weather systems

meterorology

the study of the atmosphere and by extension, the study of weather

weather

the short-term, day to day conditions of the atmosphere

weather systems

patterns of atmospheric circulation that lead to distinctive weather events

Meteorology includes the study of

Hydrometeors

hydrometeor =

suspended liquid or frozen water in the atmosphere

foundation of weather systems are

Air Masses

Air masses have a

distinctive body of air with fairly uniform temperature and moisture characteristics

we classify air masses according to the

general moisture and temperature characteristics of their source region

Summer air masses are similar to

winter ones

summer air masses are similar to winter ones except for

continental tropical

polar air masses are milder..

in the summer

Tropical air masses are warmer…

in the summer

Air masses form by…

Remaining fixed over a given surface

As air masses begin to move they can..

modify from the changing surface beneath them

The longer an air mass sits over a given region the more…

uniform its properties become

modification of cP air can lead to

lake-effect snow

Air mass humidifies due to

evaporation from unfrozen lake

Air rises on leeward shore causing

persistant snowfall

increased friction with land surface and/or topography force..

air to rise on leeward shore

A front is defined by

a zone of a strong horizontal temperature gradient

A front is formed by

a narrow zone of transition between two different air masses

The four types of cold fronts

cold, warm, occluded, stationary

cold front is when

cold air pushes against warmer air

a warm front is when

warm air pushes against cooler air

A occluded front is when

a cold front catches up to a warm front and lifts it off the surface

a stationary front

Boundary between air masses that doesn’t move much

leading edge of cold air is a

cold front

cold air lifts

warmer air

relatively steep frontal surface leads to relatively…

strong vertical motion and potentially severe weather

leading edge of a warm air mass is a

warm front

warm air tends to —— — and —- the cooler air

slide up over

warm air tends to slide up and over the cooler air, forming a

gentle slope and a large area of rising air and precipitation

what type of front is less likely to be associated with severe weather?

warm

when a faster-moving cold front overtakes a warm front a —- front is formed

occluded

once occlusion forms, low pressure typically begins to

fill

—- can fall along an occluded front

precipitation

when two air masses meet and remain in place for an extended period a —— front is formed

stationary

along a stationary front, air flow on either side is almost…

parallel to the front and might produce (light to moderate) precipitation

A new low pressure can form along this front, which can then change the front into…

warm/cold fronts

thunderstorm

a type of turbulent weather accompanied by lightning and thunder

thunderstorms develop out of growing

cumulus clouds

thuderstorms may develop within an

air mas, in a line along a front or where orographic lifting occ

cb’s contain (three things)

large ice (graupel) smaller ice and supercooled liquid water

collisions between the three different cbs can lead to

charge transfer

cb’s are very

turbulent

lightning

flash

flashes of light in lightning result from the

discharge of electricity

sound of thunder that follows lightning comes from the…

violent expansion of the abruptly heated air

single-cell thunderstorms consist of

a one time updraft and downdraft

In the towering cumulus stage, the rising updraft will

suspend growing raindrops until the point where the weight of the water is grater than what can be supported

As rain falls, it transforms the updraft into a…

downdraft

when an updraft transforms into a downdraft it…

cuts off the supply of rising moist air and eventually dissipates

a single cell thunderstorm lasts no more than

30-60 minutes

The lifecycle of single-cell thunderstorms can be divided into 3 stages

growing (cumulus), mature, and dissipating

growing stage of thunderstorms =

all updraft

Mature stage of thunderstorms =

updraft and downdraft and peak intensity

Dissipating stage of thunderstorms =

downdraft

multi-cell thunderstorms are

group of single-cell storms in various stages of their lifecycle

Multi-cell thunderstorms allow the storm system to..

persist for longer and impact a greater area

the primary environmental factor that seperates single-cell from multi-cell thunderstorms is…

vertical and wind shear

Squall lines produce primarily

straight-line wind damage

straight line wind damage is a result of the force of the downdraft speading

horizontally as it reaches the earth’s surface

example of a multi-cell thunderstorm is a

squall line

squall line is a line of storms that can

ectend for hundreds of miles

not all multi-cell thunderstorms are

squall lines

supercell thunderstorm is a (I.E., Mesocyclone)

single cell with a persistent rotating updraft

supercells can produce various

modes of severe weather

supercells are favored in environments of…

high instability and large wind shear

wind shear is a

change of wind speed and/or direction with height

Derecho is a

widespread, long-lived wind storm

derecho is associated with a band of

rapidly moving showers or thunderstorms

Derecho wind damage swath must extend > _____ _____ and include wind gusts of at least ___ _____ __ ____ along most of its length

240 miles 58 miles per hour

Derecho travel in straight paths, fanning out along wide, curved-wind fronts, producing..

destruction similar to tornadoes, but with a direct damage pattern

hail storms are most common in the (I.E., Great plains and midwest united states)

continental interiors of the mid-latitudes

ice storm

storm that produces at least 0.25 inches of ice on surfaces

blizzard is a (> 35 MPH for > 3 hours and visibility < 0.25 mi due to blowing snow)

snowstorm with frequent gusts or sustained winds

mid-latitude cyclones ( also called extratropical cyclones) is…

migrating low-pressure weather systems that occur in the middle latitudes

mid-latitude cyclones often initially develop along

a stationary front

The three parts of the mid-latitude cyclone lifecycle

cyclogenesis, open/mature stage, occluded stage

Cyclogenesis is…

The initial development of a low-pressure center typically along a stationary front

open/ mature stage of a mid-latitude cyclone is identified by…

the clear presence of a warm and cold front

the occluded stage of a mid-latitude cyclone seperates…

low from warm air at the surface, and low begins filling