You can put together a script.
As an example combining this:
http://forum.mikrotik.com/t/voltage-monitoring-in-ros-v-7-and-send-message-to-telegram/168752/1
with this:
http://forum.mikrotik.com/t/script-output-to-a-file/160856/1
Or - way easier if you are not into scripting, try splunk:
http://forum.mikrotik.com/t/tool-using-splunk-to-analyse-mikrotik-logs-4-0-graphing-everything/153043/1
you can have something like:
https://forum.mikrotik.com/download/file.php?id=49435