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.
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.
MetService forecaster James Lunny (second from right) manning our trade display at last week’s National Fieldays.
MetService has been attending Fieldays for the past 15 years, and this year our display proved as popular as ever, attracting several thousand people.
A call for a new name for a variety of cloud.
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, 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?”
Today’s weather map shows how this cold southerly is being produced by a combination of a HIGH or anticyclone in the Tasman Sea, and a LOW or depression between Canterbury and the Chatham Islands. For want of a better phrase, we could call this an eggbeater southerly.
May 4th/5th 2009
I work as a public forecaster and my main tasks include writing regional, urban and mountain forecasts. I either work mornings (which start at 5:50AM and finish mid afternoon), or afternoons (which commence mid afternoon and run until 10:45PM).
Several years ago, while on a trip to the UK, I noticed something of meteorological interest that was not in the sky. I was outside Westminster Abbey, one of the worlds greatest landmarks, and the burial place of many famous people. Sir Isaac Newton, a man who had a profound influence on all branches of science (including atmospheric science) being one such esteemed individual. As I walked around the Abbey, I noticed a plaque that nicely describes what mariners might call "variable 10 knots"...
With clear skies over most of Canterbury on Monday, we got a good look at the fresh snow that fell on Sunday (10th May). Here's the view late Monday morning (around 10:30am) from NASA's Earth Observing System Terra Satellite,
Fresh snow on the Alps and Canterbury foothills - Monday 11 May 2009. (Image courtesy of MODIS Rapid Response Project at NASA/GSFC.)