NOAA radar colors.

:? Just wondering about the colors on the NOAA radar sites. Usually lite rain is displayed as shades of blue and progress to green and so forth but many times the real light precip and everything else starts out orange, yellow etc. Is this because of the sensitivity of the radar, long wave or short wave? What gives?

Dennis
 
Assuming you are looking at images from the noaa.gov site, and you're talking about when the radar is in precipitation mode (color bar to the left of the image from 5 to 75 dBZ), then it may have to do with how far the returns are from the radar, and how dry the lower levels are. Green colors associated with returns from precipitation size droplets near the radar should correlate pretty well with precipitation being experienced on the ground nearby. As one gets farther from the radar, the same returns (say from areas beyond 100 miles from that radar where the beam is above 10000 ft AGL) could be virga as the radar beam would be intercepting the "echoes" well above the ground. At such distances, even if the precipitation size droplets are reaching the ground, they may not be doing so directly under the returns as droplets can drift with the wind below the radar beam.

Or are you talking about when the color bar on the left goes from -28 to +28 dBZ, in which case the radar is in clear air mode?
 
:? I looked at the difference between the Omaha and Des Moines radar sites today and everything seemed to be properly displayed at the Omaha site while Des Moines showed the same precip as yellows, oranges and whites. The Ground clutter at Des Moines was also yellow and orange and covered half of the state.

Dennis
 
Originally posted by Dennis Gulley
:? I looked at the difference between the Omaha and Des Moines radar sites today and everything seemed to be properly displayed at the Omaha site while Des Moines showed the same precip as yellows, oranges and whites. The Ground clutter at Des Moines was also yellow and orange and covered half of the state.

Dennis, the Des Moines radar is in "clear-air mode" while the Omaha radar is in "precipitation" mode. Please see this page for a description of these modes.

Walker
 
A radar will usually switch itself from clear air mode (VCP 32 or 31) into precipitation mode (VCP 21, but can be switched to VCP 11, 12, or 121 by preference of the staff on duty) by itself, when a certain portion of the radar umbrella is covered by precipitation. Sometimes, the person responsible for operation of the radar will have to force it into precip mode if it doesn't do this early enough, but this is the exception to the rule.
 
If storms are "just firing" and you don't have Level II access it is a good idea to stay in clear-air, so you can see all the boundaries and details. Once a storm is actually "in progress" the radar automatically switches over.
 
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