Weather PatternsCH. 13

Weather vs. Climate• Weather: current

state of the atmosphere

• Climate: average weather of a particular area over a long span of time

Air Masses

Air mass- huge body of air with similar temperatures and moisture– Brings different weather

to an area, lasts for several days, are classified 2 ways:

http://player.discoveryeducation.com/index.cfm?guidAssetId=2CAB90DA-3C54-49D0-9847-AFACFBFD90CA&blnFromSearch=1&productcode=US

Classified how???

1. By their temperature- Polar (P)- Tropical (T)

2. By the source region over which they form.- Continental: forms over land- Maritime: forms over water

Can you identify the air masses?

Air Masses and US (us or U.S. or both?)

• Most of US is affected by 2 air masses• Continental Polar (cP) – begins in Canada and

Alaska- cold and dry, little moisture, clear skies, lake effect snows

• Maritime Tropical (mT)- begins in Pacific or Atlantic Ocean- hot temps, lots of rain, unstable air, lots of humidity

How does cP affect Michigan in the summer?

How does mT affects states like Floridaand Louisiana in the winter?

Minor Roles…

• mP- occur in winter, bring lots of snow, come from the Pacific or the Atlantic

• cT- start in Mexico/SW US, least influence of all air masses

• What hot dry arid states are affected by cT?

Bell Ringer 1-4-2012

• Determine the type of air mass that typically plays a role in the weather in your area. Describe the type of weather that is commonly associated with the air mass and where the air mass originates. Describe the season in your area which result from that air mass.

• (Looks somewhere around pg. 302 and 303 ) • No you do not have to write this if you write in

complete sentences!

Bell Ringer: January 6, 2012

• Weather is a great metaphor for life - sometimes it's good, sometimes it's bad, and there's nothing much you can do about it but carry an umbrella. ~Terri Guillemets

• What do you think about this quote?• Is it true? Why/ why not?

Fronts

• A front forms when 2 air masses meet• The 2 fronts usually move at different

speeds. There are 4 types:1. Cold 2. Warm3. Stationary 4. Occluded

Extra: Big diff b/w air masses causes dramatic weather when fronts form

Warm Fronts

• Warm air moves into an area with cooler air• A red line on the weather map: • Symbol = • Temperature difference (Temp Δ) at boundary• Moves slowly, produces rain over a large area for an

extended period• Clouds = cirrus, cirrostratus, altostratus,

nimbostratus • Weather gets slowly warmer with light rain and wind

• Warm Front moving in!http://www.youtube.com/watch?v=4QPkjP7EzaI

Cloud Types

Cold Fronts

• Cold, dense air moves into an area occupied by warmer air.

• A blue line on the weather map: • Symbol:• A steep face advance rapidly• Heavy downpours, gusty winds, violent

weather, cumulonimbus clouds move quickly• Calmer weather follows.

Cold Front video! http://www.youtube.com/watch?v=0NoPXm7d5Tc (Colorado)

Better Cold Front Video! http://www.youtube.com/watch?v=nPFMKw1_wKM (Latvia)

Stationary Fronts

• Fronts are not overtaking, but rather moving parallel to each other; don’t really move… stationary!

• Red & blue on the weather map: symbol?

Extra: Very little “weather” happening if stationary for a short time. If stationary for a long time, warmer weather will occur

Occluded Fronts

• Cold front overtakes a warm front• Complex weather patterns- CRAZY! And

unpredictable

Fronts, much like all of nature, do not always behave as we would expect (they may produce weather that varies from our descriptions)