Gulf Radar

[Cookiely]

What does the color purple indicate on radar in a cell. I don't think I've ever seen the color purple. It didn't give an index so I have no idea.

[Category 5]

It's a step above red, I don't see it often myself.

Basically, blinding rain and most likely plenty of other goodies.

[feederband]

Purple is a very high storm dumping heavy rain with hail sometimes...

[tropicana]

i cant even imagine being under the color purple. That must be something horrific.

[Ptarmigan]

Purple is above red. It means to rain is very heavy and perhaps hail is falling. It does not mean severe weather. The highest is white and I have never seen it on radar period. Not even in severe thunderstorms or hurricanes. White equals 16 inches of rain per hour.

[vbhoutex]

Purple is above red. It means to rain is very heavy and perhaps hail is falling. It does not mean severe weather. The highest is white and I have never seen it on radar period. Not even in severe thunderstorms or hurricanes. White equals 16 inches of rain per hour.

I'm surprised you haven't seen white on the radar before. I have in a couple of hurricanes and once or twice in Super cells, fortunately never over me!!!

[Ptarmigan]

I'm surprised you haven't seen white on the radar before. I have in a couple of hurricanes and once or twice in Super cells, fortunately never over me!!!

I must of missed it then. I know Supercells would be white not surprisingly. I wonder which hurricanes had white on Doppler Radar? Being under one would be no good. Thank God I haven't.

[vbhoutex]

I'm surprised you haven't seen white on the radar before. I have in a couple of hurricanes and once or twice in Super cells, fortunately never over me!!!

I must of missed it then. I know Supercells would be white not surprisingly. I wonder which hurricanes had white on Doppler Radar? Being under one would be no good. Thank God I haven't.

I wish I could remember, but I don't. And those whites did not last too long either. I know it would be in the last 10 years or so since that is when I started watching storms more closely.

[snoopj]

Some of the feeds I was getting of some of the supercells near KC a couple of nights ago were bringing back 70-73dbz in a few locations. Not for very long, but it was there. I think 70+ is where you start to see white colors in the radar imagery.

--snoopj

[Cyclenall]

I haven't seen very many "purples" on the radar but I think it's mainly hail. I think I saw a few whites in a tornado outbreak last year. What does "dbz" mean anyway? I never found out what that stands for .

[snoopj]

Found a good explanation over at Weather Underground (http://www.wunderground.com/radar/help.asp)

The dBZ Scale

The colors on the legend are the different echo intensities (reflectivity) measured in dBZ. "Reflectivity" is the amount of transmitted power returned to the radar receiver. Reflectivity covers a wide range of signals (from very weak to very strong). So, a more convenient number for calculations and comparison, a decibel (or logarithmic) scale (dBZ), is used.

The dBZ values increase as the strength of the signal returned to the radar increases. Each reflectivity image you see includes one of two color scales. One scale represents dBZ values when the radar is in clear air mode (dBZ values from -28 to +28). The other scale represents dBZ values when the radar is in precipitation mode (dBZ values from 5 to 75).

The scale of dBZ values is also related to the intensity of rainfall. Typically, light rain is occurring when the dBZ value reaches 20. The higher the dBZ, the stronger the rainrate. Depending on the type of weather occurring and the area of the U.S., forecasters use a set of rain rates which are associated to the dBZ values. These values are estimates of the rainfall per hour, updated each volume scan, with rainfall accumulated over time. Hail is a good reflector of energy and will return very high dBZ values. Since hail can cause the rainfall estimates to be higher than what is actually occurring, steps are taken to prevent these high dBZ values from being converted to rainfall.