Violent Weather

Question 1

How do Ice storms occur?

Answer 1

Ice storms occur when a layer of warm air is between two layers of cold air. When precipitation falls through the warm layer into a below-freezing layer of air nearer the ground layer, it may form a variety of freezing precipitation including freezing rain, ice glaze, and ice pellets

Question 2

What is freezing parcipitation?

Answer 2

Freezing precipitation

Freezing rain, ice glaze, or ice pellets.

Question 3

What is a Blizzard?

Answer 3

Blizzards are snowstorms with frequent gusts or sustained winds greater than 40 km · h−1 for a period of time longer than 4 hours and blowing snow that reduces visibility to 400 m or less. These storms often result in large snowfall and can paralyze regional transportation both during the storm and for days afterward.

Question 4

What is a tunderstorm?

Answer 4

By definition, a thunderstorm is a type of turbulent weather accompanied by lightning and thunder. Such storms are characterised by a buildup of giant cumulonimbus clouds that can be associated with squall lines of heavy rain, including freezing precipitation, blustery winds, hail, and tornadoes. Thunderstorms may develop within an air mass, in a line along a front (particularly a cold front), or where mountain slopes cause orographic lifting.

Question 5

What fuels a thunderstorm?

Answer 5

A thunderstorm is fuelled by the rapid upward movement of warm, moist air. As the air rises, cools, and condenses to form clouds and precipitation, tremendous energy is liberated by the condensation of large quantities of water vapour. This process locally heats the air, causing violent updrafts and downdrafts as rising parcels of air pull surrounding air into the column and as the frictional drag of raindrops pulls air toward the ground

Question 6

What is turbulence in a thunderstorm?

Answer 6

A distinguishing characteristic of thunderstorms is turbulence, which is created by the mixing of air of different densities or by air layers moving at different speeds and directions in the atmosphere.

Question 7

What is wind shear?

Answer 7

Thunderstorm activity also depends on wind shear, the variation of wind speed and direction with altitude—high wind shear (extreme and sudden variation) is needed to produce hail and tornadoes, two by-products of thunderstorm activity.

Question 8

What are downbursts/macro bursts/microbursts?

Answer 8

Thunderstorms can produce severe turbulence in the form of downbursts, which are strong downdrafts that cause exceptionally strong winds near the ground. Downbursts are classified by size: A macroburst is at least 4.0 km wide and in excess of 210 km · h−1; a microburst is smaller in size and speed.

Question 9

What are supercells?

Answer 9

The strongest thunderstorms are known as supercell thunderstorms, or supercells, and give rise to some of the world’s most severe and costly weather events (such as hailstorms and tornadoes).

Question 10

What is a mesocyclone?

Answer 10

A large, rotating atmospheric circulation, initiated within a parent cumulonimbus cloud at mid troposphere elevation; generally produces heavy rain, large hail, blustery winds, and lightning; may lead to tornado activity.

ranging up to 10 km in diameter.

Question 11

How many estimated lightning stikes occure each day on earth?

Answer 11

An estimated 8 million lightning strikes occur each day on Earth.

Question 12

What is lightning

Answer 12

Flashes of light caused by tens of millions of volts of electrical charge heating the air to temperatures of 15 000°C to 30 000°C.

A buildup of electrical-energy polarity between areas within a cumulonimbus cloud or between the cloud and the ground creates lightning.

Question 13

What is thunder?

Answer 13

The violent expansion of this abruptly heated air sends shock waves through the atmosphere as the sonic bang of thunder.

The violent expansion of suddenly heated air, created by lightning discharges, which send out shock waves as an audible sonic bang.

Question 14

What is Hail?

Answer 14

A type of precipitation formed when a raindrop is repeatedly circulated above and below the freezing level in a cloud, with each cycle freezing more moisture onto the hailstone until it becomes too heavy to stay aloft.

Question 15

What are Damaging Winds?

Answer 15

Damaging Winds
Straight-line winds associated with fast-moving, severe thunderstorms can cause significant damage to urban areas, as well as crop losses in agricultural regions.

Question 16

What are some terms used to describe damaging winds?

Answer 16

Several terms are used to describe damaging winds, including straight-line winds, downbursts, microbursts, plough winds, or derechos. The first three terms are used commonly in eastern Canada, while the term plough wind is more frequently used in the west.

Question 17

What is a straight line wind?

Answer 17

Linear winds associated with thunderstorms and bands of showers that cause significant damage and crop losses. (See Derechos.)

Question 18

What is a Tornado?

Answer 18

An intense, destructive cyclonic rotation, developed in response to extremely low pressure; is generally associated with mesocyclone formation.

Question 19

What are the beginning stages of a tornado development?

Answer 19

The updrafts associated with thunderstorm squall lines and supercells are the beginning stages of tornado development (however, fewer than one-half of all supercells produce tornadoes).

Question 20

Why dose NA experience more tornados then anywhere else on earth?

Answer 20

North America experiences more tornadoes than anywhere on Earth because its latitudinal position and topography are conducive to the meeting of contrasting air masses and the formation of frontal precipitation and thunderstorms.

Question 21

What are tropical cyclones?

Answer 21

A cyclonic circulation originating in the tropics, with winds between 30 and 64 knots; characterised by closed isobars, circular organization, and heavy rains. (See Hurricane, Typhoon.)

Originating entirely within tropical air masses, tropical cyclones are powerful manifestations of the Earth–atmosphere energy budget.

Question 22

What are the three different regional names for a tropical cyclone?

Answer 22

Tropical cyclones are classified according to wind speed; the most powerful are hurricanes, typhoons, or cyclones, which are different regional names for the same type of tropical storm. The three names are based on location: Hurricanes occur around North America, typhoons in the western Pacific (mainly in Japan and the Philippines), and cyclones in Indonesia, Bangladesh, and India

Question 23

What are the wind speeds of a full fledged cyclone?

Answer 23

A full-fledged hurricane, typhoon, or cyclone has wind speeds greater than 119 km ∙ h−1 (64 knots)

Question 24

Tropical cyclone classifcations

Answer 24

Hurricane (Atlantic and East Pacific), Typhoon (West Pacific), Cyclone (Indian Ocean, Australia) -Greater than 119 km · h−1; 64 knots -Circular, closed isobars; heavy rain, storm surges; tornadoes in the right-front quadrant

Tropical storm - 63 –118 km · h−1; 34 – 63 knots - Closed isobars; definite circular organization; heavy rain; assigned a name

Tropical depression - Up to 63 km · h−1; up to 34 knots - Gale force, organizing circulation; light to moderate rain

Tropical disturbance - Variable, low - Definite area of surface low pressure; patches of clouds

Question 25

How do Cyclonic systems forming in the tropics differ from midlatitude cyclones?

Answer 25

Cyclonic systems forming in the tropics are very different from midlatitude cyclones because the air of the tropics is essentially homogeneous, with no fronts or conflicting air masses of differing temperatures. In addition, the warm air and warm seas ensure abundant water vapour and thus the necessary latent heat to fuel these storms.

Question 26

What energy conversions are occurring during a tropical cyclone?

Answer 26

Tropical cyclones convert heat energy from the ocean into mechanical energy in the wind—the warmer the ocean and atmosphere, the more intense the conversion and powerful the storm.

Question 27

What triggers the start of a tropical cyclone?

Answer 27

Cyclonic motion begins with slow-moving easterly waves of low pressure in the trade-wind belt of the tropics (Figure 8.17). If the sea-surface temperatures exceed approximately 26°C, a tropical cyclone may form along the eastern (leeward) side of one of these migrating troughs of low pressure, a place of convergence and rainfall.

Question 28

After the tropical cyclone is initiated, what happens to get it going?

Answer 28

Surface airflow then converges into the low-pressure area, ascends, and flows outward aloft. This important divergence aloft acts as a chimney, pulling more moisture-laden air into the developing system. To maintain and strengthen this vertical convective circulation, there must be little or no wind shear to interrupt or block the vertical airflow.

Question 29

What is the structure of a tropical cyclone?

Answer 29

Tropical cyclones have steep pressure gradients that generate inward-spiralling winds toward the centre of low pressure—lower central pressure causes stronger pressure gradients, which in turn cause stronger winds.

Question 30

What is the eyewall?

Answer 30

As winds rush toward the centre of a tropical cyclone, they turn upward, forming a wall of dense rain bands called the eyewall—this is the zone of most intense precipitation. The central area is designated the eye of the storm, where wind and precipitation subside; this is the warmest area of the storm, and although clear skies can appear here they may not always be present, as commonly believed.

Question 31

What is the range of diameter of a tropical cyclone and what is their typical speed over water?

Answer 31

Tropical cyclones range in diameter from a compact 160 km–1000 km to the 1300–1600 km attained by some western Pacific super typhoons. Vertically, a tropical cyclone dominates the full height of the troposphere. These storms move along over water at about 16–40 km · h−1.

Question 32

What is Landfall?

Answer 32

Landfall

The location along a coast where a storm moves onshore.

Question 33

What are the different categories of hurricane and what are their associated wind speeds?

Answer 33

1	119–153 km ∙ h−1 (65–82 knots)
2	154 –177 km ∙ h−1 (83 –95 knots)
3	178 –208 km ∙ h−1 (96 –112 knots)
4	209–251 km ∙ h−1 (113 –136 knots)
5	>252 km ∙ h−1 ( >137 knots)

Question 34

What is Storm Surge?

Answer 34

Storm surge (8)
A large quantity of seawater pushed inland by the strong winds associated with a tropical cyclone.