The Great Northwesterly Storm of August 1975

If you were in New Zealand in the mid '70s you may remember a particularly strong wind-storm that devastated many parts of the eastern South Island. It struck on 1 August 1975, doing a huge amount of damage to pine trees in the Eyrewell and Balmoral forests in particular.

To give you an idea of the power of this storm, some of the peak recorded winds and gusts were:

Severe Thunderstorm Warning Service

From Wednesday 01 July 2009, MetService will provide a Severe Thunderstorm Warning Service. This blog entry explains why we're now able to do this, why warnings of thunderstorms are different from warnings of broad-scale weather events, which parts of New Zealand they will apply for, how you can receive them and what actions you can take to protect yourself.

Mt Taranaki Kármán Vortex street

MetService weather forecasters naturally spend a lot of time looking at satellite imagery and every so often are treated to some fascinating cloud patterns in the airflows around New Zealand. One pattern I've always liked seeing is the Kármán Vortex street, most frequently observed near our shores to the west of the North Island, generated by Mt Taranaki in a south to southeast flow.

The Wind-sock of the Lower North Island

In my previous blog post I wrote about how much the winds high in the sky differ from the winds that we are accustomed to nearer sea level. The winds aloft are usually much stronger than those near the earth's surface, this difference being  especially true in New Zealand. Another difference (which I mentioned in the last blog post) is that the wind we experience every day is more variable, suggesting that the wind aloft is more unchanging.

Red sky at night...

Red sky at night, Shepherd’s delight. Red sky in the morning, Sailor’s warning. I'm not going to argue about shepherds and sailors; that’s not important here. The questions are: “Is it a useful saying? Does is work? If it works, why?” And, “Why is the sky blue?”