Week 4 weather forecasting

Describe the evolution of cyclones

Midlatitudes→ from jet stream (W to E) disturbances

→ low pressure w circulation that lead to comma shaped patterns

-> move along w jet stream (W to E), comma shape more obvious as it evolves

Describe the formation setting of cyclones with fronts and jetstreams

Forms due to temperature gradients

1. Occurs at front→ boundary between hot/cold air, is a slope

2. Low pressure region at middle (the perturbation), where counter clockwise winds flow

3. Frontal slope deforms over time, warm front→ warm air advances poleward, cold front→ cold air towards equator

Describe the three airstreams which lead to the formation of cyclones

1. First airstream a warm conveyor belt from south

   → hits front and rises into jetstream

   → splits in two, towards east + west, forms comma shape

2. Second cold conveyor belt from east/north

   → stays near surface under warm belt

3. Third dry airstream, is dry

   → descends from upper atmosphere

Describe the formation of a cyclone

1. warm air is lifted as cyclone evolves (less warm area)

   → cyclone intensified circulation

   → cold air expands,

   → dry air becomes more wrapped up

2. Surface fronts wrap up to form occluded front

   → cold + warm front merged

Why do jet streams exist?

due to temperature differences between polar region and mid-latitudes

blows from west to east

acts as a steering mechanism for storms + weather conditions

How do jetstreams control the direction warm and cold air moves?

Undulations (rising and falling motion) in jet stream called Rossby waves

→ when jetstream moves toward equator these waves bring cold air

→ towards poles, bring hot air

these waves show boundary between warm + cold

Describe the differences between satellite vs radio imagery

Satellite (space)

1. detects reflected visible light/ emitted infrared by earth

2. Mainly clouds

Radar (ground)

1. scattered microwaves

2. Mainly precipitation sized particles

Reading radar imagery

Orange means more intense precipitation in intense storms

Blue opposite

Explain atmosphere circulation and how it affects weather

Imbalance in heat between tropics + pole lead to circulation around equator, more rain in equator

→ this rising air descends at subtropics, less clouds + rain

Cold air near poles which goes towards equator

→ meets w westerlies (from hemispheres) to form front which forms jet streams and weather variability

Describe cumulus clouds + environment which it forms

• Fluffy, individual

• Flat base w dome shaped top

• Formed in unstable environments by convection, warm air rises and cools

Describe stratus clouds + environment which it forms

• low level, uniform, continuous layer

• occur in stable conditions w little vert air movement

• leads to overcast skies + light drizzle

Describe cirrus clouds + environment which it forms

• High level, made of ice crystals

• Thin, feathery

• Forms in stable + cold environments (front of warm fronts or high up)

Describe altocumulus clouds + environment which it forms

• mid level, wavy or globular shape

• white or gray

• indicates stable weather conditions, before weather change

Describe cumulonimbus clouds + environment which it forms

• Mushroom shaped w dark dense base

• forms in unstable conditions w moisture + strong vert air

• extreme weather

Explain the scientific basis for weather forecasting and how weather forecasts are made.

Using the laws of atmosphere

→ ideal gas law, conservation of mass, wind/temp changes

→ computer models it

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