One thing I like doing is using my metric knowledge to go where few choose to travel. For example one megagram (Mg) is equal to 1.1 english short tonne (or one metric ton) and since the aforementioned cloud was calculated at weighing 550 tonnes, it would weigh one half of one gigagram (Gg). I am guessing that people who actually would have a reason to use these measure are likely to lapse into scientific notation around this point. I also suspect that the 550 tonnes estimate was originally done in metric (and is a round number in it) and then converted to english.
weights n measures