Non-Road Boards > Weather
Best Radar Websites Or Apps?
US 89:
I just took a radar meteorology course last spring, so I'm pretty familiar with some of this...
--- Quote from: wxfree on October 13, 2021, 02:41:55 PM ---I don't know know that VIL is, but it's measured in kilograms per square meter.
--- End quote ---
It stands for Vertically Integrated Liquid. Essentially, imagine a box 1 meter long, 1 meter wide, and extending from the ground all the way up through the atmosphere. VIL basically answers the question "how many kilograms of water are in that box". Higher VIL values typically mean larger drops and heavier rain. Extremely high VIL values usually indicate large hail.
--- Quote from: wxfree on October 13, 2021, 02:41:55 PM ---I don't know what differential reflectivity is
--- End quote ---
Differential reflectivity, or ZDR, is a dual-polarization product that basically compares the strength of the measured horizontally-polarized and vertically-polarized reflectivity. Positive ZDR means the target object is larger in the horizontal direction, while negative ZDR indicates the target is bigger in the vertical. Among many other reasons, this is useful because as the size of raindrops increases, air resistance starts playing more of a role, and the drops transition from a round shape to a bit "flatter", which gives them a positive ZDR.
--- Quote from: wxfree on October 13, 2021, 02:41:55 PM ---There's a significant suite of products available. Most of them are usable only when you select a local radar, I'm guessing that's because the data is based on a single source, and compositing it from multiple sources may not work very well.
--- End quote ---
It is actually impossible to combine velocity data from multiple radars into one big map, because those red and green values aren't absolute wind speeds or directions - they only measure the component of the wind pointing directly away from (red) or towards (green) the radar site. So knowing the location of your radar site is absolutely essential to interpreting those maps.
wxfree:
--- Quote from: US 89 on October 13, 2021, 04:06:49 PM ---I just took a radar meteorology course last spring, so I'm pretty familiar with some of this...
--- Quote from: wxfree on October 13, 2021, 02:41:55 PM ---I don't know know that VIL is, but it's measured in kilograms per square meter.
--- End quote ---
It stands for Vertically Integrated Liquid. Essentially, imagine a box 1 meter long, 1 meter wide, and extending from the ground all the way up through the atmosphere. VIL basically answers the question "how many kilograms of water are in that box". Higher VIL values typically mean larger drops and heavier rain. Extremely high VIL values usually indicate large hail.
--- Quote from: wxfree on October 13, 2021, 02:41:55 PM ---I don't know what differential reflectivity is
--- End quote ---
Differential reflectivity, or ZDR, is a dual-polarization product that basically compares the strength of the measured horizontally-polarized and vertically-polarized reflectivity. Positive ZDR means the target object is larger in the horizontal direction, while negative ZDR indicates the target is bigger in the vertical. Among many other reasons, this is useful because as the size of raindrops increases, air resistance starts playing more of a role, and the drops transition from a round shape to a bit "flatter", which gives them a positive ZDR.
--- Quote from: wxfree on October 13, 2021, 02:41:55 PM ---There's a significant suite of products available. Most of them are usable only when you select a local radar, I'm guessing that's because the data is based on a single source, and compositing it from multiple sources may not work very well.
--- End quote ---
It is actually impossible to combine velocity data from multiple radars into one big map, because those red and green values aren't absolute wind speeds or directions - they only measure the component of the wind pointing directly away from (red) or towards (green) the radar site. So knowing the location of your radar site is absolutely essential to interpreting those maps.
--- End quote ---
Thanks for the information. ZDR is a fascinating product. That's something that's good to know.
ET21:
RadarScope and AmbientWeather
Scott5114:
This looks like it would be really cool, but they've tied it to a single Linux distribution (RHEL) and refuse to even entertain the possibility of someone wanting to run it on another distribution, even one that is more or less exactly the same, like Fedora, which is what I'm running. (I've seen someone ask for help working around that and get shut down by some moron from the development staff saying they haven't tested it, so don't you dare try it, basically.)
I made my own attempt, hacking up the install script by judiciously commenting out lines that do things like send wget requests to 404'd pages and things like that. I'm giving up now because it wants a Fortran 77 compatibility library (just...why) that I can't track down a version of that's been released since George W. Bush stopped being President. It would be hard to find a better example of failure to properly release an open-source software package than this.
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