Outdoor Education…Character development through the outdoors

Weather

New Zealand's Climate

The climate of New Zealand is mostly cool to warm with a strong maritime influence i.e. our weather is influenced by our surrounding water. Due to our highly varied topography, microclimates are found across the country. Our mountain ranges can cause significant climate variations in locations barely tens of kilometres from each other.

On maps, North is always straight up. But if we flip the map of New Zealand so that “up” looks directly towards where our predominant wind (West to South West) comes from, it paints a different picture in your mind about where we sit on the planet. It helps us understand why we get so many windy events, sometimes for weeks at a time.

WEATHER

When in the outdoors, you should have knowledge of the current and forecast Temperature, Wind and Rain so that you can make well informed decisions of where to go and what to take.

How to read weather maps

Weather maps as they appear on TV, in a newspaper or online are called 'surface charts'. They show what is happening at a set time where most of us need it - at the Earth's surface.

Air Pressure

Air pressure is the force exerted on a surface by the air above it as gravity pulls it to Earth. Atmospheric pressure is commonly measured with a barometer. In a barometer, a column of mercury in a glass tube rises or falls as the weight of the atmosphere changes.

Average air pressure = 1013 hPa (hectoPascal - the weight per square area of air)

Air pressure above 1013 is a high or anti-cycline with the air moving in an anti-clockwise direction

Air pressure below 1013 hPa is known as a low or cyclone with the air moving in a clockwise direction

The Isobars

Those plain black lines that curve across the map are called isobars (iso = equal, bar = pressure). They join together places with the same air pressure.

Isobars and the Wind

From looking at the isobars you can estimate the wind, but it is not easy. Here are some wind tips:

Winds blow almost directly (but not quite) along the isobars.
In the Southern Hemisphere the flow is CLOCKWISE around LOWS and COUNTER-CLOCKWISE around HIGHS. In the picture on the right, the wind direction is given by the arrows.
If you LOOK into the wind, the LOW pressure is on your LEFT.

The closer the isobars, the stronger the winds.
The wider the isobars, the weaker the winds.

Let's take a look at the current wind. Can you visualise the isobars?

The Highs

When isobars enclose an area of high pressure this is called a High or anticyclone and its centre is labelled on a weather map by an 'H’.

Near a High's centre are light winds and sometimes areas of low cloud. Winter Highs often bring frost; summer Highs may bring thunderstorms and hail.

The Lows

When isobars enclose an area of low pressure this is called a 'Low' or 'depression' and its centre is labelled on a weather map with an 'L’.

A low pressure system is like a giant funnel of wind spiralling inwards and upwards forcing warmish air in the centre to rise. As air rises it cools and clouds form. Then as clouds become too dense, rain begins to fall.

How to PREDICT WEATHER CHANGES

TASK 1: Test your knowledge with these Weather Flashcards

TASK 2: Forecast the Auckland wind direction, temperature (i.e. cold, normal, hot) and weather (i.e. settled, changeable, wet) for the surface charts A to F in your Self-Management workbook.

Report abuse