Tornado Watch Performance at SPC

Basic objective verification, 1985-1997.

From Joe Schaefer, SPC

This table gives some verification statistics, year-by-year, for SPC tornado watches -- based only on tornado occurrences.

YEAR # of tornado watches % of tornado watch with tornados # of tornados POD tornado in tornado watch Tornado watch lead time Median tornado watch area # of F2 or greater tornados POD F2 or greater tornados

1970 220 31 653 21 2.24 23479 234 28

1971 274 40 889 33 2.33 25172 320 38

1972 181 43 737 22 2.08 22300 222 32

1973 379 45 1102 35 1.95 24307 386 49

1974 238 48 944 38 2.13 25330 339 54

1975 291 44 919 29 1.93 25362 236 35

1976 212 50 834 33 2.03 24243 231 44

1977 199 48 852 30 2.24 26145 182 40

1978 201 47 789 30 2.21 26190 128 41

1979 208 44 855 30 2.26 23832 150 46

1980 207 51 866 36 2.07 28398 199 44

1981 179 49 782 32 2.16 25885 179 45

1982 257 56 1047 45 2.51 28243 251 58

1983 251 54 931 46 2.31 27741 209 60

1984 223 56 907 48 2.1 28938 182 64

1985 207 51 684 43 2.56 29844 117 63

1986 197 46 763 36 2.21 25205 140 46

1987 156 40 656 28 2.31 25136 77 53

1988 168 48 702 43 2.5 25814 108 69

1989 261 50 856 45 2.44 24893 123 59

1990 314 53 1133 53 2.25 23781 211 72

1991 294 56 1132 51 2.31 24674 149 78

1992 348 52 1297 52 2.34 22696 186 75

1993 350 48 1173 50 2.33 24299 116 71

1994 275 52 1082 47 2.02 23355 116 66

1995 420 48 1234 61 2.17 25986 129 84

1996 479 48 1171 63 2.11 25317 114 72

1997 324 51 1148 54 2.14 24170 124 88

1998 379 58 1426 57 2.05 23760 160 84

1999 255 64 1343 57 1.94 25395 188 89

2000 226 60 1071 40 2.08 23607 85 76

NOTES: %Tor Verf is percent of all tornadoes nationwide in tornado watches. [Severe thunderstorm watches not included.] POD is probability of detection, the percentage of watches containing at least one tornado. Lead T (also "projection time") is the lead time between watch issuance and first tornado report. Median Area is the middle value of all watch areas for the year. The annual counts of reports are number of reports through time verification was calculated, and may not include reports received late.