Daily Archives: June 29, 2007

Bob McDavitt: The Man, The Meterorologist…

what follows is an indepth and highly informative interview with the Met Services’ media spokesperson, the wonderful Mr Bob McDavitt, weatherman extrodinaire, conducted by your intrepid reporter shenanigans..

mr Mcd

Q: Many New Zealanders may well know you as the face of the NZ meteorological service, but for the benifit of our international readers, could you please describe your role?

A: As MetService Weather Ambassador I act as a go between for the weather and weather users. I foster friendly relations with weather users so they know how best to use our services.

Q: As a small child, did you always want to become a meteorologist? Did you have to study hard to achieve this aim?

A: Not as a kid , but I suppose I did find the Wahine Storm awesome – it bowled our chimney and almost caused a roof fire in our house.

Q: Do you recall what it was that sparked your interested in meteorology?

A: I got a degree in Mathematics and information science in the early 1970s when the theory of chaos was being formulated. There wasn’t much work around for mathematicians in those days and I decided I’d try to do some computer modeling of the weather as an example of a chaotic system.

Weather is a mix of pattern and chaos. a weather map uses the here and now weather data to capture the pattern and then a mathematical /computer model can extrapolate the captured pattern into the future – lets call it isobar land. But we all know that the real world deviates away from isobar land. The background hum of many chaotic changes occurring on this planet, such as doors opening and closing, etc, kaleidoscopically changes our weather patterns , jiggling them into something else. Often this noise fades away, but sometimes the atmosphere feeds back on itself…That’s why weather forecasting is limited in its accuracy, as soon as we produce a forecast, someone, somewhere lights up a cigarette, etc, and changes things. As Lorenz put it in describing the butterfly effect.. sometimes the flap of a butterfly’s winds is sufficient to produce a storm a few days later.

This motivation to improve weather modeling got me into weather forecasting

Then I got hooked. Weather forecasting combines pattern-recognition skills, communication arts, detective craftiness, scientific know-how, and the use of computer-modeling tools with the aim to help people brace for natures extremes. All sectors of the community use weather in different ways so there’s always something to learn. The skill becomes progressive so that the sense of achievement grows with age. Name another job that can beat that !

Q: Bob Dylan famously sung ‘I don’t need a weatherman to know which way the wind blows’. When he comes here in august for his concerts, are you planning to have words with him?

A: That line from Dylan also popped up on a garden fence outside the kiwi camp at Fremantle during the America’s Cup in Perth in the late 1980s (already being recycled even then). Dylan was simply saying we can work out what’s happening by watching the signs. A weather forecaster is able to tell you what may happen NEXT by taking a larger view of the situation…. and we all know how important the NEXT wind change is in winning the America’s cup.

Q: Have you seen some exciting weather events? Typhoons? Tornadoes?

A: nope

Q: What’s been the highlight of your career within the met service? Apart from being interviewed by TMC, of course.. a ha..

A: Olympics meteorologist in Barcelona 1992 – we got 6 yachting medals that year.

Q: There seem to be many freak weather events occurring around the planet. just in the last week for example in the UK there are reports of over 7 inches of rain falling in one day the north of the country, leading to one mans’ death, and in other news I heard that there were recorded temperatures of 47degreesC in Italy. Would you attribute such peculiar phenomena to man made climate change? Or is it merely the cyclic nature of the planet?

A: Perhaps . There is some suggestion that the number and violence of natural disasters is increasing after a dip in the 1970s.

Between 1980 and 2005, nearly 7 500 natural disasters worldwide took the lives of over 2 million people and produced economic losses over 1.2 trillion US dollars. 72% of these deaths were due to weather (drought 60%, wind 12%, flood 10%) Weather disasters kills more people than war or terrorism.

(see: http://www.pitt.edu/~epi2170/lecture15/sld011.htm) however , disasters are rare enough that many factors may be contributing and more study is required. It is like playing cricket. every time you start a new game records get broken. there are millions of places on this planet and only a small percentage of these have an extreme event in any one year.

Q: Is it true that there is a raging debate amongst your meteorological colleagues about this very subject?

A: The debate seems to be about how much we need to do to mitigate future weather storms. I’m not a climate scientist so what I add to this debate is not an expert opinion. The science of climate change itself is well understood. CO2 holds heat, and the clouds are getting taller. We can mitigate this by minding what we burn. There is discussion on how much mitigation, but no one is suggesting that the economy need to suffer. Even if mitigation is too small a factor to impact on future weather disasters, the concept of “minding what we burn” is valid. By designing more efficient ways to use energy we save money and few people deny that wisdom. lets turn the lights off when we leave the room and save the planet. We measure our isobars in hectoPascals to honour the experiment that the French Mathematician did to show that air pressure varies with height. If you are wondering whether any mitigation is worth it, then let Pascal’s wager be your guide (put that in google to see what I mean)… Pascal was wondering whether he should believe in the existence of God and decided the best payout would be to do so. The same applies to reducing co2 as a means of mitigating future weather storms.

Q: Would you agree that we are in a period of intense climate change?

A: Yep. Its because we are adding CO2 to the atmosphere much much faster than it was taken from there in the first place. CO2 holds heat — you can prove that yourself by taking a couple of bottles of coke (or beer) from the fridge— drink half of each bottle then cap it and put them in the sun or somewhere warm. Shake one bottle and not the other , enough to get some co2 from out of the liquid and into the bottles atmosphere. then leave them for 10 minute or so and some back and feel each bottle (or measure their temperature with infra red detector) — the one you shook warms faster and holds heat longer— its the CO2 that does that. Venus is one of our neighbouring planets and has an atmosphere 97% CO2 and has a much hotter surface temp than Mercury(even tho Mercury is closer to the sun). We are .3% co2 and that helps to make Earth’s surface temp around 20 deg warmer than if we were 0% co2 . Do we want to go to .4%?

Q: Is it possible to predict with any accuracy the sort of weather we might be experiencing in 50 years?

A: Let’s use the following definitions: A prediction is saying what might happen before it happens perhaps with no current data. A forecast is to cast the current data into the future, and an outlook is to take a wider view and see what’s coming from over the horizon. A prophecy is words describing the future without any reference to the here and now. And a warning is a statement that a damaging event is about to occur. Weather is the daily ups-and-down of wind and rain. Climate is the way a place responds to its surroundings .

OK: The global climate models are producing climate scenario forecasts and outlooks — these are not predictions because they are based on proven mathematical models that have been given todays data and trended into the future. OK the real world will deviate from the models world so the forecasts have a fairly large plus-or-minus…. but the trend is easy to pick.

The scope of the forecast limits the parameters that can be forecast , we have to use variance as a guide to what parameters can be forecast. Thus if we reduce the scope to a week or two then can forecast the next storm or two, and even forecast isobars. But air pressure goes up and down (varies) so much over several weeks that we can not forecast isobars weeks ahead. A Seasonal outlook will comment on what type of weather pattern may be likely over the next season, or how wind and rain may behave when compared with its monthly average. The parameters used for seasonal outlooks are sea-surface temperatures– something that doesn’t vary much from one month to the next. For a climate change outlook the parameters used are annual temperatures and rainfall. These have variations some of which are quasi-cyclic (come-and-go) and some which are trends (climate change) and some which are caused by one-off events , such as volcanic eruptions. It is possible to even forecast the climate change trends and the impact of quasi-cyclic changes with useful accuracy. It is possible to predict the impact of one-off events, but accuracy will be limited. It is not possible to predict weather for 50 years with useful accuracy, but it is possible to use the climate trend forecast to anticipate what type of weather may be around.

A complication is that we are adding CO2 back to the atmosphere faster than has ever happened on this planet ever before… so we are entering a climate that this planet has never seen before.

Q: People in NZ often talk about the good old days of very long hot summers.. is it true that they are getting shorter??

A: You will find that it is the 40 to 50 year olds that talk this way. That’s because they are finding that the climate at present is replicating to some extent what it did when they were in their 20s and they have rose-coloured spectacles (selective memory (for those years in their live. the climate cycle they are reliving is called the Pacific Decadal Oscillation, and at present it is encouraging La Nina patterns.

Q: Is there such a thing as a typical NZ winter or summer? What about this season, with the heavy snow fall in the south island? And why does it always seem to come as a surprise when these events happen, when it seems the occur with regularity?

A: Typically NZ in winter gets about one good storm a week, and in summer the wet events get further apart. We have a temperate climate and that means our weather is tempered by the surrounding sea. As for this season , there was a 30 to 40sm snow fall an parts of Southland and Otago but then a 1 to 2 metre carpet of snow which fell last June over much of Canterbury was much more significant. We were anticipating (see http://www.metservice.com/default/index.php?alias=farmniseasonal) that people would find the change from May to June to be sharp this year , and its this sharpness that may have come as a shock to some.

Q: Do you have a favorite weather and or season? And if so, why?

A: Autumn is best, cool enough to sleep by night and warm enough to bike during the day. it is also the time of the year with least wind.

Q: What sort of music do you listen to if there was a raging storm going on outside? Or would you listen to the rain drumming on your rooftop?

A: I dunno- if its raining hard I’ll probably be monitoring the news. I like to use baroque style music or droning space music to help me think when compiling a seasonal forecast.

Q: You obviously have a passion for your job, do you think if nz’s weather wasn’t so unpredictable you would soon get bored?

A: Having NZ ‘s variable weather under my belt has helped me forecast in more predictable places such as Perth and Barcelona… but I’ve always managed to get a good measure of accomplishment from my forecasts. I thought forecasting in Fiji in the mid 1970s would possibly be boring until I tried it, and wow… I found for myself a cycle there which is now called the Madden Julian oscillation and it can help forecast cyclones. So boring is a state of mind, not of data.

Q: Is it me or does it sometimes seem colder earlier in the evening than later? Or I am I just getting used to the temperature?

A: Once the sun goes it should cool off at around a degree per hour. If it warms at night, you can usually take that as a sign that a warm front is almost on you, and it’ll rain before dawn. So I think you may just have had an initial sharp change to the cooling and then got used to it.

Q: You must hear this all the time, but how accurate would you say the forecasts from the met service are?

A: For Urban areas tomorrow we are within our target thresholds 90% of the time , using monthly average stats.

Q: And compared to 10/15/20 years ago?

A: 10 years ago 85%

15/20years ago — no data , but I’d say about 80% , but in the 1980s we did not forecast all parameters for tomorrow

(max and min were only forecast for today).

Q: Do you have a favorite TV weatherperson? Or can you not say??

A: Augie Auer (Rip). Karen Olsen.


augie auer

Q: Do you tie your work in with the global meteorological community? I ask this because the weather across the planet must be linked.

A: Not just this planet.. it is also useful to watch what’s happening on other planets to get a good trend. The rain reaching New Zealand this weekend is from air that is fresh from this year’s monsoon. I’d say the Himalya plateau is the source of a lot of weather all round this planet , and data from this regeion will bear useful fruits– once it is better collected and understood.

Q: And is there tightly knit global community of met-service workers? Do you have big conferences and the like?

A: Lots and from all walks of life .. in NZ many attend the Met Society city -meeting and annual conference and I edit their newsletter and they also have a scientific journal. For the storm-chasers and weather-watches there is a very well attended weather forum , which mentions all the weather happening in NZ . No thunderstorm can occur in NZ nowadays without being mentioned on the weather forum.

Q: I’m originally from the UK, and fondly, albeit vaguely, recall the night before the ‘big storm of ’87’, and the BBC weatherman saying how he’d received a letter from a viewer saying there was a huge storm coming, and he said, don’t worry viewers, no such thing will happen. Needless to say ‘it’ did happen. I would imagine that would be legendary among the various met-staff. Have you ever had to eat you own words in such a dramatic way?

A: The weather presenter said he’d had a call from a lady saying a hurricane is coming , and he reminded people it wasn’t , technically , a hurricane. The word hurricane is reserved for use in the tropics. The event did have hurricane-force winds, and I think a storm warning was in effect. We in NZ are the same, we often get hurricane-force winds but we do not call these events hurricanes, we call them storms.

Eating your own words is a way of learning and understanding the world. Once you stop doing that, you’ll learn no more. For some reason the event that comes to mind to me now is back in the 1980s when I was based in Christchurch. It was a wet summer and a farmer wanted to make hay and was running out of time – the grass was losing condition –I told him he could cut, but a few days later we had a morning drizzle and he “lost his lot”. for him it was the difference between a profit and a loss for that year and the bankers were barking for his farm. I wasn’t aware of these risk factors and learnt that sometimes the risk factors have to be taken into account in the forecast.

Q: How closely linked is the met-service to the media? Do the TV weather-people have to attend special training?

A: We depend on the media (and Internet) 100%. Even if we can produce 100% accurate forecasts , we need a clear concise understandable dependable and trusted delivery system. TV presenters are specially trained to be all of this.

Q: Have you ever heard of people being able to forecast the weather via their bunions? Or perhaps more strange devices? I seem to recall a piece of seaweed attached to a wall can become a barometer, of sorts..

A: yep, changing air pressure and humidity levels affect many things and sensitive people. As the air pressure around you falls, the gaps in your joints expand, and this can draw fluid out of the surrounding tissue and be felt. Dolphins frolic in falling pressure. Fish will feed, for the can fell the pressure fall thru their gills and they know the incoming storm will toss the surface and reduce good feeding later. Horses and cows like to weather vane , rather than lie across the , most will put their backside to the wind. Sheep and goats will come to the bottom of the hills when pressure is falling … they know the clouds are coming. Sea gulls will go inland well in advance of an incoming storm.

Q: Do you have a particular song or piece of music you would like us to play when we next do our show?

A: Looking for one mentioning the weather — How about Gordon Lightfoot, Wreck of the Edmund Fitzgerald

Q: Is there any exciting advances being made in the weather prediction/control arena that you can tell us about?

A: Snow making . Works well too.

Q: Speaking of weather control, do you think in the future we will be able to fully control the weather? I seem to recall a documentary where they had some foam or something they could drop in to a storm to absorb the water.. and then there are cloud-seeding experiments to start rain..

A: Cloud seeding only really works in places like Tasmania. In NZ it will work well with the clouds in Southland, but Southland already has reliable rainfall. There has been some talk about trying to direct cyclones away from land, all talk so far.

Q: Is there much known about pre-European Maori weather prediction?

A: Maori weather lore is documented in a poster produced by NIWA

Q: Is there any weather phenomenon that you haven’t seen/experienced that you would dearly like to? For example, a tornado or ball lightning maybe? I’d love to see some of that.. is it true it can linger about for a few minutes? Am I right in thinking that some scientists have made this in the lab as well??

A: Maybe Ball lightning. I can easily decide not to see a tornado . I have a rare photo of ball lightning … and there is plenty of photos of it not on the web and it seems to do less harm than a tornado.

Q: what are your hopes for the future of the met service?

A: May it live long and prosper.

Q: Do you have any other comments you wish to pass on to our listeners and readers? Maybe a prediction about next weeks weather? Or when it might start getting warm again?

A: Coldest day of your year is still to come , and will occur in late July.

Q: It must be nice always being in the know about the forthcoming weather. Do you rarely get caught out?

A: Getting “caught out ” is part of the learning process. I remember once in Fiji looking at the satellite imagery and the weather maps and telling the local church attendees that it will rain all day during their fundraising fair. They huddled into a prayer session and it stopped raining— the cloud stayed but the rain seemed to stay away just from the local area just for the daylight hours. Was this a catch out ?

Thank you very much for taking the time to complete this interview, your comments are highly appreciated here at The Magic Cauldron.

Shenanigans, signing off…




Filed under Interviews

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