The art of weather prediction, part two

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There have been a few studies recently which looked at the use of traditional forecasting in places such as Africa and India and, on the whole, the methods fall into a number of categories:

  • Looking at the sky
  • Animal and plant behaviour
  • Astronomical observations
  • Current weather and recent changes
  • Seasonal patterns
  • Long term cyclical patterns

I had hoped to focus on traditional British forecasting but most of the information I could find was about people who still use traditional methods.  To give a flavour of these approaches, I’m going to give a few examples for each method.

Looking at the sky

This can involve the clouds and as we’ve seen, cloud type, cloud coverage and cloud movement all help to predict the coming weather.  Black clouds mean heavy rain is coming, black clouds preceding strong winds means thunderstorms.

Animal and plant behaviour

You’ll notice these methods involve specific species and this is important as the behaviour of a particular plant in one region could well signal something very different in another.

This area of observation can include migration patterns, the arrival or disappearance of a bird or animal, the different sounds they make and their behaviour.  For example, in a certain part of Uganda, the appearance of bush crickets is one of the signs that the dry season is coming and cuckoo birds starting to call signals the approach of the wet season.

High-flying swallows means stable, fine weather as they are likely to be chasing insects on updrafts of warm air.  On the other hand, bees don’t like rain so if wet weather is on it’s way, they’ll stick around the hive.  Frogs are particularly associated with the rainy season and I touched on the use of frogs to predict wet weather in Australia before.

In terms of plants, we look to when they flower, when they blossom, when they drop their leaves as well as the amount of flowers and fruit etc.  A study in south Africa reported that above average blossoming was a sign of good rains to come and farmers would plant accordingly.  If fruit was being dropped too early and unripe, it was a sign of drought and farmers then knew to plant drought resistant crops.

More locally, dandelions close when it clouds over and scarlet pimpernels close when humidity increases.

Astronomical observations

One of the studies, I think it was a UNESCO one, I really should have made note, was looking at farmers in Peru and Bolivia.  These farmers observed the Pleiades constellation on a certain date and used ancestral knowledge to forecast the timing and quantity of the rain as well as the size of the harvest.  I know that some of you will be reading this thinking that you can’t possibly predict the harvest from a constellation but:

The apparent size and brightness of the Pleiades varies with the amount of thin, high cloud at the top of the troposphere, which in turn reflects the severity of El Niño conditions over the Pacific. Because rainfall in this region is generally sparse in El Niño years, this simple method provides a valuable forecast, one that is as good or better than any long-term prediction based on computer modeling of the ocean and atmosphere.
Orlove et al, 2002

Other astronomical observations include looking at the moon.  Poor rain at the new moon was said to be followed by a dry month and a halo round the moon is a sign of rain.  The shape and the colour of the moon were also used.

Current weather

Looking at the weather now can tell you a lot about what is to come.  In parts of Uganda, winds blowing from the east to the west mean the dry season is near and when they change and blow from west to east, they signal the wet season.  Looking to the mountains can help with short term forecasts – frequent mist or fog on the mountain tops can signal rain.

The occurrence of intense hot or cold spells at certain points in the year are used to indicate the timing and amount of rainfall in the wet season.

Rainbows are another tool used in traditional forecasting.  If they are dominated by red it’s supposed to mean more rain is coming but if they’re dominated by blue it means the rain has passed.

Seasonal change

Being in tune with the seasons helps farmers to understand what weather to expect, but they don’t just turn over a calendar and say it’s spring, they tend to have seasonal markers which they use to inform their practices.  We’ve already looked at some of those which signal the arrival of the wet and dry seasons above.

Long term patterns

This is one area which doesn’t seem to be covered much in the literature but there are weather forecasters who believe that weather comes in cycles, such as the idea there will be a harsh winter every 15 years or so.

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