Hail radar products
Here you'll find general information about the Swiss weather radar network.
The C-band, Swiss weather radar network is able to provide information about the precipitation type, thanks to its dual-polarization capabilities.
The Probability of Hail (POH) product
The grid-based POH (Probability Of Hail) product estimates the probability of hail of any size at the ground, based on the heuristic method of Waldvogel. The probability of hail is computed from the difference between the maximum height at which a reflectivity of 45 dBZ is observed (45 dBZ Echo Top altitude) and the height of the freezing level. When the height difference is larger than 1.6 km, a positive indication of hail exists. The probability of hail increases with the height difference. A 100 % probability is obtained for a height difference of 6 km. The height of the freezing level is extract-ed from the NWP model. The nearest forecast based on the most recent analysis is used for this purpose.
The Maximum Expected Severe Hail Size (MESHS)
The grid-based MESHS (Maximum Expected Severe Hail Size) product estimates the maximum expected size of severe hail (> 2cm), based on a heuristic method developed by Treloar. The expected hail size is computed using the difference between the altitude of the maximum height at which a reflectivity of 50 dBZ is observed (50 dBZ Echo Top altitude) and the height of the freezing level. Hail sizes less than 2 cm are not shown. The height of the freezing level is extracted from the NWP model. The nearest forecast based on the most recent analysis is used for this purpose.
Please be aware that Hail products (POH and MESHS) are only calculated between 1 April and 30 September each year. If there are files published outside this date range, they will be empty.
Data download
The Open Data from MeteoSwiss may be used without restriction; the source must be cited when reproducing or redistributing ("Source: MeteoSwiss").
✅ By using 'Open Data' from MeteoSchweiz, you confirm that you have taken note of the Terms of use.
Download files per parameter automatically via FSDI's REST API: https://data.geo.admin.ch/api/stac/v1/collections/ch.meteoschweiz.ogd-radar-hail
The STAC Browser can be a useful tool to facilitate the use of the API: https://data.geo.admin.ch/browser/index.html#/collections/ch.meteoschweiz.ogd-radar-hail
In the STAC Browser, click on the 'Next' button under 'Items' to find data from the previous few days.
Please note that the STAC item for the following day has already been created. From midnight onwards (between 1 April and 30 September), this item will continuously fill with files ('Assets').
Archive data is available on request. Please contact us via our contact form.
Data structure
The data is split by parameter, calendar date (see STAC 'items' respectively 'features') and time resolution. It is provided via a rolling time window covering the last 14 days.
The available parameters are:
| Parameter | Time resolution; Update frequency | Filename format |
|---|---|---|
| POH | 5 minutes | BZCyyjjjHHMM\*.\*01.h5 |
| MESHS | 5 minutes | MZCyyjjjHHMM\*.\*01.h5 |
All timestamps are the respective 5-minute values, except for:
- BZCyyjjj2400vl.845.h5 is the 24-hour sum (between 00:00 and 24:00 UTC) and
- BZCyyjjj3000vl.845.h5 is the 24-hour sum (between 06:00 and 06:00 UTC) and
- MZCyyjjj2400vl.850.h5 is the 24-hour sum (between 00:00 and 24:00 UTC)
- MZCyyjjj3000vl.850.h5 is the 24-hour sum (between 06:00 and 06:00 UTC).
Naming convention of the files:
For POH: BZCyyjjjHHMMKK.XYZ.h5
BZC= product codeyy= two last digit of the yearjjj= Gregorian day of product creation (1-366)HHMM= product time (UTC)KK= (reserved)XYZ= x01 (reserved)
For MESHS: MZCyyjjjHHMMKK.XYZ.h5
MZC= product codeyy= two last digit of the yearjjj= Gregorian day of product creation (1-366)HHMM= time of product creation (UTC)KK= (reserved)XYZ= x01 (reserved)
Data format
The data is provided in the ODIM HDF5 standard format, described here with an estimated volume of less than 1 MB per file.
Please note, that for the processing of HDF5 files, specialised software packages may be needed.
The coordinate system is Swiss LV95 / EPSG:2056.
Metadata
The metadata is included in each HDF5-File.
| Parameter | Long Name | Standard Unit | Temporal Aggregation |
|---|---|---|---|
| POH | Probability of Hail | % | 5 minutes |
| MESHS | Maximum Expected Severe Hail Size | mm | 5 minutes |