ML19312D387

Review of Severe Weather Meteorology at Bmi

ML19312D387
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Issue date:	09/30/1977
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Text

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REVIEW OF SEVERE WENITIER METEOROLOGY i

at BATTELLE MEMORIAL INSTITUTE-COLUMBUS, ' OHIO 4

by T. 'Iheodore Fujita Professor of Meteorology The Universi / of Chicago s

e September 30, 1977 Under Contract No. 31-109-38-3731 i

Argonne.Nat%nal Laboratory L

9700 South Cass Avenue

!~

Argonne Illinois 60439 E

f800s24 9 3[1f

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Review of Severe Weather Meteorology

. at Battelle Memcrial Institute Columous,: Ohio 4,

T. neodore Fujita Professor of Meteorology he Universitf of Chicago 1.

INTRODUCTION De Battelle Memorial Institute, Columbus, Ohio is located just to the west of the Big Darby Creek at 83*15'W and 39*58'N, De elevation of the site, esti-mated from the West Jefferson Quadrangle 7.5 minute topographic map, is 910 ft MSL.

As shown in Figure 1, the overall topography within the 10-mile range is flat, sloping up slightly toward the west. ' Here are no mountains or hills of significant height which might induce orographic upslope or downslope currents.

For most design purposes, the environment of this site may be regarded as being flat.

According to Pautz (1%9)U) he SELS Log reported 18 occurrences of 50 kt

,t and greater windstorms and 20 tornadoes within the one-degres box of latitudes -

and longitudes which includesthe Battelle site. It is the purpose of this review to determine the intensity of sewre weather events which could affect this location, with return periods ranging between one and ten ttillion years.

Both straight-line winds and tornadoes are regarded as prime phenomena, because no hurricane with significant winds has ever been reported in this area.

1

' Ibis site is located in Region II of WASH-1300 De calculated tornado windspeed by five-degree squares for 10. per year probability is 340 mph, b

I }Pautz,.Maurice E. (1969): Severe Local Storm Occurrences, 1955-1967

. ESSA Tech. Memo WBTM FCST 12. !

.j I

f I kWASH-1300 by Markee, E. H., Jr;, J. G. Beckerley, and K. E. Sanders (1974):

Technical Basis for Interim Regional Tornado Criteria.

U.S. Atomic Energy i

Commission, Office of Regulation..

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Figere 1.

Battelle Me=orial Institute and vicinity. The Institute is located just to the west of the 31g Darby Creek.

The elevation of the site is 910 ft MSL. Hei6bt contours in this map were drawn at 100-ft intervals.

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2 STRAIGH-LINE WINDS Straight-line winds occur more frequently than tornadoes, but their inter-pretation and evaluation are difficult. " Climatological Data.@ includes Columbus and Dayton, Chio from whfch the fastest-mile windspeeds of the year (and month) are available.

Presented in Table 1 are the maximum fastest-mile windspeeds of each year between 1950 -76 at both Columbus and Dayton, Ohio. It should be noted thac windspeeds are highly dependent upcn the anemcmeter environment and exposure (including the height) of the inst ument.

De mean speed at Columbus is 43.4 mph which is 4.1 mph lower than the

52. 5 mph mean speed at Dayton, C3:io, ne two stations are 71 miles apart and their elevations az e 1115 ft (Columbus) and 1274 ft (Dayton).

Table 1.

Maxinum fastest-nile windspeeds in aph by year at Colunbus and Dayton, Ohio during the 27-year period, 1950-76. From m Ntological Data for these years.

Years 1950' 1951 1952 1953 1954 1955 1956 1957 1958 '1959 colunbus 57 4

61 43 49 63 57 48 42 56 Dayton 78 56 62 51 56 61 56 49 56 63 Years 1960 1961 1962 1963 '1964 1965 1966 1967 1968 1969 colunbus.

h2 40 45 4

54 56 47 54 42 36 Dayton 56 59 39 53 43 41 45 60 43 40 Years 1970 1971 1972 1973 1974 1975 1976 Mean speeds ~

colunbus 56 47 41 42 52 37 51 mph 48.4 aph Dayton 61 56 52 47 47 42 45 aph 52 5 nph I1) Climatological Data. Publication of NOAA, published monthly with an Annual

- Summary. May be obtained from Environmental Data Service, National Climatic Center, Federal Building, Asheville, North Carolina 28801.-

1 en-w w

y m

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6-4

. In oroer to combine de fastest-mile speeds from these two stations and obtain windspeed probabilities, speeds were normalized by multiplying the

- following ratios, p

Mean of Columbus and Dayton., 50.45~

1.04 (for Columbus) i

=

Mean at Columbus ea. 4 and Mean of Columbus and Dayton 50.45 0.96 (for Davton)

=

Mean at Dayton o2.o Windspeeds computed by multiplying each of 6ese ratios by the fastest-mile speeds frem each station are called 6e " normalized fastest-mile windspeeds ".

- They are then used in obtaining the statistical results presented in 61s review.

In cen:ral Ohio, the fastest-mile winds of the year.in de cold seasons (late autumn,' winter and early spring) are the result of well-developed continental cyclones. 'Ihe fastest-mile winds in the varm seasons (late spring, summer, and

- early autumn) are often caused by so-called " straight-line winds " induced by severe thunderstorms.

Table 2 was prepared to show the seasonal variation of the fastest-mile winds of de year by month. April through September are regarded as warm

- ser. sons and Octcher through March, as cold seasons.

' Table 2.

Normalized fast 9st-mile windspeeds of the year i..

obtained by malcing the mean-speed correetion. Speeds are tabulated by month. year god at Columbus and Dayton, Ohio.

j Months.

.Apr May_ Jun Jul Aus Sep Oct Nov.: Dec Jan Feb - Mar i

l 58 58 74 53 43 53 63 48 58 59 65 mph 54-56 30 51 43 59 45 53 59 60 53 50 48 49 58 43 46 57 58 i

53. 39

43. 44 47

43. 56 53 l'

45 38 ~42

'37

'56 49 41 18 53 45 L

41-43 45

' 40 37 41-Maximum 58.58 74 53 43-53 63 48.58

.59 65 nph

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6-5 Table 3.

Probabilities of nor:nalized fastest-mile speeds of the year during vara seasons (April-Septenter), cold sea-

{

sons (October-March), and all year. Frequencies (Freq.),

cumulative frequencies (Cun.), and probabilities per year (Prob.) are tabulated. 27-year period, 1950-76, at Columbus and Dayton, Ohio.

Norma W ed Warm Seasons Cold Seasons All Seasons windspeeds Freq. Cum. Prob.

.Freq. Cum. Prob.

Freq. Cum. Prob.

37 mph 0

25 0.46 yr-'

2 29 0.54 yr-'

2 54 1.00 ri'

.38 2

25 0.46 0

27 0.50 2

52 0 96 39' i

23 - 0.41 0

27 0 50 1

50 0 93 40 1

22 0.41 0

27 0 50 1

49 0.91 41 2

21 0 39 1

27 0 50 3

48 0.89 42 1

19 0 35 0

26 0.48 1

45 0.83 43 3

18 0 33 3

26 0.48 6

44 0.81 44 1

15 0.28 0

23 0.43 1

38

,0.70 45 i

14 0.26 3

23 0.43 4

37 0.69 46 0

13 0.24 1

20 0 37 1

33 0.61 47 0

13 0.24 1

19 0 35 1

32 0 59 48 1

13- 0.24 1

18 0 33 2

31 0 57 49 1

12 0.32 1

17 0.;i 2

29 0 54 9

50 2

11 0.20 0

16 0 30 2

27 0 50 51 1

9-0.17 0

16 0 30 1

25 0.46 52 0

8 0.15 0

16 0 30 0

24 0.44 53 3

8 0.15 4

16 0 30 7

24 0.44 54 1

5 0.093 0

12 0.22 1

17 0 31 55 0

4 0.074 0

12 0.22 0

16 0 30 56 1

4 0.074-2 12 0.22 3

16 0 30 57 0

3 0.056 1-10 0.19 1

13 0.24 58 2

3 0.056 3

9 0.17 5

12 0.22 59

'O 1

0.019 3

6 0.11 3

7 0.13 60 0

1 0.019 1

3 0.056 1

4 0.074 63 0

1

- 0.019 1

2 0.037 1

3 0.056 65 0

19 0.019 1

1 0.019

_1 2

0.037 74 1

1 0.019 0

0 0.000 1

1 0.019 l

l l

9 9

9 m.a 2

r-

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.3 -...

6.

From a meteorological point of view, one may assume the maximum wind-speeds of a continental cyclone to be 70 to 80 mph, which correspond to the low F1 scale or low hurricane winds. - The maximum possible windspeeds of straight-line winds have not been known very well, but they could reach the 90 to 100 mph

. range or even higher. ~ The Northern Wisconsin downbursts of the 4th of July,1977

'\\

were estimated

• up to les F ? 'or 110 to 120 mph fastest-1/4 mile speed.

.Due to anticipated differences in the nature of winds in warm and cold

seasons, their probabilities were first computed separately. - They were then com-bined into all-season probabilities (see Table 3),

i Figure 2 reveals the trend of probabilities given in Table 3 Apparently, the windspeeds in cold seasons tend to saturate at or with 10" to 10" year"'

. probabilities, while those in warm seasons keep increasing with decreasing prcha-bility. These resalts indicate that 1.0 to 0.1 per year probabbity is dominated by the winds in cold seascus (condnental cyclone origin). A 0.01 per year probability or lower is, however, dominated by the winds in warm seasons, which are induced by severe convective stczms.

Table l+.

Froquencias of fastest-nile wind directions by During warm seasons west-northwesterly winds of seasons.

connective origin dominate frequencies; while in cold sea-p sons west-southwesterly winds of continental cyclone or181n dominate frequencies.

Wini directions S-SE S

SW W

NW N

NE Unimown' Total Warm seasons-0 1

1 5-7.

9 i'

0' i

25 Cold seasons.

0.

0

.2 12 11 3

1 0

0 29-t l

All seasons 0

1' 3

17 18 12 2

0 i

\\'

Directions of the fastest-mile winds in Table 4 also reveal a major difference

' between warm-and cold-season winds. During the cold seasons,' directions are predominatnly from southwest to. west, while those in warm seasons are from west

- to northwest.(see Figure 3).

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6-7 10' ^ 40 50 60 70

'80 90 mph

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ALL 5EASONS

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E O%o STRAIGHT-LINE WINDS Figure 2.

Probabilities of the speeds 'of the fastest-nile winds of the year at Colunbus and Dayton, Ohio. Based on a 27-year record, 1950-76. Probabilities were estimated by separating the speeds in warm and cold seasons, because the

- nature of winds is apparently different in these seasons.

From Table 3

~

6-8 WARM SEASONS 8

( APR - SEP)

Running Mean

.(

i 6

4 2

o i

W_ L E

SE S

SW W.

NW N

NE' E N

COLD SEASONS to (oC r - MAR) 8 d

6 Running Mean 4

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2 A1 o

i E.

SE

.S SW W

NW-N NE ' E i

Fi6ure 3. -Directions of fastest-mile winds of the year at i

Columbus ani Dayton, Ohio during warm and cold seasons. It

!~

should be noted that the fastest-mile winds in. warm seasons are predominantly from west to northwest while those in' cold seasons, from southwest to west. From Table l+.

6-9 The probabilities of de occurrence of maximcm windspeeds should be

~ defined differently from.those cf tornadoes, because windspeeds at each station are measured in time domain at a fixed point._ Their spatial variations around the.

K anemometer are usually unknown.

For tornadoes ' the National Weather' Service lists all storms based on the best possible information.; Tornadoes are listed separately, even if they occur

on the same day or even a few minutes later.

The maximum fastest-mile speeds are listed in " Climatological Data " by month and by year. : There is no mention as to how often te maximum speed occurred within one month or one year. The periods of straight-line winds, especially the ones caused by continental cyclones, are long, lasting hours or even

days. There will be numerous maxima during such a long period. We should,

-therefore, define the following terms:

Fa. nest-mile day -

-- the day on which the speed occurred Fastest-mile month -- the month in which the speed occurred

[

Fastest-mile year ~. - :the year in which the speed occurred These are similar to the term -

Tornado day -- the day in which one or more tornadoes occurred.

In these cases, the number of occurrences witin the stated period is not impcrtant. -

4 Probability of the fastest-mile year can be computed by L

Number of years in which specific speed or larger speed occurred p

l Total number of years used in statistics I

where P. denotes the occurrence probability per year.

!?

.The probabilities in Table 3 were computed by en=hining the observation years at Columbus (27 years) and Dayton (27 years), thus resulting in statistics of 54 observation years.

i.

I Windspeeds of peak gusts are higher than those of fastest mile winds, because the duration of a peak gust is considerably shorter than the period of the

-fastest-mile wind. In this review, the former is regarded as being 25% longer 6an

de latter. J Namely, -

- Peak Gust

• 1.25 Fastest-mile Speed.

+ - -..

.6 -10 c

13.s'1DRNADO FREQUENCIES FROM NSSFC TAPE He NSSFC Tornado Tape lists-567 tornadoes wi6in 144 miles from Battelle Memorial Institute during the 26-year period. 1950-75.

De cumulative frequencies were ccmputed to determine the trend of their

increase as'a fuEction of the rang,e from the site. As shown'in Figure 4. the

- best-fit parabolic curve is '

~ N = 0. 0295 - R" '

where N is the number of tornadoes within range, R. in miles. A gradual decrease -

in the number of tornadoes 'at renges in excess of 100 miles is in part an effect of Lake Erie. Another reason being a decrease in tornado frequencies in the south-

eastern sector.

A breakdown of tornado f' requencies by year in Table 5 shows relatively low l

frequencies in the early 1950s when de tornado reporting system by de U.'S, Weather Bureau was in the process of being improved. The maximum frequencies of 74 occurred in 1973 followed by 59 in 1974, which was de year of 6e April 3-4 super-outbreak.

' Table 5.

Frequencies of tornadoes within 144 miles from Battelle Memorial Institute by year. 3ased on the NSSFC

. tape, 1950-75. :

l Years :

' 1950 -1951. 1952 1953 1954 ~1955 1956 1957 1958 1959.

Frequencies-6:

5-2 12 17 12 20-14 19-11 I'

t

[-

-Years 1960 '1961 1962 1963 1964 "1965' 1966 1967 1968 1969 Frequencies -

-11 33 5'

28 17 59 4

17 33 27 i

I --

1

- Years 1970' 1971 1972 1973-1974 1975'.

~Mean' i-Frequencies

!31 21 14 ' 74-59

. 16 21.8 f

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400 O*

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300 200 -

100 -

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-20 40 so ao 10 0 120 I40 miles Figure 6. ' Cumulative number of tornadoes as a function of the distance from Battelle Memorial Institute. Based on 367 tornadoes in NSSFC tape, 1950-75 e

8

i:

r 6 -12 Torna' o frequencies by_ month reveal that April with 163 tornadoes is the d

~

month of the highest frequency.; he lowest frequency month is January, with only 2 ' tornadoes out'of 567 or 0.35% '(see Table 6).

Table'_6. - Frequencies of tornadoes within' 144 miles from

-Battelle Memorial Institute by month. Based on t.he ?E3FC tape, 1950-75

' Months Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Total-

. Frequencies-2;.16 31 163 97 95 64 - 43 23 6

19 8

567 4.

STATISTICS FROM DAPPLE TAPE De DIPPLE Tornado Tape introduced by Fujita (1977)- 01 can be used in computing the path lengths of F-category tornadoes within 15 x 15 min sub-boxes of longitudes and latitudes anywhere inside the contiguous United States. An attempt was made, in this review, to make use of the DAPPLE Tape as a new potential tool in assessing the tornado risk at the Battelle site.

U. S. Tornado Map by Fujita and Pearson (1976) reveals a significant.

1

- decrease of tornado frequencies toward the southeast from the Battelle site, ne frequency gradient is', more or less, perpendicular to the line connecting Cincinnati, Ohio with Cleveland, Ohio.

i.-

' II)Fujita, T. T. (1977): Tornado Structure for Engineering Applications. To be.

L published as SMRP Research Paper No. l153 I )Fujita, T. T." and A. D. Pearson (1970): U.S. Tornadoes, 1930-74. ne

University.of Chicago. -

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6.

[ A realisde assessment of tornado frequencies can, therefore, be achieved

. by. generating a coordinate system with their axes parallel and perpendicular to the maximum gradient of the frequencies.

DThe X-Y coordinates in Figure 5 were constructed based on the above con-siderations. 'Ihen, the banded reeas, A through L', were drawn. Each area is 200 miles long'and 20 miles wide, distributed equally on both sides of X axis.

He total path lengd wi61n each 15 x 15 min sub-boxes of longitudes and

latitudes was computed over the entire area of de bands, A throughIL (see Figure 6).

Pas lengths in miles reveal the largest values of 50 miles (in Indiana)

- followed by 48 miles (in Michigan), and 44 and 43 miles (in Indiana). Here are a i

4

- number of sub-boxes with zero path lengd. As expec,ted, we see more zero numbers to the southeast sector of the Battelle site.

In an attempt to compute the total path lengths in bands A through L, the area of each band was modiSed in such a manner that the band boundary becomes

- de composite' boundaries of 15 x 15 min sub-boxes, ne bands reconstructed from these sub-boxes are called the modified bands,- A drough L (see Figure 7).

Naturally the area of a modified band is differen:'am that of the original bantiwith approximately 200 x 20 = 4,000 square miles. For most bands, areas were expanded by adding a sub-box at each end of the original band.

He path lenge in' miles per unit area or the " path-lengt density " in each modified band was computed from p3g 1,,g gg

, Path length within modified band Area of modified band the unit of which is miles /sq. mile or mile ~'. He unit can be expressed also in

. any other units with identical dimensions,' such as 10 mile * '= miles /10,000 'sq. miles etc.

. m.

EPath-length densities in Table 7 are given in 1.0 mile unit. He last E column of this table reveals that de path-length density of total tornadoes

( FO through F5) decreases from 850 to 38 between modified bands A and L.-

r L

E

9 6 -14 86-85

' 8'4 83 p'2 8l

~42 1

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38-h, 82 85 84 83 81 I

Figure 5 Bands A through L placed around the Battelle site.

Each band 200-mile long and 20-mile wide, is oriented approxi-

nately in a SSW-IME direction.

m-

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. E.

6-l5 86 85 84 83 82 81 I2

'42

[;

N 48 18 5

3 y

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3 2 10 3

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4 4 0

0 1

12 14 13 i

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i Ol'7 18 4 5

17 11 17 15 8 4

13 7

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i 41 13!14 14 18 15 2!

16 9 4

3 2

6 3

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18 0

5 I

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17 5

7 5

4 3

0 1

6 0

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14 7

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16 11 2

3 0

1 12 19 2 I

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2 6

5 2

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8 0

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4 7 19 10 9

28 20 5

1 6

6 0

1 0,

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43 27 21 21 10 6

3 12 19 0 2

9 30 6 I

5 2

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38 POth Lengths Of Oil TOrnOdoes Figure 6.. Total path length within each 15 x 15 sin longitude-latitude sub-box.

From the DAM tape includin For DAFFJ tape, refer to Fujita (1977)g 1950 tor-nadoes.

Tornado Struc-

- ture for Engineering Applications.

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' Figure 7 Modified bands A throu6h L mnsisting of 15 x 15 l

sin longitude-latitu:ia sub-boxes.

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6-17 Table 7.

The path-length density is' defined as the total path length divided'by the area which includes the paths.

The area of modified band varies fron band to band. See Figure 7.'

Modified Path-len6th in each band 2and area Path-length density in 10-*mi" band (F0+F1) -(F2+F3) (F4+F5)

(sq.-ni)

(F0+F1) (F2+F3) (F4+F5) (Total)

A.

100 214 58 4333.

231-494 134 859 3

' 53 158 34 4114 129 384 83 596 c

52 119 44 5030 103 237 87 427 D

24 55 47 3904 61 141 120 322 3

26 65 at 3665 71 177 224 472 F

24 111 70 4624 52 240 151 443 G~

80 112 28 4620 173 242 61 476 H

85-46

-16 4h06 193 104 36 333 I

12 32 17-4640 26 69 37 132 J

22 55 0

4186 53 131 0

184 I

5 11 0

4668 11 24 0

35 L

8 9

0 4440 18 20 0

38 l

This dramatic decrease is shown in graphical form in Figure 8.

'Ibe data

~

points given with painted circles show an appreciable scatter, probably due to the short statistical period, time variations of tornado activities, and other unknown causes. Nevertheless, a smooth line s.

ng down from A to L represents the genet,'. trend of the path-length density applicable to the Battelle site and vicinity.

A breakdown of the path-length density into three-category tornadoes results naturally in large scatters (see Table 7). Nonetheless, we are able to draw a smooth curve for each category tornado (see Figure 9),

i-l-

Table 8 shows the path-length densities at the Battelle site obtained by l

this smoothing method. Results indicate that strong ( F 2 + F3) tornadoes were the largest in density, 0.02 mi~' (mi/sq. mi), followed by both weak and violent category tornadoes, each with 0.01 mi density.. These path-length densities, thus 'obtained, can immediately be used in computing tornado probabilities using the DAPPLE Method.'

)

+- i w

=

w-

.w 6-18 Poth -length Density in mi/lo,000 sq mi e

800 SITE I

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.i-

,1 e e

e 410 mi/lO,000 sq mi 400 l

e e

l 200 O

o e

o

'A ~

B' C

D E

.F G

H I

J K

L Figure 8.

Path-length density (miles per 10,000 sq. mile unit) defined as the total path length wi+h a modified band divided by the band area. Path-length density in this figure l-1acludes all tornadoes, FO.through F5 From Table 7..

l l~

1

• - =

ene,,

p

'w-M m

=--

• s 6-19 FO + F I e-300

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SITE 200 l

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6 4

10 ml/10,000 sq mi I00 -'

0 A

B J

D E

F

-G H

I J

K L.

F2 + F3

- 400 h-9.T E 300 l

e ie 200 200 ml/lo,000sq mi i

e 100 e

e i

a A

B C

D E

F G

H I

J K

L 300 -

F4 + F5 200,,

8 SITE ~

e ei O

100 -

-g 100 mi/lo,000 sq mi O

3 A

B C

D E-

F G

H I

J K

C l

Figua 9. - Fath-length densities (miles per 10,000 sq. mila unit) of three-cate6ery tornadoes averaged ovre the area of p

each band, A through L.

From Table 7 i

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l l.

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- - - - - - = = ' - - - -

.j.c 1

6-20 Table 8.

Path-length density (ni/10,000 sq ni or 10" nile ) of three-categorf-Arnadoes, Weak (F0+F1), Strong (F2+F3)', and Vio1*nt -(Fh?3) applicable to the Battelle Site.

I Weak..

' Strong Violent All torradoes 110.

200 100 410

-1 5 WINDSPEED PROBABILITIES OF TORNADOES t

The DAPPLE (Damage Area Per Path Length) MEnlOD developed trf Abbey and Fujita (1975)(I) is capable of compudng tornado probabilldes as a function of the F-scale damage categories, wnich can be converted into windspeeds (see

- Table ?).

)

Using the DAPPLE METHOD, the area of specific windspeed can be computed j

by the product, i

Windspeed Area = Path Length X DAPPLE,

^

where path length denotes that of specific F-scale tornadoes and the DAPPLE values vary with F scale.

Table 9 Ranges of F-scale winispeeds ani their weighted, mean values. (Refer to Abbey, Robert (1977): Risk proba-bilities associated with tornado windspeeds. Froc. of Symp.

J on Tornadoes, Assessment of knowledge and inplications for man.)

F. Scale F0

'F1-F2 ~

F3 F4 F5 Range of Windspeed 72 73-112113-157 158-206 207-260 261-318 nph Weighted :nean spe;d 59 92 131 177 227 276-

~

ID Abbey, R. F. and T. T. Fujita (1975): Use of tornado path lengths and

- gradadan of damage to assess tornado intensity probabilides. Preprint of.~

' 9th Conf or. Severe Local Storms, 286-293 y

--4

.w.-.,-.

.--...-u

~-. ~,... - - - -..

')

...c

~

q 6-21 L

l:

~

JSince F-scale assessments assume an accuracy of one scale, tornadoes are classified into three categories: WEAK ( F 0 + F 1), STRONG (F2 + F 3),

and VIOLENT. (F 4 + F 5 ). DAPPLE values were then obtained based on the 147 tornadoes of A' pril 3-4,1974 Super-outbreak tornadoes (see Table 10).

At the present time. DAPPLE values are being updc ed by adding new survey data. Since' we /.o riot expect to survey a large number of F5 tornadoes in the near future, we will have to use these DAPPLE values for our immediate solutions.

Table 10 DAPPIS, in niles, as a function of tornado windspeed. Unit in sq. mile per path mile. EAPPL., values are given for 3 categories 1f tornadoes. From Abbey, R. F.

and T. T. Fujita (1975): Use of tornado path lengths and gradations of damage to assess tornado intensity probabil-ities. _ Preprint of 9th Conf. on Severe Local Storms. 286-L 293 l

l Windspeedn Violent (F4k5) strong (m3)

Weak (F0&i) 50 mph 0 51 mile 0.43 mile 0.074 mile 100 0.14 0.062 0.0028 150 0.036 0.0198 0.000052 200 0.0081 0.0012 0.000000 250 0.0016 0.000087 0.000000 300 0.00023 0.000000 0.000000 350 0.000016 0.000000 0.000000 Now the path-length density in Table 8 and the DAPPLE values in Table 10

~can be combinedinto a product which may be. called the " area density",

area density =

imit =

'where A-denotes the area in which the area of a specific windspeed is located.

For example, a 0.03 square-mile nas located inside a 10 square-mile area

. results in 0.003 area density.' Naturally, the area density decreases with windspeed.

' The areas of three-category tornadoes in Table 11 are given as square miles of windspeed area per 10,000 square miles or 10". Values were computed from Tables 8 and 10 i-7'[

. _, _ ~..

6-22 stable 11. Areas of thres-category tornadoes during a 26-year period,- 1950-75 applicable.to the Battene Site.

Values are -in sq-ni/10,000 sq ni or 10~

Windspeeds

. Violent Strong Wealc All tornadoes 50 mph 51 86 8.14-145 1 100-14 12.4 0 308 26.7 150 36 1 96.

0.0057-56 200 0.81 0.24 0.0000 1.05 250 0.16 0.0174 0.0000 0.18 300-0.023 0.0000 0.0000 0.023 350 0.0016 0.0000-0.0000 0.0016 The windspeed probabilities are now computed from

""8 #

Probability = Years of Statistics unit Year The totalnumber of years usedin these statistics is 26 years,1950-75. The probability of any inna, peed can be obtained by simply dividing the area dcnsity of specific windspeed by 26 fears.

Shown in Table 12 are probabilities per year of various windspeeds at 50 mph intervals. Values indicate that 10 year probability occurs when wind-speeds are between 250 and 300 mph.

1.

l l

[.

-Table 12. Probabilities (year ) of various windspeeds by.all tornadoes r4 the Battelle Site.

Windspeeds Probabilities (yr)

50 rPh 5 58 x 10

100

'1.03 x 10'*

.150-2.15 x 10

i 200 w

4.04 x 10

250 6.92 x 10

'300 8.85 x.10

-350 6.15 x'10

_,,, - + -

a?

o.

6-23 6.1

SUMMARY

AND ' CONCLUSIONS -

.Results of the foregoing computations of windspeed probabilities are

. summarized in Figure 10 which includes 2ree curves applicable to the Battelle

~ site. De fourth curve represents the peak-gust probabilities from the SELS

. Log. 3e three curves are (A)

Probability of fastest-mile year (B).

Probability of fastest-mile year

.-(C)

Tornado probability

%ese curves reveal that the speeds of straight-line winds are higher than tornado winds when the probability is greater than about 10" per year.

Table 13 gives the rnavimum windspeeds corresponding to curves ( A),

~

(B), and (C).' Values for te return periods of one to 10-million years are tabu-lated. It is seen that tornadoes dominate the windspeeds when te probability decreases below one in 100,000 years.

Dree-category probabilities are used in this site analysis:

High probability

-- 10 per year Low probability

-- 10" per year Remote probability -- 10 per year It should be noted that 10 per year is used in determining the design-basis tornadoes for nuclear power plants in WASH-1300.

Table 13. Mar 4="" windspeeds' expected at the 3attelle Memorial Institute Site as a' function of the probability Per_ year. (A)---fastest-mile speeds of straight-line winds (3)--gust speeds-computed as 125 of A.

(C)-

tornado

-windspeeds baned on 1950-75 data.

Protabilities -

Return periods.

Windspeeds in miles per hour

~

.(A)

(3)

(0)

- 10'

'10" per year

.-1 year 38 nph-.

48 mph

10 61 76 10 '

100-72-90 10 '

.1,000~

-86

'108 10"

.10,000 101 126 102 mph:

L 10* *

'100,000 113 141 171 10'*i

-1,000,000 125 W

237 10

10,000,000

~

297

+,

f b

i

O 6-24

10. o 50 10 0 15 0 200 250 300 mph

.N'.

t 10-'

5 k

\\.

PEAK GUST (1955-72) 48 States in SELS LOG

~m s

s 10'a G M O

ik Q

\\\\

m t-s wm 1

N 8-l o

g

\\c

\\ C.

\\a%

10

,i

\\

-s to C

\\

3

~>

I o-*

' l o'#

10 10 Figure 10. Probabilities of straight-line and tor:wio winds.

The probability of strai ht-line winds (6ust) is higher than 6

br ado winds when windspeeds are less tPAn 130 mph. Peak gusts from SEIS IDG are also shown in this fi ure for comparison pur-6 poses.

se e

9 9

e,-w-

m.

u 6 -25 i

For secondary or short-life structures, one may wish to use the maximum windspeeds corresponding to the low-or even high-probability category defined above..

De storm characteristics in Table 14 were computed for 6ese three proba-bilities. If one wishes to protect a structure against the high-probability (10)

windspeed,'a 108-mph gust of straight-line wind is to be used as design cribria.

j Tornadoes may be disregarded for such a high-probability case.

Table 14 Characteristics of stoe.s corresponding to three probability categories, re=ote (10'# ), low (10~'),

and high (10** per year). Air density at the Institute site, 910-ft NSL, is assumed 1.2 kg/m3 and radius of maximum wind,150s for computational purposes.

Probe'ailities.(per year)

Remoto(10'#)

Low (10~*)

High (10'* )

Storm types Tornado Tornado Straight wind Av4="= total speed (mph) 297 237 108 Translational speed (mph) )

59 47 Nax. tangential speed (mph 238 190 Total press. drop ab) 135 8 86.6 1) 1 97 1.26

(

l

. Rate of pr. drop (Ps sec) 23 9 12.1 sec) 0 35 0.18 I

i I

De translational speed. T, was assumed to be T = 0. 20 V.,

where V., is the maximum total speed expected to occur at the radius of maximum i~

i..

'. wind, r.. De radius of maximum wind or that of tornado 's outer core was n

assumed to be j

r. = 150 m.

l..

+

l.

~

6 -26 Under' the assumption of the combined Rankine vortex and cyclostrophic wind

~

. equation, the total pressure drop was computed from' p V.'

P.

r

- wheF F at the 910-ft MSL Institute site was assumed to be 1.2 kg/m 8

%e rate of pressure drop was computed from and dr = Tdt

=

~

or dP T

a

? y*

dt f.

which is identical to Equation (3) of WASH-1300, It is reccmmended that the team of structure analysts determine the proper probability category to be applied to each structure or portions of structure of the Battelle Memorial Institute. Table 14 will, then, be used to determine the characteristics of the design-basis storm.

O Assd*_/

4 T. Deodore Fujita 5727 South Maryland Avenue Chicago, IIIInois 60637 W'

M 4

l 6

+

APPENDIX LIST OF VIOLENT TORNADOES l

WITHIN 140-MILE RANGE OF BATTELLE MEMORIAL INSTITUTE

'Ibe DAPPLE Tape (1950-75) includes 16 violent (F 4 & 5 ) tornadoes' which affected the area within a 140-mile range of the site. 'Ihese tornadoes are liste.d in Table 15 and shown in Figure 11 in this appendix.

Table 15 violent tornadoes (F 4 & 5) within 1M-sile range of the Battelle Mammal Institute. 16 tornadoes of this category are included in DAPPLE tape. Tornado with

• was surveyed by Fujita.

No.

Year Month Day Name of tornadoes F scale Path length 1

1953 Jun 8

cleval.,ra Tomado, OH 4

100 miles 2

1%1 Apr 25 Shelbyville Tornado, OH 4

65 3

1965 Ayr 11 Mrafton Tornado, D 4

25 4

1965 Apr. 11

• Kokomo Tomado, H 5

75 5

1968 Apr 23-Newtonsville Tornado, OH 4

25 6

1968 Apr 23 Hipley Tornado, KY-CH 4

50 7

1969 Aug.

9 c4""4""=ti Tornado, OH 5

22

.8 1972 May 14 Tnd4=n= polis Tornado, 27 4

29 9

1W4 Apr 3

• Bear Branch Tornado, D 4

28 10-1974 Apr 3

• Frankfort Torrado, KT 4

36 11 1974 Apr 3

• Hamburg Tornado, IN-4 37 12 1974 Apr 3

• Kennard Tornado, H 4

20 13-1974 Alt 3

• Madison Tornado, D 4

38 14 1W4 'Apr 3

• Parker, Tornado, D 4

22 15-1W4 Apr 3

• Sayler Park T.,

E-KY-0E 5

21 16 1W4 Apr 3

• Ienia Tornado, OH 5

32 O

O

6 i

(k

-- - - x. _.

1 Jute 8 S F4 g,6S l

g NQJ l

i

=4 1

l FS, Apg II,65 d

FS, APM 3,74

\\

\\>4

/

NQ/4l BATTELLE MEM. INSZ

/j F4, APR 3,74 '

g/',

NG/2 M /6

.g,6\\

l FS, APM 3,74 3

qs WN02 l

)

l

~ ^ *'

j

,,, M',s ms g

l F4, APR 23,68

\\

)

gt.3'4' h \\

A AUYs as M8 t

M /5 }

F4, APR 23,68 4

'i c-1p

"'j'

/

CD l _[w ~fu,

]

s M 13 s

}

g\\

\\

_~.

F4, APM 3 74

\\

f NO./0 s

l l

Fig =e i 1.

Paths of violent 'e.adoes within 140 niles of l

the Battelle site. The Xenia tocado (F5) of Ag.13,1974 was the closest to the site.-

i t

I

,~

i s

~

f

\\

)

i i

i

---

x.._

l i

\\

1 FA, Jugs,53

,65

=e

.I FS. APR ll,65 l na4 i

g F5, APR 3,74 i'

/

l+'

Na/4l BATTELLE NEM. INSE 4-l j

6

1. 0

• F4, APR 3,74 *

/

f Natz Nais

,ts,6\\

l F5, APR 3,74 j

ge # N02 l

f n

f ),/

aai, S'+

l na5 gS l

F4, APR 23,68 ga, f

h NQ7 M

/5 g

F4 J, AP 23,68

{/

ja G

.w r

v h;

F4, APR 3,74 N0.10 g

1I s

l Figure i1. Paths of violent tornadoes within 140 miles of the Battelle site, The Xenia tornado (F5) of April 3,1974 was the closest to the site.

,k'

((

q

- - s _._._._ _._._

l.

I I

k NQ3 I

F5. APR li, E5 l 1

Nas g

j

)l FS, APR 3,74

\\

NQl4l BATTELLE MEM. INSE j

/F4, APR 3,74 y,f JNQ/2 yaig I

s,6\\

e

, APR 3,74

,s,#*Na2 I

/

k

/

No.// g'i NO.3

-)g/

Jd' g%

l F4, APR 23,6E

@,$ gh Na7 ga /

if F5, AUG 9,69 NO.S j

g fa/ns 4 5

/, APR 23,68

/ \\g e

p F4 f

X J,_s b

O j

F4, APR 3,74 I

g NO./O

}

(

s Figure i1. Paths of violent tornadoes within 114) miles of the Battelle site. The Ienia tornado (F5) of April 3,1974 was the closest to the site.

l-e e

.