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Old 24-03-2013, 14:20   #1
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Understanding weatherfax charts

I'm sitting and trying to understand weatherfax. Most weathercharts are easy, but I have uploaded a chart here wich I have trouble understanding. One thing is highpressure and lowpressure, but what does the two digit numbers mean?

Anyone who can help?
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Old 25-03-2013, 07:14   #2
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Re: Understanding weatherfax charts

1050-mb high would be written as a 50 and a 960-mb low would have 60, so you have to ad a 9 or a 10 in front of the digits in the chart.

http://www.sailnet.com/forums/seaman...ax-charts.html

Lars
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Old 25-03-2013, 07:41   #3
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Re: Understanding weatherfax charts

You are looking at the ANPS Prognosis, which a little Googling will tell you is the Ambient Noise Prediction System. Ambient ocean noise levels are used by military and various scientific services to help correct readings from acoustic based instruments (depthsounders, sonar, etc.).

http://www.sea.co.uk/Docs/Defence/Ca...nt%20noise.pdf
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Old 25-03-2013, 08:03   #4
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Re: Understanding weatherfax charts

This does not appear to be a weather chart. I believe it is produced by the Ambient Noise Predictions System (ANPS). I don't really know what this chart is about, but I guess it used by the military for anti-submarine operations.

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Old 25-03-2013, 08:20   #5
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Re: Understanding weatherfax charts

^^ Yes to the two above posts . . . Amadeus, you want a MSLP (or surface) prognosis, Not this ANPS prognosis - this is no use for you. (as an aside, the measurement is "Pressure Spectral Density" and the units are Db vs a reference level, which I believe = 6.5 x 10 ^-19 W/m^2)

And for the third post up (Lars), Northwood in fact uses the full four digits for MSLP pressure and does not truncate it to two digits.
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Old 25-03-2013, 12:57   #6
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Thanks alot for all answers. Been bothering me for some time this.
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