Krusty
Well-Known Member
There seem to be generally accepted guidelines that a fall of 5mb in three hours indicates probability of a gale, and change of 8mb in three hours makes it almost a certainty.
On the 27th August last, we heard a warning of gale-force winds on the passage of a trough over Scotland, with Southerly winds veering Northerly.
With a falling barometer, I chose to move to land-locked L. Drombuie and anchor close south of Oronsay I. to set out V-twin riding sail and have a relatively peaceful night.
We were awakened around midnight by the riding sail suddenly drumming like never before, and with increasing volume. Sheering was no more than ten degrees (it never is with that sail set) but the boat began to pitch: over the next hour it all worked up to quite a racket of wind, sail and plunging into the head sea, to the acute discomfort of the non-sleeper in the forecabin, although the windward shore was only 2 to 3 cables away.
By 0600 it was quiet in the anchorage, but blowing F6 outside.
We have an ageing but reliable 'Weathertrend' digital recording barometer which has always matched the old aneroid unless hot sunshine has settled on its place on the bulkhead. It updates every couple of minutes, and will display readings for the previous 24 hours.
Scrolling back to the overnight readings, I found the pressure had fallen 8mb in two hours, and risen 13mb in the next three hours!
Just how extraordinary is this?
On the 27th August last, we heard a warning of gale-force winds on the passage of a trough over Scotland, with Southerly winds veering Northerly.
With a falling barometer, I chose to move to land-locked L. Drombuie and anchor close south of Oronsay I. to set out V-twin riding sail and have a relatively peaceful night.
We were awakened around midnight by the riding sail suddenly drumming like never before, and with increasing volume. Sheering was no more than ten degrees (it never is with that sail set) but the boat began to pitch: over the next hour it all worked up to quite a racket of wind, sail and plunging into the head sea, to the acute discomfort of the non-sleeper in the forecabin, although the windward shore was only 2 to 3 cables away.
By 0600 it was quiet in the anchorage, but blowing F6 outside.
We have an ageing but reliable 'Weathertrend' digital recording barometer which has always matched the old aneroid unless hot sunshine has settled on its place on the bulkhead. It updates every couple of minutes, and will display readings for the previous 24 hours.
Scrolling back to the overnight readings, I found the pressure had fallen 8mb in two hours, and risen 13mb in the next three hours!
Just how extraordinary is this?
