1. © Crown copyright Met Office Hail Threat Standardisation Gennaro Cappelluti, Paul Field & Will Hand Atmospheric Processes & Parametrizations

2. © Crown copyright Met Office Hail Threat

3. © Crown copyright Met Office

4. kinetic energy diameter thickness

5. © Crown copyright Met Office Ice Water Path 12h 2004-8 AMSU-B NOAA15, 16, 17 89, 150, 183 GHz 830 km, 101 min, 16 km hail, graupel, snow, anvil ice, sea ice, desert sand

6. © Crown copyright Met Office Diurnal Cycle of Flash Density PDD photodiode detector FORTE satellite non imaging 1200 km WWLLN em energy sensors 28 stations world wide 5/28 stations

7. © Crown copyright Met Office Flash Density 12h Climatology NASA Global Hydrology and Climate Center

8. © Crown copyright Met Office Hail Water Path 12h 2004-8 HWP(s,t) = IWP(s,t) · H · FD(s,t) / FDmax(s)

9. © Crown copyright Met Office HWP Peak Hour 2004-8

10. © Crown copyright Met Office Convective Diagnosis Procedure

11. © Crown copyright Met Office USA Point hail climatology from NSSL according to day of year Hail days per year (1980-1999) from NSSL NSSL observations peak over Oklahoma (9 hail days per year) with almost no hail precipitation over the West; the CDP data show New Mexico and Arizona as the areas with the highest density of hail days (20 hail days per year). The NSSL point climatologies show a constant increase of hail days over the years, probably due to increasingly higher accuracy in the observations.

12. © Crown copyright Met Office Canada Mean annual hail day frequency in China 1961-2005 (Zhang et al., 2008). The 30 year hail climatology for Canada points out a peak of 5 hail days per year between May and September over the Rockies, while the CDP analysis highlights a peak of 8 hail days per year in the same period, the mean being 2.

13. © Crown copyright Met Office New South Wales Total number of hailstorms and hail days occurring in each month in NSW from 1791 to 2003. The solid line is the monthly average number of hailstorms and the dashed line is the monthly average number of hail days (Schuster et al, 2005). ma=538 me=70 ma=100 me=17 ma=43 me=2 ma=247 me=51

14. © Crown copyright Met Office Africa Mean annual frequency of hail over Africa (10 year record). max = 183 hail days / year

15. © Crown copyright Met Office Europe Preliminary climatology of large hail (> 2cm) over Europe showing average number of reports per year per 10000 km 2 in the period 2000-2007 (http://www.essl.org/research/). The CDP data show high densities of hail days over the Alps, Italy, Romania, ex Yugoslavia and Greece, while the ESSL over Germany and Romania, with lack of record over Italy and ex Yugoslavia. As the ESSL data are biased over Germany due to a very dense observing network prior to 2005, the CDP peak areas matches broadly the ESSL, over Romania and the Pyrenees. max = 22 hail days / year

16. © Crown copyright Met Office United Kingdom Monthly percentage distribution of hail storms with hail diameter greater than 1.5 cm over the British Isles in the period 1930-2004 (Webb et al., 2008). Number of hailstorms (per 1000 km 2 per 100 years) containing hail reaching or exceeding 1.5 cm diameter, for counties of England and Wales, 1930-2004 (Webb et al., 2008). Mean number of days of thunder in the British Isles (1971-2000). Key: black = 15–19 days, dark grey = 10–14 days, light grey = 5–9 days, white = under 5 days (Webb et al., 2008).

17. © Crown copyright Met Office HWP climatology Peak hour analysis Hail days climatology Local climatologies Aircraft material and dimensions Aircraft routes Summary