A Look Back at Summer

The story of summer 2012/13 was rain, or rather the lack of it. Drought was declared for the North of the country on the 27th February, shortly followed by the rest of the North Island and parts of the South Island. The prolonged dry spell was due to presence of large lingering areas of high pressure that dominated the weather across New Zealand. These areas of high pressure acted as blocks, sitting over the country while areas of low pressure, and their associated rainfall, skirted either side of the country.

MetService Satellite Dish Installation.

A satellite receiver ("dish"), for improved reception of data from polar-orbiting weather satellites, was installed at MetService Head Office in Kelburn in February 2013.

Benefits

Polar-orbiting weather satellites yield rich information about the atmosphere, valuable for New Zealand weather forecasting. Benefits of faster access to more data, and sharper identification tools, include:

Why it Was So Dry in February 2013

During the summer of 2012-2013, anticyclones dominated the New Zealand area. Many places had little or no rainfall since early February.

The map below shows the average mean sea level pressure over the New Zealand area over Jan/Feb 2013. There's no doubt about the pressure being high and not changing very much. Because this map shows averaged pressures, we don't see the few troughs that passed across Aotearoa New Zealand during that time.

It’s a fine day. Isn’t it?

What do we mean when we say the weather is “fine”? The word fine is often used to convey the positive attributes of something. It is synonymous with good, well, enjoyable.

How are you? I’m fine!
How was the movie? It was fine.
This is a fine bottle of wine.

When we write weather forecasts we define the term fine to mean that the sun casts sharp shadows. If cloud is thick enough to stop the sun from casting sharp shadows then, even if it doesn’t rain, we don’t think that’s a fine day.

Convergence Lines and Sea Beezes

In the English language we have many words in common usage that have related but more specific meanings in a scientific and mathematical context. The key word of this blog post, “convergence”, is a good example of this. We sometimes hear of people’s views on some matter initially disagreeing and then, later, coming together or “converging”. In fluid dynamics we’re often interested in regions where different air flows come together. We call this type of flow convergence, and say that the air is converging

Not all El Niños are the same

This blog created just prior to spring 2012. 

The phrase La Niña was possibly heard a lot during the Summer of 2011-12, going into spring 2012 another similar term is El Niño. We all know that El Niños bring different types of weather to New Zealand compared to La Niñas but what is an El Niño? Does it always mean the same sort of weather for New Zealand? Not necessarily -  The season of 2012-13 might not have the typical sort of El Niño weather. So what is a typical El Niño?