General February Weather

NZ Thunderstorm Soc · Sun 31/01/2016 22:08

Will February be the same as January ?
Overcast with claggy conditions dispersed with fine warm days and thunderstorms in the north?

TonyT · Unread post by **TonyT** » Sun 31/01/2016 22:25

EMON_phase_51m_full.gif

The latest MJO forecast from the ECMWF shows the next MJO pulse emerging from the null zone into phase 4 (the green line on the chart among the "spaghetti" of the ensemble model runs) for the first week of February, and moving through 5 to 7 in roughly each of the following 3 weeks. The last MJO (the red line) dipped from phase 8 to the null area from about the 11th January till now, skipping the phases which usually favour west and southwest airflow (this being one of the reasons we didn’t get much westerlies in January).

Phase 4 favours higher than normal pressures over the country (which could be anticyclones, or could be weaker than usual depressions and troughs). However, the models are suggesting a fairly significant low pressure system to develop in the eastern Tasman this week and move over the North Island next weekend, so this is in direct conflict with what we would expect from this phase of the MJO! Interesting!

Phase 5 (approx week 2 of February) favours higher pressures to the east of New Zealand, and lower pressures in the Tasman, while phase 6 (week 3) starts to bring those lower pressures onto the country and can bring increased easterlies (or reduced westerlies). Phase 7 (possibly last week of Feb) is the low pressure phase which is the same one we were in at the very start of January (and we all remember what happened then, don’t we?!). So that could be a wet or unsettled time for the country, and is the same wet period I signalled for late February in an earlier post.

So, put all that together, and we may not see much in the way of west to southwest flow in February either, maybe two wetter and rather unsettled months in a row, bang smack in the middle of the declining El Nino which is supposed to increase our westerlies and bring us drier weather in Canterbury! Of course, all this is based on the assumption that the MJO works out as forecast.

spwill · Unread post by **spwill** » Mon 01/02/2016 07:39

There was too much west/southwest flow in the later part of 2015, atleast NZ has received good rain from the current pattern , hopefully more rain in Feb.

RWood · Unread post by **RWood** » Mon 01/02/2016 08:01

I want the westerlies back, or far more anticyclonic conditions over and/or just to the west of the country than the above suggests. January was abysmal here, especially in contrast to the sunny December.

Richard · Unread post by **Richard** » Mon 01/02/2016 18:37

After a few grey cool days the heat is back today with 29deg

NZstorm · Unread post by **NZstorm** » Mon 01/02/2016 18:47

The Environment Waikato site is showing 35mm for Waingaro (near Raglan) this afternoon. Some low topped convergence going on over west Waikato today.

Same deal again tomorrow with some low topped cb's possible.

TonyT · Unread post by **TonyT** » Mon 01/02/2016 21:31

Interesting how the models are starting to want to build the ridge over the South Island at the weekend and keep the depression well to the north - compared to a few days ago when they wanted to bring the low pressure onto the country. This increasingly fits with the MJO phase 4 idea.

Tornado Tim · Unread post by **Tornado Tim** » Mon 01/02/2016 22:17

Nice bit of Rain falling over the central Waikato, got around 6mm or so from it so far from low topped convection.
A warm the rest of this week coming up ahead it seems. Highs progged late 20's to early 30's for around Hamilton!

David · Unread post by **David** » Tue 02/02/2016 11:49

18Z GFS is insane for Auckland on Waitangi day... 400mm rain in a day LOL

TonyT · Unread post by **TonyT** » Tue 02/02/2016 11:54

It looks more and more as though that trough is going to get squeezed northwards by the southern ridge, so all the rain will get "compressed" into a smaller area. Some heavy falls in northern areas definitely on the cards.

spwill · Unread post by **spwill** » Tue 02/02/2016 13:43

GFS is showing some big instability numbers over northern NZ this weekend, hopefully the worst of the rainy weather will not be over Auckland. Looks very warm anyway with the high humidity moving in.

NZstorm · Unread post by **NZstorm** » Tue 02/02/2016 21:38

I see there was an isolated thunderstorm over inland Bay of Plenty this evening. Some very good convergence in that area this evening. Just add the 500mb temp is -8C!

Willoughby · Unread post by **Willoughby** » Wed 03/02/2016 12:02

GFS pulling back considerably it's rainfall progs over the North Island, bringing it more into line with what the EC and CMC models have been suggesting. So looking at a mostly dry outlook for the three ODIs, lucky scheduling. Still looking rather wet for Northland to BoP Friday night through Waitangi Day, EC showing high confidence.

ecmwfued---new_zealand-78-D-mslpthkpcpmet6[1].png

spwill · Unread post by **spwill** » Wed 03/02/2016 15:02

Sunday looking better now for Auckland /Waikato as the flow over the upper North Island turns more southeast.
Heavy rain or showers Friday -Sat .
We are into our third week of humid weather, dewpoint today 18-20C, some fresher weather looks likely next week.

Andy · Unread post by **Andy** » Wed 03/02/2016 15:52

Hot day here 34 at the mo

Richard · Unread post by **Richard** » Wed 03/02/2016 17:15

Been warm inland alright, got to max 32.1deg

Andy · Unread post by **Andy** » Wed 03/02/2016 20:04

Max today of 36 still 31 now Phew...

NZ Thunderstorm Soc · Wed 03/02/2016 20:22

Been warm down south with Gore and Wanaka getting to 32C and Invercargill getting to 31C, from what I could find.

It would be Interesting to see what temps we get here tomorrow?

Nev · Unread post by **Nev** » Thu 04/02/2016 06:30

Yes, some high temps recorded by MS in the south yesterday:

34C at Alexandra Aero, Omarama (Tara Hills) and Roxburgh.
33C at Pukaki Aero.
32C at Gore, Wanaka Aero, Reefton and Palmerston North Aero.
31C at Invercargill Aero, Dunedin Aero, Lumsden, Levin and Taumarunui.

spwill · Unread post by **spwill** » Thu 04/02/2016 08:16

Some early signs of a possible pattern change after the 15th to westerlies and some cold troughing.

Richard · Unread post by **Richard** » Thu 04/02/2016 09:10

Nev wrote:Yes, some high temps recorded by MS in the south yesterday:

34C at Alexandra Aero, Omarama (Tara Hills) and Roxburgh.
33C at Pukaki Aero.
32C at Gore, Wanaka Aero, Reefton and Palmerston North Aero.
31C at Invercargill Aero, Dunedin Aero, Lumsden, Levin and Taumarunui.

What would be the record for places like Invercargill Aero&Gore,

Richard · Unread post by **Richard** » Fri 05/02/2016 07:22

According to the radar this morning its raining here, but its not, and looking at the cloud there's no rain anywhere in the district. What causes the radar to do this?

Nev · Unread post by **Nev** » Fri 05/02/2016 07:53

Richard wrote:What would be the record for places like Invercargill Aero&Gore,

Gore's 32.2C on Wednesday was reportedly the second highest temp (after 32.9C in Feb 1999) recorded at that rural site just west of the township since records began there in 1971. However, higher temps appear to be more common at two previous Gore township sites going back to 1907, with their all-time record of 35.0C in Jan 1959, followed by 34.7C in Dec 1909 and 34.2C in Jan 1956.

Invercargill Aero's 31.2C on Wednesday isn't too rare, but seldom gets any higher. Invercargill's highest ever temp since records began in 1905 is 33.8C in Jan 1948 (station site). Its second highest is 32.2C in Jan 1921, and third highest is 32.1C in Feb 1999.

Weather Watcher · Unread post by **Weather Watcher** » Fri 05/02/2016 08:32

Richard wrote:According to the radar this morning its raining here, but its not, and looking at the cloud there's no rain anywhere in the district. What causes the radar to do this?

This is due to the way the different radar images are combined to produce the NZ composite image. The echoes are coming from the Wellington radar which extends southwards to just north of Christchurch, but at this range the Wellington radar is scanning about 6km high. It's therefore scanning through the high level wave cloud which is producing mostly virga, although if you look at the 120km range Canterbury radar, there is a bit of rain reaching lower levels in North Canterbury.

TonyT · Unread post by **TonyT** » Fri 05/02/2016 08:35

Richard wrote:According to the radar this morning its raining here, but its not, and looking at the cloud there's no rain anywhere in the district. What causes the radar to do this?

Rained lightly for best part of an hour in Amberley till about 8.15am. Only very light though. The radar beam gets progressively higher above ground level as it gets further away from the radar tower (due to the curvature of the earth) so further out the radar is showing you rain higher up in the atmosphere which may well evaporate before it reaches the ground.

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