If this is a one off thing, you can run the Send Scheduled Mailings as a one off directly from the user interface from Administer >> System Settings >> Scheduled Jobs. Select More and then Execute Now against Send Scheduled Mailings.
I don't think that tinkering with the cron jobs to do this is a sensible way to do this, though it would work. Some environments (externally hosted) will not want cron jobs to run too frequently as it wastes resources. Personally, I would try and set the time for emails to fit the cron schedule.
I agree with Lars SG about the 11:48 entry. If you look back at the Log for the Send Scheduled Mailings job you will also see 09:48 (and I expect 10:48 at least depending on the frequency.