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"Unfiltered" vs. "Filtered" reports?

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6.11 What are the differences between the filtered and the unfiltered Storm Reports?

Unfiltered: On March 8, 2011, the SPC started providing unfiltered storm reports by removing space/time filtering on incoming National Weather Service (NWS) Local Storm Reports (LSRs). This approach is consistent with NWS storm-based verification methods. However, identical reports are removed from SPC logs and should not appear on the preliminary maps and lists.

Filtered: The space/time filtering had been used by SPC in an attempt to reduce duplicate reports and limit artificially inflated initial estimates of severe weather events when many reports arrived for the same event. The filtering is applied to each of the tornado, hail and wind reports separately.

The logic implemented for filtering is as follows:

Same county and state

Same regular expression of deaths/fatalities

Spatial/Temporal differences between pairs

Less than 5 miles and 5 minutes for tornadoes

Less than 10 miles and 15 minutes for hail and wind reports. (the higher wind speed and larger hail size reports are kept.)

The filtering logic is applied to tornado, hail and wind reports separately. For example, a tornado report and hail report for the same location and time are kept in their respective reports.

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