[gradsusr] New meteogram with 0.25-degree GFS data

Fri Jan 23 12:32:55 EST 2015

Dear Antonio,
Thank you for this thoughtful email about the meteogram content! Please see comments inline…

On Jan 21, 2015, at 4:45 AM, Bonan Antonino <abonan at arpa.veneto.it> wrote:

> This work on meteograms is very useful. We adapted the available script (retrieved from grads functions library) for our operational aims, since a long time, to get visual ideas about weather forecasts from models. We use ECMWF data.
> So, just to get a better and fast visual forecast from thise kind of model output, we are left with (successful?) trials problems to solve.
> Our plots of temperatures at 2 m not only contains the values at definite time steps (every 6 hours), together with dew point values... but also minimal and maximal temperatures of the (6-hourly) period ending at each step. The right visualization can let forecasters understand the plot without big efforts. We find that the shading by Jennifer is beautiful, but not so useful.

I think the horizontal color blocks in the 2m temperature panel help the user get a quick impression of whether the temps are warm or cold without having to look closely at any numbers, but I can appreciate that there’s a lot of ink being added without any new information. 

Here are my proposed changes:
1. Softer colors, with a few more levels including one exactly at freezing temperature, plus a noticable change from purple to blue at the freezing line. 
2. 2m temperature in a solid dark line without cmarks, dew point in a dashed line of the same color. 
3. Use of ‘gxout errbar’ to show the min/max range over the past 6hrs

> Plots of precipitation still have the problem of scaling, making different meteograms so difficult to compare…
I have added a “Run Total” at the upper right corner of the precip panel, which is the total accumulation over the 10-day period. Perhaps this will help in comparing meteograms. There is no way a fixed precip scale will work for the wide range of values that exist in meteograms from different locations. Small changes and small values would be impossible to detect. I am not going to alter the dynamically-generated ‘vrange’ values in the precip panel. 

> The directions of wind in the upper plot can be badly understood by some forecasters, e.g. confusing between southerly and upward wind. Obviously, this is a problem with their hurry and not properly with the plots…
> The upper plot has another more serious problem. Contour lines "come back in time" when (e.g.) an inversion layer is temporary. You can see that in the plot showed by Jennifer, let's say in the afternoon of 20JAN. As you can think, reality cannot be a freezing point which starts from the afternoon, lifts in the evening, go back to the same afternoon, get a time folding, then lowers in the same evening... It'just a graphical artifice, used by grads in its trial to plot a line being continuous in time/level surfaces. It is more difficult to avoid a wrong intepretation by forecasters, as they look for weather evolutions in meteograms: they could avoid the problem, only by looking for single snapshots... time step by time step. That is, they should abandon the comprehensive point of view of a meteogram!
> I feel this problem could be faced with a new particular grads function: to get reliable plots in time/level surfaces, stopping contour lines when they "come back in time". I feel a script cannot be enough for such a purpose: at least, it would be too complicated.
I agree that the wind barbs in the top panel are tricky to interpret. They are meant to be soundings, but it is easy to forget and think of them as a spatial wind field, or showing sinking/rising motion. That is why I wish there was more space in between each one, perhaps drawing them every 6 hours instead of every 3… 

The temperature and humidity contours are meant to give a feel for air mass changes. I think the green blobs of moist air in the top panel connect visually to the cloud and precip panels in the bottom panels and provide good visual anchors as you look for vertical alignment of meteorological events in the time series. I agree that contours are a bit misleading because of the implied continuity, and it would probably be better to have a grfill instead, but then it would be impossible to have temp, humidity, and wind all in the same panel. 
—Jennifer

> Thank you for you work and good luck....
> 
> Dr. Antonino Claudio Bonan
> Meteorologo
> ARPAV- Servizio Meteorologico
> via Marconi, 55
> 35037 Teolo (PD) - Italy
> ----- Original Message -----
> From: Jennifer Adams
> To: GrADS Users Forum
> Sent: Friday, January 16, 2015 11:09 PM
> Subject: [gradsusr] New meteogram with 0.25-degree GFS data
> 
> Dear Users,
> I am working on transitioning my wxmaps.org scripts to use the 0.25-degree GFS output. The first script to test was the meteogram, below is a sample based on today’s 12Z forecast. I thought I would share it here and see if any of you want to give me some feedback while it is sitting on the top of my to-do list. I don’t modify these scripts all that often, so now is the time to express yourself, if you have an opinion. 
> 
> The 3-hourly output goes out to hour 240, so now it’s a 10-day meteogram. That forced me to draw it in an 11x11 page to keep it readable. The image size will be bigger, too. The increased vertical resolution makes the top panel a bit crowded, even though I expanded its vertical real estate by merging the SLP and 1000-500mb thickness panels. I know the cloud cover variables are not of great interest, but please don’t vote to have them removed, I really like the way it appears that the bars in the precip panel are falling out of the clouds. For comparison, here is the link to the 0.5-degree meteogram: http://wxmaps.org/pix2/dcagfs.png. 
> 
> If you are kind and helpful, I will package up the new script with a wrapper to get the needed data from our GDS to make it easier to draw a high-res meteogram for any location. 
> —Jennifer
> 
> 
> <Screen Shot 2015-01-16 at 4.38.11 PM.png>
> --
> Jennifer M. Adams
> Center for Ocean-Land-Atmosphere Studies (COLA)
> 111 Research Hall, Mail Stop 2B3
> George Mason University
> 4400 University Drive
> Fairfax, VA 22030 
> 
> 
> 
> 
> 
> 
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--
Jennifer M. Adams
Center for Ocean-Land-Atmosphere Studies (COLA)
111 Research Hall, Mail Stop 2B3
George Mason University
4400 University Drive
Fairfax, VA 22030 

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