ES1002 Week 5: Weather and Forecasting

What are the four main steps in creating a weather forecast?

Observing the atmosphere, assimilating observations, running the model, and interpreting the model.

Why does weather forecasting require international cooperation?

Because atmospheric data must be collected globally and shared to create accurate forecasts.

What makes weather forecasting chaotic?

The atmosphere is a chaotic fluid where small changes in initial conditions can lead to very different outcomes (the butterfly effect).

What is the Lorenz Equations' relevance to forecasting?

They describe chaotic systems and show how small changes can result in large, unpredictable effects.

What is the current limit for deterministic weather forecasts?

About 2 weeks.

How have weather forecasts improved over time?

A 10-day forecast today is as accurate as a 7-day forecast was in the 1990s.

What 3 physical laws govern atmospheric models?

Laws of motion, thermodynamics, and conservation of mass.

What is the difference between global and regional weather models?

Global models cover the whole Earth (~64 km² resolution), while regional models have finer resolution (~1 km²) and cover smaller areas.

Why can't weather models use extremely small grid cells?

Smaller cells require more computing power, which is limited.

What is data assimilation in weather forecasting?

The process of integrating global observations into models and evaluating their accuracy.

Why are weather forecasts less accurate in the Global South?

High-resolution forecasts require computing centers and a lot of energy, most of which are in the Global North.

What is ensemble prediction in weather forecasting?

Running multiple forecasts with slightly different starting conditions to capture a range of possible outcomes. (Pendulum analogy)

What defines a reliable weather forecast?

When the observed frequency of an event matches its predicted probability.

Can we forecast long-term climate?

We can predict general climate patterns weeks or months ahead, but not specific weather on exact dates.

Why do clouds form?

Rising air cools, leading to condensation of water vapor into clouds. This can be caused by solar heating, mountains, or weather fronts.

What are the 4 major cloud types?

Stratus, Cumulus, Nimbus, Cirrus.

What type of cloud indicates dreary weather and forms in layers at low altitude?

Stratus.

Which cloud looks like cotton wool and indicates good weather?

Cumulus.

What cloud is responsible for thunderstorms and can reach the tropopause?

Cumulonimbus.

What does a nimbostratus cloud bring?

Continuous rain or snow, often associated with overcast skies.

What kind of cloud often precedes a warm front and sits at mid-altitudes?

Altostratus.

What high cloud type looks wispy and is often the first sign of approaching rain or snow?

Cirrus.

How do clouds affect climate?

Low clouds cool the surface by reflecting sunlight; high clouds warm it by trapping radiation.

How are UK weather warnings determined?

By combining likelihood (confidence in the forecast) and impact (potential damage).

What affects the impact of extreme weather?

Time of year, time of day, regional climate, and prior conditions.

When are UK storms named?

When they are likely to cause amber or red warnings.

What conditions are needed to form a tornado?

An unstable atmosphere and wind shear under a rotating thunderstorm.

What is the EF scale?

A scale from EF0 to EF5 used to classify tornado intensit