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JoCoSailor 02-25-2019 03:30 PM

ambient wind vs true wind
 
I just saw where Jeff_H used the term 'ambient wind' as in "Thomas Point was showing an ambient wind of 38 knots with gusts to 42"* I recalled reading (I think in a Navigation book) that ambient wind is different from true wind. I googled ambient wind vs true wind. All I got was True & Apparent wind. Seems like it was part of a set and drift discussion. Maybe ambient wind is what you have standing on a rock and true wind is on a boat that current could be moving. Am I in the ballpark?

*Not wanting to hi-jack that thread I started this one

MarkofSeaLife 02-25-2019 03:54 PM

Re: ambient wind vs true wind
 
I think we need @Jeff_H to explain himself. :)

I don't mind the term Ambient if that's what works in someone's mind.


Apparent is the 'proper' usage, of course. Isn't it?

Jeff_H 02-25-2019 05:57 PM

Re: ambient wind vs true wind
 
'Ambient Wind', 'Gust', and 'Apparent Wind' are three separate terms. Ambient wind and gusts are both true winds in that they are measured from a stationary position. They are solely meteorological. Ambient wind is the average steady wind measured at a stationary point such as a weather station like Thomas Point. As NOAA defines the term 'Ambient', it means, "Of the surrounding area or environment." Gusts are a sudden and short lived increase in wind speed above the ambient wind speed. NOAA defines gust as "A rapid fluctuation of wind speed with variations of 10 knots or more between peaks and lulls." but we all know it as that sudden increase in wind.

If this was a college entrance exam, 'Apparent wind' would the one term which one does not match the other two of the three. Apparent wind is the wind measured from a moving object, such as a boat under way. It is the wind that results from combining the velocity (speed and direction) of the true wind with the boat's velocity relative to that true wind velocity.

Jeff

BarryL 02-25-2019 05:58 PM

Re: ambient wind vs true wind
 
Hey,

I would think that
ambient = true

Barry

Jeff_H 02-25-2019 06:12 PM

Re: ambient wind vs true wind
 
Ambient= the average true wind (in the absence of gusts.)

paulinnanaimo 02-25-2019 07:19 PM

Re: ambient wind vs true wind
 
I think that the meteorologists are using the word incorrectly. Ambient means the same all over, as in the ambient temperature is 40 degrees outside my house. If the ambient wind is 20 knots, it's 20 knots all over. If it gusts to 30 knots in some places, it is no longer ambient as it is changing. That's my take on it.

tempest 02-25-2019 08:52 PM

Re: ambient wind vs true wind
 
I would think .. Ambient wind is what NOAA says is it, it's their term. ;-) As Jeff so carefully explained.

Just saying.

Barquito 02-25-2019 09:31 PM

Re: ambient wind vs true wind
 
NOAA defines gust as, "A rapid fluctuation of wind speed with variations of 10 knots or more between peaks and lulls."

So, this may be ridiculous, but, WOULD it be a gust if the wind dropped 10 knots momentarily?

Capt Len 02-25-2019 09:49 PM

Re: ambient wind vs true wind
 
I would read it as true and apparent are telling where from and ambient refers to how much (average.

Minnewaska 02-26-2019 06:55 AM

Re: ambient wind vs true wind
 
This isn't all that different from how wave height is published. They vary, so you get the average of the highest third and they call it significant wave height. There will still be many waves, both higher and lower.


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