"Graham Easterling" wrote Philip,
I think you've hit upon the major problem here, any classification is
likely
to be very subjective.
The largest sea, and the most damage to the Penzance/Newlyn/Mousehole
sea
defences for 40 years was done on 27th October 2004.
The depression itself was nothing really special, and if you lived 2
miles
inland you would have hardly noticed it. It was the track and speed of
movement of the depression, which generated a massive sea from an
unusual
direction, combined with an exceptionally high tide which created the
problem. SNIP

Isn't that the point: i.e. the *effects* (of unusually severe damage,
loss of life etc) are what really matter, rather than a simple comparison
of the "severity" of various events, in terms of windspeed, rainfall,
temperature etc.

Every year, locations at higher altitudes, even in the UK, experience
rainfall and windspeeds that would cause chaos and devastation in lowland
Britain (particularly further south!) but these are unnoticed by the rest
of us, because few, if any, live there, or those who do are used to them
and cope.

Although the press chose to sensationalise it, Mousehole was a case, was
it not, of a topography contributing to a major incident, with injudicious
development (over a very long period, I'll admit) in the narrow valley
exacerbating the effects. There was a large amount of rain in a short
period but when that amount of rain happens somewhere else, less prone to
flooding, not particularly inhabited or with buildings and roads away from
the valley floor, the most we say is that there were a few heavy and
persistent thunderstorms around that day.

Surely it's the severity combined with the unusualness of the event for
that area, coupled with (some might say, leading to) the vulnerability of
the population to that event that is the key, although how you work out
the classification for that is not something I'd like to tackle.

- Tom.