Traceback error using `Level2File` opening a start L2 radar chunk file

[nevets963]

What went wrong?

I get a traceback error when trying to opening the start file of a L2 chunk of a volume for specific radar towers: KJKL, KCCX, KMBX, KDDC, KTYX and potentially others too.

Most towers work fine and I'm not familiar enough with the msg formats to know why/how these sites are different.

Operating System

Linux

Version

1.6.1

Python Version

3.10.13

Code to Reproduce

# Download: https://unidata-nexrad-level2-chunks.s3.amazonaws.com/KJKL/160/20240227-102059-001-S

from metpy.io import Level2File
l2file = Level2File("20240227-102059-001-S")

Errors, Traceback, and Logs

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/opt/conda/lib/python3.10/site-packages/metpy/io/nexrad.py", line 193, in __init__
    self._read_data()
  File "/opt/conda/lib/python3.10/site-packages/metpy/io/nexrad.py", line 255, in _read_data
    getattr(self, decoder)(msg_hdr)
  File "/opt/conda/lib/python3.10/site-packages/metpy/io/nexrad.py", line 551, in _decode_msg18
    els.append(self.vcp_el_fmt.unpack_from(dat, off))
  File "/opt/conda/lib/python3.10/site-packages/metpy/io/_tools.py", line 97, in unpack_from
    return self._create(super().unpack_from(buff, offset))
struct.error: unpack_from requires a buffer of at least 1218 bytes for unpacking 46 bytes at offset 1172 (actual buffer size is 1172)

[dopplershift]

Looks like some metadata bytes we were parsing at some point got converted to spares, which is fine...except when those "spares" contain seemingly random bytes that break the parsing.

Thanks for reporting. Fixed in #3415.