ATMO EXAM 3

What is an Air Mass?

A large body of air that has similar characteristics, such as temperature and humidity

What is an Air Front?

The boundary or transition zone separating two large air masses with different temperatures, densities, and humidity levels.

What are air masses and fronts associated with?

They are associated with regions of calm winds and generally form flat/uniform topography

P =

Polar

T =

Tropical

A =

Arctic

M =

Maritime

C =

Continental

Arctic is:

COLDER than Polar

Which three would be considered an example of vertical wind shear? wind speed and direction not changing with height, wind speed and direction changing with height, wind direction changing with height, wind speed changing with height - The following three would be considered an example of vertical wind shear:

wind speed and direction changing with height,

wind direction changing with height,

wind speed changing with height.

True or False: The key ingredient that is needed for a thunderstorm to be more than ordinary is vertical shear.

True

The primary factor that distinguishes a supercell thunderstorm from an ordinary thunderstorm is -

The presence of a rotating updraft, known as a mesocyclone

True or False a downdraft is associated with sinking air:

True

The level at which a parcel becomes less dense than the surrounding environment is known as what abbreviation -

The Level of Free Convection (LFC)

When a parcel is saturated and rising, it will cool at what lapse rate -

the moist adiabatic lapse rate, which is approximately $6 \, \text{°C/km}$.

When a parcel is not saturated and rising, it will cool at what lapse rate -

the dry adiabatic lapse rate, which is approximately $10 \, ext{°C/km}$.

What is a waterspout?

A rotating column of air that is connected to a cumuliform cloud over a large body of water

Cyclostrophic -

A balance between the Coriolis force and the pressure gradient force is essential for the development and maintenance of these phenomena.

Non-supercell tornadoes-

The presence of moisture and instability in the atmosphere often enhances storm intensity, leading to severe weather events.

Non-supercell tornadoes have what attributes?

Boundaries give rise to low level rotation

Convection stretches rotation

Bookends and bow echoes

Doppler radar measures -

The speed of precipitation toward and away from radar

Forecasters look for -

A velocity couplet and TVS (Tornado Vortex Signature)

NEWRAD is -

The National Doppler System

Doppler Radar -

A shift in frequency allows radar to see motion towards or away from the radar only

What is a tornado outbreak -

A series of tornadoes spawned by the same weather system, often during severe thunderstorm conditions.

Tornado Outbreaks usually favor -

A large area for supercells, and we have many tornadoes for a synoptic event.

What are tornado families -

Single supercell, multiple tornado “drops”

A tornado rating is given -

After the tornado

Enhanced Fujita scale

Created in the 70’s updated to 2007

First EF5 (new scale) was -

Greensburg KS, May 4, 2007

Tornado Characteristic of the funnel

Funnel cloud until circulation reaches ground

Tornado Characteristics of the mph -

Mostly < 135 mph, but can exceed 250 mph

Tornado Characteristics of diameters -

Diameters: most are 300 to 2000ft and are as small as 20ft and as big as 1 mile long!

Tornado Characteristics of motion -

Most have a counterclockwise motion

Tornado Characteristics of motion -

Mostly move SW to NE, 25 to 50mph

Tornado winds are -

Winds are asymmetric

The strongest tornado winds are -

On the left side

What is a tornado?

Defined as a violently rotating column of air, in contact with the ground, and below a cumuliform cloud.

What are the three ingredients for a tornado?

moisture, instability, lift, and strong vertical wind shear

Not all super cells -

Produce tornadoes

Wind shear along the rear flank downdraft causes -

A spinning vortex tube that is pulled into thunderstorm by the updraft

Spinning vortex tube is -

“stretched” by the mesocyclone into the vertical

Before a tornado forms, what kind of cloud would we see?

A wall cloud

What does the wall cloud indicate?

It indicates strong upward motion and the potential for tornado formation.

Tornadoes have the same favorable conditions as a -

Supercell

Favorable conditions for a tornado -

wind shear, moisture availability, atmospheric instability

What is a squall line -

A type of band of severe thunderstorms that can produce heavy rain, strong winds, and tornadoes. It often forms along a cold front.

Land warms up faster than -

Surrounding bodies of water

cA: Cold air rushes down into U.S. from Canada: is called an:

Arctic High

cP: cold, dry, stable

(this is what we normally have with cold front passage here in TX)

mP:

cool, moist, somewhat unstable

Orographic lift creates -

A rain shadow effect on the eastern side of the mountains, resulting in drier conditions in the interior regions of the state

cT:

Hot dry, stable aloft but unstable near the surface

Where does cT occur?

Only really occurs in the U.S. in summer southwest

What clouds and rain does cT produce?

Few clouds and minimal precipitation

What is cloud electrification -

the process by which clouds develop electric charges, leading to lightning. This occurs due to the collision of ice particles and water droplets within the cloud.

How does lightning occur -

Lightning occurs when the electric charges within a cloud build up and create a potential difference between the cloud and the ground or within the cloud itself, resulting in a discharge of electricity.

How does Accretion occur -

On hail/graupel, latent heat release keeps the hailstone warmer than the surrounding drops and ice crystals

What happens to ions during cloud electrification -

The warmer the hail/graupel transfers positive ions to the colder ice crystals (at contact)

What is a typical charge distribution during cloud electrification -

Positive charge accumulates near the top of the storm cloud, while negative charge is more concentrated at the base.

What does typical charge distribution in cloud electrification lead to -

This distribution leads to the development of strong electric fields that can result in lightning discharges.

What is lightning -

A discharge of electricity in a cloud

What is thunder -

Thunder is the sound produced by the rapid expansion of air surrounding a lightning strike, creating shock waves that result in a booming noise.

Lightning can heat the air up to -

30,000 C

What does lightning cause the air to do -

causes the air to expand explosively and creates thunder

Light travels faster than -

sound

Thunder travels about a mile in -

5 seconds

What are the types of lightning -

cloud-to-ground, intra-cloud, cloud-to-cloud

What are the supercell flavors -

classic, low-precipitation, high precipitation

Supercells ALWAYS -

rotate

What is a classic supercell -

a variant that typically produces less rain compared to classic supercells, often leading to weakened updrafts but can still generate severe wind gusts and isolated tornadoes.

What is a low precipitation supercell -

a variant that typically produces less rain compared to classic supercells, often leading to weakened updrafts but can still generate severe wind gusts and isolated tornadoes.

What is a high precipitation supercell -

characterized by very heavy rainfall, often leading to flash flooding, while the strong updrafts can also produce large hail and an enhanced risk for tornadoes. (and hidden tornadoes)

What is a supercell -

a highly organized thunderstorm characterized by a rotating updraft, capable of producing severe weather phenomena such as large hail, damaging winds, and tornadoes.

A supercell can last -

for many hours because of a nearly steady, rotating updraft

In strong wind shear (speed and/or direction are changing with height) -

thunderstorm updrafts can rotate - necessary for a supercell

Wind shear creates -

horizontal rotation

What happens to horizontal rotation -

it is stretched by the updraft to make a rotating storm

Rotation keeps the precipitation and the cold downdrafts

way from the updraft, so the storm can last for hours

Main features of a supercell -

a strong rotating updraft (mesocyclone)
Anvil shaped top

heavy precipitation and hail

severe weather potential

What is a gust front -

a boundary that forms when cold air from downdrafts spreads out, lifting warm air ahead of a storm, often leading to new storm development.

What is MCS motion -

Mesoscale Convective System motion refers to the movement of a cluster of thunderstorms that can affect weather patterns and precipitation over large areas.

Individual cells are -

Carried by the wind aloft

As new cells form and old ones dissipate -

systems as a whole ends up moving to the right of the wind

Generally, if the relative humidity in the storm environment is fairly low -

strong downdrafts will form and the system will move quickly

If the RH is high -

the downdrafts will be weaker, leading to slower movement of the system and allowing for greater moisture retention, which can enhance storm development.

When multicell storms grow into even larger groups

they are called mesoscale convective systems (MCS)

MSCs provide about half of the summer rainfall in the plains and Midwest and nearly -

60% of rainfall in the tropics

What is a bow echo -

a radar signature indicating a line of thunderstorms that bows outward, often associated with severe weather such as damaging winds.

What is a squall line -

a line of thunderstorms that can extend for hundreds of miles, typically associated with a cold front, producing severe weather and heavy rainfall.

What is convection -

the process of heat transfer through the movement of fluids, causing warm air to rise and cool air to sink, often leading to cloud formation and precipitation.

How long do multi-cell thunderstorms last -

Each cell lasts 15-30 min, but the whole system can last for many hours

The gust from one multicell -

will provide the lifting to form a new one

Wind shear allows a storm to tilt -

in such a way that the updraft rides up and over the downdraft

What is a multi-cell -

thunderstorm that consists of multiple cells in various stages of development, typically producing severe weather such as heavy rain, hail, and tornadoes.

What is the difference between multicell and ordinary cells -

Multicell thunderstorms have multiple updrafts and downdrafts, whereas ordinary cells consist of a single updraft that quickly dissipates. Multicells can produce longer-lasting severe weather compared to ordinary cells.

What are the three stages of an ordinary thunderstorm -

air mass, pulse, popcorn

What is the mature stage for thunderstorms -

Dry air is “entrained” and leads to downdraft and gust front - heavy precipitation

What is the cumulus stage in thunderstorms -

moist air rises and condenses

What is the dissipating stage in thunderstorms -

Downdraft cuts off moist updraft, clouds and raindrops evaporate