10: Tornadoes

Question 1

what is a tornado, produced by, visible due to, and lifetime

Answer 1

• violently rotating column of air in contact with ground and produced by a severe thunderstorm
• made visible by condensed water droplets
• funnel cloud formed by localized lowering of cloud base
• most violent of weather systems
• small and short lived

Question 2

path lengthm width, speed, and lifetime of two types of tornadoes

Answer 2

1. weak tornado
   * length:1.6km
   * width: 100m
   * lifetime: few minutes
   * speed: <180km/hr
2. Violent tornado
   * length:160 km
   * width: 1000m
   * lifetime: up to 2 hours
   * speed: up to 500km/hr

Question 3

which part of the world has the most tornadoes worldwoide and what is it called

Answer 3

• central USA
• tornado alley: north south corridor stretching from texas thorugh oklahoma, kansas and south dakota

Question 4

where does canada rank in tornadoes

Answer 4

• Canadian prairies ranks second behind US

Question 5

odds of tornado in 100 thunderstorms

Answer 5

• 1 of 100 thunderstorms there is a tornado
• 1 of 100 tornadoes are strong and 1 of 1000 are violent

Question 6

what is the tornado scale called

Answer 6

fujita tornado intensity scale

Question 7

what is the fujita tornado intensity scale

Answer 7

• in this order: f scale, category, km/hr
  0 weak 65-118
  1 weak 119-181
  2 strong 182-253
  3 strong 254-332
  4 violent 333-419
  5 violent 420-514

Question 8

what makes a tornado stronger and where are they formed

Answer 8

• a stronger vertical wind shear
• form in supercells

Question 9

clouds that sign a tornado formation

Answer 9

mammatus clouds

Question 10

environment that develops supercells and how it develops

Answer 10

• develop sin an environment with horizontal wind that has strong shear in both speed and direction
• sher in windspeed causes air to rotate about a horizontal axis in a rolling motion
• consists of one updraft and down downdraft
• updraft tilts horizontal rotation into rotation around vertical axis (which creates rotation in the updraft aka mesocyclone)
• horizontal extent of mesocyclone is 3-10km

Question 11

what is a funnel cloud

Answer 11

• cloud that extends to the surface and when it touches down it converts to a tornado
• most tornadoes occur about 10-20 mins after rotating wall clouds become noticeable

Question 12

characteristics of the wall cloud

Answer 12

• circular lowered portion of the rain free base of the supercell
• usually associated with a mesocycone
• wall cloud about 3km in diameter and is in the region of the strongest updraft
• most wall clouds do not produce a tornado

Question 13

things radar image shows

Answer 13

• radar reflectivity image depicts a hook echo in the south east side
• hook echo shows rainfall as it is drawn around the mesocyclone

Question 14

F0 - F5 Fujita Scale Descriptions

Answer 14

F0: light damage
F1: moderate damage
F2: considerable
F3: extreme
F4: devastating
F5: incredible

Question 15

5 other torando like phenomena

Answer 15

1. gustnado
2. dust devil
3. fire whirls
4. steam devils
5. waterspout

Question 16

what is a gustnado

Answer 16

• smaller tornado
• small vertical swirl associated with a gust front or downburst
• not connected with a cloud base

Question 17

what is a dust devil

Answer 17

• also known as whirwind
• resembles a tornado but they form under clear skies
• form when a strong updraft is formed near the ground on a hot day (dust goes up)

Question 18

what is a fire whirl

Answer 18

• small tornado near intense surface heat source. Ex: near wildfires
• not considered tornadoes except in the rare case where they connect to a pyrocumulus or other cumulus cloud

Question 19

what is a steam devil

Answer 19

small tornado that involves steam or smoke

Question 20

components of tornado airflow and what does it lead to

Answer 20

• 3 components: rotational motion (azimuthal velocity), radial inflow (radial velocity), upward motion (vertical velocity)
• combo of all 3 leads to inward and upward spiral
• objects are destroyed by tornadoes mostlu by drag force and not by suction

Question 21

draw pic of of 3 velocities

Answer 21

image 20

Question 22

what is a suction vortex and what is it a result of

Answer 22

• secondary vortex that is associated with the main tornado
• made when you combine tornado velocities (Vtotal): radial (Vr), suctionial (Vs), translational (Vt)
• Vt: movement horizontally
• Vr: rotation
• Vs: rotation in main vortex rotation
• image 21

Question 23

speed/velocity ds of suction vortex rotation

Answer 23

• image 22
• velocity at bottom is faster: 340km/h
• velocity at top is slower: 140 km/h

Question 24

what is rotation quantified by

Answer 24

• azimuthal velocity (V) and radius (R)
• time period of full rotation (T)in seconds
• frequency of rotation (F) in 1/sec or Hz

Question 25

formula for F and F of tornado typically

Answer 25

* F of tornado usually <1Hz (merry go round) F = V/2piR (circumference of circle)

Question 26

what is vorticity and the formula

Answer 26

* rotation in a fluid * Vorticity = 4piF * vorticity is a vector and the vector is defined using the right hand rule (thumbs up --> vortex lines are parllel to the vorticity * so if vortex line are vertical from ground to sky the spin is counterclockwise * image 23

Question 27

what are vortex lines and how they affect funnel direction

Answer 27

* vortex lines need to be perpendicular to the ground to produce circulation * can be distorted by the airflow causing the funnel to bend

Question 28

how does vorticity arise in a fluid

Answer 28

1. Spin: like solid body rotation 2. Shear: unique to a fluid; one region of fluid slides over another region

Question 29

how is horizontal vorticity and what can it be converted to

Answer 29

* horizontal vorticity is created by wind shear in the atmospheric boundary layer * can be converted into vertical vorticity when the updraft tilts the vortex lines * vertical vorticity is necessary for a tornado * image 24

Question 30

two counter rotating vortices is made by what and what it creates

Answer 30

* updraft creates two counter rotating vortices * if there is a downdraft there are multiple vortex tubes due to storm splitting * image 25

Question 31

conservation of angular momentum affect on tornadoes and formula

Answer 31

* smaller radius means faster * V1R1 = V2R2

Question 32

how to increase vorticity

Answer 32

* by convergence (radial inflow) using conservation of angular momentum (smaller radius) * inflow is caused by cyclostrophic balance

Question 33

Cyclostrophic balance and formula

Answer 33

* inward and outward force balances * steady rotation requires inward pressure gradient force (P) balances outward centrifugal force (C) * requires low pressure centre on the axis of rotation * P = C = V^2/R

Question 34

what height does cyclostrophic balance occur and its purpose

Answer 34

* occurs at heights >50m above the surface in a tornado * cyclostrophic balance minimizes radial flow and maintains low pressure in the centre, maintaining funnel cloud

Question 35

what happens to cyclostrophic balance near the groundz

Answer 35

* friction near the ground reduces the angular velocity * outward centrifugal force is lower and inward pressure gradient force remains the same * unbalance pressure gradient force pulls the flow radially inward near the surface * think of stiring ur tea and the tea leaves go in the middle

Question 36

how does the mid level rotation in a thunderestorm get to the surface

Answer 36

* dynamic pipe effect: - cyclostrophic balance in rotating mid level air prevents radial inflow so it acts like the wall of a vacuum - produces low pressure at centre - below this level, air is sucked in towards low pressure centre and begins to rotate faster, producing cyclostrophic balance at lower levels too - rotation works its way down to the surface