Extra-tropical windstorm

Extra-tropical windstorm

European winter storms, nor'easters and derechos bring gusts that strip roofs, break cladding and bring down structures. The gust damages the asset and the site stops while it is repaired. The hazard prices both Property damage (% of asset value) and Business interruption (% of annual revenue). It is masked where tropical cyclones dominate, so the two risks do not price the same storm.

What the map shows

• Today: the 3-second gust for the 100-year storm, present climate (2005-2024), on a ~55 km grid. No risk-layers sheet exists yet for this layer.
• Projected: a second raster shows the measured change of the 50-year gust per scenario and horizon, as a ratio to 1995-2014. 2035 reads the 2021-2040 window, 2050 reads 2041-2060 and 2080 reads 2071-2090. The ratio is measured under SSP2-4.5 and SSP3-7.0; the low emissions setting reads SSP2-4.5 until an SSP1-2.6 run exists.

How the loss is computed

The engine reads the gust at the 10, 50, 100 and 200-year return periods at the site's point. The Welker et al. (2021) European windstorm curve turns the gust into a share of asset value lost, scaled by the site type's wind tier. Business interruption is a loss-of-use relation on the same loss ratio. Both are integrated over return periods into an annual loss. At a future horizon the whole gust curve is scaled by the measured change; a change inside the sampling-noise floor is held at zero. The hazard is tagged Proposal. See Damage functions: Extra-tropical windstorm and Climate risks.

Sources

• ERA5 hourly 10 m wind gust (Copernicus Climate Change Service, Hersbach et al. 2020), Gumbel return levels on block maxima, voided where the STORM v4 cyclone 50-year wind reaches 40 m/s. ERA5: CC BY 4.0. STORM v4: CC0 1.0.
• CMIP6 daily sfcWindmax (ESGF), median of 13 models: ACCESS-ESM1-5, CanESM5, FGOALS-g3, GFDL-ESM4, INM-CM4-8, INM-CM5-0, IPSL-CM6A-LR, KACE-1-0-G, MIROC6, MPI-ESM1-2-HR, MPI-ESM1-2-LR, MRI-ESM2-0, UKESM1-0-LL. CC BY 4.0.
• Damage curve: Welker et al. (2021), the Schwierz et al. (2010) European windstorm curve calibrated on reported building damages (CLIMADA).

Limits

• The curve is calibrated on residential buildings. The factors that scale it for other site types are a Darwin proposal.
• The gust curve stops at the 200-year storm and is held flat beyond, which under-reads the annual loss.
• The gust is resampled from a 0.5° grid, so a site reads its own ~55 km cell.