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

With the equinox passing, and some cool days and nights it's apparent that autumn has started.

High pressure covers the country at the moment. It gets pushed northwards over the next few days to lie just over the North Island. This keeps a very narrow latitude belt for the subtropical ridge, only about 5 degrees of latitude (about 35S to 40S). Equatorward, TC Jasper lies safely distant, and poleward the westerlies get going.

A front crosses the South Island on Friday, with heavy rain expected on the West Coast with and ahead of it. By the time the front reaches the North Island, it becomes very weak, just a few hours of rain and nothing more. It loses almost all surface cyclonic curvature, and the upper trough becomes less sharp.

Following behind this is another mid-latitude high pressure system for the weekend and early next week.

At this stage it seems the ridge gets pushed south by some subtropical depression entering the Tasman Sea on which currently appears to be a very strange set-up.

If that ST low is ex-TC Jasper, then there is likely to be some major variations in this output over the next few days.

A pleasant day here with 20C, light northerlies. Darfield in Canterbury recorded 27C with 19% relative humidity.

At this time of the year the UV is going to soon start falling away sharply. Currently we are still seeing "High" or "Very High", and on the equinox recorded a UVI of 8. It's still a doddle to get a tan, but luckily with the UV index low compared to summer it's difficult to burn. Great stuff. :nonono:

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

The bizzare high set-up did come about.

A standard situation set up, a Tasman Sea high spreading a ridge over the country. But then the oddness began, it slid away to the southwest, to lie in the South Tasman Sea. It intensified to a central pressure of 1042hPa (not often seen over the ocean, and especially not at this time of the year!). A front then pushed up the east of the country, followed by a southeasterly surge as the high ridged in behind.

The high is going to spread over all NZ over the next few days and into the weekend (attached).

During the southeasterly surge, a reverse foehn effect setup, and led to Haast on the west coast sitting pretty on 20C with 34% RH. Whilst this is not too exciting, it is fairly rare. Notably, in a similar situation, Haast got last August's highest temperature of anywhere in NZ with 20C.

Looking forward to 4 days of sunshine and pleasant highs (17C-20C). We then get some fronts pushing up from the southwest. The middle of next week puts us in a decent SW flow, with quite a long draw on that second southerly blast for the deep South, but with the speed of the low it's likely the coldest air will be shunted east before making it very far up the country.

The UVI is still either High or Very High. It's a great time to sit in the sun, browning with ease and it's practically impossible to burn (unless you're insane or very pale). Now if only that southerly would pipe down I might actually be able to take off my shirt...

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Posted
  • Location: Lincoln, Lincolnshire
  • Weather Preferences: Sunshine, convective precipitation, snow, thunderstorms, "episodic" months.
  • Location: Lincoln, Lincolnshire

I see that the GFS has downgraded what looked like a 3-4 day southerly for NZ to a 36-hour "toppler". :)

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Posted
  • Location: City of Gales, New Zealand, 150m ASL
  • Location: City of Gales, New Zealand, 150m ASL
I see that the GFS has downgraded what looked like a 3-4 day southerly for NZ to a 36-hour "toppler". :)

UK model was keen on that outcome all along. Yesterday though it wanted a bomb low to cross the South Island, falling from 1002hPa on the west coast to 973hPa on the east coast in 24 hours. That seems to have fallen out of favour now.

It's an interesting comment about the toppler though :)

In terms of parallels with the UK, it's slightly difficult because of the latitude difference. The Azores High is approximated down here by the Tasman Sea High, which is usually found centred somewhere between 35S and 45S, pretty much the same as the AzH.

The mid atlantic high which tends to quickly ridge in and give topplers is probably approximated here by the TSH ridging down to 50-55S and bringing up a southerly that way.

The holy grail of British northerlies, the Greenland High is nigh-on impossible to get down here because of the consistent and fast moving lows to our south. For that reason we can very rarely get cold air as deeply sourced as the UK and Europe. I think it's not impossible though, there can be blocking highs to our south, it just depends on getting the longitude right.

And of course, since most of our cold air is from either the Southern Ocean or occasionally the Antarctica shores, these are cold all the time and means there is always cold air available. This is how at some point in the dim and distant past, Invercargill managed to get an 850hPa temperature of -9C.....in January. Sadly I don't know of anymore details besides that.

A front made painfully slow progress up the country, essentially it has taken 5 days to do so. This led to strong winds, high temperatures and heavy rain. Following behind, we now have very cold conditions in the south and some biting winds.

Have a look at the contrast in 9AM temperatures today! Ranging from 3C to 21C.

Todays high was 24C in Gisborne and the low was apparently 7C in Lake Rotoiti (inland South Island, about 600m ASL).

Gisborne is forecast to reach only 16C tomorrow with showers and cold southerlies...that'll be quite a shock for them :D

After Christchurch hit 25C yesterday, today it was greeted with snow on the hills down to 400 metres...

There is some instability with this cold air shooting up, and pretty cold upper air temperatures.

Sadly it's got dark here so anything that comes in won't be seen. There were some weak attempts at towering cumulus earlier but nothing worth getting exciting over. We are supposed to be getting showers later with the southerly, possibly squally with hail...

As we go into easter, the high moves in and essentially dominates our weather for the whole long weekend. Another front should affect the south of the South Island but looks weak at this stage and disappears before getting near to the North Island.

So a settled easter is expected, and gradually warming up after what will be a very cold start to Good Friday. Temperatures should be very pleasant in the day, and pretty cool at night.

Road snow warnings were out earlier, for most of the main passes on the South Island:

LINDIS PASS

A few snow showers are possible about higher parts of the road until this evening, which could produce a light coating on the road.

MILFORD ROAD

Snow showers are likely about higher parts of the road through to tonight. Between midday and 9pm Wednesday, 2 to 3cm of snow could accumulate on the road above 500 metres.

PORTERS PASS

Snow showers are likely east of the Pass above 600 metres for a time this evening, with 1 to 2cm possible between 6pm and midnight Wednesday.

LEWIS PASS

Snow showers are likely about higher parts of the road above 700 metres through to this evening, especially west of the Pass, where 3 to 5cm is possible.

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

The easter weekend has been very settled for almost everyone. Quite similar to last Easter in Wellington, though a few degrees cooler. Easter Sunday was our best day, with no wind, maximum sunshine and a high of 19C.

Nationwide highs ranged from about 15C to 26C. Northwesterlies kicked in for the east of the South Island, and this gave plenty of places highs in the low to mid 20s during today and yesterday.

Not much rain anywhere besides the west coast and the rainforests.

Now, in the outlook there is a monster northerly heading our way. The gradient on it is really something. Hurricane force winds likely around the southern coast of Fiordland. The air is also quite deeply sourced. With reasonable blocking from that high, tropical air has more time to filter down. However it's not a stationary situation, so the very warmest air will never make it onto New Zealand. I think Southland could be in for a very warm night though on Wednesday.

You can actually trace an isobar all the way from 20S to 60S in some model output. That is like being able to follow an isobar from Mauritania to Scotland!

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

Warm at midnight. Gale and severe gale warnings out for a few places, and heavy rain for the west coast with spillover into Canterbury.

Issued at: 4:31 pm 15 Apr 2009 NZST

Valid to: 0:00 am 17 Apr 2009 NZST

Forecast

*STORM WARNING IN FORCE*

Northerly 45 knots but 65 knots west of Puysegur Point, becoming westerly 40 knots everywhere late morning then easing to northwest 30 knots Thursday night. High sea in south easing. Northwest swell rising to 4 metres. Southwest swell 3 metres easing. Poor visibility in heavy rain developing tonight.

Outlook

Outlook following 3 days: Rising Friday morning northerly 40 knots with very rough sea, easing later Friday 30 knots and Saturday 20 knots. Change later Sunday southwest 20 knots. Heavy northwest swell easing Friday. Southwest swell becoming moderate Friday.

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Posted
  • Location: Lincoln, Lincolnshire
  • Weather Preferences: Sunshine, convective precipitation, snow, thunderstorms, "episodic" months.
  • Location: Lincoln, Lincolnshire

A very unusual setup could arise in a week's time with a low stalling off the North Island and bringing strong easterly winds. Seems that there's a lot of unusual blocked stuff going on around NZ at the moment instead of the usual mobile westerlies.

http://www.wetterzentrale.de/pics/Rsavn1501.gif

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

The westerlies are kind of doing their thing it's just it's too early in the season for them to be dominant equatorward of about 45S. Easterlies over the north of the NI are not unusual, but the stalling of that low is. Practically stationary for a while. I've seen some model output doing some odd stuff with it, hurling it over to aussie and then back over here, or just bringing it straight over the North island. It seems to coincide with a southwesterly hitting the South Island next week, which I thought might bring some significant excitement or a pattern change away from the current summery mode, but the UK model insisted on just bringing another high in the Tasman Sea in a weeks time, clearing off both troughs relatively quickly.....

On the otherhand, looking at the latest run it now wants the low to sit stationary right over the NI on Tues/Weds/Thurs.

Mid April is often the time for a break down of summer weather patterns. Maybe this is it...

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

Dunedin Airport is always interesting for temperatures. Last night it had a brief dip to 18C, then rose to 20C at 4AM and remained that way (or higher) right through the night.

The 9AM temperatures are shown in the attachment. Dunedin Airport is the warmest place in the country at 21C, and South West Cape is the coldest at 14C.

At 11:30AM, Dunedin Airport is now 23.5C...

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

Got warm today, westerly change burst in down south, but before that we had 28C in Alexandra, and mid 20s in a swathe of locations.

At 8PM it was 21C in Kaikoura. It's still 20C there at 11PM.

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

Subtropical low makes impact tomorrow. It's a warm cored system. Meanwhile, a southerly change pushes up the South Island and onto the Wellington region in the early hours. The low to the north, coupled with a strong intensifying ridge pushing onto the SI creates quite a strong southerly surge:

*STORM WARNING IN FORCE*

Variable 10 knots, becoming southeast 15 knots overnight. Rising to 45 knots during Monday morning and to 55 knots west of Hawera to Farewell Spit in the afternoon. Sea becoming very high in west. Southwest swell 2 metres in west. Southeast swell 2 metres developing. Fair visibility in showers developing in the afternoon.

In terms of airmasses, there is one heck of a contrast. 850hPa temperatures should fall to -5C in the southeast midday tomorrow, and remain around +13C in the north. I guess tomorrow night could be the coldest of the year so far down south, but unlikely to fall below 15C for much of Northland- dewpoints up there should be around 17C-19C in the middle of the day.

Here in Wellington, 6 months ago on the 18th October was a lovely warm Spring day, exactly 6 months later, yesterday had the same conditions. Temperatures hovering around 19-20C for us over the last few days.

We've had very little rainfall for a while now. 8mm so far in April, and only 20mm in March, so 28mm in the last 50 days. I think we had about 250mm in February though!

With exemplary timing, farmers in Gisborne are worried about drought, just as major rain is only 24 hours away!

Farmers in the Gisborne region are calling on the government to declare their area a drought zone as dry conditions start causing problems.

Many are being forced to sell extra stock which will leave them short next financial year.

Gisborne farmer Hamish Cave has done a lot of counting recently. He has sold off nearly 2,000 lambs in the past three weeks.

"It's about a 25% drop. That is stock that we would've normally carried over into the next financial year," he says.

He has been forced to sell because his Gisborne farm is parched.

"Right now should be peak growing conditions to build up feed for the winter," Cave says.

But the grass isn't growing. A dry spring, a dry summer and now a dry autumn have left pastures parched and looking more like they would in the peak of summer.

Farmers are having to buy in feed in case things don't get better. There's only been half the average rainfall over the past nine months.

Even the grass that is green doesn't provide much relief for the farmers. In its current state, while it might feed a few sheep, it's of no use to the cattle.

That's why local farmers have asked the government to declare parts of Gisborne, Mahia and Wairoa a drought zone. This would make farmers eligible for a tax relief scheme which allows them to defer some payments until the next financial year.

The weather may also provide its own relief.

"The weather forecast from the MetService I think's for some rain up that way the next few days. So we're expecting that things will wetten up over the next few weeks and months," says James Renwick of NIWA.

If rain doesn't come soon the whole region could suffer.

"The fertiliser company wont' have our business. The aircraft company who apply our fertiliser they won't get our business and the trucking company that carts the fertiliser also won't have any business," says Cave.

It's expected the government will announce whether it is declaring the region a drought zone by early Monday ahead of a visit from the Agriculture Minister.

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http://tvnz.co.nz/national-news/gisborne-r...-relief-2655382

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

Today's UV forecast was 4.6 for Wellington. It should only be a few weeks before the UK starts getting higher UVI than us.

Here is an interesting contrast between UV indices in New Zealand and Europe on equivalent dates.

In NZ- max UVI is 9 at 35 degrees; and 8 at 40 degrees.

In Europe - max UVI is 7 at 35 degrees; and 6 at 40 degrees.

This corresponds to the UVI being about 30% greater at equivalent latitudes. It's been shown that in summer, UVI tends to be 40-45% higher in NZ than at equivalent latitudes in the northern hemisphere. This "summer season" probably only starts properly in November/May (in winter, the UVI is pretty much comparable).

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

Some decent rain earlier in the week up north, but nowhere else. Whitianga had the heaviest of all the towns, with 13mm an hour for several hours. Gisborne, land of parched farms, got 30mm in total - very helpful.

The contrasts I spoke of came about. Dunedin Airport on Tuesday morning, 8AM was -4C. Just 5 days earlier, 8AM the previous Thursday, it was 20C. How about that for a range of minima in one month?

A bit of uncertainty with the subtropical low. Wellington will go northeasterly for a while, which should mean warm and dry before the rainband comes in. Won't be substantial for us, and April will come in as one of the driest for a long, long time unless something surprising happens....

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

Finally rained here.

Across the country, the highs today were 27C in a number of places such as Alexandra, Dunedin and Kaikoura. All on the South Island of course. At 9AM this morning, it was 23C in Christchurch.

Meanwhile, bucketing down with rain on the west coast (just 60 miles from Alexandra), with up to 400 mm expected in some parts of the Alps.

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

It's been warm again, with dewpoints up to 20C in the north. Much drier in the east of the South Island, with temperatures again reaching 26C in a few places.

Meanwhile, it's continued to pour with rain on the west coast, with 500 mm in 48 hours for some places. Tens of thousands of lightning strikes embedded in the northerly flow, with squally thunderstorms necessitating a severe thunderstorm watch and the possibility of damaging tornadoes.

All this led to hot, dry gusty northwesterly winds in the east.

....a land of contrasts.

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Posted
  • Location: Lincoln, Lincolnshire
  • Weather Preferences: Sunshine, convective precipitation, snow, thunderstorms, "episodic" months.
  • Location: Lincoln, Lincolnshire

J07,

Do you have any idea what sort of processes cause these warm, moist north-westerly flows to bring severe thunderstorms to the west of New Zealand?

In the UK the equivalent, the tropical maritime south-westerly, is almost invariably associated with cloud and rain/drizzle and nothing convective.

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

Sorry, late reply...

The mass of thunderstorms last week was due to the release of potential instability. Potential instability implies that if a layer of the atmosphere (as opposed to a surface particle) is lifted en-masse, then it at some point on the ascent be buoyant. The typical criteria for this is to look at a sounding, and if the theta-w decreases with height, then there is potential instability.

In order to unleash this instability, there needs to be some mechanism to lift an entire layer (it doesn't need to be the surface layer). This can often be due to large scale synoptic ascent. This is what tends to give northern NZ thunderstorms in a warm, moist northerly flow. If you looked at the sounding it would probably be saturated through a very deep layer, but the theta-w would still decrease with height. The lifting mechanism would be around a front or trough where ascent is typical.

The thunderstorms that happened last week were probably partially due to this frontal ascent, but also very significantly would be from the orographic lifting. The north to northwest flow would be strongest along the frontal surface, and just ahead of the front, and the lifting there would be very strong, enough to release the potential instability.

There was a very different situation in the last few days as a depression moved near Auckland, and the city was overcast and rainy for much of the day, with pretty chilly southerlies. The resulting high was a pitiful 12C, Auckland's coldest day for 9 months, and apparently the coldest May day since 2001. Today they fared much better with 17C and non-stop sunshine.

Kaitaia had the nationwide high of 19C, in Wellington it was a very pleasant and sunny 15C with hardly a breath of wind.

I cannot be certain of this, but we have now had two consecutive days that have failed to record 20C anywhere in the country. I suspect it's the first time this has happened since last September.

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Posted
  • Location: Lincoln, Lincolnshire
  • Weather Preferences: Sunshine, convective precipitation, snow, thunderstorms, "episodic" months.
  • Location: Lincoln, Lincolnshire

Looks like you're in for a spell of cyclonic/southerly weather according to the GFS- maybe some snow over higher parts, especially in the South Island? The -5C 850hPa isotherm doesn't really reach the mainland (the thrust of cold air being too far west) so I wouldn't envisage any snow to low levels though.

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

Yes it's a pretty unusual set-up. Planetary trough lies over us, stationary high in the Aussie Bight. Everything very slow moving. Not normal. Temperatures should struggle to reach 5C in the high country tomorrow. Also up north it's looking more like mid winter with highs of 15C and showery cold southwesterlies.

There is a snow warning out:

SEVERE WEATHER WARNING.

ISSUED BY MetService AT 8:14 pm 09-May-2009

MEDIA

SNOW EXPECTED TO FAIRLY LOW LEVELS IN SOUTHERN FIORDLAND, SOUTHLAND,

SOUTH OTAGO AND DUNEDIN, ALSO ABOUT THE FOOTHILLS OF CANTERBURY ON

SUNDAY

A very cold southerly flow is forecast to spread over the southern South Island

and Canterbury on Saturday night or Sunday morning bringing a spell of cold rain

and sleet with snow to fairly low levels for the time of year.

For the hills and ranges of southern Fiordland, Southland, South Otago and

Dunedin, 15 to 20cm of snow may accumulate above 300 metres with lesser falls

down to about 200 metres. In southern Fiordland and Southland snow may continue

to fall until early Monday morning but not quite as low.

For eastern Canterbury cold rain will probably become persistent for a time on

Sunday and turn to snow down to about 300 metres on the foothills, before easing

in the evening. 10 to 15cm could accumulate down to 400 metres but there may be

more above 500 metres.

Note that snow falling to these levels is likely to affect many of the higher

roads in these regions. People are advised to keep up to date with the latest

forecasts and check road conditions before travelling.

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

Got some decent snow down south today. Seems like it settled above 200-300m, with accumulations up to 20cm on some of the medium-height roads (500-600m).

A high here of 10C, but not a bad day. Highs in inland South Island about 3C-5C, and up to 8C along the coast but with a very strong cold southerly.

850hPa temperature at Invercargill was -5C at midday.

It's only 3 months ago that I was last on the Desert Road, a scorching hot day with the temperature reaching 33C in the shade (not that there was any shade). Now there's warnings of 5-10cm about the higher parts.

DESERT ROAD

Snow showers are expected on higher parts of the road through to Monday afternoon. 5 to 10cm is likely to accumulate near the summit between 8pm Sunday and 1pm Monday, with lesser amounts down to 900 metres.

ARTHURS PASS

Occasional snow showers expected on higher parts of the road today. 2 to 4cm may accumulate near the summit at times until about 6pm Sunday with lesser amounts down to 500 metres.

LINDIS PASS

Expect occasional snow showers until this evening. 1 to 3cm may accumulate at times near the summit until about 9pm Sunday, with lesser amounts lower down.

MILFORD ROAD

Further snow showers are expected on the road east of the tunnel until Monday afternoon, especially south of Lake Gunn. 2 to 4cm of snow is likely between 8pm Sunday and 1pm Monday, with the heaviest falls about southern parts of the road early Monday morning.

PORTERS PASS

Snow showers are forecast to clear overnight, with another 1 to 2cm likely above 500 metres between 8pm Sunday and 2am Monday morning.

SEVERE WEATHER WARNING.

ISSUED BY MetService AT 8:15 pm 10-May-2009

MEDIA

FURTHER SNOW TO LOW LEVELS IN SOUTHERN FIORDLAND, SOUTHLAND AND SOUTH

OTAGO THROUGH TO MONDAY MORNING, BUT CLEARING ABOUT THE FOOTHILLS OF

CANTERBURY OVERNIGHT

A cold southerly flow is expected to bring further snow about the hills and

ranges of southern Fiordland, Southland, South Otago and Dunedin through to dawn

Monday, with another 5 to 8cm likely above 400 metres and lesser amounts down to

200 to 300 metres. The snow level is expected to steadily rise above 600 metres

by late morning or early afternoon, with any remaining sleet turning to rain

below this level.

Showers of rain and sleet over eastern Canterbury, falling as snow above 300

metres, are expected to clear overnight, although a few may persist about Banks

Peninsula through to Monday morning. Any further snowfalls are not expected to

reach warning criteria, although another 1 to 2cm is possible above 400 metres

in some places.

Note that snow will be affecting many of the higher roads in these regions.

People are advised to keep up to date with the latest forecasts and check road

conditions before travelling.

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

Some pleasant warm weather recently, but now the wind is back. W-NW flow covers the country. Becoming severe gale ahead of an approaching cold front. Shedloads of rain expected on the west coast again (falling right now). Severe TS Watch issued for West Coast.

Currently 21C in Christchurch, 17C here.

Full warnings:

SEVERE WEATHER WARNING.

ISSUED BY MetService AT 9:19 am 16-May-2009

MEDIA

HEAVY RAIN ON THE WEST COAST WITH SIGNIFICANT SPILLOVER FOR THE

HEADWATERS OF OTAGO AND CANTERBURY, STORMY WEATHER ABOUT THE SOUTHERN

ALPS AND DAMAGING GALES IN EASTERN AREAS FROM CANTERBURY TO WAIRARAPA

INCLUDING WELLINGTON

An active front over the Tasman Sea will move over the southern and central

South Island this afternoon or evening and reach the central North Island about

midday on Sunday. It is preceded by a strengthening north to northwest flow with

heavy, thundery rain on the West Coast, prolonged in Westland, also significant

spillover for the headwaters of Otago and Canterbury.

MetService forecasters expect 50 to 150mm of rain in Fiordland until Saturday

evening and 200 to 300mm for the ranges of Westland as far north as about Otira

through to Sunday morning. This is on top of what has already fallen. Expect 90

to 130mm in the ranges of northern Westland and Buller with the heaviest falls

on Saturday night and early Sunday morning. There will probably also be 70 to

90mm about the ranges of Nelson including the Richmond range with the bulk of it

on Sunday morning.

Heavy rain is also expected to spill into the headwaters of Otago and Canterbury

with 70 to 100mm reaching 25km east of the Divide.

People in these areas including recreational river users in Otago and Canterbury,

are advised that streams and rivers are expected to rise further and quickly.

Trampers especially are warned that weather conditions will be severe in the

mountains.

Ahead of the front northwest gales are expected in many eastern areas from

inland Southland to Wairarapa. Gusts around 120 km/h are likely in Canterbury

and eastern Marlborough from afternoon but 140 km/h or more for Marlborough

Sounds, Wellington and Wairarapa on Sunday morning. Gusts of this strength are

likely to damage trees,powerlines and insecure roofs, and make driving hazardous,

especially for high sided vehicles and motorcycles.

FOR THE LATEST WEATHER AND FORECAST CHARTS PLEASE GO TO

http://metservice.com

MORE DETAILED INFORMATION FOR EMERGENCY MANAGERS AND TECHNICAL USERS FOLLOWS:

HEAVY RAIN WARNING

AREA/S AFFECTED: FIORDLAND, RANGES OF WESTLAND AND BULLER, THE HEADWATERS OF

OTAGO AND CANTERBURY SOUTH OF THE WAIMAKARIRI RIVER

FORECAST:

FIORDLAND

In the 15 to 18 hours from 9am Saturday, 50 to 70 of rain is expected

south of Doubtful Sound and 100 to 150mm further north where it is

likely to peak at 25mm per hour at times.

RANGES OF WESTLAND FROM OTIRA SOUTHWARDS

In the 21 to 24 hours from 9am Saturday, 200 to 300mm of rain is

expected peaking at 40mm per hour at times in embedded thunderstorms.

RANGES OF WESTLAND NORTH OF OTIRA AND RANGES OF BULLER

In the 21 to 24 hours from 9am Saturday in northern Westland and from

noon in Buller expect 90 to 130mm of rain peaking at 25mm per hour at

times on Saturday night and early Sunday in some embedded

thunderstorms.

RANGES OF NELSON INCLUDING NELSON LAKES AND RICHMOND RANGE

In the 15 to 18 hours from 3pm Saturday expect 70 to 90mm of rain

with the bulk of it early Sunday morning peakng at 15 to 20mm per

hour.

HEADWATERS OF THE OTAGO AND CANTERBURY RIVERS AND LAKES SOUTH OF THE WAIMAKARIRI

RIVER

In the 21 to 24 hours from 9am Saturday expect 200 to 250mm of rain

near the Main Divide. 150mm is expected to reach 10 to 15km east of

the Divide and 70 to 100mm to spread 25km east of the Divide.

FREEZING LEVEL/SNOW CONDITIONS: 2000 metres falling to 1200 metres in

Fiordland and 1600 metres in northern Westland on Saturday night.

STRONG WIND WARNING

AREA/S AFFECTED: EXPOSED AREAS OF CANTERBURY, MARLBOROUGH, WELLINGTON AND

WAIRARAPA FORECAST:

INLAND CANTERBURY ALSO HIGHER PARTS OF BANKS PENINSULA

Expect northwest gales today. In the 9 to 12 hours from about noon on

Saturday gusts could reach 120 km/h at times in exposed places.

EASTERN MARLBOROUGH

Expect northwest gales from this afternoon. In the 12 hours from

about 3pm Saturday gusts of 120 km/h are likely at times in exposed

places.

MARLBOROUGH SOUNDS, WELLINGTON AND WAIRARAPA SOUTH OF EKETAHUNA

Northwesterlies are expected to reach severe gale at times from this

evening.

In the 15 to 18 hours from about 6pm Saturday, expect gusts of 120

km/h but 140 km/h or more between midnight Saturday and 9am Sunday.

NEXT SEVERE WEATHER WARNING WILL BE ISSUED AT OR BEFORE

9:00pm Saturday 16-May-2009

Forecast prepared by: Ian Miller

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

Approaching 11PM:

16/15 here, with northerlies gusting to 75mph in the city. Expected to rise overnight.

Meanwhile, Kaikoura is at 22C with northeasterly breezes, but northwesterlies above the surface mixing down and adding some warmth. Humidity there is about 40-50%, so clearly too moist for a pure foehn.

Lovely day up north. Northland and Auckland saw highs of 19C-21C with dewpoints as high as 16C. Sunny with northwest breezes. Splendid autumn day for them.

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

Wind has eased and the weather is now fine.

Overnight, hilltops around Wellington saw sustained wind speeds of 66mph, and the highest gust was 97mph.

9AM temps ranging from 5C to 19C.

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

Cold blast on the way again. This month has had it all. Moderate risk of heavy snow above 300m in the south. The Desert Road (North Island) is also a concern.

Today a few places got to 20C. Won't be seeing that for a while though with this southerly. Northland should end up with highs around 15C, quite wintry for them but will feel colder once the SW wind gets going.

ISSUED BY METSERVICE AT 11:02am Monday 18-May-2009

SPECIAL WEATHER ADVISORY FOR SOUTHLAND OTAGO CANTERBURY

ICY BLAST ON THE WAY

Cold weather already affecting parts of the South Island is expected to get even

colder between now and mid week, as south to southwest winds become established

over the country. Worst affected areas are expected to be Southland and eastern

parts of Otago and Canterbury.

In Southland and eastern Otago, snow showers are expected to gradually come down

to 300 metres during Tuesday, and even lower for a time on Wednesday.

By the end of Wednesday, there could be some quite significant accumulations of

snow above 400 metres.

These conditions are likely to be accompanied by strong winds, causing stress to

vulnerable stock. Driving conditions are also likely to be hazardous on higher

roads.

A few snow showers are also likely to penetrate into central Otago, but no

significant accumulations are expected here.

In Canterbury, snow should gradually lower to 500 metres on Banks Peninsula

during Tuesday. On Wednesday, snow is likely to come down even further, with

some light accumulations possibly developing on higher parts of the Plains.

The weather is expected to turn cold over the whole country, and snow showers

are likely to affect the top of the Desert Road from Tuesday night.

The next Special Weather Advisory will be issued by 10:20 Tuesday 19-May-2009

SEVERE WEATHER OUTLOOK:

Issued: Mon 18 May 2009 at 0232 pm, Valid from Wed 20 May 2009 to Sat 23 May 2009

During Tuesday and Wednesday a cold south to southwest flow spreads over New Zealand with lowering snow levels. From Tuesday afternoon or evening, snow is likely to lower to 200 or 300 metres in the far south of the South Island,and should persist through most of Wednesday. MetService now has moderate confidence in warning amounts of snow above about 300 metres on Wednesday for the hills and ranges of southern Fiordland, Southland, South Otago and near Dunedin. Further north in Canterbury, snow is expected to fall mostly about higher parts of Banks Peninsula, but there is minimal risk of warning amounts at this stage. Over the North Island snow is likely to affect the Central Plateau (including the Desert Road) on Wednesday and early Thursday, but again the risk of warning amounts is minimal. During the remainder of the Thursday, freezing levels should rise as a narrow ridge moves onto the country. On Friday, another cold southerly change is expected with strong or gale winds about eastern coasts of both islands. Strong southerlies are forecast to continue over the North Island on Saturday, but should ease over the South Island as a ridge moves onto southern New Zealand.

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Posted
  • Location: Lincoln, Lincolnshire
  • Weather Preferences: Sunshine, convective precipitation, snow, thunderstorms, "episodic" months.
  • Location: Lincoln, Lincolnshire

Looks like it will be a notable early taste of winter for you (analogous to the UK mid-November northerlies) with the -5C 850hPa line getting well north across the South Island. I'll be interested to see what you get.

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