General May Weather

[NZstorm]

May rainfall will be well below average for Auckland when you consider high pressure looks to dominate the rest of the month. Probably the same for many areas.

[wembley]

Source of loud rumble near Dunedin confirmed:

https://www.odt.co.nz/news/dunedin/myst ... -uncovered

[tornado]

yes i read that get w can that harbour heard from queenstown?

[Orion]

Nor'west arch visible this morning, but overcast above has made the day very dull indeed so far.

[NZstorm]

Source of loud rumble near Dunedin confirmed:

Active polar jet stream just off the Otago coast Thursday night.

I once read that thunder in polar airmasses can be louder because more energy is used expanding the air? Not sure how accurate that statement is.

[Richard]

Source of loud rumble near Dunedin confirmed:

Amazing that a single lightning strike about 50km out to sea could still be heard as load in the city, I think that's too far way
to be possible

[NZ Thunderstorm Soc]

Nor'west arch visible this morning, but overcast above has made the day very dull indeed so far.

Like that down here but now the sun has come out as the thick high moves away and warming up nicely.
Temperatures in the single digits until about midday.

[mattyj46]

https://i.stuff.co.nz/the-press/news/11 ... is-weekend

[wembley]

The storm off the Otago coast was referred to as a "squat thunderstorm". Must mean a low topped storm

[NZstorm]

I once read that thunder in polar airmasses can be louder because more energy is used expanding the air? Not sure how accurate that statement is.

just add that colder air is more dense than warm air and so requires more energy for the lightning bolt to expand the air as it travels through the atmosphere. I suppose the theory as merit.

[tornado]

heavy rain shower in auckland just now. next week looks dry.

[Richard]

Surely cold air being dryer than warm would be less dense, heavier yes.

[spwill]

Source of loud rumble near Dunedin confirmed:

Amazing that a single lightning strike about 50km out to sea could still be heard as load in the city, I think that's too far way
to be possible

Maybe some cloud lightning occurred in a Cb that was much closer to the city.

[TonyT]

Surely cold air being dryer than warm would be less dense, heavier yes.

Think carefully about what you mean by "drier". Yes, cold air contains less total moisture per cubic meter, but it can be just as saturated RELATIVELY as warmer air (so while warm air at 50% relative humidity contains more total water vapour than cold air at the same relative humidity, relatively speaking they are the same). Cold air is denser because the molecules (all of them, including the water vapour ones) are more tightly packed together. A cubic metre of cold air contains more "air" than a cubic metre of warm air.

[harleyb]

I once read that thunder in polar airmasses can be louder because more energy is used expanding the air? Not sure how accurate that statement is.

just add that colder air is more dense than warm air and so requires more energy for the lightning bolt to expand the air as it travels through the atmosphere. I suppose the theory as merit.

It's probably just a matter of sound transmitting better through cold dense air. Thinking of how well sound carries on a frosty night, or, taken to an extreme, through water. Even so, 50 km seems quite a distance for thunder to be so widely heard.

[Cyclone Tracy]

Source of loud rumble near Dunedin confirmed:

https://www.odt.co.nz/news/dunedin/myst ... -uncovered

I've only just picked this up in the thread, so thought I'd do my own little investigation and give my 2 cents worth. On GFS's 00Z run for 16 May, it was projecting a temperature inversion around Dunedin at around 400 to 700m above the earth's surface. In my opinion what has occurred is 'Inversion thunder' which would explain why the sound travelled so far and was so loud from the single CG bolt.

[Razor]

The rest of May looking to continue the drier than usual trend for us here in the ChCh. Less than half the rain of this time in last couple of years, and well below average I would hazard to say

[spwill]

I think it is the quietest May I can recall but the country may see some widespread decent rain before the end of the month with the early signs of a big system next week.

[RWood]

A sunny dry May here so far (and in many other parts of course). May 1930 and May 1931 set the benchmark for sunnier than average weather over the whole country - they were dry and cool (though not unduly cool for those times). The highest sunshine totals were 223 hrs at Nelson (1931), 222 (Nelson, 1930), 220 (Blenheim, 1930 & 1931).

[RWood]

I think it is the quietest May I can recall but the country may see some widespread decent rain before the end of the month with the early signs of a big system next week.

May 1991 had a brief headline summary: "Summary: May was extremely dry and sunny over much of New Zealand. These conditions were caused by very persistent anticyclones in the Tasman Sea giving dry southwesterly winds over the country."

[melja]

I'm in Europe for a month but see you guys in the south island are getting some great temperatures still for so close to June with 18C in tekapo. Day temperature in Netherlands very similar to chch at the moment.
A lot to happen for Mt hut to open in the coming weeks.

Sent from my Redmi Note 4 using Tapatalk

[Chris Raine]

May has been dynamic in Southland .My station(Thornbury) rain figures to date are 130.9mm .Very windy with severe gales on 15th .Gusts hit 45 knots when the anemometer was hit by a disintegrating TV aerial and smashed the internal magnet and locked the cups in place. Spare cups now up , changed when a lull in wind on Friday 17th for two hours occurred. We have had thunderstorms and big hail, cool days with max's around 12 C but almost no frosts compared with April

[tornado]

low pressure loks likely next week

[NZstorm]

GFS 300mb jet pattern mid next week. Polar jets in the Tasman which will produce thunderstorms over the west of the North Island if verifies.

[tornado]

yes hopefully auckland gets some thunderstorms. weatherwatch.nz says theres a possibility