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Forecast in Knots while Sensors Read in MPH??? Plus...

 
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WNDZRFR



Joined: 28 Mar 2000
Posts: 124
Location: Greater East Bay Area

PostPosted: Thu Oct 08, 2015 1:16 pm    Post subject: Forecast in Knots while Sensors Read in MPH??? Plus... Reply with quote

I understand that we are in a wind water sport and all but why is the forecast in knots while the sensors read in mph?

Am I the only windsurfer that this drives crazy? Because if I'm not mistaken there is a sizable difference in the two measurements - of about 3 mph at 20 knots. A sail size for me.

Why not just write up the forecast in mph and everything will be kosher!

Also since I'm on a roll here, can we please stop updating Anita Rock & TI like every half minute??? Is the wind reading 30 seconds from now really going to change how you rig? If one wants to see the wind trend over say the last half hour one has to scroll down dozen of pages! Very annoying!

The Americas Cup is long gone so can we please go back to what we have at all other Bay Area sites - 4 minute updates that give us usable wind information? Please

Thanks in advance, a continuous iwindsurf patron since the days of pagers!
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windsrf



Joined: 01 May 1998
Posts: 464

PostPosted: Thu Oct 08, 2015 1:46 pm    Post subject: Reply with quote

Here Here!

Good luck though - took a long time just to get the Berkeley sensor changed back to 4-5 minute updates. MUCH easier to read/interpret.
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johnl



Joined: 05 Jun 1994
Posts: 1330
Location: Hood River OR

PostPosted: Thu Oct 08, 2015 2:39 pm    Post subject: Reply with quote

I'm sure you will get a better answer but the weather charts are in knots. Personally I can deal with a forecast in knots but changing the sensors over to knots (so both would be the same) would take a while to get used to...
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windfind



Joined: 18 Mar 1997
Posts: 1899

PostPosted: Thu Oct 08, 2015 3:27 pm    Post subject: Re: Forecast in Knots while Sensors Read in MPH??? Plus... Reply with quote

WNDZRFR wrote:
I understand that we are in a wind water sport and all but why is the forecast in knots while the sensors read in mph?


Hi WNDZRFR,

John is right. The models charts and models are in knots since knots is a unit of distance that is approximately the length that spans one minute of arc on the surface of the Earth measured along any meridian. So it is the international standard on nautical and weather charts since it is rationally related to Long. and Lat.

Whereas mph is based on feet which is an irrational system based on a measure of 1/3 an arm length. Worse there were Italian miles, Arabic miles, English miles etc. In 1959 the "International Yard and Pound Agreement" settled on the current Statute mile which is 0.9144 meters.

The difference between knots and mph is well within the gust range and sensor location inaccuracy (not to mention forecast inaccuracy) until you approach 30 mph so basically don't worry about the difference other than to remember that the wind is slightly different between the forecast and the sensor reading. (you have probably noticed that anyway Smile

Also remember that our customer base is much broader than windsurfing and kiting and most of those customers want forecasts in knots and as frequent of updates as possibly.

If you really can not get knots vs. mph out of your mind just use the new iwindsurf.com at this link:

http://wx.iwindsurf.com/map#37.914,-122.134,10,1

Then use the instructions below to set what ever unit of measure you like.

When I do forecasts for GoogleX projects they want meters/second which really drives me crazy since the numbers are very different than mph or knots. Worse if I forget to reset the unit of measure when I am done I get wind maps that don't make any sense because they are in m/s.

The 5-10 minute average on some of the sensors is very misleading. It artificially makes it look like the wind is much steadier than it really since it averages out all the actual ups and downs.

I know the 1 minute updates look very busy but they are much closer to reality. Just learn to look at the average of all those + and - jags and you will have a much more accurate feeling for the quality of the wind.

Hope this helps.

Mike



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isobars



Joined: 12 Dec 1999
Posts: 20935

PostPosted: Fri Oct 09, 2015 8:32 pm    Post subject: Reply with quote

Select a wind plot.
Look at the toolbar immediately above the plot.
At its far right, click on Options.
In the ensuing dropdown, roll your cursor over "Units".
Click on your preferred windspeed display scale.

Oops; Just oooooone little problem: that accomplishes nothing.

I'll bet you could dig deeper into the MyWind setup and find a solution related to that.
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windfind



Joined: 18 Mar 1997
Posts: 1899

PostPosted: Sat Oct 10, 2015 11:11 am    Post subject: Reply with quote

Hi Isobars,

You did not include a link to the pages you are having trouble adjusting the unit of speed.

I am guessing it is one of the legacy versions of iwindsurf.com that use Adobe flash. I just checked one of those flash based pages clicking on "options" then "Units" and it worked great for knots, mph, mph etc. on 3 different computers.

If you are wedded to this legacy version of iwindsurf you might try installing flash and browser updates and check that you don't have any of the many different ad blockers that block Flash.

As you know the industry is fleeing from Adobe Flash as fast as possible because of the unending security problems and because of hick ups like you describe. The new standard is becoming html5 which does not require a bunch of plugins, minimizes java script, produces superior web pages and is compatible with all mobile devices. Plus with html5 we are no longer dependent on the whim of Adobe to issue updates.

Mike Godsey
iwindsurf.com/ikitesurf.com
Weatheflow.com



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isobars



Joined: 12 Dec 1999
Posts: 20935

PostPosted: Sun Oct 11, 2015 5:45 pm    Post subject: Reply with quote

windfind wrote:
I am guessing it is one of the legacy versions of iwindsurf.com that use Adobe flash. I just checked one of those flash based pages clicking on "options" then "Units" and it worked great for knots, mph, mph etc. on 3 different computers.

If you are wedded to this legacy version of iwindsurf you might try installing flash and browser updates and check that you don't have any of the many different ad blockers that block Flash.

Thanks, Mike, but I wouldn't know a Legacy from an Outback if I didn't have an Outback parked in my garage. I just use the same iW I've used since the 1900s for one simple reason: it works (I WANT my windspeed in mph).

I've not found another iW site (besides WAP) that lets me select the sailing spots I want to see when I click on myiWind, so I've found no reason to change. My eyes glaze over at this
http://wx.iwindsurf.com/map#44.431,-124.089,7,1
when what I want is
http://www.iwindsurf.com/myWeather.iws?home .
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