Why are tmp files generated when using tshark’s -w option?

I have a tshark process using the -b duration:[seconds], -b files:[numberoffiles], and -w [outputfile] options.

The process writes to the output files as expected

Unexpectedly, however, it continues to generate /tmp/ files.

I had thought that because the process is writing to an output file that the tmp file was not necessary.

Is tshark working as designed? Do I just need to create a local cron job to cleanup the /tmp/ directory?

For clarification, the version I'm running is part of wireshark-1.8.10-17.el6.x86_64 package.