[evlatests] VLA site forecast graphics

[Brian Svoboda]

Dear colleagues,

I am circulating some information related to the forecast graphics I 
have developed for near-term operational guidance on phase stability, 
cloud cover, and wind speed. I'm preparing a memo describing them in 
detail, but I think they can be useful in the meanwhile for, e.g., fixed 
date scheduling, tests requiring high-frequency, and supplemental use by 
the operators. Complementary figures for the VLBA are in progress.

The latest figures can be retried from and are updated every hour at 
roughly ~35 min after the hour:

/home/birdseye2/bsvoboda/atmosphere/site_forecast/plots/latest

All figures us UTC time. Figures of interest (as PDF or PNG) are 
described below.

- "summary" a (-1.5, +9.0) hour forecast of phase RMS, wind speed, and 
cloud cover. A strip of colors at the top indicates the band limit when 
considering the limits for phase, wind, and cloud cover. A relatively 
conservative threshold in cloud column density is used for the latter. 
Black shows measured values and forecasted in red. The phase RMS panel 
overplots the previous 12 forecasts in transparent red with the latest 
in dark red. The forecast wind speed is shown in red with gust potential 
as an upward shaded region. The dotted vertical magenta line shows the 
time that the forecast was generated.

- "summary_long" a (-3.0, +72) hour forecast (i.e., 3 day) equivalent of 
the above. The primary differences are: (1) the phase model does not use 
the most recent measured API data so is less accurate in the nearest 
~1-3 forecast hours, and (2) the cloud cover data is more crude using a 
limit of ~25% coverage at mid-level altitudes. Guidance on less than +12 
hours should use the former figure. Note that the hour and date on the 
x-axis labels can look very similar. The calendar date is listed at UTC 
0 hours and has a centered dot separating the day and month (e.g., 
"08·Nov").

- "cloud_combo" shows an areal view of ~50 km on a side centered on the 
VLA with, listed roughly in the order of severity, optical cloud cover 
in gray, cloud liquid column density in blue, and cloud precipitating 
liquid in red. Panels are shown in 15 min intervals.

Please find examples attached. The cloud figure is from August 15 since 
there were no forecasted clouds today. Several other quantities are also 
plotted. Specific forecasts can also be found in a (UTC) 
"year/month/day/hour" structure rather than in "latest". For those 
interested, the data themselves are stored in a directory called 
"forecasts" instead of "plots" and follows a similar structure.

Clear skies,
Brian

-- 
Brian E. Svoboda, PhD
Associate Scientist
National Radio Astronomy Observatory (NRAO)

Office: DSOC 312
Office Phone: +1 (575) 835-7246
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