Plot Description:

• Event Count: The number of distinct VTEC events. A distinct event is simply the usage of one VTEC event identifier.
• Days with 1+ Events: This is the number of days within the period of interest that had at least one VTEC event. A day is defined within the US Central Time Zone. If one event crosses midnight, this would count as two days.
• Percent of Time: This is the temporal coverage percentage within the period of interest. Rewording, what percentage of the time was at least one event active.
• Rank of Event Count: The ranking from least to greatest of the given period's event count vs period of record climatology.
• Departure from Average of Event Count: The number of events that the given period differs from the period of record climatology.
• Standardized Departure from Average of Event Count: The departure expressed in sigma units of this periods event total vs the period of record climatology.

PLEASE USE CAUTION with the departure from average plots as they are not exactly straight forward to compute. If you are plotting small periods of time, individual events will heavily skew the averages. The exact start date of each event type is not an exact science due to the implementation of some products and other complexities. For Severe Thunderstorm, Tornado, Flash Flood, and Marine Warnings, the IEM has a special accounting of these back to 2002. For other event types, the archive starts with the VTEC implementation, which varies by product.

Note that various VTEC events have differenting start periods of record. Most products go back to October 2005.