Low pressure sequence April 10 - 14

talbotmj15 · Unread post by **talbotmj15** » Sat 07/04/2018 09:53

Given most models are in agreement i thought its worth starting a thread. Tony is now suggesting snow to near sea level in southland and very low in Canterbury

TonyT · Unread post by **TonyT** » Sat 07/04/2018 11:08

talbotmj15 wrote: ↑Sat 07/04/2018 09:53 Given most models are in agreement i thought its worth starting a thread. Tony is now suggesting snow to near sea level in southland and very low in Canterbury

I've pointed out that some model guidance shows that. I'm still on the fence as to whether it will happen. We need to get a bit closer, but its one of the cards on the table. A stormy, wet cold week for sure, and probably the defining weather event of the month.

tich · Unread post by **tich** » Sat 07/04/2018 12:21

Unusual for so early, but only 3 years ago we had snow to low levels on the Port Hills in mid April.

Cyclone Tracy · Unread post by **Cyclone Tracy** » Sun 08/04/2018 11:24

I think this set up deserves it's own thread with it's wide reaching impacts. All models locking in gale to storm force winds, rain, snow, storms, across large parts of NZ. Then a follow up system pushes in late Thursday which potentially combines into the initial system and an ex tropical cyclone off the east of NZ producing a 3 way Fujiwhara effect. The MS website is going to look very busy quite soon.

Tornado Tim · Unread post by **Tornado Tim** » Sun 08/04/2018 14:28

Yes, this weather event is probably going to be quite significant, The possibility of severe squalls on the leading edge on the front is significant, due to the still abnormally warm sea sfc temps, and due to the very cold upper level air coupled with a strong dynamic upper level jet.
I will be watching this event very closely as the squall line potential is quite high, might head to Brians if he's around on Wednesday if the prognostic doesnt change much.

David · Unread post by **David** » Sun 08/04/2018 17:22

GFS showing midday temp 14C in Auckland on Wednesday. That will be a shock! It has consistently been around 23C most days this month.

NZ Thunderstorm Soc · Sun 08/04/2018 17:53

Maybe colder than that.
Interesting to see how this system pans out

Today's MS's SWO is the longest I've seen, they even had to leave bit's out for later in the week as not to jam up their SWO map

snowchaser01 · Unread post by **snowchaser01** » Sun 08/04/2018 17:57

Certainly an interesting few days coming up. If snow falls as low down here as what some people are saying... surely thats near to unheard of for April?

NZ Thunderstorm Soc · Sun 08/04/2018 18:43

Maybe interesting weather for the anniversary of the Wahine Disaster, a replay

tich · Unread post by **tich** » Sun 08/04/2018 20:37

snowchaser01 wrote: ↑Sun 08/04/2018 17:57 Certainly an interesting few days coming up. If snow falls as low down here as what some people are saying... surely thats near to unheard of for April?

Unusual, but far from unknown. (snow to low levels on Port Hills in mid-April 2015)

Bradley · Unread post by **Bradley** » Sun 08/04/2018 21:03

tich wrote: ↑Sun 08/04/2018 20:37
snowchaser01 wrote: ↑Sun 08/04/2018 17:57 Certainly an interesting few days coming up. If snow falls as low down here as what some people are saying... surely thats near to unheard of for April?
Unusual, but far from unknown. (snow to low levels on Port Hills in mid-April 2015)

There certainly was!

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NZstorm · Unread post by **NZstorm** » Mon 09/04/2018 06:57

The snow event will come in two parts, warm advection snow tomorrow, mostly Canterbury to Malborough and then cold advection (cb's) coming up later in the day.

Chris W · Unread post by **Chris W** » Mon 09/04/2018 07:29

After the Northern Hemisphere winter dragged on and ended with a major bang it seems ours is starting early with a similar bang! Ok, not -15 850s and sea-effect snow like over England but extreme at any rate.

It may be being missed but coastal Canterbury is also under a heavy rain watch for today and tomorrow, and the outlook has moderate confidence for a warning for this rain going towards Wednesday. Accompanied by southerly gales.

Selfishly I hope this clears by the weekend, I'm hoping to do the Tongariro crossing then!

NZstorm · Unread post by **NZstorm** » Mon 09/04/2018 07:43

I see a small cluster of storms has developed on a shortwave in mid Tasman, will reach Taranaki and then Waitomo later tonight. Main action comes in after day break tomorrow with severe thunderstorms possible.

spwill · Unread post by **spwill** » Mon 09/04/2018 07:47

David wrote: ↑Sun 08/04/2018 17:22 GFS showing midday temp 14C in Auckland on Wednesday. That will be a shock! It has consistently been around 23C most days this month.

The only cool day I can remember in Auckland this year was on Feb 12th, the max was 18C but the temperature much of the day was around 16C in rain and low dps, caused partly by a tropical low.

mikestormchaser · Unread post by **mikestormchaser** » Mon 09/04/2018 08:34

I definitely see a risk of a thunderstorm/hailstorm up the coastal fringes of Otago and Canterbury tomorr ow afternoon/evening.
More wintry set up yes but thunder on the cards given we are still only in April and with the warmth we have had lately. Will keep watch

David · Unread post by **David** » Mon 09/04/2018 08:44

Today's TS outlook from Metservice

Valid to: Midnight Monday 9 Apr 2018

Issued at: 8:17am Monday 9 Apr 2018

Late today an intense frontal band moves onto western areas of central New Zealand. This system brings a high risk of thunderstorms tonight in Taranaki,Horowhenua Kapiti Coast, the Marlborough Sounds, the far west of Nelson and Buller with heavy rain, 10 to 25 mm/hr, hail, strong wind gusts 90 to 110 km/h,and possibly small tornadoes. In this area there is a moderate risk of severe thunderstorms bringing damaging wind gusts of more than 110 km/h and there is a chance of localized damaging tornadoes as indicated on the chart.

There is a low risk of thunderstorms in a broader area as indicated on the chart.

No thunderstorms or significant convection expected in other areas of New Zealand during this period.

melja · Unread post by **melja** » Mon 09/04/2018 11:50

40-60cm of snow porters pass! Wow.
Potential for chch south to be cut off from the rest of NZ if heavy rain closes SH1 kaikoura and heavy snow closes all other freight routes

mikestormchaser · Unread post by **mikestormchaser** » Mon 09/04/2018 14:03

David wrote: ↑Mon 09/04/2018 08:44 Today's TS outlook from Metservice
Valid to: Midnight Monday 9 Apr 2018

Issued at: 8:17am Monday 9 Apr 2018

Late today an intense frontal band moves onto western areas of central New Zealand. This system brings a high risk of thunderstorms tonight in Taranaki,Horowhenua Kapiti Coast, the Marlborough Sounds, the far west of Nelson and Buller with heavy rain, 10 to 25 mm/hr, hail, strong wind gusts 90 to 110 km/h,and possibly small tornadoes. In this area there is a moderate risk of severe thunderstorms bringing damaging wind gusts of more than 110 km/h and there is a chance of localized damaging tornadoes as indicated on the chart.

There is a low risk of thunderstorms in a broader area as indicated on the chart.

No thunderstorms or significant convection expected in other areas of New Zealand during this period.

Should be risk out for thunderstorms Otago /Canterbury coast tomorrow afternoon/evening to.
Probably will be when they update the charts tonight

Cyclone Tracy · Unread post by **Cyclone Tracy** » Mon 09/04/2018 14:44

A bit of weather in the models

Just had a close look at the latest runs and all the big models and local high res models are fairly well synced. Using the latest GFS 18z as an example, there are extreme differences from 850 to 500 hPa. Throw in the SST's and this looks atomic on storms. I'm not surprised tornadoes is in the MS language now. Maybe even the rare snowspout is a chance over some of the lakes in the southern Alps

Cyclone Tracy · Unread post by **Cyclone Tracy** » Mon 09/04/2018 16:14

Access R and GFS 00z just increased the size of 60 knot sustained wind field at 850 hPa over parts of the upper North Island tomorrow evening. MS warning now up to gusts of 65 knots on the waters. I think that might be conservative if Access R is correct. Have dinner early and get your candles ready around Auckland tomorrow evening.

Orion · Unread post by **Orion** » Mon 09/04/2018 16:53

Cyclone Tracy wrote: ↑Mon 09/04/2018 14:44 A bit of weather in the models Just had a close look at the latest runs and all the big models and local high res models are fairly well synced. Using the latest GFS 18z as an example, there are extreme differences from 850 to 500 hPa. Throw in the SST's and this looks atomic on storms. I'm not surprised tornadoes is in the MS language now. Maybe even the rare snowspout is a chance over some of the lakes in the southern Alps

"Atomic" meaning ? http://www.thesaurus.com/browse/atomic

melja · Unread post by **melja** » Mon 09/04/2018 16:55

Rain really setting in here, 5mm and temp dropped quick to 8.6C

Sent from my Redmi Note 4 using Tapatalk

Cyclone Tracy · Unread post by **Cyclone Tracy** » Mon 09/04/2018 17:33

Orion wrote: ↑Mon 09/04/2018 16:53
Cyclone Tracy wrote: ↑Mon 09/04/2018 14:44 A bit of weather in the models Just had a close look at the latest runs and all the big models and local high res models are fairly well synced. Using the latest GFS 18z as an example, there are extreme differences from 850 to 500 hPa. Throw in the SST's and this looks atomic on storms. I'm not surprised tornadoes is in the MS language now. Maybe even the rare snowspout is a chance over some of the lakes in the southern Alps
"Atomic" meaning ?
Just a descriptive term for the release of a lot of energy but weather wise

spwill · Unread post by **spwill** » Mon 09/04/2018 17:37

Looking chilly in Dunedin now, 5.6C.

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Re: Low pressure sequence April 10 - 14

Re: Low pressure sequence April 10 - 14

Re: Low pressure sequence April 10 - 14

Re: Low pressure sequence April 10 - 14

Re: Low pressure sequence April 10 - 14

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Re: Low pressure sequence April 10 - 14

Re: Low pressure sequence April 10 - 14

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Re: Low pressure sequence April 10 - 14

Re: Low pressure sequence April 10 - 14