NZ Weather Forum

Yep another stunning day here. Mostly sunny with 24.3C max, highest of the month so far.

Sensational weather continues. Many South Island places roaring into the early to mid 30s, especially inland. As is well reported its suddenly extraordinarily dry now

I see Cromwell hit 33.4, new record for November

RWood wrote: ↑Thu 23/11/2017 19:19

NZ Thunderstorm Soc wrote: ↑Thu 23/11/2017 13:12 Hot days for Novemeber are not really a rareity. I can remebering Morris Dancing down at Oamaru in 33C heat and really gasping to go to the pub afterwards....
....and tradtionally hot NW days used to go hand in hand with Show Days, which probably was a myth.

I'm skeptical that Oamaru has ever had 33C in November.

Here is an extract from my weather diary for the WE of the 16th November 2008

by NZ Thunderstorm Soc » Mon 17/11/2008 21:20
No reading s from West Melton over the last 3 days over Show WE as I have been away in Oamaru but the thermometer did rise to 33Cthere on Saturday, with 27.9C yesterday here.
Today was much cooler depsite a NW sky with scattered cloud. Low level southerly through around 10am had some low level stratus but nothing much and becoming fine and sunny later.
In the afternoon some messy cloud forms with fractus but it was from 4pm when skies darkened to the south. Some distant rumbles of thunder. Hail reported in Ashburton and Rolleston but we got nothing here.
Some weak vortex on leading edge of cloud just to the south of here but NW into the cloud weakoning everything and eventually the storm dwindled and died away as it moved away out to the east.
Fine and calm now this evening. Down to 8.1C at 10pm.

NZ Thunderstorm Soc wrote: ↑Thu 23/11/2017 20:56
Here is an extract from my weather diary for the WE of the 16th November 2008

NIWA have 30.9C at Oamaru Airport for the 15th.

I see both Tauramanui and Te Kuiti recorded 29C yesterday.

NZstorm wrote: ↑Fri 24/11/2017 06:02

NZ Thunderstorm Soc wrote: ↑Thu 23/11/2017 20:56
Here is an extract from my weather diary for the WE of the 16th November 2008

NIWA have 30.9C at Oamaru Airport for the 15th.

I could beleive 33°C in town and 30.9°C at the airport, it is a way out of town, Town being better sheltered.

I checked Nov 2008 - Oamaru AWS (not the airport) recorded a monthly high of 31.3C. Report noted Waione had nation's top temp. for the month, 33.3C. Can't remember the NZ all time record, I think it was set at Hastings. in Nov 1958 Ashburton recorded a max. of 92.8F (33.8C), probably still the current SI record.

Seems like one of those days where convergence zone is totally stuck over eastern suburbs. Neither sea breeze is strong enough to win out yet. I notice it reached 24C quite quickly just after 11am then went down and never came back up, I assume due to persistent thick clouds. Yet it's been quite sunny in the central city...

Surprisingly quite windy late afternoon here considering the high air pressure we are under, gusting to 35kmph. Got to 22.5deg under a layer of thin high cloud.

just got back from a day trip to ChCh.
Rather cloudy and cool except around 2pm when the sun came out for a short period.
Looked bleak towards inland areas ( nothing scenical about '72 Scenic Highway' today ) but noticed no rain there except for posssible drizzle patches.
Lots of irrigators working with the irrigation ponds arounnd the Rangitata river being very low.

For tomorrow's thunderstorm outlook map, why have they drawn "Localised Downpours" for the central North Island but "Severe Thunderstorms" for Central Otago? Is it the hail that makes the difference?

dogmelon wrote: ↑Sat 25/11/2017 13:24 For tomorrow's thunderstorm outlook map, why have they drawn "Localised Downpours" for the central North Island but "Severe Thunderstorms" for Central Otago? Is it the hail that makes the difference?

Its because they think will not have any Lightning in the convective cell, but still has similar characteristics as a Thunderstorm, just without the Lightning.

If you had a hard nose attitude to what you would define a Thunderstorm and had a perfect outlook/watch/warning system, Meteorologists wouldnt include it in the outlook as the area is not deemed Thunderstorm, but the NZ warnings/outlooks are structured in a way there no other appropriate avenue for the convective forecasters to output this info, so they include it in the Thunderstorm Outlook.

A rename of the "Thunderstorm Outlook" to "Convective Outlook" could be used to get around this.

A similar issue occurs when a heavy shower exhibits the exact same features as a Severe Thunderstorm, ie: more than 25 mm/hr (ie: slow-moving cell(s) or multiple cells that grow and dissipate in a convective chain over a static area), gusts past 90ks, it just has no Lightning activity in the convective cell.

Metservice tags such cases as a "Severe Thunderstorm" and issues a "Severe Thunderstorm Warning" even though its not a Storm, the features identified are Severe and need an avenue to be broadcast to people.

If you compared the same situation above and apply it to the NWS in the U.S, they would label it a "Flash Flood Warning", because the convection itself is not Severe, just the consequences of that convection are causing the severe outcome.

Different countries, different systems, all Meteorologists are trying to do is utilize each system as much as they can and give out as much info as they can in each briefing.

Thanks for the above Tim. Interesting with the definitions for terms describing thunderstorm features which I haven't sort of come across, despite my efforts from MetService.
I have always interpreted 'showers, some heavy' as being a thunderstorm without lightning as described in your/MS for 'locoalized downpours' and at several stages on this forum, I still really, haven't found out what the difference is between 'showers, sometimes heavy and thundery' ' and 'showers with isolated thunderstorms'

Okie dokie, thanks for the detailed explanation Tim.
Tomorrow may even be worth a drive somewhere if its not too far distant.

Re severe definitions
I think flash flood is a better term to use for the NZ convection in summer rather than severe thunderstorm. But there needs to be a comprehensive monitoring system to have a flash flood warning system. USA have a great flash flood warning system for thunderstorms.

Current wind speed only 2knts at Manukau heads. Don't see that very often at this time of day.

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NZstorm wrote: ↑Sat 25/11/2017 17:05 Re severe definitions
I think flash flood is a better term to use for the NZ convection in summer rather than severe thunderstorm. But there needs to be a comprehensive monitoring system to have a flash flood warning system. USA have a great flash flood warning system for thunderstorms.

The unforcasted thunderstorm on October the 26th in Geraldine was a 'flash flood' thunderstorm which produced an inch of rain (25mm) in an hour which produced flooding in our street and property.
Possibly a 'downpour' or a shower 'sometimes heavy', wouldn't cover this event ,but it did poroduce a lot of cloud to cloud lightning as it backed into the hills, with one earth stroke (fork) which cut off the power to the town for an hour or so.
no deaths did occur in this thunderstorm so that it was why nothing was mentioned on the media or in NIWA's report for last month.

low risk if this high cloud /dust/haze keeps sticking around. Must be from Australia ? any thoughts ? Maybe metservice should look ooutside and see how much of this murk is still upwind ?

treetopkk wrote: ↑Sat 25/11/2017 20:26 low risk if this high cloud /dust/haze keeps sticking around. Must be from Australia ? any thoughts ? Maybe metservice should look ooutside and see how much of this murk is still upwind ?

Whats your location treetopkk?

Cirrostratus is caused by the upper trough. I think the haze is some local pollution.

my location is tauranga . Quite widespread up here, waikato/taupo bad as well [today and yesterday] Had similar conditions in vanuatu last month but that was volcanic ash. Reminds me of a European summer day

treetopkk wrote: ↑Sat 25/11/2017 22:04 my location is tauranga . Quite widespread up here, waikato/taupo bad as well [today and yesterday] Had similar conditions in vanuatu last month but that was volcanic ash. Reminds me of a European summer day

I remember the haze in Europe. It used to get really bad in London too during humid weather. On a thundery day you would hear the storm approaching but couldn't see the cb the haze was so bad.

Mod Note: The afternoon convective activity occurring at present now has its own thread. Have endeavoured to move the most relevant posts across without cluttering it up too much

Some heat showing up on gfs over inland South Island at the weekend. Inland Southland/Otago will top 30C on 2-3 days from Friday.

Given chch has had 1.8mm in the last 30 days and another 10 days forecast to be dry and the extreme temps over the coming weekend we could be looking at a good fire risk.

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So... Driest Nov records coming up where?