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Natural Hazards > Tornadoes > Flashcards

Tornadoes Flashcards

1
Q

What are tornadoes

A

Short lived, very intense, localised storms.

Violently rotating columns of air descending (sometimes to ground level) from a thunderstorm cloud.

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2
Q

Why are tornadoes often visible

A

Due to dust and debris suck up

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3
Q

What is a wedge tornado

A

Wide base - 100k across

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4
Q

What is a rope tornado

A

Thin air localised tornado. Small diameter

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5
Q

What are waterspouts

A

Tornadoes over water are called waterspouts

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6
Q

Example of waterspout

A

Gerona, Spain. 6 people killed when the waterspout collapsed onto the pier

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7
Q

How do tornadoes form

A

Vortex produced when strong winds bringing cold dry air pass over warm moist rising air. Two different air masses moving in different directions, rolling motions where they interact with each other. Strong updraft - gearing of the ground, evaporation so rolling air mass gets lifted up vertically into tornado

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8
Q

Where are tornadoes often spawned

A

By thunderstorms and hurricanes as they travel inland

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9
Q

What is the structure of a tornadigenic thunderstorm

A

Overshooting top.
Anvil shape thunderstorm cloud.
Outflows.
Mesocyclone - strong updraft, below you tend to get tornadoes

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10
Q

What is the overshooting top of a tornado

A

Above the troposphere in the stratosphere it is the area directly above the area of strong updraft. Pushing cloud top up higher

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11
Q

Where do tornadoes occur

A

Tornado alley (central USA) suffers the most numerous and devastating tornadoes

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12
Q

How many tornadoes per year in tornado alley

A

1000 causing 100 deaths

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13
Q

Which states are in tornado alley

A 
Texas
Oklahoma
Kansas
Colorado
Nebraska
S.Dakota
Iowa
Minnesota
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14
Q

Why is tornado alley a thing

A

Low level winds bring warm moist air from the South East (gulf of Mexico), and high level winds bring cool dry air from the west (Rocky Mountains)

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15
Q

Example of tornadoes in the uk

A

Tay bridge train disaster, 1879, caused by a waterspout in Scotland. 75 killed.
Birmingham tornado, 2005, wedge shape.

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16
Q

What are the features of a typical tornado

A

Diameter - 250m.
Pressure at centre - 10% lower than surroundings.
Path length - 25km.
Forward speed - 45km/h.
Duration - 15 minutes.
Spin anti-clockwise in Northern Hemisphere.

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17
Q

Can you out drive a tornado

A

If the conditions are good

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18
Q

Can you get multiple tornadoes formed by the same thunderstorm

A

Yes

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19
Q

What is used to analyse tornado strength

A

Enhanced Fujita Tornado Damage Scale (EF0-EF5)

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20
Q

What is the tornado strength a relationship between

A

Wild speed and destructiveness

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21
Q

What is the strength of most tornadoes

A

Weak so EF0-EF1. Only 2% are EF4 or EF5

22
Q

What percentage of deaths are EF4 or EF5 caused

A

70%

23
Q

What are wind speed based on

A

Degrees of damage of vegetation and building.on 3 second gusts, not continuous wind speed but still causes damage

24
Q

What is damage to buildings caused by

A

The force of the wind itself.

Flying debris and objects such as cars.

25
Q

How many categories are in the tornado damage

A

6

26
Q

How is damage localised

A

Total obliteration of one street while the next street is unscathed

27
Q

In the USA what is the most vulnerable area

A

Mobile homes

28
Q

Example of a record holding tornado

A 
The tri-state tornado 1925 and outside the peak season for tornadoes.
3.5 hours.
700 killed.
15,000 homes destroyed.
350km path.
1.5km widest oaths
29
Q

What is the peak season for tornadoes

A

June to October bc sea surface temperature have risen enough to feed positive feedback loop

30
Q

How to reduce vulnerability

A

Long term preparedness.

31
Q

What is the long term preparedness for reducing vulnerability

A

Difficult to design tornado proof buildings.
Construct concrete/ underground shelters.
Educate vulnerable communities.

32
Q

What do they educate

A

How to spot when a tornado is coming and how to use a shelter

33
Q

Example of w tornado warning system

A

Operated by NOAA since 1953 in the USA

34
Q

How does the tornado warning system work

A

Forecast tornadigenic weather conditions like mesocyclone.
Issue a tornado watch alert and intensify monitoring.
Try to detect tornadoes.
Issue a tornado warning.
Initiate emergency plans.

35
Q

How to detect tornadoes

A

Radar station, spotter networks and satellite images

36
Q

Where should you take refuge in a tornado

A

Underground is best.
Indoors, away from Windows, is next best.
If outdoors, lying in a ditch is best (beware flooding).
Evacuate vehicles.

37
Q

What is a spotter network

A

Look for characteristic cloud formations e.g mammatus clouds often presage US tornadoes

38
Q

Warning signs of tornados

A 
Dark greenish/black sky.
Large hailstones falling.
Clouds moving very fast, especially in a rotating pattern or converging toward one area of the sky.
Rushing/ roaring sound.
Debris dropping from sky (animals too).
39
Q

How to use satelittles to detect tornadoes

A

Visible - look for shadow cast by overshooting top of thunderstorm cloud.
Infrared - thunderstorm clouds tend to be cooler (higher in atmosphere) than other clouds.
Moisture - look for adjacent moist (white) and dry (black) air masses

40
Q

What is infrared

A

Temperature information and colour enhanced

41
Q

What is the structure of a tornadigenic thunderstorm

A 
Overshooting top (top of updraft) in stratosphere.
Rotating updraft.
Flanking line (new storms forming) 
Rain shaft.
Storm movements
42
Q

Thing to detect tornados

A

Doppler radar

43
Q

Info on the Doppler radar

A

155 fixed DR stations in USA. Since 1990s.
Mobile stations enhance coverage.
Emits pulse of radio waves and measure the wavelength (or frequency) and intensity of pulse reflected from raindrops.

44
Q

What does the Doppler radar provide info on

A

Size, location, storm speed, wind speed and rainfall intensity

45
Q

How does the Doppler radar work

A

Radar sweeps and beems of radio waves going out. Estimate how big from time taken to go out and come back tells us how far they travelled and the size, speed and winds of the storm. If it was stationary then the radio waves would have the same wave length as one that’s being beamed out but if it’s moving towards a system it has shorter radio waves but if it’s moving away then it would have longer wave lengths than they were on the way out.

46
Q

What do hook shapes indicate

A

Mesocyclonic rotation. Red is more intense and moving away from the station

47
Q

What does reflectivity show

A

Rainfall intensity

48
Q

What does velocity show

A

Direction of air movement. Green is air moving inbound towards the radar. Red is air moving outbound away from the radar.

49
Q

Why can’t tornadoes be detected by radar

A

They are too small

50
Q

What do meteorologists look for

A

Adjacent red (outbound) and green (inbound) areas in a larger thunderstorm. Indicates rotation which may spawn tornadoes

51
Q

Limitations of using the Doppler radar

A

Detection more likely and earlier (around 15-30 mins before tornado forms).
But false alarms and undetected tornadoes are quite common.
Not all tornados are associated with mesocyclones.
Can’t detect circulations that are too close, too far or blocked from views

Natural Hazards (7 decks)

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