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Re: [Phys-L] depicting uncertainty on maps



Don,
- I think that it would be more productive to try to correlate weather
predictions with marketing needs.
- For example, if winter wear sales has taken a hit, expect more dire
forecasts involving low temperatures, snow, ice, wind etc.
Bill Norwood, U of MD at College Park

On Tue, Mar 14, 2017 at 12:18 PM, Donald Polvani <dgpolvani@verizon.net>
wrote:

In my local area (near Baltimore, MD) the local weather station is now
putting out "contour area maps" with a range of snow falls specified within
each area (e.g. 1 - 3 in, 3 - 5 in, etc.). This same procedure could have
been used with the experimental NWS page, since the specified overall area
stayed the same with only the internal contour lines changing from map to
map. As a user of the information, it's simpler for me to just have to
look at one map rather than three, and I should get the same predicted
snowfall range for my particular location. Averaging the low and high
values to get the expected value is pretty simple to do in one's head. Of
course putting all the information on one map also saves the weather person
and the TV station expensive presentation time.

Don
-----Original Message-----
From: Phys-l [mailto:phys-l-bounces@mail.phys-l.org] On Behalf Of John
Denker via Phys-l
Sent: Tuesday, March 14, 2017 9:33 AM
To: Forum for Physics Educators <Phys-L@Phys-L.org>
Cc: John Denker <jsd@av8n.com>
Subject: [Phys-L] depicting uncertainty on maps

Hi --

Here is a timely example of uncertainty handled in an intelligent way.
Note the contrast:
++ For a point forecast, the National Weather Service routinely
expresses
the uncertainty in the amount of snowfall by quoting a range, e.g. 12
to 18 inches. In physics it might be more conventional to write that
as 15±3 inches, but quoting the range is perfectly reasonable also.
-- On a map, the contours and color-coding don't lend themselves to
representing a range.
++ You can do a lot better by putting out *three* maps: lower limit,
nominal, and upper limit. The NWS has an experimental page that
does just that. Here is a screen grab:
https://www.av8n.com/physics/img48/snowfall-map-brackets.png



By way of contrast, note that as usual in the real world, the
uncertainty is
neither calculated nor communicated using sig figs or anything like that.
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