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. 

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?

The August 7th 2012 eruption at Mount Tongariro set in motion MetService’s volcanic ash monitoring process for the aviation industry. The Volcanic Ash Advisory process involves interaction between aircraft operators, Airways Corporation and MetService, with important volcanic information input from GNS Science.

This information is also provided to Civil Aviation (CAA) and is used by them to designate Volcanic Hazard zones around those volcanoes that are known to be Volcanic Alert Level 1 or higher.

Written by Ross Marsden, Meteorologist
August 2012

One evening, having just arrived home after the short walk from Trentham Station, I remarked to my family that it was unusual for the wind to blow from the northeast in Upper Hutt. Five days later and it was still blowing from there.

On Thursday 26 July 2012 a cold southeasterly airstream flowed onto the North Island, around an anticyclone centred just east of the South Island.
In this blog post we’ll look at some interesting small-scale cloud structures around the country on this day.
Below is the weather map at midday on Thursday 26 July. The red arrows show the sense of the broad-scale rotation around the anticyclone.

Sunny weather dominated the country due to a large anticyclone covering the country and the Tasman Sea during the second week of July 2012. 

Written by Erick Brenstrum and first published in New Zealand Geographic 96, March-April 2009 

We think of Benjamin Franklin as American, but for the first seventy odd years of his life he thought of himself as British. In turn, the British thought him one of theirs and embraced Franklin’s ideas and inventions as British discoveries.

Introduction

This short article is in response to an emailed complaint about temperatures displayed on the Christchurch Towns & Cities page on Thursday evening, 24 May 2012.

Sent: Thursday, 24 May 2012 10:26 p.m.
To: Enquiries
Subject: Christchurch weather issues!

Dear sir/madam,

On Thursday 19 April 2012, New Zealand was completely surrounded by a very large High (or anticyclone). The air pressure at sea level was above 1030 hPa everywhere over New Zealand at midday on that day. Highest pressures were over inland Otago and Canterbury, peaking at 1039 hPa. Christchurch Airport was reporting 1038.2 hPa ... that's very high indeed.

By Peter Kreft (2012)

It's been a while since a rapidly-deepening low passed close to, or over, New Zealand. I thought it might be interesting to take a quick look at why the "bomb" low of Saturday 03 March 2012 deepened so quickly and why the winds around it affected the areas they did. First of all, here is a series of weather maps covering the period 1pm Friday 02 March to 1am Sunday 04 March.