Polar Blast 19th to 21st June - Reports/Discussion

[Manukau heads obs]

trending towards a weak la nina at the moment
which favours lows from the north tasman
and easterly rain events
i.e the wetter trend could continue through the spring

[Razor]

Must be going to be a few dry months if some places have had 1/3 of there yearly rainfall in one month, just cant see to many more wet months again before the end of the year or chch will doulble its normal yearly rainfall.

Not as much rain out here with only 7mm today, 9mm yesterday and 18mm thur. im up to 180mm for the month so far. Still sleet fallng and 3C and its be there for 2 days now.

Amazing how much less you are getting. Some high numbers coming in from areas in and around town and to the SW of ChCh out through Selwyn

[03Stormchaser]

To be honest, I'm getting so frustrated with all the smart arse comments that a few people make. There's absolutely no need to do it. I like reading the posts on here and seeing what's happening in different areas of the country. I like reading throgh what people think might happen with our weather. What I dont want is to have to read through childish posts from members who should be mature enough to know better.

100% agree with you, these type of comment shouldnt be here but kept on a trademe message board, even better add them as comments under an article on stuff! I think us Mods will have to take a stronger view on them, becasue they come from a very few... hmmm

Wise words said by Joecam, Cook and Tim. We live in times when social media is were people want to get there information. I personally think metesrvice are struggling in this aspect, although there likes have gone up over this event.

A quick look on facebook shows the following likes on the biggest NZ weather forecasting pages :

- Canterbury Weather Updates 29,500
- Metservice 25,500
- Weatherwatch 12,200

[mikestormchaser]

still absolutly chucking it down here, just not letting up and nor is the radar!, surface flooding really taking affect in patches on the open roads to, doesnt take long to get to them either.

[CHCH Weather Chaser]

Yeah Mike the rain is just relentless. Looking at possibly getting 50mm for the day. 35mm currently.

[Lawrence]

You can say that again Mike.Just anouther heavy shower here 2.0mm an hour 24.9 mm total since midnight

[CHCH Weather Chaser]

Houses aroun the corner are flooded. The road is now shut. A car also had to be rescued out of raging water crossing the road from the paddocks on hendersons road. The road should be shut, its crazy, recipe for disaster!

[tich]

Persistent rain on Banks Peninsula, but snow levels alot higher. (above about 450m, only a little around Hilltop, where it was raining midmorning, not snowing)

[RWood]

Stuff are talking (stuff and) nonsense!

Yes, the 270kph was unofficial due to instrument considerations but there's no doubt many hilltops would have been getting 250+kph gusts. At Kelburn (from memory) speeds averaged near 130kph for some time and gusted to 200kph. This time Kaukau managed 202kph. I have also responded directly to Stuff!

I think Hawkins Hill recorded gusts to 235 km/m during the 1968 Wahine storm. And yes, Kelburn had gusts to 198 km/h in 1968, compared to 141 km/h on Thurs (similar comparative speeds at the airport).

Re the 270 km/h, assume that's from Oteranga Bay, which flanks of the narrowest part of Cook Strait. One of the more plausible reports I've read had mean-winds of 181 km/h and gusts to 243 km/h at that site in 1968, compared to 181 km/h gusts at Brothers Island on Thurs. NIWA also notes that seaspray could affect Oteranga Bay's readings in gale onshore winds (presumably that means it was more likely to under-read?).


Also, here's a report by NIWA yesterday with some further comparisons about Thursday's storm…

'Storm information update (June 21)'

Yes, that was Oteranga Bay. The 181/243 certainly sounds OK, if perhaps a bit conservative.

[RWood]

interesting graph there re welly airport Nev
I have seen similar reports that the windspeed at Kelburn is not as high as the goold ol days
(some of that is due to trees growing higher)
Certainly the 80's had bigger storms in this area than we have had since
(especially for westerly and NWerly gales)

Re Kelburn wind records: The original site with the anemometer not far from vegetation was identified as not giving reliable comparisons for daily windrun over the years because of growth-reduction cycles in that vegetation. Now retired met. scientist Steve Reid (et al) identified that issue quite a long time ago - growth lowered the numbers, which then jumped up again after pruning.

However the instrument on a tall pole on the roof has records in CliFlo for at least 1972-present for maximum gust data. This was not affected by vegetation. I computed some "maxgust" monthly/annual tables and graphs for that timespan, where the "maxgust" average for the monthly was the average of the daily maximum gust values. This showed an overall reduction in average speed, about 8-10% over whole timespan from memory, but more notable in summer months than winter ones. (the records from the last few years were from a different instrument but the results are basically the same whether or not these are included). I forwarded these results to Steve Reid who stated he had reached the same qualitative conclusion by analysing pressure differentials.


I could show the graphs if they could be attached - is this possible?

[Manukau heads obs]

use the post reply button at the bottom of the quick reply to be able to upload attachments

[katipo]

Rain still falling, Heathcote River is running very high at the moment.

[NZstorm]

According to the NIWA report Methven only got 10cm snow. That figure is surprisingly low.

These types of weather systems are a good learning opportunity.

The 2006 event had embedded thunderstorms and I think convection could be the thing to watch out for in such set ups, as convection turns over the air and brings colder air down (lowers the freezing level).
This set up looked weak regards convection.

[Bradley]

According to the NIWA report Methven only got 10cm snow. That figure is surprisingly low.

These types of weather systems are a good learning opportunity.

The 2006 event had embedded thunderstorms and I think convection could be the thing to watch out for in such set ups, as convection turns over the air and brings colder air down.
This set up looked weak regards convection.

As long as the Metservice and some other forecasters learn from this that's all anyone can ask, I've never thought kiwi's just accepted being wrong and not being willing to try and learn from the experience so let's hope that's the case here!!

[Manukau heads obs]

yes, as alluded early on by Dan from M/S , the problem was with the marine layer...
that needed to be mixed out by convective systems..once convective showers arrived , CHCH suddenly got snow showers

[mikestormchaser]

still raining hard out in rolly, i dont have a rain gauge so unable to say totals but id say i would of had to tip it out by now in order for it to start filling up again lol

[CHCH Weather Chaser]

Yup still raining very steadily, now 44mm for the day.

[Ferngrower]

58.3mm since 5pm last night, 115.1 for the event so far, 235.3 for June. Keeping a watchfull eye on the Halswell river across the road(which ECAN says is 2M above normal), has invaded the Tai Tapu domain and rugby field. Was fixing a powerline fault up Huntsbury hill at the end of road,start of the track, around 2pm, and was heavy sleet with brief snow flurries thown in. Bitterly cold.

[Bradley]

Up to 80mm here in Waddington for the last 3 days on top of 90mm a week ago - 170mm in 8 days!!!

[joecam]

Leeston.JPG

I just flew over Leeston, Lincoln and Halswell. Very waterlogged Lake Ellesmere is very full and encroaching over the farmland it borders. The Selwyn river has broken its banks before the Selwyn Hutts therefore relieving a bit of pressure at the mouth. All creeks that flow into the lake are full and overflowing. I would not be surprised if there were not evacs tonight.

[Storm Struck]

All this rain is actually from one low system which started last weekend on Sunday when the heavy rains fell across the region, I know it feels like two systems but remember that other low sat in the Tasman until Thursday so there must be some kind of record for duration of a low system there too .

Rain got heavy before with some sleet thrown in, its been light moderate falls all day here but that was more intense.
Come to think about it if all this precipitation was snow since Thursday we would possibly be sick of it by now and we wouldn't be going very far from our front doors.

[CHCH Weather Chaser]

Come to think about it if all this precipitation was snow since Thursday we would possibly be sick of it by now and we wouldn't be going very far from our front doors.

If it was all snow then we would have over a metre here

[mikestormchaser]

still raining steadly!! not stopping, radar showing it starting to ease but only very slowly. then getting these showers chaining up and making it more persistant.

[CHCH Weather Chaser]

I see Hendersons road is shut now, common sense prevailed! Drains in the middle of the road are now bubbling water out of them....sewers failing?

[Razor]

Been out running very serious problems in lower cashmere and beckenham loop. Quite breathtaking how fast the heathcote is still rising so bloody fast