"Norman" wrote in
:

There was one that I can remember 20 or 30 years ago that got below
920 mb SW of Iceland. I think that one holds the record.

Stephen Burt has done some research in this field that was published
in 'Weather'

Oddly enough there was a thread on this a couple of days over 10 days ago -
well deepening rates anyway, but related to a certain extent:

http://www.weather-banter.co.uk/uk-s...-weather/9336-
extratropical-storms-record-deepening-rates.html

Richard