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Spring Storms In Southern Ocean/new Zealand


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Posted
  • Location: City of Gales, New Zealand, 150m ASL
  • Location: City of Gales, New Zealand, 150m ASL

    October is the windiest month (maybe cruellest? :) ) for New Zealand. The Southern Ocean has a tendency to be on fire through the Spring period, giving a very strong precedence to Westerly winds in this part of the world. This is what some people call "The Ten Week Westerlies".

    Looking at the charts for the past few weeks, the periodic blocking at about 50S that appeared in winter has been obliterated (in the planetary waves, too, I think). Over about 20 degrees of latitude, there have been very tight gradients of constant Westerly winds extending from ~60S to ~40S.

    Being the windiest, cloudiest ocean in the world, with probably the fastest tracking depressions this leads to much excitement, provided you are not on a ship in the Southern Ocean!

    September was quite windy, again lots of northwesterlies, leading to heat and drying out in the east, which is a worry because it's hard for them to get significant rainfalls in summertime (unless a neutral SOI prevails in which case they may be OK).

    A week ago last Friday, a low tracked at about 61S with a central pressure of 927hPa.

    Today a less intense depression from the Tasman Sea moved eastwards, directing storm force northwesterlies ahead of its main cold front.

    Wellington was in the firing line, as it always is in such flows.

    There was nothing unusual about this, in fact exactly one year ago the city had a gust of 87mph.

    Today, we saw mean wind speeds of 70mph through the Cook Strait for a few hours in the morning, which have since eased significantly. Gusts about exposed hilltops got to 102mph, whilst in the city itself we had gusts of 69mph, though the mean wind speed was relatively low.

    I've always thought it a credit to Wellington that there are always reports of damage and emergency services out in force, but rarely anything serious wind related (landslides are a different thing) . Considering the city is a fair bit windier than those in the UK and has far more trees, I'm impressed we don't see dozens of fallen trees all over the place. I imagine people have learned over time what trees can cope and what cannot. Though apparently, trampolines cannot cope with wind.

    I loved how the ferries crossing the Strait were not disrupted. I swear they are a bit gung ho at times. Their excuse was that there was "only 1 metre swells". Well, yes, that's true. But with 70mph mean winds you can easily get wind waves of ~10m. I would not want to be on one of their ships in such conditions. It practicaly takes a cyclone to stop them sailing.

    Things have definitely slackened off now as the flow is more southwest, a direction from which we receive some sheltering.

    Winds picking up again over the next few days but nothing quite like today.

    The weekend looks to be dry and warm - very welcome at this time of the year.

    No doubt we are not yet done with Spring storms. In Wellington, November is apparently the second windiest month (interestingly, July, mid-winter, is the least windy month in the year), although there is always hope for things to calm down halfway through the month.

    Last October, was the 4th windiest on record. It was horrible. However, in the middle of November all the action weather stopped and we got into the settled, warm and very dry summer that lasted until mid April (the best summer for a decade). Unless there's a re-emergence of La Nina that is quite unlikely this year.

    A major health hazard now is the level of UV we get on a clear day. Forecasts in the Far North are for clear sky indicies of 9. We are still a long, long way off the peak UV levels of early January*. Given the coolness of the air (especially in a southwest flow) the risk of getting sunburned is a very real worry.

    It's particularly annoying if you get sunburn on a cool, windy day, which is typical for Spring and it's all too easy for it to happen.

    One thing's for sure, with the sun now this strong already- this weekend is going to feel pretty hot out of the shade.

    * Disturbingly, in January we can get UV levels of 8 (or 10 in the North) with completely overcast skies.

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    Posted
  • Location: City of Gales, New Zealand, 150m ASL
  • Location: City of Gales, New Zealand, 150m ASL

    There was a confirmed Tornado that hit Cambridge on Friday, with a bit of a mess to clean up.

    http://www.weatherwatch.co.nz/content/tornado-photos

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    It appears a small tornado has ripped through Cambridge, lifting roofs, downing trees and leaving the area without power.

    Emergency services received around 30 calls between 3 and 3.30am, when the tornado travelled in a near straight line through the middle of the town.

    Head weather analyst Philip Duncan says the small tornado or squall was caused by humid, unstable, conditions as a cold front moved through. "I've been through one of these and they are incredibly scary. Last night the humid, unstable air created some big clouds and some very heavy downpours - this was either a small tornado or a squall, both of which can turn a gentle breeze into a wall of wind moving at well over 100km/h in just a matter of seconds".

    It lifted the roofs of several properties including the Oakdale Resthome on Tennyson St. Tracy Espin who was working at the home says she heard what at first sounded like a truck approaching at around 3am. But she says the noise became very loud, so she opened the sliding doors to take a look and saw the funnel of wind rushing towards the building. She says it lifted the roof of one wing of the complex and blew out manholes. A water main has burst, causing flood damage to several residents' rooms.

    Residents were awoken and assembled in one room while the situation was assessed. Most were able to return to their rooms.

    A Fire Service communications spokesman says there are massive problems due to the number of powerlines downed by the fierce wind.

    Mr Duncan says the front that brought the heavy downburst is now moving into the Tauranga region.

    Insurance claims following Friday's tornado in Cambridge could be about $10 million.

    More than 100 insurance claims have been made following the twister in the Waikato town on Friday morning, which damaged buildings, brought down power lines and uprooted trees.

    Assessors were considering whether five particularly badly affected residences should be restored or demolished.

    Insurance Council chief executive Chris Ryan said just over 100 claims had been made by late Friday, and he expected more would have been made in the meantime.

    "The damage from these types of events tend to be in pretty specific areas," Mr Ryan told NZPA.

    "They are all pretty similar, relating to roofing and structural damage."

    Mr Ryan said it was difficult to be sure of the cost, other than to say that "within reason, it won't be a huge cost for the industry".

    "It won't be anything like the massive cost of the Northland floods last year, which was about $60 million-$70 million."

    When asked if $10 million could be an accurate estimate, Mr Ryan said "it's very hard to know but that's probably not a bad figure".

    Mr Ryan said the cost could spiral upwards if it hit any valuable land but he wasn't aware if it had.

    The tornado hit the Leamington area in the southeast of Cambridge. It is close to a couple of valuable thoroughbred horse studs, which appeared to escape the worst of the damage.

    "We lost a couple of trees and had a garage lifted and got carted about 200-300m before it got smashed, but that was the extent of it," The Oaks Stud general manager Rick Williams said.

    "As far as I know we were the only horse farm affected."

    The tornado missed the town's central business district but badly damaged the Oakdale Rest Home and a service station. There were no reported injuries.

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    Posted
  • Location: City of Gales, New Zealand, 150m ASL
  • Location: City of Gales, New Zealand, 150m ASL

    We've had to wait a while for the next good Spring storm.

    Today, severe northwesterly gales across the country, followed by a southerly change.

    Highest gusts in the country were to 98 mph about the Wellington hilltops, followed by 92 mph in Wellington City itself (the airport was much calmer). I think this is our highest wind gust here of 2008.

    Today's high was 26C in Kaikoura.

    Christchurch reported temperature drops of 12C in one hour as the southerly change went through.

    Things will clear quickly, with tomorrow looking sunny and pleasant for most of the country.

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