The 4 Color Code
The Northern IL MCS has developed a 4 color
"state of readiness" code, one that spotters can easily
understand--
it's based (more or less) on a traffic light. For severe thunderstorm
season, here's how it works:
- Condition BLUE : Mnemonically,
the sky is usually blue at this point. It is early in the day,
but a threat of severe weather later on is recognized. This is
issued upon recommendation by the National Weather Service, or
the College of DuPage Weather Office. This is simply to alert
the spotter that activation may be necessary.
- Condition GREEN : Mnemonically,
green means GO!, it is time for the spottter to act. This means
that a severe thunderstorm or tornado watch (equal in importance
as far as the MCS is concerned) has been issued. Not all spotters
are deployed; mostly just full time employees who have the ability
to watch the sky as a part of their job (Police, Fire, etc). Emergency
Operations Centers are required to activate and become staffed.
Spotter reports are actively solicited.
- Condition YELLOW : At this
point, weather conditions are about to deteriorate. "Alert"
spotters, IE, volunteer spotters and amateur radio operators,
are now called into action. The National Weather Service or the
College of DuPage may issue this, but any county who feels threatened
may also go to yellow. Even rapidly developing cumulus in a weather
watch box may call for a condition yellow.
- Condition RED : Mnemonically,
this means WARNING.
This occurs when the National Weather Service issues a tornado
or severe thunderstorm warning. Spotter reports are actively solicited.
At the Dupage EOC, a Kavouras radar system is used to help deploy
spotters in areas needed most, and to monitor a storms progress.
Reports of damage are sent to the National Weather Service via
NAWAS, a national warning system.
The 4 color code is also used in the
winter months for snow, ice and wind storms. Here's how it
works:
- CONDITION BLUE: If the National
Weather Service in Chicago issues a winter storm outlook 1-3 days
in advance...and if Chicago mentions significant snow possible,
then condition blue is issued.
- CONDITION GREEN: A winter storm
watch is issued for all or part of the Multi-County SKYWARN coverage
area by the National Weather Service in Chicago.
- CONDITION YELLOW: Winter weather
type advisories, such as winter weather, freezing drizzle/rain,
snow/blowing snow.
- CONDITION RED: Winter weather warnings,
such as winter storm, blizzard, ice storm, freezing rain, heavy snow,
wind chill.
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