Rain/ Snow / Flooding SI 8/9 Nov 2018

[RWood]

With reference to December 1957 flood levels - an excerpt from the Met. summary :

"Rainfall: Rainfall was above normal, except in northern and eastern districts of the North Island, the Waimea Valley of Nelson, and the Kaikoura coast. In the South Island high country it was twice as wet as usual. Bay of Plenty, Gisborne and Hawkes Bay received less than half the normal value; Gisborne city was one of the driest places, with only a third of an inch. In the Alps it was the wettest of any month in over 50 years of records. Arthurs Pass received 47”; and the Hermitage, Mt Cook, received 51”, of which 19.34” fell on the 26th. Serious flooding disrupted road and rail transport across the Alps on at least three occasions, namely the 4th, 14th and 26th. On the last occasion the township of Otira was under water and a considerable portion of the railway track was washed out. At the same time major floods developed in several Canterbury and Westland rivers, especially the Rakaia and Waimakariri."

December 1957 is still the wettest December at Arthurs Pass, but its monthly record is now held by November 1994. The all-months record-holder at the Hermitage is now December 1979 - 1447 mm, boosted by 537mm on the 2nd. Tekapo and Ohau still have 1957 as their wettest December. The period October 1957 to March 1958 was exceptionally wet for the West Coast, Fiordland and the Alps - Milford Sound had more than its annual average in that time, and recorded 10015mm for the 12 months ending May 1958.

[Richard]

Some amazing figures there Rupert

[Chris W]

Yes, staggering amounts of rain. That also applies to the past two days though, just it hasn't had the same impact on the Waimak.

[TonyT]

With reference to December 1957 flood levels - an excerpt from the Met. summary :

"Rainfall: Rainfall was above normal, except in northern and eastern districts of the North Island, the Waimea Valley of Nelson, and the Kaikoura coast. In the South Island high country it was twice as wet as usual. Bay of Plenty, Gisborne and Hawkes Bay received less than half the normal value; Gisborne city was one of the driest places, with only a third of an inch. In the Alps it was the wettest of any month in over 50 years of records. Arthurs Pass received 47”; and the Hermitage, Mt Cook, received 51”, of which 19.34” fell on the 26th. Serious flooding disrupted road and rail transport across the Alps on at least three occasions, namely the 4th, 14th and 26th. On the last occasion the township of Otira was under water and a considerable portion of the railway track was washed out. At the same time major floods developed in several Canterbury and Westland rivers, especially the Rakaia and Waimakariri."

December 1957 is still the wettest December at Arthurs Pass, but its monthly record is now held by November 1994. The all-months record-holder at the Hermitage is now December 1979 - 1447 mm, boosted by 537mm on the 2nd. Tekapo and Ohau still have 1957 as their wettest December. The period October 1957 to March 1958 was exceptionally wet for the West Coast, Fiordland and the Alps - Milford Sound had more than its annual average in that time, and recorded 10015mm for the 12 months ending May 1958.

And looking at the peak river flows for the Waimak in the graph on p2 of this thread, both 1994 and 1979 had peak flows higher than today's level.

[spwill]

The Mackenzie and North Otago hydro lakes must have got a good top up, Mt Cook showing 244mm and Twizel 95.4mm from this event.

[Simon Culling]

Photos on this link of settling snow in Mt Somers, which is at between 380-390m amsl.

https://www.weatherwatch.co.nz/content/ ... canterbury

Some of the rainfall totals on the mountain ranges are also impressive - 652mm at Ivory Glacier in just under 2 days.

https://twitter.com/NiwaWeather/status/ ... 5455155200

[NZstorm]

Are warm advection snow events becoming more common? I suspect they are, this was the third warm advection snow event this spring in the South Island. And last spring there was an event on November 11th.

[Richard]

Just had a look at the highest mountains west of here (about 1500 m) no snow at all, so all that warm advection snow was to the south.

[Cyclone Tracy]

In my humble opinion - this is where it is all starting. https://www.weatherforum.nz/phpBB3/view ... 00#p177457

Sudden warming at both poles across the layers is moving the Polar Jetstream further north (south for NH)during late Autumn and Spring and that combines with higher SST's. Both Stratospheric and Troposphere polar vortex have shown significant signs of weaken during these times in recent years.

[RWood]

Photos on this link of settling snow in Mt Somers, which is at between 380-390m amsl.

https://www.weatherwatch.co.nz/content/ ... canterbury

Some of the rainfall totals on the mountain ranges are also impressive - 652mm at Ivory Glacier in just under 2 days.

https://twitter.com/NiwaWeather/status/ ... 5455155200

As a reference point, the 2-day record for NZ sites is 1049mm at Cropp Waterfall.

[Dean.]

Inland Mid Canterbury a picture this morning

[harleyb]

Impressive rainfall!

Speaking of records, I had to trawl through some Taranaki rainfall data for a job a while ago and it included this for October 1998 at North Egmont... 2.8 metres for the month & if I recall correctly over 11 metres for the 1998 year.

Date mm
1-Oct-98 24
2-Oct-98 36.5
3-Oct-98 15
4-Oct-98 45.5
5-Oct-98 17.5
6-Oct-98 0
7-Oct-98 8
8-Oct-98 241
9-Oct-98 513
10-Oct-98 363
11-Oct-98 73
12-Oct-98 109
13-Oct-98 240
14-Oct-98 17
15-Oct-98 129
16-Oct-98 28.5
17-Oct-98 3.5
18-Oct-98 0
19-Oct-98 85.5
20-Oct-98 216
21-Oct-98 50
22-Oct-98 26
23-Oct-98 24.5
24-Oct-98 0.5
25-Oct-98 0
26-Oct-98 0
27-Oct-98 198
28-Oct-98 268
29-Oct-98 46
30-Oct-98 14
31-Oct-98 9

[RWood]

Impressive rainfall!

Speaking of records, I had to trawl through some Taranaki rainfall data for a job a while ago and it included this for October 1998 at North Egmont... 2.8 metres for the month & if I recall correctly over 11 metres for the 1998 year.

Date mm
1-Oct-98 24
2-Oct-98 36.5
3-Oct-98 15
4-Oct-98 45.5
5-Oct-98 17.5
6-Oct-98 0
7-Oct-98 8
8-Oct-98 241
9-Oct-98 513
10-Oct-98 363
11-Oct-98 73
12-Oct-98 109
13-Oct-98 240
14-Oct-98 17
15-Oct-98 129
16-Oct-98 28.5
17-Oct-98 3.5
18-Oct-98 0
19-Oct-98 85.5
20-Oct-98 216
21-Oct-98 50
22-Oct-98 26
23-Oct-98 24.5
24-Oct-98 0.5
25-Oct-98 0
26-Oct-98 0
27-Oct-98 198
28-Oct-98 268
29-Oct-98 46
30-Oct-98 14
31-Oct-98 9

Pretty close - 10765mm at North Egmont in 1998. Many stations set an all-months rainfall record in October 1998. The NZ record for a month is 2927mm at Cropp Waterfall in December 1995, and it also holds the 31-day record of 3813mm during a portion of October-November 1999.

[Simon Culling]

This tweet from MetService gives a satellite view of the extent of the snowfall - I wonder how accurate it is, especially when the snow cover is very thin in places?

https://twitter.com/MetService/status/1 ... 5059720192

This would be equivalent to a snowfall on the higher hills (>300m) here in the UK in May - which in recent years has not been a common occurrence. The last time I can remember a snow cover to low ground in May was on 2nd May 1979 - which was the day Mrs Thatcher was elected PM!

[Thunder081]

Very interesting on those highest rainfall months here's a satellite time lapse of October 1998

Better quality: http://agora.ex.nii.ac.jp/digital-typho ... 998-10.mpg