7/30/2019 Tornadoes - Deadly forces
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SUSAN BATSFORD, GRAPHICS EDITOR,TWITTER @SBATS1; QMI AGENCY
Most tornadoes are related to the strength of a thunderstorm,and
thunderstormsnormally gain most of their energy from solar heating
and latentheat released by the condensation of water vapour.
Therefore,most tornadoes occur in the afternoon and evening
hours.
TORNADO TIMING
Atmospheric conditions combiningto create tornado alley.
Average number of tornadoes per year, by state.
Deadly forces
DEADLIEST U.S. TORNADOESDate Class State Deaths
Mar. 18, Missouri,1925 F5 Illinois, Indiana 695
May 6, Louisiana,1840 N/A Mississippi 317
May 27, Missouri,1896 F4 Illinois 255
Apr. 5,1936 F5 Mississippi 216Apr. 6,1936 F4 Georgia 203
Mondays tornado in Oklahomawas not unique to the area. Oklahoma
lies in tornado alley the area ofthe United States where tornadoes
are most frequent.
Tornadoes cause an
average of70 fatalitiesand 1,500injuriesin the U.S.
eachyear.
Ore.3
Nev.2
Calif.11
Idaho5
Mont.10 N.D.32 Minn.
45
Wis.24
S.D.36
Neb.57
Iowa51
Wyo.12
Utah3 Colo.
53
N.M.11
Kan.96
Okla.62 Ark.
39
La.37
Miss.43
Ala.44
S.C.27
Ga.30
Fla.66
Mo.45
Texas155
Ill.54 Ind.
22
Mich.16
Ohio19
Pa.16
Wash.
3
Ky.21
Tenn.26
W.Va.
2 Va.18N.C.31
N.Y.10
Maine3N.H.
1Vt.
1Mass.
1R.I.
0Conn.
1N.J.
2Del.
1Md.
0D.C.
1
Ariz.5
COLD DRY AIR
TORNADOALLEY
WARM
MOIST AIR
JET STREAM
Moore
MooreMedical Centre
Debrisfield
Norman
Midwe i
Blanchard
Tuttle
BethanyWill
RogersPark
Newcastle
BridgeCreek
O K L A H O M AC I T Y
35
3540
40
240
44
May 20, 2.56pm: Category 4tornado touches down withwinds of up
to 320km/h.On ground for 40 minutes,striking town of Newcastleand
suburb of Moore
May 1999: Category 4Tornado claims 48 lives
Plaza Towers andBriarwood ElementarySchools destroyed
Moore
Debrisfield
Newcastle
O K L A H O M AC I T Y
35
3540
40
240
44
Plaza Towers andBriarwood ElementarySchools destroyed
MooreMedical Centre
May 20: Category 4 tornado; winds up to320 k.p.h. On the ground
for 40 mins., ittravelled 65 km, striking a path 3-km widethrough
Newcastle and suburb of Moore.
May 1999: Category 4tornado claims 48 lives.
WARM DRY AIR
AVERAGE NUMBER OFTORNADOES PER MONTH300
250
200
150
100
50
J F M A M J J A S O N D
NUMBER OF TORNADOES
BY YEAR IN THE U.S.
TIME OF OCCURRENCE, U.S.
1950 55 60 65 70 75 80 85 90 95 2000 05 10
1200
1400
1000
800
600
400
200
1600
1800
0.14
0.18
0.1
0.06
0.020-1
2-3
4-5
6-7
8-9
10-11
12-13
14-15
16-17
18-19
20-
21
22-
23
