Appendix A

Fujita Tornado Intensity Scale

The Fujita Tornado Intensity Scale is a scale of wind damage intensity which wind speeds are inferred from an analysis of wind damage.

Category Definition and Effect
FO Gale tornado (40-72 mph): Light damage. Some damage to chimneys; break branches off trees; push over shallow-rooted trees; damage sign boards.
F1 Moderate tornado (73-112 mph): Moderate damage. The lower limit is the beginning of hurricane wind speed; peel surface off roofs; mobile homes pushed off foundations or overturned; moving autos pushed off the roads.
F2 Significant tornado (113-157 mph): Considerable damage. Roofs torn off frame houses; mobile homes demolished; boxcars pushed over; large trees snapped or uprooted; light-object missiles generated.
F3 Severe tornado (158-206 mph): Severe damage. Roofs and some walls torn off well-constructed houses; trains overturned; most trees in forest uprooted; heavy cars lifted off ground and thrown.
F4 Devastating tornado (207-260 mph): Devastating damage. Well-constructed houses leveled; structure with weak foundation blown off some distance; cars thrown and large missiles generated.
F5 Incredible tornado (261-318 mph): Incredible damage. Strong frame houses lifted off foundations and carried considerable distance to disintegrate; automobile-sized missiles fly through the air in excess of 100 yards; trees debarked; steel-reinforced structures badly damaged; incredible phenomena will occur.


Appendix B

Spencer, South Dakota, Tornado

May 30, 1998

Chronological Log

Valid Time CDT Product Type/Report Counties Affected NWR Log Time EAS Log Time Remarks
0405 SFP Southeast SD NA NA "some thunder/ storms could be severe south/ east" - tonight
0405 ZFP

Hanson, McCook and Turner

NA NA "some thunder/ storms could be severe" -tonight
0435 SPS Southeast SD NA NA "Moderate Risk of severe weather today"
1100 ZFP

Hanson, McCook,

Turner

NA NA "some thunder/ storms could be severe" - tonight
1147 SPS Southeast SD NA NA

"severe winds,
large hail and tornadoes possible" /

"spotter activation likely after 4 PM"

1550-2200 SEL8 McCook 1548 NA Tornado Watch #468
1625 ZFP

McCook,

Hanson, Turner

NA NA Tornado Watch for McCook, "severe thunderstorms" Hanson and Turner
1730 NOW

McCook,

Hanson,

Turner

NA NA Thunderstorms this evening "could become severe"
1845-1955 SVR Beadle NA NA
1850 NOW Huron (city) NA NA storms impact on Huron
1903 SVS Beadle NA NA Pathcast update
1919 .75 inch hail Beadle 3 W of Huron
1923 SVR Beadle NA NA
1940-2010 SVR Sanborn 1937 NA 10 to 40 miles northwest of Spencer
1944-2015 SVR

NE Davison

N Hanson

NA NA
1945 TORNADO Kingsbury Between Desmet & Lake Preston
1946 SVS Sanborn NA NA

Updated location and

movement

1955 FUNNEL CLOUD NE Davison Spotter
1955 SVS Beadle 1956 NA Warning Expiration
2001-2035 TOR

NE Davison

N Hanson

NA NA

Replaced SVR

(NAWAS only)

2002 TORNADO Kingsbury 5 W Lake Preston
2008 TORNADO Hanson 8 NE Mitchell
2012 TORNADO Hanson W of Farmer. Report from EAX WCM
2012-2045 TOR N Hanson NA NA
2013 LARGE TORNADO Hanson NE of Mitchell
2013 SVS NE Davison NA NA Cancelled TOR for NE Davison
2015 1.75 inch hail Hanson 7 E Loomis
2016-0300 SEL9

Hanson,

McCook,

Turner

2039 NA

Tornado Watch #469

PDS Watch

2023 TORNADO Hanson

5 NW Fulton.

Report from Mitchell PD

2024-2055 SVR Miner 2026 NA
2025 TORNADO Hanson

1 W Spencer.

Report from McCook Co. Sheriff

2029 LARGE TORNADO Hanson W of Spencer. Report from Mitchell PD
2032-2105 TOR McCook 2032 2034 Live and recorded simultaneously on NWR
2034 SVS Miner NA NA
2044 TORNADO McCook 1 Dead, 47 Injured. Extensive damage in Spencer
2045 TORNADO Hanson 5 W Emery
2045-2120 TOR Hanson NA NA
2050 TORNADO McCook 9 N Bridgewater
2052 SVS Miner 2052 NA Cancelled Warning
2054 SVS N McCook 2058 NA Tornado report near I-90 & Bridgewater exit
2055 TORNADO Hanson At Alexandria
2055 ZFP

Hanson,

McCook,

Turner

NA NA Updated for Tornado Watch #469
2059 SVS Hanson NA NA Tornado report & radar indication near Alexandria
2100 Wind G60 W Lyon From Lyon EM
2104-2140 TOR McCook 2106 2107 Live and recorded simultaneously on NWR
2109-2140 SVR

E Lake,

Moody

2110 2112 Live and recorded simultaneously on NWR
2110 TORNADO McCook At Bridgewater
2111 SVS McCook 2117 NA

Tornado reported near Bridgewater.

Radar indicated near Bridgewater & SW of Montrose

2115 Wind Damage Lyon MN N Russell
2116-2150 SVR

Lincoln MN,

Lyon MN

NA NA
2117 Funnel Cloud Minnehaha 2 W Wall Lake. Source Spotter
2120 TORNADO Turner 2 E Monroe
2120-2210 TOR Minnehaha 2122 2124 Live and recorded simultaneously on NWR
2121 SVS Hanson NA NA Warning Expiration
2125 NOW Most of CWA NA NA Severe Weather Potential
2128-2200 TOR N Turner 2129 2131 Live and recorded simultaneously on NWR
2131 SVS

E Lake,

Moody

2134 NA Updated location
2134 SVS McCook 2136 NA Updated tornado location (radar)
2136 Wind Damage Lyon MN 5 N Russell
2138 SVS

Lincoln

Lyon MN

NA NA Updated storm location
2141 SVS Moody 2143 NA Warning expiration
2144 SVS E McCook 2146 NA Warning expiration
2146 SVS Lyon MN NA NA Warning expiration
2148-2220 SVR Lincoln (N&C) 2149 2150
2148 SVS N Turner NA NA Updated storm location
2150 SVS Minnehaha 2154 NA Public report of tornado west of Sioux Falls
2156-2220 TOR Lincoln (N&C) 2157 2159
2201-2255 SVR

Rock MN

Lyon IA

2205 2205 Live and recorded simultaneously on NWR
2203 SVS N Turner 2206 NA Warning Expiration
2208-2240 SVR

S Lincoln

Sioux IA

2210 2211 Live an recorded simultaneously on NWR
2210 SVS Minnehaha 2213 NA Warning Expiration
2218 SVS Lincoln (N&C) 2219 NA Warning Expiration
2228-2300 SVR Nobles 2229 2230 Live and recorded simultaneously on NWR
2229 SVS

Rock MN

Lincoln

2231 NA Warning Expiration
2232 SVS

Sioux IA

Lincoln

2241 NA Warning Cancellation
2240 ZFP All covered by Watch #469 NA NA Remove Tornado Watch
2240 SVS Sioux IA NA NA

Warning

Expiration

2242 SVS Nobles MN 2245 NA Updated location & pathcast
2300 SVS Nobles MN 2302 NA Warning Expiration

Notes: For Column 3, Counties Affected, only Hanson, McCook and Turner Counties are listed, as applicable, for ZFPs, SPSs, and Watches.

NA = Not Available or Not Applicable.


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