ambient wind vs true wind - Page 2 - SailNet Community
Seamanship & Navigation Forum devoted to seamanship and navigation topics, including paper and electronic charting tools.

 15Likes
Reply
 
LinkBack Thread Tools
post #11 of 28 Old 02-26-2019
Senior Member
 
SanderO's Avatar
 
Join Date: Jul 2007
Location: Northport, NY
Posts: 2,916
Thanks: 2
Thanked 77 Times in 77 Posts
Rep Power: 0
 
Re: ambient wind vs true wind

If you think of TRUE wind as an instantaneous report... if could be showing you a GUST or a LULL and neither would tell you want the AVERAGE TRUE wind is.

AMBIENT, I believe, refers to the average wind at a particular location

Usually when we say the wind is blowing 25 knots, for example... it's actual speed varies... 22, 24, 27 and so on...

pay attention... someone's life depends on it
SanderO is online now  
Sponsored Links
Advertisement
 
post #12 of 28 Old 02-26-2019 Thread Starter
Senior Member
 
JoCoSailor's Avatar
 
Join Date: Dec 2015
Location: Overland Park, KS
Posts: 183
Thanks: 91
Thanked 10 Times in 10 Posts
Rep Power: 4
 
Re: ambient wind vs true wind

Quote:
Originally Posted by Jeff_H View Post
'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
What he said!

Thanks Jeff!

At least I was in the ballpark with "Maybe ambient wind is what you have standing on a rock and true wind is on a boat that current could be moving". Okay not nearly as eloquent, accurate, or complete as Jeff answer.

Also, relieved to know I had not forgotten a very necessary part of set and drift.

Chrysler Buccaneer 18

If you want to save the world...eat farm-raised oysters!

“Every man dies. Not every man really lives.” – William Wallace
JoCoSailor is offline  
post #13 of 28 Old 02-26-2019
Senior Member
 
Join Date: Dec 2016
Location: Nanaimo BC
Posts: 727
Thanks: 0
Thanked 39 Times in 39 Posts
Rep Power: 3
 
Re: ambient wind vs true wind

To say that the ambient wind is 20 knots with gusts to 30 knots is contrary to what the word ambient implies i.e. the same all over. Around here, the marine weather forecast will say wind speed 20 knots with gusts to 30...or, wind steady at 20 knots. You can't have winds steady (or ambient) with gusts. If NOAA says otherwise, I disagree.
paulinnanaimo is online now  
 
post #14 of 28 Old 02-26-2019
Senior Member
 
Join Date: Feb 2010
Location: Narragansett Bay
Posts: 19,223
Thanks: 82
Thanked 539 Times in 516 Posts
Rep Power: 11
   
Re: ambient wind vs true wind

The definition of ambient is the environment that surrounds you. An average doesn't seem to contradict that definition. I can't find a definition that says its the same all over.
jblumhorst likes this.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

Jeanneau 54DS

In the harsh marine environment, something is always in need of repair. Margaritas fix everything.
Minnewaska is offline  
post #15 of 28 Old 02-26-2019
Senior Member
 
SanderO's Avatar
 
Join Date: Jul 2007
Location: Northport, NY
Posts: 2,916
Thanks: 2
Thanked 77 Times in 77 Posts
Rep Power: 0
 
Re: ambient wind vs true wind

Current has no practical measurable impact of wind.

If you are measuring wind on a not stable platform... such as a boat... your wind speed measurement will sum the vectors of

current speed and direction
boat speed and direction through the water

a stable platform reads the instantaneous wind speed which likely is not constant in speed and direction

When a weather service reports wind speed and direction... they will report an AVERAGE usually noting gusts.

I have not heard the term *ambient wind* used and other than meaning some sort of average... as true is an instantaneous measurement and not reliable because of variations over time... the reported wind term may be *ambient*.

wind... YMMV

pay attention... someone's life depends on it
SanderO is online now  
post #16 of 28 Old 02-26-2019
Sailnet Vendor
 
jblumhorst's Avatar
 
Join Date: Apr 2002
Location: San Francisco Bay area and West Coast by trailer
Posts: 146
Thanks: 14
Thanked 10 Times in 9 Posts
Rep Power: 18
 
Dock
Re: ambient wind vs true wind

From
https://www.ncdc.noaa.gov/crn/measurements.html#ws

Wind Speed
A Met One Model 014A anemometer measures wind speed (in meters per second) at each station. The datalogger samples the anemometer every two seconds. Every five minutes these two-second samples are averaged to obtain 5-minute values.
SanderO likes this.

Judy B
San Francisco Bay and Delta
F24 Trimaran
jblumhorst is online now  
post #17 of 28 Old 02-26-2019 Thread Starter
Senior Member
 
JoCoSailor's Avatar
 
Join Date: Dec 2015
Location: Overland Park, KS
Posts: 183
Thanks: 91
Thanked 10 Times in 10 Posts
Rep Power: 4
 
Re: ambient wind vs true wind

Ok to confuse things more or maybe clarify (it's the offseason right) I found text that led to my question. The term there was not ambient wind it was ground wind.

It's from NauticEd Sailing School - Learn to Sail and Get Certified the course is, "learn electronic-navigation"

If anyone is interested here's the text:

"More about True Wind

By definition, the True Wind is the wind you feel when you are stationary with the water. Note that in this case the apparent wind equals the true wind.

Thus, we must define the difference between Ground Wind and True Wind. But wait, are they not the same? Well no! Think of this: In a current flowing at 5 knots, you stop the boat and drift perfectly with the current while measuring the wind speed. Since boat speed is zero, True Wind must equal Apparent Wind right? Right!

Now hop off the drifting boat and stand on a rock. The wind you feel will change. Since you are stationary now on the ground and with satellites, this is called the Ground Wind and you can see it is potentially significantly different from True Wind. But that’s not really a problem because since the sailboat operates in water albeit moving, the boat is not too concerned with Ground Wind. It’s almost like acknowledging that the Earth is spinning and moving through the solar system, the boat is not concerned with that at all.

The above discussion helped us understand that True Wind is the wind the boat feels when stationary with the water.

You probably had not considered that before, but it now makes sense. If we were operating in a high tidal current situation, by definition, when we tack the boat on moving water, the true wind must stay a consistent direction throughout all of the directions that the boat will head.

When sailing, you are more interested in the effect the wind has on the boat rather than measurements from a purely meteorological point of view, so True Wind is the preferred choice over Ground Wind.

However, racing navigators constantly convert between True Wind and ground wind to determine the accuracy of weather forecasts which use Ground Wind. This would be especially pertinent when navigating the Gulf stream off of the east coast of the USA or the EAC (East Australian Current)."

Chrysler Buccaneer 18

If you want to save the world...eat farm-raised oysters!

“Every man dies. Not every man really lives.” – William Wallace
JoCoSailor is offline  
post #18 of 28 Old 02-26-2019
Senior Member
 
Join Date: Dec 2016
Location: Nanaimo BC
Posts: 727
Thanks: 0
Thanked 39 Times in 39 Posts
Rep Power: 3
 
Re: ambient wind vs true wind

An informative piece JoCoSailor but there is nothing in there about ambient wind, isn't that what we were discussing? The previous post by jblumhorst explains a bit about how wind is measured but again, no mention of ambient wind.
paulinnanaimo is online now  
post #19 of 28 Old 02-26-2019 Thread Starter
Senior Member
 
JoCoSailor's Avatar
 
Join Date: Dec 2015
Location: Overland Park, KS
Posts: 183
Thanks: 91
Thanked 10 Times in 10 Posts
Rep Power: 4
 
Re: ambient wind vs true wind

Quote:
Originally Posted by paulinnanaimo View Post
An informative piece JoCoSailor but there is nothing in there about ambient wind, isn't that what we were discussing? The previous post by jblumhorst explains a bit about how wind is measured but again, no mention of ambient wind.
Right, that was my mistake I was confusing the two. "I found text that led to my question. The term there was not ambient wind it was ground wind.:

Chrysler Buccaneer 18

If you want to save the world...eat farm-raised oysters!

“Every man dies. Not every man really lives.” – William Wallace
JoCoSailor is offline  
post #20 of 28 Old 02-26-2019
Senior Member
 
Join Date: Feb 2002
Location: Jackson WY
Posts: 2,071
Thanks: 42
Thanked 74 Times in 73 Posts
Rep Power: 18
 
Re: ambient wind vs true wind

Quote:
Originally Posted by JoCoSailor View Post
What he said!

Thanks Jeff!

At least I was in the ballpark with "Maybe ambient wind is what you have standing on a rock and true wind is on a boat that current could be moving". Okay not nearly as eloquent, accurate, or complete as Jeff answer.

Also, relieved to know I had not forgotten a very necessary part of set and drift.
Ignore current for this concept when you think of apparent wind factor in the boat's speed over ground which factors in current a little bit but mostly speed through the water.

The apparent wind is the angle and wind speed the boat feels. What the wind indicator at the top of the mast shows would be your apparent wind angle. Which would factor in the true wind and the boats speed and course over ground. I thought the AC72s would be a good example of the difference between these because the boat speed could actually exceed wind speed so the angle difference between true and apparent is fairly significant.

Americas Cup AC72 true versus apparent wind | Sailing Blog by NauticEd
JoCoSailor likes this.

Jordan
West Wight Potter 14 "Lemon Drop"
Oceanside CA
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
.
jephotog is online now  
Reply

Quick Reply
Message:
Options

By choosing to post the reply above you agree to the rules you agreed to when joining Sailnet.
Click Here to view those rules.

Register Now



In order to be able to post messages on the SailNet Community forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
Please note: After entering 3 characters a list of Usernames already in use will appear and the list will disappear once a valid Username is entered.


User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in











Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



Similar Threads
Thread Thread Starter Forum Replies Last Post
ST60 Wind Transducer does not show correct true wind TakeFive General Discussion (sailing related) 18 09-19-2016 02:00 PM
Calculating true wind MarkSF Gear & Maintenance 11 01-24-2013 10:16 AM
ST80 Shows No Difference Between True/ Apparent Wind OffshoreDreamer Gear & Maintenance 8 08-03-2012 07:58 AM
True Wind vs Crazy Speed Transducer bacampbe Electronics 16 10-15-2009 10:17 AM
True Wind Speed and Direction SEMIJim Gear & Maintenance 34 12-01-2008 05:28 AM

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome