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Old 20-05-2016, 11:35   #76
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Re: Do I really need a barometer? Which one?

http://www.bethandevans.com/pdf/Weatherrevis.pdf

key line: "Expecting a barometer to forecast the next six hours of weather based on the current trend is a bit like expecting the depth sounder to forecast whether or not the boat will be aground in the next six hours. "

you will have to read the rest to get the explanation
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Old 20-05-2016, 11:50   #77
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Re: Do I really need a barometer? Which one?

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Originally Posted by RedHerring View Post
Guess what, inspired by all the UNCIVILIZED curmudgeonry on this thread, I've fixed my decorative aneroid tonight!

So, gonna have FOUR barometers onboard now:

* electronic weather station on the bulkhead, for displaying the pressure trend and the beer temperature,
* the brass one for the salty looks,
* and a barograph app on both my and wife's mobile devices

If that doesn't cover all the bases, dunno what else can. Thanks to everyone who contributed their valuable wisdom. You, people, are awesome.
As long as it has the beer temp.. The rest is academic.
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Old 20-05-2016, 16:31   #78
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Re: Do I really need a barometer? Which one?

Quote:
Originally Posted by estarzinger View Post
http://www.bethandevans.com/pdf/Weatherrevis.pdf

key line: "Expecting a barometer to forecast the next six hours of weather based on the current trend is a bit like expecting the depth sounder to forecast whether or not the boat will be aground in the next six hours. "

you will have to read the rest to get the explanation
Good article Evans. I hadn't read that one. Thanks.

Sent from my SM-G930F using Cruisers Sailing Forum mobile app
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Old 20-05-2016, 18:22   #79
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Re: Do I really need a barometer? Which one?

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Originally Posted by El Pinguino View Post
A little something re the use of baros in the tropics... from the book Meteorology for Mariners published by HMSO.

' In tropical regions irregular changes are usually much smaller than the diurnal change from which they cannot be distinguished until the diurnal change has been subtracted. The procedure is important in tropical regions because a fall of pressure 2 or 3 mb below the value appropriate for the locality , after allowing for the regular diurnal change of pressure, may be the first indication of the approach of a tropical revolving storm.'
Something similar in Admiralty Sailing Instructions - Pacific Islands Pilot:

"When disturbances occur, significant falls or rises in in the mean pressure value can be masked by diurnal variations. It is thus important to take into account the latter when....

If the barometric pressure , after correction for diurnal variation, show a pressure fall of more than 3mb in 24 hours or a value of 5 mb or more below the appropriate normal monthly average, the existence or impending development of tropical depression in the vicinity should be suspected..."
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Old 21-01-2017, 21:06   #80
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Re: Do I really need a barometer? Which one?

As I'm sitting in La Paz, winding down a 7 months cruise of west coast, one thing I can say is that I did not actually need the barometer during this trip. Between VHF forecasts, weather forecasts from satellite messenger and plain old looking at the sky, knowing what to look for, there was not one situation where barometer told me something I didn't already know. YMMV.
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Old 21-01-2017, 21:34   #81
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Re: Do I really need a barometer? Which one?

A digital thermometer which warns when the pressure drops is handy. Unless you diligently log an analog barometer I agree. Quite useless unless you use it.

The barometer is also useful when you cant get weather forecasts. It has a much longer track record as a safety critical device than our electronic crapware.

The barometer does not give answers only one piece of information, barometric pressure. You need to look about, understand weather and critically observe the weather. Then its very useful.
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Old 22-01-2017, 03:32   #82
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Re: Do I really need a barometer? Which one?

I was Captain of a small Naval vessel in the North Sea. We logged the bp every hour. Weather forecast good. An hour into our voyage I noticed that the bp was falling - unforecast. An hour later it had fallen 10 points. We headed for the next harbour and got in before a storm hit us. No problem with the ship in that weather, but in a vessel being thrown around, injury to a crew member was likely. No point in being out there when it is not essential.
I always have a barometer which records the bp in graph form. I can then refer to it easily and make a judgement. It rarely happens that the forecast is wrong, but forecasts are based on wide area synopsis and cannot always take local issues into account.
Camping shops sell such machines for little money. A truly worth while investment.
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Old 30-01-2017, 16:31   #83
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Re: Do I really need a barometer? Which one?

I throw my hat in with Reed, Snowpetrel and El Pinguino. A barometer is one of the tools a wise mariner uses while afloat. Anytime under sail, we record hourly barometric readings. It is not necessarily the individual reading but the trend that is important. Being a traditionalist or perhaps a Luddite, as a former contributor once described me, we use an aneroid barometer. Don't leave home without one. Good luck and safe sailing.
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Old 30-01-2017, 17:00   #84
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Re: Do I really need a barometer? Which one?

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Originally Posted by rognvald View Post
I throw my hat in with Reed, Snowpetrel and El Pinguino. A barometer is one of the tools a wise mariner uses while afloat. Anytime under sail, we record hourly barometric readings. It is not necessarily the individual reading but the trend that is important. Being a traditionalist or perhaps a Luddite, as a former contributor once described me, we use an aneroid barometer. Don't leave home without one. Good luck and safe sailing.
I've been monitoring an Android barometer app on my phone for months now and I've found it to be very accurate. It records pressure every 15 minutes (user adjustable) and displays a historical graph with an X axis of your choice from last 12 hours to 14 days.
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Old 30-01-2017, 17:05   #85
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Re: Do I really need a barometer? Which one?

It wouldn't be the accuracy of the app, but of the phone sensor I believe. I wouldn't think they would be all that accurate, I'm surprised
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Old 30-01-2017, 17:29   #86
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Re: Do I really need a barometer? Which one?

Digital barometers are very accurate and inexpensive. They can provide useful information when everything else fails. I see no reason not to have one on board. Analog brass barometers on the other hand no longer have a place on board, IMHO.
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Old 30-01-2017, 18:13   #87
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Re: Do I really need a barometer? Which one?

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It wouldn't be the accuracy of the app, but of the phone sensor I believe. I wouldn't think they would be all that accurate, I'm surprised
It's both precise and accurate.

Precise:
- I can clearly see the expected diurnal variation in pressure.
- When I drive to somewhere like the airport from the marina, I can clearly see the downward and upward changes in pressure (Jackson's Airport is 125ft above MSL).

Accurate: The app includes the ability to synchronize with airport QNH - using AYPY (Jackson's) puts my altitude on the boat at pretty close to 0 every time. (after an initial calibration)

Here's a shot of the last 4 days - you can clearly see the diurnal variation, a slow drop over the last few days, and when I drove up to Boroko at lunchtime on Monday
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Old 31-01-2017, 08:45   #88
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Re: Do I really need a barometer? Which one?

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Digital barometers are very accurate and inexpensive. They can provide useful information when everything else fails. I see no reason not to have one on board. Analog brass barometers on the other hand no longer have a place on board, IMHO.
They still look pretty. I'm not sure they ever were very good unless there was a drastic change but better than nothing in the day.
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Old 31-01-2017, 09:33   #89
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Re: Do I really need a barometer? Which one?

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Originally Posted by StuM View Post
I've been monitoring an Android barometer app on my phone for months now and I've found it to be very accurate. It records pressure every 15 minutes (user adjustable) and displays a historical graph with an X axis of your choice from last 12 hours to 14 days.

Stu,
Will your phone barometer work out of cell phone range? If not, would you need a satellite connection for the readings offshore or is the sensor built into the phone.. . questions asked honestly from a purposeful low tech sailor. Thanks.
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Old 31-01-2017, 10:34   #90
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Re: Do I really need a barometer? Which one?

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Stu,
Will your phone barometer work out of cell phone range? If not, would you need a satellite connection for the readings offshore or is the sensor built into the phone.. . questions asked honestly from a purposeful low tech sailor. Thanks.
Stu,

Thanks for asking my question. It would seem to me, also low tech, if the pressure readings are not measured where you are, they are not worth a thing.

I'm guessing the old recording barometer with the stylus and round piece of chart paper have a better onboard replacement digitally. Of course the analog one didn't rely on power just a key an remembering to use it.
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