I've sent an inquiry off to my local NWS Forecast Office on this topic.
I think you are right about the grid squares being "pre-ordained", John. See
http://www.srh.weather.gov/srh/jetstream/webweather/pinpoint_max.htm
You will see there that the forecast grid points are as close as "1.6 mi
(2.5 km)" from each other. All the meteorological and climatological
models I have ever seen use metric units. So, I would guess that the 2.5
km value is the real one.
I looked more closely at my chart and indeed the point I picked is off a
bit from the center of the square.
Hopefully I will hear soon from my NWS Forecast Office with more details
being provided.
It still beats the technique we used in NW Ohio in the '50s -- tuning in
to Plains states AM radio stations west of the Mississippi in the
evenings (1-hop radio paths) and taking their current weather reports as
our forecast for the next day.
Jim
--
James R. Frysinger
632 Stony Point Mountain Road
Doyle, TN 38559-3030
(C) 931.212.0267
(H) 931.657.3107
(F) 931.657.3108
On 2013-03-13 14:58, John M. Steele wrote:
Yes, there are several ways to "pick a square." But the squares are
'pre-ordained" although I can't figure out the algorithm that defines
them. The best you can do is the square that contains your location.
Zip codes may be bigger than the squares, or overlap them in funny ways,
so you are one square off. The map is the best way to tweak.
I'm fairly well centered east/west (the squares are at a slight angle to
true north), but very close to the southern edge of one square or the
northern edge of the next. But I either have to choose one square or
the other. They are NOT UTM squares (grid north would be wrong), but
they might be State Plane or some other grid system; I can't figure out
what though.
Because I am stuck on the edge of a square, I wasted a lot of time
trying to recenter the square, but "no joy."
------------------------------------------------------------------------
*From:* James Frysinger <j...@metricmethods.com>
*To:* U.S. Metric Association <usma@colostate.edu>
*Sent:* Wed, March 13, 2013 3:40:03 PM
*Subject:* [USMA:52518] Re: Weather Forecasts
I did not input a ZIP code, city, or town to obtain my point forecast. I
used the topo map on the page to click on the location of my house and
farm. That relocated the green square on the map, centering it on the
point I chose by clicking. As I recall, I then modified the filename for
that file (it's in CGI formatting, I believe) to insert the GPS
coordinates more exactly.
I am still of the opinion that the resulting display is based on that 2
km by 2 km grid square. Perhaps it's 1 NM by 1 NM; I cannot tell at that
chart scale. (1 NM = 1.852 km by definition.)
Jim
--
James R. Frysinger
632 Stony Point Mountain Road
Doyle, TN 38559-3030
(C) 931.212.0267
(H) 931.657.3107
(F) 931.657.3108
On 2013-03-13 13:09, John M. Steele wrote:
> Jim
> I had the same experience, having commented to the Detroit/Pontiac
> office of NWS. I got the same response as you. Basically all scripts
> are written centrally to produce the pages from data tables in their
> model, and are "common software." However, many of my comments were
> addressed in the new scripts released last year.
>
> ------------------------------------------------------------------------
> *From:* James Frysinger <j...@metricmethods.com
<mailto:j...@metricmethods.com>>
> *To:* U.S. Metric Association <usma@colostate.edu
<mailto:usma@colostate.edu>>
> *Sent:* Wed, March 13, 2013 1:54:55 PM
> *Subject:* [USMA:52512] Re: Weather Forecasts
>
> When Weather Underground first started up years ago I swapped many
> emails with their top staff on formatting issues. They were extremely
> responsive to my comments, which I also documented on the USMA mail list.
>
> A couple of days ago I sent off a detailed email to NWS Nashville
> commenting on some formatting issues on their SI version of the
> point-forecast pages they produce. I got a nice reply saying that my
> comments were being forwarded to their Science and Operations Officer
> and their Warning Coordination Officer for input, direction, and advice.
>
> I agree with John regarding the general quality of Weather Underground
> as compared to NWS but for one thing. The NWS site does provide "point"
> forecasting, centered on a specified latitude and longitude with
> elevation as a factor. Here on the escarpment of the Cumberland Plateau
> that makes a large difference in the forecast values, reflecting the
> difference in actual weather conditions as compared to the "valley"
> below or the plateau above. The "point" is still an average of an area
> but it is a small area, probably one grid square on their model. If the
> graphic is to be believed, I would estimate it as 2 km by 2 km in
> extent. I've tweaked this and it has my elevation within 10 m and my
> location as near as I can get it to the actual lat/long of the wireless
> Davis Vantage Pro2 weather station near my house. The forecast high and
> low temperatures for the next 24 h are almost always within 1 °C. Those
> who live in the "flatlands" with fewer effects due to orothography would
> not need such sensitivity to local microenvironment.
>
> Jim Frysinger
>
> -- James R. Frysinger
> 632 Stony Point Mountain Road
> Doyle, TN 38559-3030
>
> (C) 931.212.0267
> (H) 931.657.3107
> (F) 931.657.3108
>
> On 2013-03-13 12:15, c...@traditio.com <mailto:c...@traditio.com>
<mailto:c...@traditio.com <mailto:c...@traditio.com>> wrote:
> > Reference was made on this list by John Steele to the www.National
> > Weather Service's forecast page (www.weather.gov). I would like to
> > point out that the NWS site is quite an inferior source for such
> > information.
> >
> > I would recommend instead Weather Underground
> > (www.weatherunderground.com) as by far the best resource available,
> > better even than Accuweather. Its metric usage is perfection, having
> > been worked on by our own USMA meteorologist, Dr. Don Hillger.
> >
> > EVERYTHING is in SI units, if you set it that way under Settings
(Metric
> > instead of English units, as they are called there). Moreover, the
> > amount of information far surpasses that of the NWS site, as thousands
> > of local digital weather stations in backyards are included, with more
> > data, lists, and graphs than you can imagine.
> >
> > Martin Morrison
> > Metric Training & Education Columnist, USMA's "Metric Today"
> >
> >
> >
> >
>
