General September Weather

NZstorm · Unread post by **NZstorm** » Thu 03/09/2015 20:39

spwill wrote:Looks bitterly cold over the South Island Sun/Mon, Wintry precipitation, south eastern parts of the North Island look like catching the very cold weather as well.

Looking like a few cm snow could accumulate at sea level for Otago into Canterbury. 10cm on the Dunedin hill suburbs.

Bradley · Unread post by **Bradley** » Thu 03/09/2015 21:34

Looks even colder then the September 2005 event but way less precipitation - I wasn't in Christchurch then was that more of a southerly flow?

NZstorm · Unread post by **NZstorm** » Fri 04/09/2015 07:21

Looking like the cold front will generate some lightning/hail Sunday morning over the west of the North Island. Currently GFS has 500mb -26C and dp 10C for West Auckland. Something to watch out for. Possibly a few strikes in the east of the country as well Sunday!

Bradley · Unread post by **Bradley** » Fri 04/09/2015 07:38

It has become substantially colder overnight as well, 850hpa temps of -9C over Christchurch for nearly 12 hours

the winds also seem to have swung more southerly for a time to allow for some orographic enhancement of the precipitation...here's hoping anyway!

hozza95 · Unread post by **hozza95** » Fri 04/09/2015 11:12

Here's the Weather Watch just issued for the event, looks like it could be a decent one for us here in southland

HEAVY SNOW

This WATCH is also for the possibility of heavy snow in:

SOUTHLAND, CLUTHA AND SOUTHERN FIORDLAND From late Saturday morning to Monday morning, periods of heavy snow are possible above 200 metres with lesser amounts to sea level.

OTAGO (EXCEPT CLUTHA) From Saturday afternoon to Sunday evening, periods of heavy snow are possible above 200 metres with lesser amounts to sea level.

CANTERBURY From Saturday evening to mid-morning Sunday, heavy snow is possible above 400 metres with lesser amounts to 200 metres.

03Stormchaser · Unread post by **03Stormchaser** » Sat 05/09/2015 17:26

Lovely spring day today topping 18C, oddly enough before the NW picked up.

NZstorm · Unread post by **NZstorm** » Sun 06/09/2015 10:26

More showers this morn in Auckland with about 60mm for September so far. The wet continues!

mikestormchaser · Unread post by **mikestormchaser** » Mon 07/09/2015 13:21

Friday see's another cold blast. Inland snow for Canterbury and I'd say a chance thunderstorms for coastal otago and Canterbury aswel but the timing of the change doesn't look favourable.

matttbs · Unread post by **matttbs** » Tue 08/09/2015 12:11

Models still going for another cold outbreak for Thursday/Friday. Looks quite cold so could be a bit of snow for inland canty as moisture is pretty decent also

Bradley · Unread post by **Bradley** » Tue 08/09/2015 14:24

matttbs wrote:Models still going for another cold outbreak for Thursday/Friday. Looks quite cold so could be a bit of snow for inland canty as moisture is pretty decent also

EC wants nothing to do with it though Matt (only going for around 5-8mm for mid Canterbury with snow only down to 500m) and I know Tony uses that model aheap more then GFS and ACCESS for his forecasts, a do you think perhaps EC might have it wrong on this occasion?

matttbs · Unread post by **matttbs** » Tue 08/09/2015 16:11

Bradley wrote:
matttbs wrote:Models still going for another cold outbreak for Thursday/Friday. Looks quite cold so could be a bit of snow for inland canty as moisture is pretty decent also
EC wants nothing to do with it though Matt (only going for around 5-8mm for mid Canterbury with snow only down to 500m) and I know Tony uses that model aheap more then GFS and ACCESS for his forecasts, a do you think perhaps EC might have it wrong on this occasion?

I think the gfs is the one this time, I don't really look at EC as when I used to it was rubbish. Metservice also onto it now also

Bradley · Unread post by **Bradley** » Tue 08/09/2015 16:15

Yep EC is definitely the odd one out this time with GFS, ACCESS and Metservice all going for 10-20mm of rain/snow down to 300m asl for Thursday/Friday. Will be interesting to see what tomorrow morning EC run will bring...if it doesn't start ramping things up by tomorrow morning I'm thinking it never will!

TonyT · Unread post by **TonyT** » Tue 08/09/2015 16:28

Bradley wrote:Yep EC is definitely the odd one out this time with GFS, ACCESS and Metservice all going for 10-20mm of rain/snow down to 300m asl for Thursday/Friday. Will be interesting to see what tomorrow morning EC run will bring...if it doesn't start ramping things up by tomorrow morning I'm thinking it never will!

Yesterday's 12Z run ECMWF data for Chch was 14mm for Thursday and Friday, today its 8mm. This mornings 12z GFS run was about 10mm. So not a huge difference. I see the 18Z GFS run is up around 20mm, but I never put much stock in the 6Z/18Z runs.

The ECMWF was quickly onto the almost zero precipitation of the weekend's cold period, whereas the GFS had higher numbers which didn't pan out.

Bradley · Unread post by **Bradley** » Tue 08/09/2015 16:37

Yep EC performed brilliantly with that last system and a number before that, this winter at least it's been the best performer of the 3 models by a long way! That's why if it still doesn't have snow for somewhere like Sheffield (300m asl) and a decent amount of precipitation on tomorrow mornings run then I think we can safely say it won't happen, at the end of the day we aren't dealing with a low pressure system here, it's not a hugely complex system like the June snowstorm one was...

TonyT · Unread post by **TonyT** » Wed 09/09/2015 08:25

This morning, the ECMWF has about 10mm for Thursday and 3mm for later on Friday (and a frost for Friday morning!), whereas the GFS has dropped to 5mm for both days combined.

Bradley · Unread post by **Bradley** » Wed 09/09/2015 10:38

Yes it looks like the Metservice will be dropping their "low confidence" risk of heavy snow for Canterbury above 300-400m in their severe weather outlook today...

Orion · Unread post by **Orion** » Thu 10/09/2015 14:26

Two peals of thunder in the last couple of minutes $\:D/$

Richard · Unread post by **Richard** » Thu 10/09/2015 14:37

Orion wrote:Two peals of thunder in the last couple of minutes $\:D/$

Good work

though it was starting to look interesting down your way

Orion · Unread post by **Orion** » Thu 10/09/2015 14:38

A few small hailstones falling with the heavy rain that's just started.

dogmelon · Unread post by **dogmelon** » Thu 10/09/2015 15:30

Holly cow, that was scary! A heap of kicked up dust in the strong southerly change hit and it sort of looked like a tornado. The really strong wind was a bit frightening. There was a cannon of a lightning strike too, well it sounded like thunder, perhaps something heavy got blown over..

Razor · Unread post by **Razor** » Thu 10/09/2015 15:33

Impressive incoming front....

JP. · Unread post by **JP.** » Thu 10/09/2015 15:35

Yeah some amazing dark clouds out to the south / southwest.

Skywatcher · Unread post by **Skywatcher** » Thu 10/09/2015 15:37

Yes, a real southerly buster! I thought there might have been thunder as well - lightning detector picked up something. Temps dropped from 20C to 12C in about 10 minutes. Biggest gust here was 53km/h but the anemometer is a bit sheltered from the southerly.

Karliosis · Unread post by **Karliosis** » Thu 10/09/2015 15:40

Sure is impressive! Big gust front now big raindrops with strong wind!

Razor · Unread post by **Razor** » Thu 10/09/2015 15:42

This is a real humdinger, lightning seen here

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