Weather – GRLevel3



GRLevel3 Version 2 is a Windows viewer for live and archive NEXRAD Level III data. It displays high resolution base products, dual polarization products, and derived products along with Local Storm Reports and severe weather warnings.

GRLevel3 is a highly customization tool that I have found myself referring to more and more. I live very close to Galveston Bay in southeast Texas. We tend to get severe storms, from thunderstorms to hurricanes. Tornadoes are a fairly common occurrence since we are on the southern most border of Tornado Alley, albeit they tend to not be as severe as, say, Oklahoma. As of the righting of this page, Houston experienced the “Tax Day” flood.

One would probably ask, “Why would I want to use this program and monitor the weather? I have the local news and internet for that.” This is true, but keep in mind…this is a hobby and service. The hobby portion of this is to gain an understanding of weather; perhaps to learn something new. The service aspect is becoming a certified storm spotter with SkyWarn or sharing the readings from your personal weather station.



One of my favorite features is how easy it is to customize most aspects of GRLevel3. Most customizations can be done via simple, editable text files. I recommend using Notepad++, a versatile text editor used extensively by programmers and linux users; which is the same text editor that I use in my other projects.

Color Tables

Color Tables are simple text files that can be edited to customize the colors that you see on your radar samplings. Here is an example, the screenshots below show the same data with two different color tables. The first image uses the the National Weather Service default colors which uses a narrow spectrum; notice the scale on the left of the image. The lower image uses a broader spectrum that, frankly, looks better on television and images; this color table is refereed to as the Solid TV color table.

NWS Color Table


I mention, spectrum, in my descriptions of the color tables. This deserves some explanation. If you are not familiar with how radar works lets just say it is an echo. A microwave radio signal is broadcast outward from the radar dish. The signal will bounce of off what ever it hits, thereby echoing back to the dish. The radar software then assigns a value to the strength of the echo in the form of DBZ.

dBZ stands for decibel relative to Z. It is a logarithmic dimensionless technical unit used in radar, mostly in weather radar, to compare the equivalent reflectivity (Z) of a radar signal reflected off a remote object (in mm6 per m3) to the return of a droplet of rain with a diameter of 1 mm (1 mm6 per m3). It is proportional to the number of drops per unit volume and the sixth power of drops diameter and is thus used to estimate the rain or snow intensity. With other variables analyzed from the radar returns, it will help to determine the type of precipitation, too. Below is the NOAA dBZ scale.

dBZ versus Rainrate
dBZ R (mm/h) Rate (in/hr) Intensity
5 0.07 < 0.01 Hardly noticeable
10 0.15 < 0.01 Light mist
15 0.3 0.01 Mist
20 0.6 0.02 Very light
25 1.3 0.05 Light
30 2.7 0.10 Light to moderate
35 5.6 0.22 Moderate rain
40 11.53 0.45 Moderate rain
45 23.7 0.92 Moderate to heavy
50 48.6 1.90 Heavy
55 100 4 Very heavy/small hail
60 205 8 Extreme/moderate hail
65 421 16.6 Extreme/large hail

Using the Color Table Specifications you can customize the color ranges to your liking. On the Resources page, I have included links to freely available color tables. Referring back to our two example images, the Solid TV table uses a broader dBZ value range than the NWS table. This gives the NWS image more colors to work with and a more sensitive and accurate image. However, the Solid TV palette looks more dramatic, hence being used on TV, wbsites, and social media; plus the benefit of being easier to understand by the layman.

Place Files

Shape Files