Chapter 5 Overview

Supercell thunderstorms form over land where there is ________ and ________. These conditions frequently occur in spring in North America over the southern Great Plains in Kansas and Oklahoma.

humid air ; strong wind shear

When abbreviating air mass types, ________ characteristics come first and are followed by ________ characteristics.

humidity ; temperature

________ persists more than a year and has global effects.

El Niño (with its counterpart La Niña)

Only about ________% of the 100,000 thunderstorms that form in the United States each year are classified as severe.

10% (10,000)

Each day, there are about ________ thunderstorms worldwide. At any given moment, some _______ thunderstorms are in progress.

40,000 ; 2,000

About ________% of all thunderstorms occur over land in the tropics.

70%

On average, more than ________ thunderstorm days occur in the orange and red seas of South Florida.

80

The ________ United States has the highest frequency of thunderstorms in the country.

Southeastern (particularly Florida)

What is a squall line?

a line of multi-cell thunderstorm cells that typically forms along a cold front on a midlatitude cyclone

A(n) ________ is a large region of air, extending over thousands of kilometers, that is uniform in temperature and humidity.

air mass

Why does the southeastern United States (particularly Florida) have the highest frequency of thunderstorms in the country?

as a result of warm and moist air masses that move north from the Gulf of Mexico

The two most important factors that determine thunderstorm type are ________ and ________.

atmospheric humidity ; wind shear

Orographic lifting over the southern Rocky Mountains increases thunderstorm activity for ________ and ________.

central Colorado ; northern New Mexico

What is wind shear?

changes in wind speed and direction with altitude

What does the abbreviation cA stand for?

continental Arctic the polar high / very cold and dry

What does the abbreviation cP stand for?

continental Polar the polar high / cold dry (forms in winter)

What does the abbreviation cT stand for?

continental Tropical the subtropical high / hot, dry (forms only in summer)

What are thunderstorms?

cumulonimbus clouds that produce lightning and thunder

Describe the dissipating stage (third/last stage) of single-cell thunderstorms.

following the mature stage, downdrafts and net evaporation cause the storm to weaken, The falling downdrafts block the updrafts that feed moisture to the cloud. Once updrafts are weakened, the cloud quickly evaporates.

Single-cell thunderstorms typically experience a predictable sequence of ________ , ________ , and ________.

growth, maturation, and dissipation

A severe thunderstorm is defined as one that produces either ________ , ________ , or ________.

hail 2.54 cm (1 in) in diameter, a tornado, wind gusts 93 km/h (58 mph) or greater

How are multi-cell thunderstorm systems arranged?

in clusters called mesoscale convective systems or linearly in squall lines

What happens when air remains over a region for weeks or longer?

it absorbs the characteristics of that region (for example: air over a warm desert will become warm and dry ; air over a warm ocean will become warm and humid)

Single-cell thunderstorms develop in the ________ as unequal heating of the ground creates unstable air parcels. As these air parcels rise, they cool to dew point, which results in ________ and cumulonimbus cloud formation.

late afternoon ; condensation

________ indicates thunderstorm activity.

lightning

Single-cell thunderstorms form within ________ air masses where wind shear is weak.

mT

Individual cells within a multi-cell thunderstorm persist for only about an hour (like single-cell thunderstorms) but as a whole the system persist for ________.

many hours

What does the abbreviation mP stand for?

maritime Polar the polar high and sub polar low / cold, humid

What does the abbreviation mT stand for?

maritime Tropical the ITCZ and the subtropical high / warm, humid

mT refers to a ________ air mass, meaning that it formed over an ocean in the tropics and is humid and warm. This air mass is essential for ________.

maritime Tropical ; thunderstorm development

Multi-cell thunderstorms are ________ systems consisting of thunderstorm cells organized in ________.

mesoscale ; long lines or clusters

________ thunderstorms form under conditions of moderate wind shear with wind speeds of about 40 to 65 km/h or 23 to 40 mph.

multi-cell

Supercell thunderstorms usually produce severe weather and almost all ________ are produced by supercell thunderstorms.

powerful tornadoes

The term supercell refers to the thunderstorm as a whole, and the term mesocyclone refers to the ________ within the supercell.

rotating cylindrical updraft

Multi-cell thunderstorms are sometimes severe and typically last ________.

several hours

Multi-cell thunderstorms often produce ________.

severe weather

________ thunderstorms are almost always relatively mild, short lived thunderstorms that last up to an hour.

single-cell

________ thunderstorms are short lived and occupy little geographic space.

single-cell

What are the 3 types of thunderstorms?

single-cell, multi-cell, and supercell

There is a direct relationship between the ________ and ________ of these atmospheric storm systems.

size ; duration

Storm systems derive their energy from ________ of earth's surface and the ________ of water vapor in the atmosphere.

solar heating ; condensation

The warm Gulf of Mexico and the Atlantic Ocean readily evaporate and increase atmospheric moisture. This moisture increases thunderstorm frequency in the ________ United States.

southeastern

Dry air from Mexico reduces thunderstorm activity in the ________ United States.

southwestern

________ can extend for hundreds of kilometers, persist for hours, and bring severe weather.

squall lines

Describe the mature stage (second stage) of single-cell thunderstorms.

strong updrafts develop, and rain drags air downward as it falls, forming downdrafts. The upper regions of the clouds are so cold that the liquid cloud droplets become glaciated and freeze into ice. At this stage, lightning, thunder, heavy rain, and hail are possible.

The least common but most powerful thunderstorm type is the ________ thunderstorm, which contains a rotating cylindrical updraft.

supercell

How do multi-cell thunderstorms differ from single-cell thunderstorms?

they persist longer and form mainly along boundaries between air masses (called fronts) rather than within air masses

Most ________ do NOT occur in isolation. They are embedded within larger synoptic-scale systems, such as hurricanes and midlatitude cyclones.

thunderstorms

The most localized storm systems are ________.

thunderstorms

Describe the cumulus stage (first stage) of single-cell thunderstorms.

a cumulonimbus club forms in warm, upward flowing currents of air called updrafts. Air in updrafts rises and cools to its dew point. As condensation occurs, latent heat is released into the cloud, warming the interior and causing it to rise more vigorously.

In the ________ United States, dry air reduces the number of thunderstorms and the cold Pacific Ocean inhibits evaporation and atmospheric moisture.

western