NZ Weather Forum

Worthy of its own thread I thought. Only an inch of rain so far in ChCh but that on its own is significant given the saturated state of the countryside. I fear much worse to come.

I see Mt Lyford is reporting 3.3-3.7 metre snow base prior to this event, and metservice are predicting over a metre and a half more in the next couple of days...there are goingto be some frightening avalanche situations in the mountains.

Saw a pic in the paper the other day of Lake Angelus Hut in Nelson Lakes National Park- buried in snow to its roof

8o

300mm for Kaikoura? Cripes thats ark building material


Severe Weather Warning (full text)
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Issued by MetService at 08:39am 25-Aug-2008

HEAVY RAIN EXPECTED OVER KAIKOURA COAST AND NORTH CANTERBURY TODAY AND TOMORROW

A large area of low pressure should move slowly eastwards across the North Island today. The associated front has become slow moving over the northeast of the South Island. Over the North Canterbury/Kaikoura Coast area, the heavy rain is likely to persist through Tuesday. In parts of the Kaikoura Ranges 300mm could fall over the two days while up to 150mm is likely over North Canterbury.This amount of rain is likely to cause flooding and slips.

We're on 38mm now, since it started yesterday afternoon, currently falling at between 3-5mm per hour. Plenty of surface flooding and overflowing drains already with just this much rain, but I can hear machines working on the coastal lagoon outlets, so hopefully the water can drain away more easily this time.

TonyT wrote:We're on 38mm now, since it started yesterday afternoon, currently falling at between 3-5mm per hour. Plenty of surface flooding and overflowing drains already with just this much rain, but I can hear machines working on the coastal lagoon outlets, so hopefully the water can drain away more easily this time.

How bad do you see this getting Tony? that Kaikoura warning is scary, on top of the best part of 300mm a few weeks back thats one heck of a loading

We have some people wanting to get some work done up that way shortly, I'm not liking their chances of getting up the farm tracks

Its not even raining here in hoon hay where i am today and its only delivered 22mm so far! When is the heavy stuff coming here? it was meant to overnight. Only got 7 mm so far today typical

MarkThomas wrote:Its not even raining here in hoon hay where i am today and its only delivered 22mm so far! When is the heavy stuff coming here? it was meant to overnight. Only got 7 mm so far today typical

Mark do us all a favour and stop complaining. There are a large number of people around that do not want to see this event get any worse

Razor wrote:

MarkThomas wrote:Its not even raining here in hoon hay where i am today and its only delivered 22mm so far! When is the heavy stuff coming here? it was meant to overnight. Only got 7 mm so far today typical

Mark do us all a favour and stop complaining. There are a large number of people around that do not want to see this event get any worse

Amen to that, brother! (on BOTH points....)

Razor, just to add a little perspective, the warning was actually for 250 to 300mm expected over 40 hours in parts of the Kaikoura Ranges, but a little less on the coast at 150 to 200 mm ...

Severe Weather Warning
Issued by MetService at 08:39am 25-Aug-2008

THE KAIKOURA COAST In the 40 hours from 8am today until midnight tomorrow (Tuesday), 250 to 300mm of rain is expected in the ranges and 150 to 200 mm on the coast. Intensities should reach 10-15mm at times.

CANTERBURY NORTH OF BANKS PENINSULA In the 40 hours from 8am today until midnight tomorrow (Tuesday), 120 to 150mm is expected. Intensities could reach 10-15mm per hour at times.

Razor wrote:How bad do you see this getting Tony? that Kaikoura warning is scary, on top of the best part of 300mm a few weeks back thats one heck of a loading

We have some people wanting to get some work done up that way shortly, I'm not liking their chances of getting up the farm tracks

The models have been very consistent in suggesting 50-100mm, probably around 80mm, for the event, since about last Thursday, and thats whats been in our forecasts over that time. So far it seems to be on track for that. Double those numbers for the ranges and hill country (as usual). This looks like being a solid 48 hour fall, rather than the intense 4 hour burst we got last time, so the flooding may not be as extreme or as sudden, but its still a lot of rain for this part of the world at the best of times, and with the soils at field capacity it is all running off. So, cross fingers.

Nev wrote:Razor, just to add a little perspective, the warning was actually for 250 to 300mm expected over 40 hours in parts of the Kaikoura Ranges, but a little less on the coast at 150 to 200 mm ...

Severe Weather Warning
Issued by MetService at 08:39am 25-Aug-2008

THE KAIKOURA COAST In the 40 hours from 8am today until midnight tomorrow (Tuesday), 250 to 300mm of rain is expected in the ranges and 150 to 200 mm on the coast. Intensities should reach 10-15mm at times.

CANTERBURY NORTH OF BANKS PENINSULA In the 40 hours from 8am today until midnight tomorrow (Tuesday), 120 to 150mm is expected. Intensities could reach 10-15mm per hour at times.

Thanks Tony/ Nev- it is unfortunately in the Kaikoura hills and the Canty foothills where our work is

Steady rain out on Banks Peninsula since yesterday morning, but mostly drizzly stuff rather than heavy. Looks like we're just outside the warning area, though the watch is still in place.

Tony (or someone else), just wondering, do you expect the rain band to overcome the blocking effect of BP and deliver heavy rain to Chch/surrounding areas?

Based off the model runs I have seen, Inny Binny, the winds will shift from a more NE/E flow to a SE then S flow...this would make sense as the low begins to move away from us (though it sure is taking its time, being squashed between 2 big highs the way it is)

Take a look at the M/S radar loops and sat loops and you can see the above happening as well...I think there will be parts of CHCH and immediately surrounding areas that will get the sheltering effect, whereas other parts will get dumped on..I'd say more inland areas (e.g. Darfield, Oxford, Rangiora, etc) will be affected...perhaps Tony and others wish to clarify/set me straight?

Seems to be holding off so far today around ChCh at least, thank god. Although I see Blueskies suggest tonight and tomorrow may be the wettest. perhaps that BP shading effect coming off?

Radars suggest theres been plenty of rain in Kaikoura/ North Catny this morning

46mm now, intensity peaked at 10mm/hr around 11am, eased back to 1.5mm/hr now.

Amberley school is closing at 12.30pm, I have just been for a drive around, the Kowhai river is a raging torrent of muddy water. A number of roads outside of Amberley have extensive surface flooding, but roads in the town seem so far unaffected. Many paddocks are filling up fast with water, and in many cases roadside drains are full and overflowing, hence the surface flooding on some roads making them down to one lane or worse.

THere is doubtless some sheltering effect from the Peninsula around Chch, but if you look at the images you can see that the heavy rain band is largely confined to the area north, so thats probably why the city isnt seeing any of this heavier rain, rather than any topographic effect.

Yes, that could be all the rain we will see for CHCH. The radar is showing a clearence for the city. I dont see this lasting till midnight tuesday. They need to change the weather warning to heavy falls about and north of huranui district. We have dry conditions and high cloud in my part of CHCH atm

No, Mark, I have to disagree...they put out their warnings for a reason and aren't gonna change them just because you think they should!! ...I think the worst is yet to come for CHCH...the winds have not quite shifted around to the s/ssw flow...we are getting the shelter affect right now from BP...i think we will start to see the "chain" effect start firing up as well....and that won't be until tonight, I reckon, after it gets established (there is even some evidence of it starting to form on the latest radar loop from the M/S).

Just like many other previous threads, Mark, you may not see it RIGHT NOW, but that is because these things happen on their own timescales...these things don't happen on MarkThomas' I-want-to-see-it-now-because-that's-what's-in-the-model scale...sure, we haven't seen the precip amounts forecasted, but all it takes is one doosey of a downpour/good rain band to come through...

When it has shifted to a ssw flow does that mean we only get the rain from the south though? ....because all the heavier rain is to the north.

Glitz (et al) I share your frustrations with the "DoubtingMarkThomases" of the site who are seemingly unhappy with anything less than the sky falling on their head. I urge the moderators to take a dim view to such hearsay.

Wind appears to be starting to shift here in Central ChCh now, I expect the predictions made by Blueskies that the worst of this is to come tonight/ tomorrow may hold true. By geez though, having spoken to an associate in Sefton, where they are already underwater, I pray that its wrong.

MarkThomas wrote:When it has shifted to a ssw flow does that mean we only get the rain from the south though? ....because all the heavier rain is to the north.

Have you even looked at the weather maps?

yeah....

Just starting to rain steadily here now in Halswell.

Nothing overly heavy here since the brief bucket load bursts last night.
Drizzle this morning has now turned to a more persistant to steady rain and should continue to increase in the next few hours.
Note the wrapping in from the more S-SE direction now which can be seen on the 3pm radars suggests some downpours starting develope near Kaikoura which will move down towards places north of Rakaia I would think.
It certainly will be different this time to the fact that Tony suggests prolonged rather than over a short space, but this time some places will see downpours at times which could well deliver alot of rain in a short space of time.
Lets just hope the media dont hype everything up again like last time, as i am sure the civil defence will warn people in the right time frames if necessary.
Up to 28.3mm here so far since 4pm yesterday.
Cheers
Jason.

so how much rain do you think CHCH could receive tonight? Anything significant?

62mm now, and a lot of surface flooding all around. Rivers and streams seem to be coping so far.

Whats the rain intensity like there now tony? Just as heavy? Do you see CHCH getting heavier rain later tonight?