Tide heights on the river

Last week Martin Riddle suggested that the tides he observed at Franklin didn’t match predictions – that on the third of January high tide was at 6.55am rather than 7.35am. His explanation was that there might be a tidal bore. Here is a bit more fat to throw on this controversial fire.

Tide prediction graphs, such as those provided by WillyWeather, show a lovely smooth progression – see below for the days concerned.

The reality is much more ‘jiggly’. The best observations we have are the river heights at Huonville.

Helpfully the Met bureau also >>provides figures<<. Here they are for the period under discussion, with a couple of critical observations highlighted.

What this shows is that there was indeed an early ‘minor high’ at 6.13am, but later at 7.23am, and after a little dip, the tide rose even more at approximately the predicted time (who knows why there are duplicate observations at this point).

All of this to say that there was no need for Martin to get us out of bed to refloat Gretchen half an hour early.