Early October Snow

The snow that closed the Desert Road and Napier-Taupo Road on Sun-Mon-Tue 4-5-6th  October 2009 was unseasonable.  It was caused by a low pressure system deepening over the area at the same time as a cold southerly flow arrived, resulting in moist air being cooled from below in a cauldron of lowering pressure.  This produced an unusually heavy amount of snow over a wide area.

The weather map for noon on Sunday shows the low pressure system forming over the Central North Island

Types of weather

The World Meteorological Organization (WMO) sets recommended practices for coding and reporting weather observations and forecasts. For aviation reports, these codes are set in consultation with the International Civil Aviation Organization (ICAO).

Ridge-Top Winds

I started tramping as a teenager with the expectation of rain in the hills about two days out of three. So we were always prepared to change plans if confronted by a river in flood. Likewise, conditions on the tops could send us scurrying back below the bush line, as the wind over the ridge crests was sometimes strong enough to throw an adult carrying a heavy pack off their feet.

Late frosts

Earlier in the month many parts of New Zealand had frosts. Since we are now into the beginning of spring, it got me thinking about the impact that late season frosts can have on the delicate buds sprouting on trees and vines around the country.

Waikato Stadium Weather

After a week of sunny weather, it appears that rain will dampen Waikato Stadium before this weekend’s Tri Nation rugby game starts there at 7:35pm on Saturday.

Waikato Stadium

Waikato Stadium

This clash between the Springboks and the All Blacks is the first Tri Nations game to be held at Waikato Stadium (capacity 25,800).

Bottle-necks

Our weather in New Zealand is greatly modified by the shape of the land. There are many parts of the country where the air is channeled through gaps in the terrain, and I thought I would write a little about this. Especially since it relates to the thread of my earlier posts on wind.

The Thunderstorm in History

One of the pleasures of reading history is coming across stories about the weather. Thunderstorms often figure in these. One of the most dramatic examples was recorded in the sixth century AD, by Gregory, Bishop of Tours, in his Historia Francorum (The History of the Franks).

How Lows and Highs move

In my blog post about winds aloft there is a loop of satellite images for a week in winter 2008.  It shows that the big cloud features in the mid-latitudes typically travel from west to east. In other words, the features you see on weather maps affecting New Zealand have usually started out roughly in the area of southern Australia.