Windchill measurements

[treant985]

Has there been any thought to adding daily min/max/avg windchill readings to the F6 forms that the MWO staff fills out?

We can calculate it ourselves by looking at the hourly metar readings posted on the noaa.gov website, or by checking the front-page of the MWO website, but I thought it would be interesting and useful to include information on windchill readings for the 'historical record.'

Plus, I assume that the staff has access to much more continuous readings for temp & wind speed than are posted on any website, which would allow them to capture the extreme & average wind chills for each day, something that we could only do to a certain level of precision due to fewer daily readings available to us.

[Bill O]

I can tell you what the max windchill is without even knowing the windspeed.

I think we have discussed this before. My personal opinion is that windchill is more for the media than for science.

Temperature data throughout the day is driven by hourly measurements, plus the max and the min. How would you measure windchill? Would the minimum windchill count if it was driven by a 2 second gust?

[treant985]

Would the minimum windchill count if it was driven by a 2 second gust?

Would a 2-second gust count as the maximum wind speed? If so, then yes, the minimum windchill would count if it were driven by a 2-second gust.

Either way, I was under the impression that wind chill was calculated using the temperature and average wind speed over a period of say one minute, not an almost instantaneous wind gust. Granted, that would mean using the average wind speed over a certain, small amount of time, but it's not like wind chill is an exact quantity, so using the temp and average wind speed over, say, a minute's interval would give a very accurate picture of the wind chill during that time.

I don't know exactly how they take readings at the summit, but I do know that the summit of Mt. Mitchell in NC keeps what is essentially an archive of real-time data, with each row of data consisting of (among other things unrelated to this topic) temperature, wind speed, and wind gust. I'm not sure what their interval is between readings, but it's at most 1 minute.

As such, they can give a pretty accurate value to what their minimum wind chill was for a certain day.

[treant985]

If nothing else, I think it would be interesting to see what the daily average and minimum wind chills are that are reported on the front page every 15 min.

[Knapper]

I will put in my two cents here.

First, we will not be altering the F-6 by inserting extra columns for wind chill. This is a government form, therefore there are set rules on what is reported on this form. If you want it altered, you need to talk to NOAA, not MWO.

Second, wind chill, from a meteorological and climatological stand point is useless. Also, the formula has been altered many times since it was first thought up. So if we were to start putting it on any form, who is to say whether or not it is valid 10 year from now? Wind chill is useful for hikers and outdoor enthusiast though, that is why my coworkers and I include it. For some odd reason, a few studies have shown that people tend to dress more adequately when wind chill is mentioned than if just temperature and winds are mentioned. So that is why we include them in the forecast. So Bill O is right on that point, it is more for information purposes than anything else.

Third, we do show what the current hourly wind chill is on the home page. We only do official weather observations once an hour not every 15 minutes. But we do have winds and temperatures along with calculated wind chills output every 15 minutes or so at: http://www.mountwashington.org/weather/conditions.php. These readings are not official but give a rough estimate of what is going on up top.

Hope this helps
Ryan Knapp
Staff Meteorologist, KMWN

[Bill O]

....., wind chill, from a meteorological and climatological stand point is useless.

Nicely put, I second that argument.

I'm not sure what the interval is, but computers on the summit of Mount Washington are logging data every few seconds. So, in theory, you could run a program that calculates the wind chill at every data point.

A 2 second gust is all you need to get in the record books. There are no record books for windchill. Ryan's argument is good here because the definition of windchill has been redefined. Not only because it was inaccurate, but because its arbitrary.

[treant985]

I guess there's some pretty obvious hostility to wind chill in here. I know that it's only an estimate whose formula has been changed. I mentioned the F6 form as an example of where the info can be placed. MWO has already altered the form SLIGHTLY to include top gust, which is not a category on the "official" F6 form

But am I honestly the only person who thinks it would be interesting (notice I keep saying 'interesting,' not 'useful from a meteorological and climatological stand point' because yes, there is a difference between the two) to keep some record of wind chills, for comparison between very cold & windy days?

It's just a question about keeping records of very cold/windy days in an effort to give an idea of how cold it really was. You'd think I'd asked for MWO to start giving their readings in kelvin and yards/hour or something...

[Patrad Fischroy]

"It's just a question about keeping records of very cold/windy days in an effort to give an idea of how cold it really was. You'd think I'd asked for MWO to start giving their readings in kelvin and yards/hour or something..."

As an added voice to the chorus of hostility I also don't think it should be added any more than it is already used. and as far as seeing "how cold it really was", my feeling is that the temperature recorded already does an admirable job of that. Wind chill only shows how cold it feels.

Not really hostility, just an adverse feeling towards it.

[treant985]

As an alternative, could MWO post their 15-min readings online in a csv (or similar) format? Then those of us who want to calculate wind chills on a somewhat real-time basis could do so if we wished. Also, that way it wouldn't look like MWO was espousing wind chill in any way.

[Bill O]

Although the windchill equation holds together at windspeeds of 50-100mph I'd seriously argue its accuracy. Quite often, MWO puts out some incredibly low windchill readings. -70F to -100F. But, do you honestly think a 100mph wind makes it feel any colder than a 50mph wind? I sure don't. 50mph winds easily and thoroughly get the job done.

I almost forgot....

Windchill sucks, dewpoint rules!