I was more or less brought up to understand the metric system of measurement, I understand that the imperial system means that around 28" = 10000 megadoodahs.
Currently reading the 1st World War diaries of a Midshipman on one of the RN ships. (Good book by the way) he makes mention of a particular storm where the barometer reading was 280 inches - wonder whether this is an error either in reporting or transcription or have I missed another recording system ?
Last edited by: R.P. on Wed 21 Sep 11 at 14:57
|
As ever, Wikipedia
"Highest air pressure ever recorded: 1085.6 mb (32.06 inHg); Tosontsengel, Khövsgöl Province, Mongolia, December 19, 2001."
Think your Midshipman lost a decimal point
|
|
Lowest air pressure ever recorded was 882. Standard sea level pressure is 1013 mb and this is 29.9 ins of mercury. so 28.0 with the decimal point in the right place would be a very low pressure.
|
I hope he wasn't the sailor responsible for making sure the ship didn't run aground.
"Keep going, captain, we're still in 20 fathoms,"- crunch!
|
|
He died a few months later on HMS Invincible in the Battle of Jutland - so I doubt it.
|
|
It's 948 mbar (or hPa as the meteos prefer it!) - which is pretty low at sea level. My parents have sticker on their barometer at 28.4" (IIRC) from 16th Oct 1987 - in the centre of the Isle of Wight. I have a picture of my weather station showing 929 mbar - but then we are c200m ASL so that equates to about 950 at seal level.
|
>>I have a picture of my weather station showing 929 mbar - but then we are c200m ASL so that equates to about 950 at seal level.
But isn't it conventional to refer to pressures at the sea level equivalent anyway, so you calibrate your barometer accordingly? I have one of these weather stations (I tell the time by it) but now and agian I look up the pressure at Luton airport and set it to that, even though we aren't at the same height. So your 929 should be correct unless you calibrated at sea level. Uncalibrated it means nothing.
|
Often within a particular trade or profession decimal points are ignored for ease and clarity. I'm wondering whether maybe it was conventional to refer to pressures as two-eighty. two nine five, etc, ?
Garages called tyre sizes six seventy, seven fifty, etc rather than 6.70 or 7.50. The units were inches, but with an understood multiple.
"Base points" on international bond markets do something similar.
Rev counters do the opposite, and lose unnecessary zeros, 1000, 2000, 3000, 4000 rpm become 10, 20, 30, 40.
Food packets refer to Calories although strictly speaking they are Kilocalories.
I suspect the midshipman might have been following conventional useage at the time.
|
|
That sounds quite logical and sensible - cracking book as well...
|
Not sure I follow your rationale Manatee, or perhaps I do.
Luton airport is at around 520feet which will obviously afferct the local pressure. The aviators use two settings around landing and take off. The first, QNH is referenced to sea level (the altimeter reads 520feet on the apron) and QFE which is related to airfield elevation (the altimeter shows zero) at the ground.
But the published pressure is likely to be the local QNH so I guess that's what you're using.
|
>> Luton airport is at around 520feet which will obviously afferct the local pressure
I've seen a weather station at Kleine Scheidegg in Switzerland (weather stations seemed to be everywhere in the country) reading 648mb at just over 6,750ft altitude.
Last edited by: Dave_TDCi on Thu 22 Sep 11 at 18:53
|
|
What is the best way to calibrate a barometer? I was given a nice old barometer last year, and am convinced it over reads by quite a bit.
|
|
Wait for a nice settled period with a big high pressure settled over most of the country (I heard there's one coming in about 2020....). Look up your altitude on an OS map, find the correction on the 'net, adjust to suit.
|
>> What is the best way to calibrate a barometer? I was given a nice old
>> barometer last year, and am convinced it over reads by quite a bit.
>>
Go here xcweather.co.uk/ , hover over the arrow nearest to you, note the current reading and use that. No correction needed.
|
...Go here xcweather.co.uk/...
I see the pressure is generally higher in the south.
But I knew that already.
|
|
Excellent. My nearest reading is from the Bae airfield at Woodford - wonder if they will stop now that the airfield has closed?
|
|
Super; nearest weather station is 5 miles away at Bournemouth Airport, SWMBO's barometer duly calibrated.
|
Barometric Pressure measuirng standards. - lancara
