[syedhamidali]

Summary

Adds a shared NEXRAD Level 2 example case so downstream packages (radarx, and anyone else who wants it) can fetch it through open_radar_data instead of pulling from AWS when building docs or running CI.

The main case is the squall line seen by KGWX (Columbus AFB, MS) on 30 March 2022. It comes with a volume from the neighbouring KBMX (Birmingham, AL) radar for dual-Doppler examples, plus the Moore, OK tornado volume from KTLX.

File	Size	Source (s3://unidata-nexrad-level2/...)	Purpose
KGWX20220330_234639_V06	23.8 MB	2022/03/30/KGWX/	squall line, volume 1
KGWX20220330_235324_V06	23.5 MB	2022/03/30/KGWX/	squall line, volume 2
KGWX20220330_235959_V06	23.2 MB	2022/03/30/KGWX/	squall line, volume 3
KGWX20220331_000624_V06	23.2 MB	2022/03/31/KGWX/	squall line, volume 4
KBMX20220330_235713_V06	19.3 MB	2022/03/30/KBMX/	neighbour radar for dual-Doppler
KTLX20130520_201643_V06.gz	9.5 MB	2013/05/20/KTLX/	Moore tornado (azimuthal shear)

That is about 122 MB in total, and every file is below GitHub's 50 MB warning threshold. The four consecutive KGWX volumes cover about 20 minutes, which tracking, advection and multi-volume dealiasing examples need. If you'd rather keep the repository smaller, a minimal subset of two consecutive KGWX volumes (234639 and 235324) plus KBMX would still work for most examples. Let me know and I'll trim the PR.

File names are the original NOAA archive names, unchanged, as with the existing KATX/KLBB/KILX files. registry.txt was regenerated with python make_registry.py; the diff only adds the six new entries.

Data source and attribution

NOAA National Weather Service / NOAA NCEI NEXRAD Level II data, distributed through the NOAA Open Data Dissemination program (Unidata unidata-nexrad-level2 bucket on AWS). NOAA data are open and free to use without restriction.

Test plan

• Downloaded all six files through pooch from this branch's raw URL, using the updated registry.txt; all SHA256 checksums verified
• CI passes
• After merge, DATASETS.fetch('KGWX20220330_234639_V06') (and the others) works. A package release is needed so that the installed open_radar_data ships the updated registry.