Looping another line through is a good option in most weather but you need to think about how you do it. The key is to prevent movement of the lines against each other. The easiest way to do this is to have the line that you are doubling through start and end on the same cleat. Often you see it start on one cleat and end on a different one on the other side of the bow. This does not work well since the lines will chafe against each other and it will allow the boat to "sail" on the mooring more. The best thing to do if you need to have a line from both side of the bow for whatever reason is to run a separate line from each side.
If you are going to be in storm conditions, you might consider reading the MIT study on mooring pendant failures (available online) and attach the way that they suggest.