Written by Bob McDavitt, Meteorologist
A Significant Snow Event diary
2:30pm Sunday 14 August 2011
In the days following Wednesday 6 July 2011, stormy westerly conditions affected New Zealand. In this blog, we'll look at why.
The "Long Waves"
Below is the mean sea level analysis - the weather map - for 6am Sunday 10 July. In between big highs over the mid South Pacific and south of western Australia is a really large trough; it's the area shaded light blue. The weather map looked like this, more or less, since Wednesday 6 July: that is, the big features on it aren't moving much.
This seasonal lag varies around the country
The Wellington Volcanic Ash Advisory Centre (VAAC), operated by MetService on behalf of the New Zealand Civil Aviation Authority, is one of nine VAACs that operate under the International Airways Volcano Watch. Wellington VAAC is supported through the collaborative effort of MetService, GNS, Airways New Zealand and aircraft operators.
John was one of a generation that became involved with weather forecasting during the Second World War. After leaving Auckland University College in 1937 he went teaching, and then was commissioned in the Meteorological Branch of the Royal New Zealand Air Force in 1942. He served in the Pacific Islands, where forecasters often flew with aircrews as observer/gunners, and occasionally took part in combat.
Few weather events are as dramatic, dangerous or challenging to predict as tornadoes.
About the tornado of Tuesday 3 May 2011
On the afternoon of Tuesday 3 May 2011, a line of showers moved southwards across Northland. Ahead of this line the winds were moderate northeasterlies; behind it, they were moderate northwesterlies. Along the line, the winds converged - that is, pushed against each other. Below is a portion of a working chart for 3:00pm Tuesday 3 May 2011, drawn by one of the Severe Weather Forecasters.
The practice of weather forecasting in a professional environment is subject to continual change, driven by advances in the science of meteorology and computing technology, as well as the changing needs of the end users – the people, businesses and public-sector agencies that make decisions based on weather information.
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23rd March is World Meteorological Day.
Each year meteorologists around the world celebrate a chosen theme together to commemorate the anniversary of the founding of the World Meteorological Organization (WMO) on this day in 1950.