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Hail: increasing risk, better forecasting

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Whether it will be a refreshing summer rain, a menacing thunder storm or a full-blown hailstorm – even the weather experts can only make an educated guess at what that particular cloud in the sky really has in store.

Allianz Re
Singapore, Oct 20, 2014

Allianz-stowasser_162x104 Dr Markus Stowasser

• Hail is the natural catastrophe number 1 for cars
• Agriculture is particularly susceptible
• Precautionary measures can limit hail risks

Whether it will be a refreshing summer rain, a menacing thunder storm or a full-blown hailstorm – even the weather experts can only make an educated guess at what that particular cloud in the sky really has in store. They do, however, agree that severe rain storms and the damage they cause are on the increase – particularly in regions that are already at risk. When looking back at the end of the summer, the newspapers will report on "results battered by hail" if the season was a severe one. Some precautionary measures can, however, help to minimize hail damage.

"It goes without saying that we are pleased about every natural catastrophe that does not happen," says Clement B. Booth, Member of the Board of Management at Allianz SE. "We are very interested in good preventative measures and provide our customers with corresponding advice. However, when a storm does happen, we are there for our customers - as an insurer,that's quite simply our job."

Hail forecasts not easy, but not impossible

Radar forecasts can provide hour-by-hour images of thunderstorm cells forming and can generate storm warnings. The strength of the radar signal depends on the volume and form of precipitation – strong signals suggest that hail is on its way.

"Hail usually comes hand-in-hand with a violent thunderstorm," says Dr. Markus Stowasser, meteorologist and climate expert at Allianz SE Reinsurance. "But even when using modern forecasting methods, hail forecasting still bears considerable uncertainties."

Paying attention to storm warnings can determine whether you are hit by a hailstorm “out of the blue” or whether you know at least a few hours beforehand that a hailstorm might, or might not, be on its way.

Hailstones measure at least 5 mm in diameter – smaller stones are sometimes called sleet or ice pellets..Hailstones with a diameter of 2.5 cm or more can leave small dents in the bodywork of cars, or damage in roof tiles or house facades. In extreme cases, hailstones can be the size of tennis balls, baseballs or grapefruits. Despite these comparisons, hailstones are not round and smooth, instead they have a rough crystal-like structure.

The main hail season in Germany, for example, is the summer: most hailstorms happen between May and September. They can also occur at other times of the year,  but these storms then tend to be less heavy.


Hail damage: damaged plants, dented cars, damage to facades and roofs

The most recent major hailstorms in Germany happened in Bavaria and North Rhine Westphalia in mid-June. The hailstones were the size of walnuts: the storms left thousands of damaged cars in their wake.

After severe storms, Allianz Germany sets up mobile claims stations in the affected areas to ensure that customer claims are settled as quickly and unbureaucratically as possible. Partial own damage insurance picks up the costs associated with repairing dented cars.

Hail is the weather occurrence that causes the most damage to cars. Fortunately, the damage for private customers tends to be relatively limited. The average hail damage caused to a car comes in at around 2000 euros. The situation is quite different in the corporate sector. If hail affects an entire new car storage yard, the damage for the auto manufacturer can be immense. The agricultural sector, too, can be hit hard depending on the time of year, especially if plants are still young and vulnerable or if entire greenhouses are damaged by hailstones. In Germany, Allianz pays out an average of around 140 million euros a year to its customers to compensate them for hail damage.

The risk of hail damage is rising

According to a study conducted by the Association of German Insurers (GDV) (Impact of climate change on the claims situation of the German insurance sector, 2011), hail damage to residential buildings could increase by as much as 50% by 2070.

There are various reasons for the increase in the number of claims caused by extreme weather. First, numerous studies prove the link between global warming and more extreme precipitation events. Second, the volume of insured assets is on the rise - especially in Asia, which is experiencing strong growth in population figures and prosperity levels. In addition, technical developments such as solar panels mounted on roofs or housing insulation can make residential buildings more susceptible to hail damage than they were in the past, meaning that smaller hailstones can cause more damage.

Hail can occur anywhere in the world. But there are certain regions that experience more severe, or more frequent storms: namely the US, central Europe, western China and the north of India. The climatic conditions that produce thunderstorms and hail are very similar in these regions: air rises up a mountain range, intensifying the updrafts required for hail to form. If very warm, damp masses of air form at the same time, this produces extreme weather events like tornados, thunderstorms or hail. In Germany, southern parts of Bavaria and Baden-Württemberg are hit particularly often. 

Severe hail events like the Munich hail storm of 1984 occur approximately every 150 years. Experts refer to this as "return periods". However, two similarly severe weather events can occur within a shorter space of time, as was the case with the two "century floods" in central Europe (2002, 2013).

Prevention can help to avoid hail damage

People who take prevention measures to protect their property on time can limit the potential damage. Individuals can park their car in the garage when they hear a storm warning. Farmers can cover particularly delicate plants or move equipment into a shed. Farmers or manufacturers in susceptible regions can also take preventative action by not growing certain types of plants, or planning enough roofed or indoor areas.

Online services like the "Allianz WeatherSafe App" allow people to access high-quality weather forecasts while on the go. The Allianz service is free of charge and is already available in many countries as an iPhone and Android App, as well as a mobile website. In addition to the weather forecasts, registered users receive storm warnings issued by the MeteoGroup for up to three locations, which they can define themselves. Warnings can be shared by e-mail, as well as via Facebook and Twitter. MeteoGroup is one of the world's most renowned radar-based weather services.


Expert tips on how to protect yourself and your property from hail:

  • Find out about hail storms and the hail period in your region. In Germany, for example, the thunderstorm season reaches its peak in July.
  • Car: Move your car to a covered area or into the garage as soon as thunderstorms or hail are forecast. If a hailstorm occurs while you are driving, definitely slow down.
  • Garden/patio: Move loose objects from your garden indoors, including sun shades, deck chairs or potted plants. Close any sun canopies.
  • House: Find out whether your blinds or shutters should remain open or be closed. Some tend to be more delicate than glass windows.
  • Take these precautions when you go on holiday, or even during the day during thunderstorm season.
  • As fascinating as thunderstorms are, you are well advised to watch them from indoors: if you cannot make it to the house, try to avoid being close to trees. Broken branches, or even the hailstones themselves, could hurt or injure you and of course, lightning is extremely dangerous.
  • After the storm: Check your house for any damage and report it to your insurance company.

Further information on hail damage:

“Safely parked”: Allianz Global Corporate & Specialty (AGCS) insures the transportation and storage of new cars. Together with auto manufacturers, a model has been developed to evaluate and reduce the associated risks. See pages 10-14 of the Global Risk Dialogue.

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