2002 NWS TAUNTON SEVERE WEATHER STATISTICS

 A) TOTAL # OF WARNINGS ISSUED:         130   B) # OF WARNINGS THAT DID NOT VERIFY:  40   C) “WARNED SEVERE EVENTS”:              96       [   Verified Warnings  = 90     (A-B)        + Multiple Severe Events          within same warning:= 6 ]   D) # OF SEVERE EVENTS WITHOUT WARNING: 21   E) TOTAL SEVERE EVENTS:                117 (C+D)

The numbers above are used to calculate severe weather statistics, which give a measure of an office’’s performance. There are 3 statistics used in severe weather verification:

1. False Alarm Ratio, or FAR, which is the ratio of unverified warnings to the total number of warnings issued. The lower the FAR the better, since it expresses the number of "false alarms" issued.

2. Probability of Detection, or POD, is the ratio of warned severe events to total severe events. A high POD is best, since it shows the skill an office has in warning for severe weather events.

3. Critical Success Index, or CSI, takes both FAR and POD into account to give a measure of performance that includes both verified and unverified events. As with POD, a high CSI is best.

An average lead time was calculated for all warnings issued this year. Lead time is defined as the time elapsed from when the warning was issued to the time of the first severe weather occurrence in the warned county.

FALSE ALARM RATIO (FAR):

 (0 is best) UNVERIFIED WARNINGS = 21 = 30.7 % TOTAL WARNINGS 130

PROBABILITY OF DETECTION (POD):

 (100% is best) WARNED SEVERE EVENTS = 96 = 82.0 % TOTAL SEVERE EVENTS 117

CRITICAL SUCCESS INDEX (CSI):

 (100% is best) WARNED SEVERE EVENTS = 96 = 61.1 % TOTAL SVR EVENTS + UNVER WRNGS 117+21