This page describes changes made to the Tropical Cyclone Track BUFR files, to accommodate also wind radii forecasts. Guidelines for testing are available below. We encourage users of the tropical cyclone tracks (BUFR data) to test their decoding software .
Users will need ECMWF ecCodes version 2.16.0 or above to decode the new Tropical Cyclone tracks. Those users using BUFRDC will need to download and install the BUFR tables version 33. ECMWF is unable to advise on the usage of third party software, other then that WMO BUFR tables version 33 are needed.
Changes compared to existing Tropical Cyclone tracks
New radii for Tropical Cyclones wind speeds exceeding thresholds and defined per quadrant have been added. See hereafter the additional data descriptors included in the BUFR messages:
|19003||wind speed threshold||windSpeedThreshold||m/s||3 thresholds: 18, 26 and 33 m/s ( 34, 50 and 64 knots)|
|5021||bearing/azimuth||bearingOrAzimuth||deg||Two values to define the quadrant limits, e.g. 0 and 90 for quadrant 1|
|19004||maximum radius at which wind speeds exceed the given threshold within the given quadrant||effectiveRadiusWithRespectToWindSpeedsAboveThreshold||m|
We have taken this opportunity to correct in the new Tropical Cyclone tracks some inconsistent information present in the existing tracks:
- The update sequence number (ecCodes key updateSequenceNumber) is set to 0 (instead of 1).
- The year in BUFR header section 1 (ecCodes key typicalYear) is given using 4 digits, e.g. '2020' (instead of 2, e.g. '20'q)
- ecCodes key internationalDataSubCategory (BUFRDC section 1 element named DATA SUB-CATEGORY) for HRES is set to 255 (instead of 0) as a missing value. For the ENS remains as set to 0.
- The meteorological attribute significance (ecCodes key meteorologicalAttributeSignificance, data descriptor 8005) is set to 5, instead of 4, for ENS members 51 and 52 (the ENS Control FC and HRES FC). See also WMO=33 code-flag table#CF_008005.
Sample Tropical Cyclones BUFR data
Sample Tropical Cyclone tracks data in BUFR format are available for Tropical Cyclone HEROLD for at 12UTC, for HRES and ENS.
|Tropical Cyclone Track without wind radii||Tropical Cyclone Track with additional wind radii data|
Both Tropical Cyclone track files with and without wind radii use the same IFS input data. Users should be able to run their existing Tropical Cyclones decoder programs 'as they are' on the tracks data without wind radii. These files should be used as reference. Users have to make sure that their programs run with the tracks with additional wind radii. You may need to make changes to your programs, even if you don't currently plan to use the wind radii.
Testing your Tropical Cyclones decoding software
We recommend users to test their decoding software with the above mentioned sample data, even you do not plan to use the additional radii data included with Tropical Cyclones tracks. ecCodes versions 2.16.0 and above and BUFRDC with WMO tables version 33 have been tested at ECMWF and do work correctly. As the sequence of data descriptors (ecCodes key unexpandedDescriptors) is different in the new Tropical Cyclone tracks, the decoder programs previously used may need to be adapted.
If you don't use a recent version (2.16.0 or newer), you will see an error message like:
You will then need to download, install and use a newer version of ecCodes
If you use BUFRDC and don't have the WMO BUFR tables version 33 installed, you will see an error message like:
You will then need to download, install and use the WMO BUFR tables version 33. You can point BUFRDC to a different version of the BUFR tables by setting the environmental variable BUFR_TABLES, e.g.:
where <dir>/bufrdc_tables_wmo_v33/ is the directory containing the BUFR tables.
The ecCodes HOME page includes (Fortran, C and python) examples to decode BUFR messages as well as a command line tool to generate sample source code/scripts to decode any BUFR message.
The BUFRDC HOME page includes the necessary WMO BUFR tables and the BUFRDC user and reference manuals. Note that we do not release new versions of the BUFRDC software any longer. We advise users to migrate their BUFRDC codes to ecCodes.
More information on the computation and explanation of the wind radii will be made available separately.