Planetary Waves and the Hovmöller Diagram

Day-to-day weather features such as fronts and troughs, highs and lows constantly wash against New Zealand in the global atmospheric circulation.  Sometimes the weather in New Zealand is highly changeable, changing from heavy rain to blue skies with an almost daily frequency.  Other times the weather can seem to be stuck one way or another for days.  In this blog we discuss the reason for this: Planetary waves, also known as Rossby waves. We will also look at the tools forecasters have to analyse them, and the implications for New Zealand.

World Meteorological Day 2016: Hotter, Drier, Wetter

March 23rd is World Meteorological Day, a day when National Weather Services around the world commemorate the establishment of the World Meteorological Organisation (WMO), which occurred on this day in 1950. WMO is a global agency which co-ordinates meteorological and hydrological activities. Having international collaboration is very important, as weather will not stop and wait at the border between two countries!

Women in Meteorology

Celebrating the increased participation of women in meteorology

March 2016
 

International Women’s Day is held every year in March and to mark this occasion we want to give a big shout out to all the great women working here at MetService. Since 2001 we have trained 34 women and 30 men to be World Meteorology Organisation (WMO) qualified meteorologists. Twenty years ago the statistics were very different.

The difference between weather and climate

It may seem obvious. Weather is what we experience locally day-to-day and week-to-week, while climate is a background signal sitting ‘behind’ the weather, observed at the seasonal, annual or even decadal time scale. But the interplay between what is dominate in the short-term and what prevails in the longer run, is not so straight forward. For example, 2015 was a very dry year for regions in the north and east of both islands of New Zealand. But there were rain events in these areas, and some of them were very heavy.

Wellington Airport Sea Fog

The annual average fogs for Wellington Airport is 6 fogs per year, much rarer than at Christchurch (50 days per year) or Dunedin Airport (64 days per year) or Hamilton (92 days per year), yet it is very disruptive when it does roll in off the sea and can last for hours at a time.  Interestingly, Wellington gets more fog days in summer while fogs occur in winter for many other airports. Wellington airport is a hub for domestic commercial air traffic, therefore even short closures have major flow on effects for passengers and other airports around the country.

Isolated showers

The Auckland forecast for Monday 12 October 2015 included mention of the following: '... isolated showers ...' and ' ... southwesterly winds ...'. From time to time you’ll hear the word 'isolated' in weather forecasts, so let’s see what it means with reference to observational data, some of which is available on www.metservice.com.  

Himawari Satellite Data

The Japan Meteorological Agency launched a geostationary weather satellite called Himawari-8 in October 2014. “Himawari” means sunflower, and the name has been given to a series of satellites that we can look forward to in coming years. “Geostationary” means the satellite rotates “in sync” with the Earth, always above the same point over the equator.