – a one-off for France?

Many industry experts believe Lothar to be higher than a 100-year return period loss event for France; however this should be interpreted as a long-term average and France could potentially experience a similarly extreme storm this winter.

Using current industry exposures, RMS calculated the potential French losses that would result from a Lothar-like storm striking different locations in France. By relocating Lothar’s peak gusts along points up to 500 km in each direction from their original location, our modelers concluded that Lothar was the fourth worst-case storm that could have happened out of a total of 437 scenarios.

The worst-case scenario for France is a Lothar-like storm relocated approximately 100 km west of the original event but which would still significantly impact Paris. The losses from this scenario are not much higher than Lothar’s. At only 15 percent higher the small increase in loss reinforces Lothar as an exceptional benchmark for the insurance industry.

We found that the majority of scenarios in the study produced notably lower losses. This is because the displacement of the storm, by even small distances, meant that the most extreme wind speeds impacted much lower concentrations of insured exposures. The study reinforces our understanding of the sensitivity of windstorm loss to a storm’s path. It also highlights the importance of using a stochastic model containing tens of thousands of events to be able to comprehensively evaluate potential windstorm losses.

London at risk

No European city is immune from damaging windstorms. RMS also re-located Lothar over Londononly a 350 km shift to the northto see what the impacts would be. We calculated the insured loss for Europe could be as much as 25 percent higher than Lothar’s losses and potentially bigger than the $8.6 billion loss caused by Daria.

The uncertainty inherent to the climatic phenomena that drive windstorms makes it impossible to forecast exactly when and where the next strong storm will hit France or Europe. However, catastrophe models can at least help to evaluate the potential financial impact of extreme storms like Lothar.

What to expect this 2014-2015 Europe Winter Windstorm Season

When it rains in Sulawesi it blows a gale in Surrey, some 12,000 miles away? While these occurrences may sound distinct and uncorrelated, the wet weather in Indonesia is likely to have played some role in the persistent stormy weather experienced across northern Europe last winter.

Weather events are clearly connected in different parts of the world. The events of last winter are discussed in RMS’ 2013-2014 Winter Storms in Europe report, which provides an in-depth analysis of the main 2013-2014 winter storm events and why it is difficult to predict European windstorm hazard due to many factors, including the influence of distant climate anomalies from across the globe.

Can we predict seasonal windstorm activity during the 2014-2015 Europe winter windstorm season?

As we enter the 2014-2015 Europe winter windstorm season, (re)insurers are wondering what to expect.

Many consider current weather forecasting tools beyond a week to be as useful as the unique “weather forecasting stone” that I came across on a recent vacation.

I am not so cynical; while weather forecasting models may have missed storms in the past and the outputs of long-range forecasts still contain uncertainty, they have progressed significantly in recent years.

In addition, our understanding of climatic drivers that strongly influence our weather, such as the North Atlantic Oscillation (NAO), El Niño Southern Oscillation (ENSO), and the Quasi-Biennial Oscillation (QBO) is constantly improving. As we learn more about these phenomena, forecasts will improve, as will our ability to identify trends and likely outcomes.

What can we expect this season?

The Indian dipole is an oscillation in sea surface temperatures between the East and West Indian Ocean. It has trended positively since the beginning of the year to a neutral phase and is forecast to remain neutral into 2015. Indonesia is historically wet during a negative phase, so we are unlikely to observe the same pattern that was characteristic of winter 2013-2014.

Current forecasts indicate that we will observe a weak central El Niño this winter. Historically speaking this has led to colder winter temperatures over northern Europe, with a blocking system drawing cooler temperatures from the north and northeast.

The influence of ENSO on the jet stream is less well-defined but potentially indicates that storms will be steered along a more southerly track. Lastly, the QBO is currently in a strong easterly phase, which tends to weaken the polar vortex as well as westerlies over the Atlantic.

Big losses can occur during low-activity seasons

Climatic features like NAO, ENSO, and QBO are indicators of potential trends in activity. While they provide some insight, (re)insurers are unlikely to use them to inform their underwriting strategy.

And, knowing that a season may have low overall winter storm activity does not remove the risk of having a significant windstorm event. For example, Windstorm Klaus occurred during a period of low winter storm activity in 2009 and devastated large parts of southern Europe, causing $3.4 billion in insured losses.

Given this uncertainty around what could occur, catastrophe models remain the best tool available for the (re)insurance industry to evaluate risk and prepare for potential impacts. While they don’t aim to forecast exactly what will happen this winter, they help us understand potential worst-case scenarios, and inform appropriate strategies to manage the exposure.

Matching Modeled Loss Against Historic Loss in European Windstorm Data

To be Solvency II compliant, re/insurers must validate the models they use, which can include comparisons to historical loss experience. In working towards model validation, companies may find their experience of European windstorm hazard does not match the modeled loss. However, this seeming discrepancy does not necessarily mean something is wrong with the model or with the company’s loss data. The underlying timelines for each dataset may simply differ, which can have a significant influence for a variable peril like European windstorm.

Most re/insurers’ claims records only date back 10 to 20 years, whereas European windstorm models use much longer datasets – generally up to 50 years of the hazard. Looking over the short term, the last 15 years represented a relative lull in windstorm activity, particularly when compared to the more extreme events that occurred in the very active 1980s and 1990s.

Netherlands windstorm variability

RMS has updated its European windstorm model specifically to support Solvency II model validation. The enhanced RMS model includes the RMS reference view, which is based on the most up-to-date, long-term historical record, as well as a new shorter historical dataset that is based on the activity of the last 25 years.

By using the shorter-term view, re/insurers gain a deeper understanding of how historical variability can impact modeled losses. Re/insurers can also perform a like-for-like validation of the model against their loss experience, and develop confidence in the model’s core methodology and data. Alternate views of risk also support a deeper understanding of risk uncertainty, which enhances model validation and provides greater confidence in the models that are used for risk selection and portfolio management.

Beyond Solvency II validation, the model also empowers companies to explore the hazard variability, which is vitally important for a variable peril like European windstorm. If a catastrophe model and a company rely on different but equally valid assumptions, the model can present a different perspective to provide a more complete view of the risk.

Lessons Learned from Winter Windstorm Season in Europe

The 2013–2014 winter windstorm season in Europe will be remembered for being particularly active, bringing persistent unsettled weather to the region, and with it some exceptional meteorological features. The insurance industry will have much to learn from this winter.

Past extreme windstorms, such as Daria, Herta, Vivian, and Wiebke in 1990, each caused significant losses in Europe. In contrast, the individual storms of 2013–2014 caused relatively low levels of loss. While not extreme on a single-event basis, the accumulated activity and loss across the season was notable, primarily due to the specific characteristics of the jet stream.

A stronger-than-usual jet stream off the U.S. Eastern Seaboard was caused by very cold polar air over Canada and warmer-than-normal sea-surface temperatures in the sub-tropical West Atlantic and Caribbean Sea. Subsequently, this jet stream significantly weakened over the East Atlantic.

Therefore, the majority of systems were mature and wet when they reached Europe. These storms, while associated with steep pressure gradients, brought only moderate peak gust wind speeds onshore, mainly to the U.K. and Ireland. In contrast, the storms that hit Europe in 1990 were mostly still in their development phase under a strong jet stream as they passed over the continent.

The 2013––2014 storms were also very wet, and many parts of the U.K. experienced record-breaking rainfall resulting in significant inland flooding. Again, individual storms were not uniquely severe, but the impact was cumulative, especially as the soil progressively saturated.

Not all events this winter season weakened before impact. Windstorms Christian and Xaver were exceptions, only becoming mature storms after crossing the British Isles into the North Sea and were more damaging.

Christian impacted Germany, Denmark, and Sweden with strong winds. RMS engineers visited the region and observed that the majority of building damage was dominated by the usual tile uplift along the edges of the buildings. Fallen trees were observed, but in most cases, there was sufficient clearance to prevent them from causing building damage.

Xaver brought a significant storm surge to northern Europe, although coastal defenses mostly withstood the storm. Xaver, as well as some of this year’s other events, demonstrated the importance of understanding tides when assessing surge hazard as many events coincided with some of the highest tides of the year. The size of a storm-induced surge is much smaller than the local tidal range; consequently, if these events had occurred a few days earlier or later, the astronomical tide would have been reduced, significantly reducing the high water level.

Windstorm3

Wind, flood, and coastal surge are three components of this variable peril that can make the difference between unsettled and extreme weather. This highlights the importance of modeling the complete life cycle of windstorms, the background climate, and antecedent conditions to fully understand the potential hazard.

This season has also raised questions about the variability of windstorm activity in Europe, how much we understand this variability, and what we can do to better understand it in the future. While this winter season was active, we have been in a lull of storm activity for about 20 years.

Given the uncertainty that surrounds our ability to predict the future of this damaging peril, perhaps for now we are best positioned to learn lessons from the past. This past winter provided a unique opportunity, compared to the more extreme events that have dominated the recent historical record.

RMS has prepared a detailed report on the 2013–2014 Europe windstorm season, which analyzes the events that occurred and their insurance and modeling considerations. To access the full report, visit RMS publications.

When Did Windstorms Become So Wet?

Looking back to the start of the European windstorm season, my colleague Brian Owens pondered whether the insurance industry would experience a windfall or windy fall? Well, a week into February, I think all observers would agree that this has been a very active season.

As the industry continues to count the cost of the succession of systems that have assaulted our shores, it is apparent that the accumulated losses over the season will make this a year from which much can be learned.

The storms impacting northern Europe have frequently brought damaging winds to coastal areas, occasionally exceeding 90mph in the most exposed areas.

However, the driving jet stream has typically been very strong to the west but tapered off in the northeast Atlantic. This has caused systems to explosively deepen and mature before they reached the U.K. and Ireland, but then decay as they approached these shores. Consequently, the long storm paths have prompted higher waves and storm surges, but the latter decay, even for extremely deep cyclones, has meant less damaging winds. This has thus far spared Atlantic-facing countries from extreme wind losses.

But as the season has developed, the main story hasn’t been storm gusts. Anyone living in or visiting the U.K. this winter can testify that it has been exceedingly wet. Not just from excessive rainfall, but from repeated coastal inundations from storm surges combined with high tides as well. Consequently inland and coastal flooding has been significant, dominating our attention.

"UK

The persistent rainfall since December has caused river catchments such as the River Severn and Somerset Levels to swell, particularly across southern England and Wales. Groundwater reservoirs and soils are also saturated, leading to pluvial and groundwater flooding.

However, perhaps most interesting this season has been the surge-driven coastal flooding. Storm surges occur when strong winds force the underlying water toward the coast. As the surge develops, water levels are influenced by the shape of the coastline and tidal interactions, both of which can act to amplify surge heights and resulting coastal flooding.

While property damage has not yet reached the scale of prior major flood incidents in the U.K., this series of events highlights the importance of evaluating the complete flood cycle, from the initiating precipitation and antecedent conditions to the final mode of flooding, as seen during the 2012 U.K. flooding.

With tidal ranges as large as 15 m in the U.K., the timing of the surge is vital for determining the scale of the hazard. Surges that impact a region at high (spring) tide pose the most risk for flooding. The storms impacting northern Europe this winter have consistently coincided with some of the highest tides of the year.

Level of surge (green), relative to actual (blue) and predicted (red) storm-tide

Level of surge (green), relative to actual (blue) and predicted (red) storm-tide

Beginning with Windstorm Xaver in December, the U.K. east coast and coastal locations in Germany were given their sternest test since the devastating 1953 and 1962 events. Fortunately coastal defenses have been improved since those historical floods and the subsequent flooding was not significant.

Numerous systems have continued to arrive through January, with southeast England and Wales, Ireland and northern France particularly affected. As recently as last week, Windstorms Petra and Ruth brought yet more coastal damage and flooding, and the risk of more flooding remains high this week.

As with the wind and inland flood impacts of each individual storm, the coastal damage may not be viewed significant in isolation. Consequently specific storms from this season may not stick in the memory, like 87J has. But the accumulating damage and cost of this continuous series of events has made this a season to remember.

It has also posed a question around how we as an industry evaluate our wind and flood risk. Do we evaluate these perils in isolation or do we consider the correlation these perils have in winter months. A question that may become more prominent as the future of flood insurance in the U.K. evolves.

How Does Southern Europe Weather the Storm?

The 2013-14 European winter storm season has been pretty active so far. Early in the season, Windstorm Christian raced across northern Europe, followed by Xaver in early December, and then storms Dirk, Erich, Felix and Anne hit the U.K., Ireland, and northwest France over the Christmas and New Year period.

To date the season has been a great demonstration of how northern Europe is a common target for winter storms. However, this week sees the 5th anniversary of Windstorm Klaus, reminding us that storms can also impact southern Europe, affecting regions not acclimatized to extreme winds and causing severe damage.

What happened when Klaus hit and what have we learned from it?

Can such a storm occur again in the near future and more importantly, can we predict it, or at least estimate how bad it could be?

Windstorm Klaus sprung to life on January 23, 2009 in the central Atlantic, directly in line with southern France. The climate backdrop to this storm was pretty uncharacteristic. The large-scale Icelandic low-pressure system and the Azores high-pressure system were farther south than usual. Also, the North Atlantic Oscillation (NAO) was entering a negative phase.

A positive phase of the NAO creates favorable conditions for strong storms to pass over northern Europe, as Lothar and Anatol did in 1999. But a neutral or negative phase of the NAO can lead to storms that affect southern Europe and this is exactly what happened with Windstorm Klaus.

By midnight on January 24, as Klaus approached land, it had a central pressure of 963 hPa, comparable to Windstorm Lothar. Winds reached severe gale force in the southwest of France, peaking with gusts above 140 km/h at coastal locations near Bordeaux, accompanied by violent seas with wave heights of several meters. Local infrastructure was severely disrupted by fallen trees and electricity pylons.

Over 1.7 million households were without power immediately after the storm and over 60% of maritime pines in the Forêt des Landes were destroyed. Once the damage had been appraised, Klaus was estimated to have caused insured losses of €2.5billion (US$3.4 billion).

Shortly after the event, RMS scientists Dr. Navin Peiris and Dr. Christos Mitas conducted a reconnaissance survey, which helped to enhance our understanding of building vulnerability in this region. They observed frequent non-structural wind damage, such as the uplifting of roof tiles and collapsed chimneys, but also direct wind damages from tree fall, due to the high density of trees in close proximity to properties.

Source: RMS 2009 reconnaissance

Closer examination of the roof damage revealed little evidence of proper fixation, particularly along roof edges, leaving them more vulnerable to wind damage. Another observation was the use of canal-type tiles, which are prone to uplift from the build up of air pressure, caused by strong winds. Also, damage was more frequent in residential properties, compared to commercial or industrial buildings that are generally engineered in line with building codes.

This survey, combined with an assessment of claims data, provided us with an enhanced understanding of regional vulnerability differences. For example, we observed a significantly lower fragility of buildings in the Perpignan area compared to the southwest of France.

Ratio of the modeled and observed losses by postcode using non-regionalized vulnerability functions. Variation supports need for distinct vulnerability regions.

Ratio of the modeled and observed losses by postcode using non-regionalized vulnerability functions. Variation supports need for distinct vulnerability regions.

This information is vital for us to continually develop and inform our models, in order to represent the risk accurately. Due to the inherent uncertainty in the climatic phenomena driving windstorms, it is not possible to forecast exactly when the next strong storm will hit southern Europe. Catastrophe models provide a range of possible events, which can help the insurance industry prepare for the next big event.

The RMS Europe Windstorm Model contains storms comparable to Klaus, including some that impart larger wind intensities and damages. The below image compares two examples of stochastic storms with the actual Klaus wind footprint to illustrate storms that could potentially cause insured losses similar to or higher than Klaus.

Klaus and Stochastics

Currently we are in a close to neutral phase of the NAO, so does that mean a Klaus type storm could occur this winter? No one can answer that question for certain, but a model at least enables us to explore the possible worst-case scenarios and be prepared.

2013/2014 Winter Storm Season in Europe

This winter storm season has seen the most severe sequence of storms since 1990.

Another windstorm to affect the U.K., Windstorm Christina, brought heavy rain, strong winds, and large waves to coastal regions of the U.K. causing further flooding on Monday, January 7. More than 300 properties have flooded to date as a result of Windstorm Christina in England and Wales. The worst affected areas appear to be the coastlines of South England and Wales.

In England, sea defenses were breached at Chesil Beach in Portland, Dorset, as a result of high waves, causing evacuations. Flooding has also affected properties in parts of the Somerset Levels, leaving some villages cut off, with roads and buildings damaged. In Salisbury, Wiltshire, residents were also asked to leave their homes.

Since the peak of the 2013/2014 winter storm season started in December, Northern Europe has been bombarded by 17 low-pressure systems. These weather systems have swept in off the North Atlantic and brought strong wind gusts in excess of 90 mph in remote locations and gusts over 70 mph over large parts of the U.K.

Extreme rainfall levels have been observed across the country, particularly in Scotland where one location observed 73.6 mm of rain on Christmas Eve. The significant precipitation contributed to December seeing 154% of the U.K. historical average rainfall for that month and in Scotland it was the wettest December since records began in 1910.

This extreme rainfall has left the ground saturated, with groundwater levels in some regions much higher than usual for this time of year, heightening the risk of flooding should the persistent rainfall continue.

At the start of December 2013, windstorm Xaver raced across northern Europe bringing strong winds and coastal flooding to the east of the U.K., northern Germany and the Netherlands. Flood damage was mitigated by improved coastal defenses, which had been upgraded following the devastating 1953 (U.K. & Netherlands) and 1962 (Hamburg, Germany) floods.

Over the Christmas and New Year period, storms Dirk, Erich and Felix brought more strong winds and precipitation, particularly to the U.K., Ireland and northern France. While the winds from these storms caused only moderate damage and disruption to power and transport networks, persistent precipitation was and remains a significant concern for flooding.

The succession of large and intense low pressure weather systems has been a function of a very strong and stable jet stream, fed by the strong contrast between the warm tropical Atlantic air masses and intensely cold Arctic air over North America.

Although this sequence cannot be directly linked with climate change – the coastal flooding will be more common in the future, while winter rainfall totals are expected to rise.

A number of towns along the west coast of England and Wales are relatively unprotected from sea flooding, and consideration will now need to be given to how they can be defended. As sea level rises it will become increasingly and prohibitively expensive to protect all these communities.

A Tale of Two Storms

“Horror and confusion seized upon all, whether on shore or at sea: no pen can describe it; no tongue can express it; no thought conceive it…”

Those were the words of Daniel Defoe in “The Storm”, which he published the year following the great 1703 windstorm, an event that saw it’s 310th anniversary on December 7. This event truly was a great storm, estimated to be one of the strongest windstorms to impact the UK.

RMS performed an innovative footprint reconstruction and estimates that wind speeds up to 110 mph were experienced across an area the size of greater London. These speeds are 30-40 mph stronger than those brought to the UK recently by windstorm Christian and are comparable to a category 2 hurricane. Such speeds can cause considerable damage, particularly to inadequately designed and constructed properties.

January also sees the 175th anniversary of the Irish “Oiche na Gaoithe Moire”; which is “The Night of the Big Wind” for those who don’t speak Gaelic.

Reports of the precise meteorological characteristics of this storm are unclear, but analyses of the event estimate that wind gusts in excess of 115 mph occurred and maximum mean wind speeds could have reached 80 mph. At the time it was considered the greatest storm in living memory to hit Ireland and its intensity may not have been rivaled since.

However, other than an interesting history lesson, is there anything valuable to note from these events from an insurance industry perspective?

Both events were severe European windstorms, causing significant widespread damage, but both would also be significant today.

Hubert Lamb’s unique study analyzing historic European windstorms over a period of 500 years places these events in the top grade of severity, at number 4 and 6 in his severity index and RMS estimates that a reoccurrence of the 1703 storm would cause an insured loss in excess of £10B ($16B).

A feature of both events at the time was the extensive and widespread damage to roofs. The 1703 event left tiles and slates littering the streets of London and the 1839 event caused parts of Dublin to look like a “sacked city”.

Roof damage was in part due to poor construction, lack of maintenance and inadequate design for the wind speeds experienced. This is a significant consideration today. Across Europe, design codes in relation to wind damage vary significantly and are a key source of uncertainty when modeling wind vulnerability.

Similar risks and construction types can perform quite differently comparing the north and south of the UK or Ireland. Properties further north experience higher wind speeds more frequently and are generally better prepared. Historically adopted construction practices and older buildings that pre-date many of the building codes and design guidance existing today further complicate the issue.

Another feature of both events were the extents of severe damage, which led to inflated repair costs due to the demand for materials and labor. These were early examples of what we now refer to as post-event loss amplification (PLA). From an insurance perspective we consider inflated “economic” costs (i.e. temporary shortage of material and labor) and also inflation of claims due to relaxed claims processing procedures after an event.

While events today exhibit different forms of PLA compared to historical events, it is clear that PLA has potentially always been an issue after large events, so we need to continue studying this phenomenon, to understand possible future costs. For example, many companies now establish mitigating measures, such as pre-event contracts, guaranteeing services, should an event occur.

For 300 years we have observed common factors across windstorms in Europe and there are lessons to learn from each event. However, the key to being prepared in the future is to:

  • Monitor changing trends
  • Maintain an accurate and up-to-date representation of exposure at risk
  • Understand how losses behave when events occur