March Monsoon Season West Coast 25-6 March

[NZ Thunderstorm Soc]

Coming onto rain from 8pm but as the Rakaia radar is out, can't see what intensities to expect.
Only light stuff though.

[jamie]

Anyone got some updated rainfall totals


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[TonyT]

Interesting that EC has 15-25mm for much of the plains and Christchurch overnight Tuesday and Wednesday whereas GFS only going for 2-5mm - EC over exaggerating the moisture from the N-NW flow perhaps?

More likely to be due to resolution differences and different implementation of the rain physics between the two models, than significant differences in moisture input. This is an interesting test case, because this is an area where the models often dont do a particularly good job of getting the rain pattern east of the ranges correct.

Looks like the GFS won this round.

[RWood]

Cropp has broken its own record for 48-hour NZ rainfall - there are totals of up to 1085mm for several timespans, e.g. 0600 on 25th to 0600 today. Latest data is up to 0700 today. I need a few more hours of data to see if there is any increase on this value - probably not as intensities were reducing in the last few hours. The old record was 1062mm set during the event on 1-3 January 2013.

Edit: bumped to 1086mm for 48 hours to 0900.

[Simon Culling]

Well over a metre of rain in approx. two and a half days at Cropp River according to this tweet from NIWA. Interesting question (and answer) about accuracy further down the tweet:

https://twitter.com/NiwaWeather/status/ ... 4479531008

Interestingly, no further update from the gauge at Milford Sound Airport.

[RWood]

Well over a metre of rain in approx. two and a half days at Cropp River according to this tweet from NIWA. Interesting question (and answer) about accuracy further down the tweet:

https://twitter.com/NiwaWeather/status/ ... 4479531008

Interestingly, no further update from the gauge at Milford Sound Airport.

See my post above... NIWA should have answered that question better. Cropp Waterfall is not really an outlier at all. There is a network of other stations with intermediate values including Cropp Base (10500 annual), Tuku (9700+ from memory) and Rapid Creek (7800mm or so). Cropp Waterfall at 975mm just happens to be further into the "Godzone Wetzone" immortalised by Trevor Chinn in his paper from the 80s.

[Bradley]

More likely to be due to resolution differences and different implementation of the rain physics between the two models, than significant differences in moisture input. This is an interesting test case, because this is an area where the models often dont do a particularly good job of getting the rain pattern east of the ranges correct.

Looks like the GFS won this round.

You just beat me to it Tony Yep it won that round but it continues the trend recently of GFS being increasingly more accurate for rainfall forecasts and EC falling back to the pack a little...EC is still overall the most accurate model though in my opinion

[Bradley]

Cropp has broken its own record for 48-hour NZ rainfall - there are totals of up to 1085mm for several timespans, e.g. 0600 on 25th to 0600 today. Latest data is up to 0700 today. I need a few more hours of data to see if there is any increase on this value - probably not as intensities were reducing in the last few hours. The old record was 1062mm set during the event on 1-3 January 2013.

Edit: bumped to 1086mm for 48 hours to 0900.

Thanks RWood, that surprises me that NZ's 48 hour record is only approx half of what Australia's 48 hour record (1947mm at Bellenden Kerr in 1979), I guess that shows how much rain those cyclones can dump in a short amount of time (which is the event that created the Bellenden Kerr record)

[TonyT]

You just beat me to it Tony Yep it won that round but it continues the trend recently of GFS being increasingly more accurate for rainfall forecasts and EC falling back to the pack a little...EC is still overall the most accurate model though in my opinion

From my perspective for this event the EC was better with the rainfall over most of the South Island, West Coast in particular, but not as good for the spill over into Canterbury. The EC was on to it earlier, and had better accuracy 5-10 days out. They all have their strengths and weaknesses.

[RWood]

Cropp has broken its own record for 48-hour NZ rainfall - there are totals of up to 1085mm for several timespans, e.g. 0600 on 25th to 0600 today. Latest data is up to 0700 today. I need a few more hours of data to see if there is any increase on this value - probably not as intensities were reducing in the last few hours. The old record was 1062mm set during the event on 1-3 January 2013.

Edit: bumped to 1086mm for 48 hours to 0900.

Thanks RWood, that surprises me that NZ's 48 hour record is only approx half of what Australia's 48 hour record (1947mm at Bellenden Kerr in 1979), I guess that shows how much rain those cyclones can dump in a short amount of time (which is the event that created the Bellenden Kerr record)

To see some mind-bending short term totals, have a look for La Reunion in the Atlantic:

https://www.aoml.noaa.gov/hrd/tcfaq/E4.html

[Nev]

Interestingly, no further update from the gauge at Milford Sound Airport.

It looks like MetService's Milford Sound rain-gauge stopped reporting after 6am yesterday.

NIWA's nearby EWS and manual gauges were up to 555mm and 627mm respectively for the 72 hours to 9am this morning.

Their 48 hour totals to 9am yesterday morning were 461mm and 525mm respectively.
And their 24 hour totals to 9am yesterday morning were 357mm and 401mm respectively.

Note that I think the 357mm in 24 hours NIWA reported as Milford Sound's '6th wettest day since records began in 1929' was meant read its '6th wettest March day'.

[melja]

MS said it went underwater and stopped responding lol

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[Cyclone Tracy]

Doing a quick review, it’s always interesting to see which model copes best with mesoscale highest total area right as the event commences. German model is becoming a short term high resolution king in many parts of the globe over the past 6 months.

Cropp River actual 1096mm to 7am Wednesday

Models forecast from 24/03 run 12Z
1st Icon – 850 to 900mm
2nd EC – 550 to 650mm
3rd UK – 400 to 500mm
4th New GFS – 300 to 400mm
5th Access G – 200 to 300mm
6th GFS – 150 to 250mm
7th CMC – 150 to 200mm
8th French – 150 to 200mm

Overall UK and EC 2403 run 12Z had the closest projection on the highest West Coast totals based off NIWA’s gauges.

[Orion]

MS said it went underwater and stopped responding lol

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That would do it!

[NZ Thunderstorm Soc]

Now this event is gone and passed over us, we have to wait for the next event this WE.
I don't think West Coasters will be happy with this

[hypersonic]

...
To see some mind-bending short term totals, have a look for La Reunion in the Atlantic:

La Reunion is in the Indian, not the Atlantic

[RWood]

...
To see some mind-bending short term totals, have a look for La Reunion in the Atlantic:

La Reunion is in the Indian, not the Atlantic

Oops - mind blank.

[Chris W]

Some amazing totals for rainfall. The hydro lakes must have had quite the top-up! Hope they get the Waiho bridge back together very soon so locals can get around and tourists get the full coast experience, though of course they'll have had some of that with the rain!

Driving back from Kaikõura this afternoon it became very windy around Greta Valley. It was still quite warm until I got back to Chch.

[Chris Raine]

Some more rain this weekend I believe for the West Coast

[NZ Thunderstorm Soc]

It's interesting with this event there was no NW here, just light winds between the south and NE.
The strongest winds were the southerly that came through at a quarter to four this afternoon, which blew lots of leaves about.

[NZstorm]

Events like these have major synoptic scale parameters so models pick up on them fairly well.
GFS showing rainfall peak at 450mm for example.

[moylanr]

Some amazing totals for rainfall. The hydro lakes must have had quite the top-up! Hope they get the Waiho bridge back together very soon so locals can get around and tourists get the full coast experience, though of course they'll have had some of that with the rain!

Driving back from Kaikõura this afternoon it became very windy around Greta Valley. It was still quite warm until I got back to Chch.

Enough energy top up in the southern hydro lakes for 200,000 EVs for a year. And then some.

Ref: https://www.transpower.co.nz/system-ope ... ly-updates

[moylanr]

[/quote]
Enough energy top up in the southern hydro lakes for 200,000 EVs for a year. And then some.

Ref: https://www.transpower.co.nz/system-ope ... ly-updates
[/quote]

That would stop over $100m being paid to import fossil fuel.

If you haven't been in an EV then I recommend checking out the nearest event on the annual national Roadtrip that's just started: https://www.leadingthecharge.org.nz/2019greatevroadtrip

[Chris W]

Looking like another deluge for the coast this Tuesday through Thursday, though not too the levels seen the other week. This will give the new bailey bridge a good test though.