Rapidly Deepening Low and Possible Snow Event July 20-22nd

jamie · Unread post by **jamie** » Fri 21/07/2017 10:06

Radar on the west coast is impressive. The alps look to be getting a hiding.

Thunder heard here just now.

snowchaser01 · Unread post by **snowchaser01** » Fri 21/07/2017 10:07

jamie wrote:Radar on the west coast is impressive. The alps look to be getting a hiding.

Thunder heard here just now.

Snowing heavy at Mt Hutt with MS predicting 83cm there today! and 48cm tomorrow!

Sandi · Unread post by **Sandi** » Fri 21/07/2017 10:15

Thunder in South Auckland

melja · Unread post by **melja** » Fri 21/07/2017 10:19

50mm in Rangiora allrady.

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Razor · Unread post by **Razor** » Fri 21/07/2017 10:55

Only half of that here

SnwAddct · Unread post by **SnwAddct** » Fri 21/07/2017 10:56

Rolling thunder here in Parnell, Auckland CBD. My partner just called me to let me know there is hail showers, lightning and thunder out in Swanson, West Auckland.

David · Unread post by **David** » Fri 21/07/2017 11:09

Unfortunately in our office building in Parnell you can't really hear the thunder... can see the heavy rain though

Just had a close one now though that I saw/heard

Storm Struck · Unread post by **Storm Struck** » Fri 21/07/2017 11:09

Really chucking it down now last half hour, with a moderate southerly again

.
The drains will be struggling for sure, although looks as though shes wrapping in on the latest radars so should ease soon.
The low centre looks to be just off the coast near Cheviot.

Razor · Unread post by **Razor** » Fri 21/07/2017 11:14

Storm Struck wrote:Really chucking it down now last half hour, with a moderate southerly again .
The drains will be struggling for sure, although looks as though shes wrapping in on the latest radars so should ease soon.
The low centre looks to be just off the coast near Cheviot.

Rain all but stopped here

SnwAddct · Unread post by **SnwAddct** » Fri 21/07/2017 11:17

snowchaser01 wrote: Snowing heavy at Mt Hutt with MS predicting 83cm there today! and 48cm tomorrow!

How much of that will actually reach the ski area base though? Freezing level looks a touch higher then base elevation of around 1400m when the bulk of precip comes in..

snowchaser01 · Unread post by **snowchaser01** » Fri 21/07/2017 11:18

SnwAddct wrote:
snowchaser01 wrote: Snowing heavy at Mt Hutt with MS predicting 83cm there today! and 48cm tomorrow!
How much of that will actually reach the ski area base though? Freezing level looks a touch higher then base elevation of around 1400m when the bulk of precip comes in..

Its been snowing at the base areas since midnight. Freezing level is often slightly higher than the actual snow level.

Orion · Unread post by **Orion** » Fri 21/07/2017 12:02

Some very strong gusts of wind here in the past couple of minutes, quite an extraordinary sound with them.
Driving rain all morning, continues.

Talbotm · Unread post by **Talbotm** » Fri 21/07/2017 12:03

Roads already under major strain south of Rolleston to Timaru. Given the amount of rain expected south of Rakaia this will be a Major Flood event for South Canterbury. The NZTA are already concerned about Fairlie, Geraldine and Waimate being cut off. I hope people have heeded all the warnings. Crazy amount of rain expected and flooding already and its only just begun in South Canterbury.

Bradley · Unread post by **Bradley** » Fri 21/07/2017 12:13

TonyT wrote:
snowchaser01 wrote: Savage... but so true! Have your thoughts changed Tony?
Niwa is no better. In yesterday's Press Brandolino was quoted as 100mm for Christchurch, today he's quoted at 25-35mm. Really? This is not forecasting, its (over)reacting to model output.

My thoughts have not changed much at all. I still expect the worst to be between Dunedin and Christchurch, with North Otago and South Canty mainly in the firing line. I can't see the snow accumulating below 500m, and I'm even starting to wonder if that is too low. Gales in that zone also. The issue will be how local environments cope with 50-100mm of rain. We know from past events that 50-70mm in the Dunedin area causes problems, and that 80-100mm in the South Canty catchments results in flooding. We also know that in the past a rapid 30mm in Chch causes surface flooding, but the CCC seem to be saying they have upgraded their drainage so we are kind of in unknown territory with that.

A big issue with this storm is not just the total rainfall expected, but the intensity. I'm seeing 25-30mm in consecutive six hour periods in some of the data and thats not picking the extreme value but reasonably widespread over South Canterbury and North Otago. So even if totals fall short of 100mm the impact in 12 hours will be substantial.

Ahhhh and there it is, Metservice has finally come to it's senses and updated their Canterbury Plains forecast for tomorrow to snow to 600m, the 300m forecast theyve been running with the last 3 days was optimistic to say the least...

NZ Thunderstorm Soc · Fri 21/07/2017 12:14

Yes, our street here in Geraldine is already flooded with 46.9mm of rain since about 5am this morning to noon.

Orion · Unread post by **Orion** » Fri 21/07/2017 12:23

Just cancelled a non-vital appointment I had for this afternoon: I did not like the sound of those wind-gusts at midday, it's bucketing down with rain, I've seen/heard several fire appliances and an ambulance this morning, and I'd rather keep off the roads.

snowchaser01 · Unread post by **snowchaser01** » Fri 21/07/2017 12:26

Mt Hutt Updated with 30cm in the base area so far.. and counting.

Dean. · Unread post by **Dean.** » Fri 21/07/2017 12:48

Crazy conditions in Ashburton,reminds me of wet season days in North Queensland.80mm since 5am in my gauge!!!!

RichyDunedin · Unread post by **RichyDunedin** » Fri 21/07/2017 12:54

There seems to be a very heavy line of storms staying stationary over Greymouth. That doesn't seem to match their predicted conditions. Is the radar reading that correctly.

Tornado Tim · Unread post by **Tornado Tim** » Fri 21/07/2017 13:37

Thunderstorm over Hamilton and Matangi now, some good cracks of Thunder

Razor · Unread post by **Razor** » Fri 21/07/2017 13:39

Lifted from a friend on FB... Thompsons Track inland from Rakaia well submerged

Razor · Unread post by **Razor** » Fri 21/07/2017 13:41

Bright sunny and dead calm conditions here in Chch now

jamie · Unread post by **jamie** » Fri 21/07/2017 13:45

Tornado Tim wrote:Thunderstorm over Hamilton and Matangi now, some good cracks of Thunder

It took power out in flagstaff rototuna area. Close to here.

NZstorm · Unread post by **NZstorm** » Fri 21/07/2017 14:33

I have recorded 38mm since last night. So wetter for Auckland than modeled.
Thunder from 10am to 12.30pm with a couple of instances of pea hail. Brighter weather this afternoon.

melja · Unread post by **melja** » Fri 21/07/2017 15:14

79 mm in Rangiora today so far, much heavier inland.

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