AGRON 2060 - KC #3

Define air mass

an immense body of air characterized by generally uniform conditions

Define source regions

the areas in which air masses originate

Define cA

continental artic

Define cP

continental polar

Define cT

continental tropical

Define mT

maritime tropical

Define mP

maritime polar

Define nor'easter

strong northeast winds, freezing temperatures, high relative humidity, precipitation, and sometimes blizzards, in the Northeast US

Define atmospheric rivers

narrow zones that transport significant amounts of water vapor from the tropics

Define drylines

boundaries between hot and dry air to the west and hot and humid air to the east

Define lake-effect snow

a band of heavy snow and is the result of cP masses moving over large bodies of water

Define midlatitude cyclones

synoptic-scale low pressures

-often exceed 1,000 km in diameter

-travel from west to east in the midlatitudes

-last from a few days to more than a week

-airflow is inward and ccw in NH/ cw in SH

-associated with surface convergence, rising air, and precipitation

Define polar-front theory/norwegian cyclone model

describes the life cycle of midlatitude cyclones from formation to dissipation

Define cyclogensis

the development and strengthening of midlatitude cyclones

define front

a boundary that separates air masses in different densities

-warm fronts

-cold fronts

-stationary fronts

-occluded fronts

-drylines

Define cold-type occluded front

cold front lifts the warm front and the cold air ahead of it

Define warm-type occluded front

cold front is warmer than the cold air ahead of the warm front

Define thunderstorm

a storm that generates lightning and thunder, it may also produce:

-gusty winds

-heavy rain

-hail

-tornadoes

Define ordinary cell thunderstorms

localized thunderstorms that form in warm, moist, unstable air

Define multicell thunderstorms

clusters or lines of thunderstorms

When are thunderstorms considered severe thunderstorms?

winds in excess of 58 mph

hail larger than 1 in

a tornado

Define squall line

a relatively narrow line of thunderstorms, some of which are severe

Define derecho

widespread, straight-line winds over long distances (58+ mph winds, 240+ miles long)

Define mesoscale convective complex (MCC)

consists of many individual thunderstorms organized into a large cluster

Define supercell

a single, very powerful cell with a rotating updraft and downdraft, often containing hail and tornadoes

Define lightning

a flash of light generated by the flow of electrons between oppositely charged parts of a cumulonimbus cloud or between the cloud and the ground or an object on the ground

What the 3 types of lightning?

Intracloud, cloud-to-cloud (intercloud), cloud-to-ground

Define intracloud

between different charge regions in the same cloud; most common

Define cloud-to-cloud (intercloud)

between two or more separate clouds

Define cloud-to-ground

between the cloud and the ground or an object on the ground

Define thunder

creates a rapid expansion of the air around the lightning strike, creating a sound wave

Define wind shear

winds blowing at different speeds and/ or from different directions throughout the depth of the atmosphere

Define convective available potential energy (CAPE)

a measure of the instability

Define convective inhibition (CIN)

a measure of the stability

Define tornado

violent windstorms in the form of a rotating column of air, extending from a cumulonimbus cloud to the ground

Define hurricanes

rapidly rotating storm systems that develop over the tropics charazterized by low-pressure centers, strong winds, and heavy rains; also called typhoons or tropical cyclones depending on the ocean basin; synoptic-scale

Define tropical depression

a tropical cyclone with maximum sustained winds of 38 mph (33 knots) or less

Define tropical storm

a tropical cyclone with maximum sustained winds of 39 to 73 mph (34 to 63 knots)

Define hurricane

a tropical cyclone with maximum sustained winds of 74 mph (64 knots) or higher

Define major hurricane

a tropical cyclone with maximum sustained winds of 111 mph (96 knots) or higher, corresponding to a category 3, 4 or 5 on the Saffir-Simpson Hurrican Wind Scale

Define eye of hurricane

the center of the storm, the usually cloud-free region where precipitation ceases and winds subside; typically smallest at the surface and wider aloft, creating a "stadium effect"

Define eye wall of hurricane

the ring-shaped wall of thunderstorms immediately surrounding the eye; the region where the greatest wind speeds and heaviest rainfall occur; the most destructive part of the hurricane

Define rain bands

the concentric bands of the thunderstorms extending outward from the eye wall; regions of rain spaced between regions of suppressed rainfail

Where is the lowest pressure of a hurricane found?

the eye

Where is the strongest winds of a hurricane found?

the eye wall

Where is the heaviest rain of a hurricane found?

the eye wall and rain bands (inner to outer)

What does a hurricane need to form?

warm ocean water

a distance of at least 300 miles

convergence

little to none wind shear

What will cause a hurricane to dissipate?

the opposite of formation:

cold ocean water

shorter distance

high wind shear

Define Saffir-Simpson Scale

ranks the relative intensities of hurricanes by their sustained wind speeds

Who developed the Saffir-Simpson Scale?

Herbert Saffir and Robert Simpson in 1971

Who is Joanne Simpson?

considered the "mother of tropical meteorology"

-developed the first cloud model

-contributed to the tropical rainfall measuring mission

-married to robert simpson

Define storm surge

a dome of water pushed onshore by winds

What is considered hurricane destruction?

storm surge

wind damage

heavy rains and inland flooding

What is used to track and monitor hurricanes?

satellites

aircraft

radar

buoys

Define track forecast cone

provides information about where the eye of the hurricane is forecast to travel

-impacts of the hurricane can still be felt outside the cone

List the criteria for source regions

-air is primarily heated from below and gains moisture through evaporation from Earth's surface

-a source region should be a large uniform area

-a source region should be located where the atmospheric circulation is relatively stagnant

Name and describe the air masses that influence Iowa weather

Continental Polar (cP) - cold and dry, brings chilly weather with clear skies and low humidity, responsible for many of Iowa's cold snaps

Continental Tropical (cT) - hot and dry, occasionally brings very hot, dry conditions during summer, sometimes leading to drought-like weather

Maritime Tropical (mT) - warm and humid, causes hot, sticky summers and provides moisture needed for thunderstorms and heavy rainfall, key factor in severe weather

Maritime Polar (mP) - cool and moist, less common, but can bring cloudy, damp, and cooler conditions, especially during spring and fall

Arctic (A) - extremely cold and dry, responsible for extreme cold waves in winter, often bringing dangerously low temps

Modifications of air masses - warming or cooling

cold air masses can be warmed > more instability

warm air masses can be cooled > develops an inversion

Modifications of air masses - moisture addition or loss

cA and cP air masses gain warmth and moisture by passing over oceans > instability

Modifications of air masses - vertical motion and stability

mid-latitude cyclones > stability

anticyclones > stability

topography: ascending air > instability; descending air > stability

What are the 6 phases of a midlatitude cyclone?

1. front develops

2. wave develops

3. cyclonic circulation established

4. mature stage

5. occlusion

6. cyclone dissipates

What are the regions where midlatitude cyclones are found?

pacific low

alberta low

colorado low

panhandle low

gulf low

hatteras low

In the NH, airflow around a sfc low is ccw and inward, this leads to sfc....

convergence

In the SH, airflow around a sfc low is cw and outward, this leads to sfc....

divergence

The accumulation of air should be associated with an .... in air pressure, "filling" or weakening the low pressure

increase, but it isn't. instead, we are "deepening" or the intensification of the low pressure

What are the various fronts?

warm fronts

cold fronts

stationary fronts

occluded fronts

drylines

What are the requirements for thunderstorm development?

lightning and thunder

- it may also produce gusty winds, heavy rain, hail and tornadoes

Describe the ordinary cell thunderstorm life cycle

A. cumulus stage

updrafts dominate throughout the cloud and growth from a cumulus to a cumulonimbus cloud occurs

B. mature stage

the most intense stage, with heavy rain and possibly small hail, in which downdrafts are found side by side with updrafts

C. dissipating stage

dominated by downdraft and entrainment, which causes evaporation of the structure

What is the criteria for severe thunderstorms?

winds in excess of 58 mph

hail larger than 1 in

a tornado

Differentiate between the various types of thunderstorms

ordinary cell thunderstorm - localized thunderstorms that form in warm, moist, unstable air

multicell thunderstorm - clusters or lines of thunderstorms

severe thunderstorm - winds in excess of 58 mph, hail larger than 1 in, a tornado

mesoscale convective complex (MCC) - consists of many individual thunderstorms organized into a large cluster

supercell thunderstorm - a single, very powerful cell with a rotating updraft and downdraft, often containing hail and tornadoes

Differentiate between the types of lightning

intracloud - between different charge regions in the same cloud; most common

cloud-to-cloud (intercloud) - between two or more separate clouds

cloud-to-ground - between the cloud and the ground or an object on the ground

How are thunder and lightning connected?

when lightning strikes, thunder is formed by creating a rapid expansion of around around the lightning strike, creating a sound wave

How are tornadoes rated?

they are rated using the Enhanced Fujita Scale (EF scale)

EF-0 tornadoes produce light damage while EF-5 tornadoes produce incredible damage

What are the various stages of a hurricane?

tropical depression

tropical storm

hurricane

major hurricane

Describe how pressure, precipitation, and winds vary throughout the hurricane

as you move inward:

pressure decreases

wind increases, then suddenly drop in the eye

rain increases, then stops in the eye

as you move outward (the opposite):

pressure increases

winds increase to a peak at the eyewall, then decrease

rain increases to a peak at the eyewall, then become spotty

How are hurricanes rated?

using the Saffir-Simpson Scale

Identify the most dangerous quadrants of hurricanes

for the NH, it is quadrant B (right front)

for the SH, it is quadrant D (left front)

-strongest winds

-greatest storm surge

-highest risk of tornadoes

-greatest risk of flooding

What are the limitations of the Saffir-Simpson Scale?

focuses only on wind speed

does not consider storm size

damage-based limitations

ignores forward speed and duration

A large body of air near the surface with nearly uniform properties (temperature, humidity, and stability) is called _______

an air mass

The weather within an air mass would __________

change very little across the air mass

Air masses form in conditions that have __________

light winds and high pressure

The maritime tropical air mass that influences weather in Chicago, IL typically originates from __________

the Gulf of Mexico

If a large body of air has a low temperature and a high relative humidity, then the air mass is called _______

maritime polar (mP)

If a large body of air has a high temperature and a low relative humidity, then the air mass is called _______

continental tropical (cT)

If a large body of air has a low temperature and a low relative humidity, then the air mass is called _______

continental polar (cP)

If a large body of air has a high temperature and a high relative humidity, then the air mass is called _______

maritime tropical (mT)

When a cP air mass travels from northern Canada across the Great Lakes in early autumn, it becomes __________

warmer and more humid

As an air mass travels over a region that is much colder, __________

its stability will increase and there will probably be clear skies

A boundary between two air masses is called _______

a front

A dryline is the boundary between _____ and _____

warm, moist air and warm, dry air

Midlatitude cyclones in the Northern Hemisphere ______

rotate ccw

Low pressure at the surface is caused by _______

divergence aloft

Convergence aloft causes _______

sinking air

higher pressure at the surface

divergence at the surface

The warm conveyor belt _______

brings warm, moist air northward along the cold front

Where do most cyclones form?

east side of the rocky mountains (united states)

Weather conditions behind a cold front would be _______

cold and dry, with winds from the northwest

Weather conditions between the warm front and the cold front would be _______

warm and moist, with winds from the south

High pressure is associated with clear skies and calm weather. A blocking high is significant because it can cause _______

frigid temperatures over much of the united states

Which location in a midlatitude cyclone is likely experiencing steady, light rain (or snow) and overcast conditions?

ahead of the warm front

Thunderstorms are most likely located _______

along the cold front