TC Debbie remnants 3rd-6th April NZ wide

NZstorm · Unread post by **NZstorm** » Sun 02/04/2017 11:32

The low pressure system reaches NZ Wednesday but its rainfall impacts likely to commence later Monday with a slow moving baroclinic zone over central NZ and subtropical moisture coming in from the north.

Looking like we could get some thundery/squally weather mid week in the north. Fingers crossed that holds in the gfs.

Heavy rain also on the cards for eastern South Island once the flow turns onshore.

Dean. · Unread post by **Dean.** » Sun 02/04/2017 11:52

http://data.theweather.com.au/access/im ... slp.96.png

Wow !

Bradley · Unread post by **Bradley** » Sun 02/04/2017 12:29

Can't see anything Dean?

einzack · Unread post by **einzack** » Sun 02/04/2017 12:44

Probably linking to this:
http://www.weatherzone.com.au/models/?l ... 6&focus=mh

Dean. · Unread post by **Dean.** » Sun 02/04/2017 14:26

http://www.weatherzone.com.au/models/?l ... 6&focus=mh

Cheers

jamie · Unread post by **jamie** » Sun 02/04/2017 16:07

First link worked for me. None of the others do.

Nev · Unread post by **Nev** » Sun 02/04/2017 16:32

Don't have a problem with any of the links, but I've uploaded the relevant images for those that do…

NZstorm · Unread post by **NZstorm** » Sun 02/04/2017 19:30

The deepening of the low mid week is triggered by a 300mb jet streak moving through north Tasman. (divergence)

Chart gfs 300mb jet/surface pressure. 12Z Wednesday.

jamie · Unread post by **jamie** » Sun 02/04/2017 20:53

Far out! Check out the latest 3 day model on metservice website. Not sure which model it is. I know they display which model they think is predicting best at that moment.

I counted 150mm for Hamilton between Tuesday and Thursday. That's a big jump from recent model runs.

Tornado Tim · Unread post by **Tornado Tim** » Sun 02/04/2017 21:22

jamie wrote:Far out! Check out the latest 3 day model on metservice website. Not sure which model it is. I know they display which model they think is predicting best at that moment.

I counted 150mm for Hamilton between Tuesday and Thursday. That's a big jump from recent model runs.

Yes, GFS Model runs are significantly changing for precipitation from Auckland down to the lower North Island.
Whereas ECMWF has the majority of the precipitation out West Coast Taranaki way.
Will be watching subsequent model runs with interest.

NZstorm · Unread post by **NZstorm** » Mon 03/04/2017 06:48

Looks to be some potential for isolated tornadoes/severe wind gusts Wednesday, Taranaki to Bay of Plenty northwards.

Fog here with a temperature/dewpoint of 20C!

David · Unread post by **David** » Mon 03/04/2017 07:46

Hmm, NIWA model showing 138mm for Auckland on Tuesday alone...

treetop · Unread post by **treetop** » Mon 03/04/2017 10:12

A lot will depend on the speed and direction of the low. Should have a good idea by tonight.

Tornado Tim · Unread post by **Tornado Tim** » Mon 03/04/2017 16:34

Metservice has a High risk of Heavy rain from North Waikato south now on Wednesday in the latest Severe Weather Outlook, looks like they are having increasing confidence in the GFS.
ECMWF has the timing a bit earlier than GFS, but similar precip totals.

Metservice wrote:An energetic low over the Tasman Sea is expected to direct large amounts of moisture originating from the tropics onto New Zealand. The heaviest rain is expected over much of the North Island and the upper South Island, associated with a slow moving trough. Very strong southeasterly winds are expected to the south of this trough and these winds could rise to severe gale. (Warnings and watches regarding SEVERE weather on Tuesday have already been issued.)

The low is likely to move off to the east on Thursday.

On Wednesday there is a high risk of rainfall accumulations reaching warning amounts in Waikato, Bay of Plenty, Rotorua, Waitomo, Taupo, Taranaki, Taihape, Manawatu, Horowhenua Kapiti Coast, Wellington, Wairarapa, Nelson, Marlborough and the far north of Canterbury as indicated on the chart. There is a moderate risk of heavy rain over a broader area including much of the remainder of the North Island, Buller and much of Canterbury.

On Wednesday there is also a high risk of severe southeasterly gales in Manawatu, Horowhenua Kapiti Coast, Wellington, Marlborough, Nelson, Buller and Westland. There is a moderate risk of severe northerly gales in Taranaki,Wanganui and Taihape.

On Thursday there is a moderate risk of heavy rain in the east of Otago and the far south of Canterbury as indicated on the chart. There is a low risk of severe southwesterly gales about coastal Otago and the Banks Peninsula.

NOTE, that there is still some uncertainty regarding the location of the heaviest rain and the strongest winds. MetService forecasters will continue to monitor this system. Since the impact of this event may be large, people are urged to keep up to date with the latest forecasts and warnings and take precautions accordingly.

7567-15b311c7400-15b3b692c00-15b31b42744.gif

NZstorm · Unread post by **NZstorm** » Mon 03/04/2017 20:51

Ukmet showing better precip prospects for Auckland tomorrow than gfs. Airmass looking unstable by tomorrow as well on both models.

NZ Thunderstorm Soc · Mon 03/04/2017 22:25

Yes. Looks likely a lot of rain over the country, except for western and southern regions of the SI.
I'm picking the Manawatu and the upper reaches of the Wanganui, for the most totals

David · Unread post by **David** » Tue 04/04/2017 07:42

Certainly a warm humid night - low of 20.4C here, which might just be the warmest April night in my records.

NZstorm · Unread post by **NZstorm** » Tue 04/04/2017 09:12

David wrote:Certainly a warm humid night - low of 20.4C here, which might just be the warmest April night in my records.

At 6am Auckland was 21C, Wellington 13C and Invercargill was just 2C. One of the reasons why there will be so much rain over central NZ, the warm humid air in the north is forced to rise as it runs into the colder air.

Airmass turning unstable over Auckland today with cb's developing/heavy rain/thunder possible.

spwill · Unread post by **spwill** » Tue 04/04/2017 09:13

See how high the dew point temperature can come up today. Currently 20-21C over Northland and Auckland.

Razor · Unread post by **Razor** » Tue 04/04/2017 10:52

Metservice rain projection for New Plymouth tomorrow alone = 150mm. Imagine what that will translate to up the mountain there!

harleyb · Unread post by **harleyb** » Tue 04/04/2017 13:49

Getting hammered here in the Manawatu with slips in the Gorge already and most of the rain still ahead if the forecast is correct.

I had a look at VUW's forecast maps and it's a doozy alright. But what caught my eye was this forecast map, it's for next week...

rain-nz-2017040318-210.gif

Razor · Unread post by **Razor** » Tue 04/04/2017 14:45

harleyb wrote:Getting hammered here in the Manawatu with slips in the Gorge already and most of the rain still ahead if the forecast is correct.

I had a look at VUW's forecast maps and it's a doozy alright. But what caught my eye was this forecast map, it's for next week...
rain-nz-2017040318-210.gif

Too early for low level warm advection snowfall?

Manukau heads obs · Tue 04/04/2017 16:17

have had a bit of a temperature drop here and a change to more easterly wind
could be the start to trigger more widespread warm frontal rain

NZstorm · Unread post by **NZstorm** » Tue 04/04/2017 17:03

Manukau heads obs wrote:have had a bit of a temperature drop here and a change to more easterly wind
could be the start to trigger more widespread warm frontal rain

22C with a northerly here, 17C with an easterly over your way Brian.

David · Unread post by **David** » Tue 04/04/2017 17:17

Heavy rain out east currently, rain rate just hit 118 mm/hr on my station a few mins ago. Awful conditions driving home.

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