The Io phase is the angle of Io in its orbit with respect to superior geocentric conjunction. In other words when Io is directly behind Jupiter as seen from Earth the Io phase is 0 degrees and when Io crosses in front of Jupiter as seen from Earth it is 180 degrees. The sub-Io longitude. The Jovian longitude at which Io is transiting at the given date and time. These are the Io-related storms.
Some storms appear to occur independent of the location of Io.
These storms are non-Io related. The hour angle of Jupiter as seen from the University of Florida Radio Observatory and from the Owens Valley Radio Observatory, California. A value of 0.0 means Jupiter is on the local meridian at the given time. These are occurence probabilities compiled by the University of Florida Radio Observatory from 1985 through 1992 using an 18 MHz Yagi antenna. The occurence probabilities are computed by dividing the number of times that a storm has been heard for a given LambdaIII and Io Phase by the number of times the given LambdaIII and Io Phase has been listened to.