Trough over NI today

C-Nimbus · Unread post by **C-Nimbus** » Mon 01/11/2004 10:27

Just following on from what Steven W has been saying over the last few days.

There are some buildups already occuring from about 9:30 am this morning. There is a fair amount of heat in the sun today, so this could prove to be interesting towards the end of the day.

Does the inclusion of Pileus cloud at the top of Towering Cu's indicate a cold upper?

Any thoughts

NZstorm · Unread post by **NZstorm** » Mon 01/11/2004 18:45

As promised by Met Service, a weak trough over the upper North Island today with a few late afternoon showers breaking out inland(Waikato) from low topped instability. Despite the fact that the upper air has cooled off abit today(by3-4C), surface temps and dewpoints are not high enough for cb's. If this trough was more moist, thunder would have been on the cards inland. As for Auckland, no sign of showers here.

Pileus is a form of oregraphic cloud.......moist air lifting over a cumulus.

I guess its a sign of moisture at that layer and obviously a good breeze to go with it.

Manukau heads obs · Mon 01/11/2004 19:26

it did look quite dark down the waikato way today....quite a marked line between fine weather here and cloud over the waikato area....
we had a light SW sea breeze on the coastm but it did not reach this side of the peninsular

Michael · Unread post by **Michael** » Mon 01/11/2004 21:31

Believe all the rain fell in Tauranga today but was sunny here

Thunder · Unread post by **Thunder** » Tue 02/11/2004 00:16

Yes Steven, had the dewpoint been a bit higher, possible thunder for inland areas would've been on the cards in the Waikato. Today the atmosphere looked to be unstable to about 3400m in the Waikato and being potentially unstable to around 7000 / 7500m. I guess that was the reason the metservice were suggesting a slight chance of storms for inland areas in the afternoon and into early evening.

Christchurch was just plain crud unstable wise but central Otago / Southland looked to be potentially unstable to about 4000 / 5000m.

Manukau heads obs · Tue 02/11/2004 06:29

somehow we had 1mm during the night, and yet the sky looks like it did last night ...just some clouds arounf....sneaky shower
good though, as fertiliser went on the farm yesterday, so now its washed off the grass

ricky · Unread post by **ricky** » Tue 02/11/2004 08:33

There was quite solid rain from the waitakeries to here while I was driving home last night..
In grey lynn we recorded almost 3mm over about 1/2 hour from 23:30 with a period of light Northerly wind..
Fine clear sky here this morning so far with light E - NE breeze

C-Nimbus · Unread post by **C-Nimbus** » Tue 02/11/2004 08:44

Cheers NZStorm for the info on Pileus. I hope you don't mind my Q which may at times seem stupid!

I was out towards Greenhithe yesterday at about midday and the buildups were slowly moving towards the NW accompanied by a few light showers. The Cu's just didn't seem to be able to gain any decent height which I geuss indicates that the upper was not that unstable. Still it was nice to feel that summery warmth which so often leads to afternoon convective activity.

Then later out at west auckland there were some nice looking Cu's over the waitaks, but they didn't amount to much. We got some showers at about 10pm.

Metservice still have their 'possible thunder warning' for northland, so hopefully it may stretch just south enuff for us to get a bit of action.

Is it likely that with the weak el nino summer that we are sposed to be getting, that this kind of activity on the edge of an anticyclone will be common? (ie a trough developing on the SW flow of an approaching anticyclone, much like this one did on sunday/monday?)

7 day prognosis shows a small low developing off ozzy on wednesday, and also on saturday. But these seem to fizzle out according to the predictions leaving a northerly flow for thursday. The one on saturday could be an intersting one as it may bring warm moist air from the tropics which could meet colder air towards the bottom of the SI.

Or I could have completely grabbed the wrong end of the stick!!! (which is more than likely)

Steven, what are your views for later in the week?

Thunder · Unread post by **Thunder** » Tue 02/11/2004 14:19

Could be some buildups with localised rain on the plains today. It looks to be potentially unstable to around 7000m on the plains but I'm not too sure on what the temp is like inland. On Sunday I did note that Darfield got up to 24C when we were at 20/21 like it is today. I allready note Cu on the plains, will be interesting to watch.

http://www.escootersnz.com/fastpage/ima ... 021104.jpg

Willoughby · Unread post by **Willoughby** » Tue 02/11/2004 15:18

C-Nimbus wrote:7 day prognosis shows a small low developing off ozzy on wednesday, and also on saturday. But these seem to fizzle out according to the predictions leaving a northerly flow for thursday. The one on saturday could be an intersting one as it may bring warm moist air from the tropics which could meet colder air towards the bottom of the SI.

Yes it looks interesting with the high pressure staying put over the North Island. The NW/SW situation will bring warm air, then cooler air over the south. But another low pressure should develop off Tasmania and the air looks much cooler. So Monday will be interesting for the south. (If the models are right!)

Hamilton has been battling under this trough, over the past few days with average temps, fresh Easterlies and low sunshine

Mostly cloudy, fresh NE, 19c currently

C-Nimbus · Unread post by **C-Nimbus** » Tue 02/11/2004 15:27

SO have you guys had any action down in the mighty waikato over the last 2 days?

Just curious as I am an ex-pat hamiltonian, and I do miss the storms that I used to see down that way

Manukau heads obs · Tue 02/11/2004 15:28

there is actualy rain falling out of the cloud around the district there...even though there is not much height to the cloud...
interesting
also, despite a 20 knot NEer, the clouds are not ,moving much

spwill · Unread post by **spwill** » Tue 02/11/2004 16:07

A fine morning here but some Cu showers just out to the our East now.

Should be a boring week weather wise up here but atleast settled.

Melbourne Radar shows plenty of rain for the Melbourne Cup today. When I lived in Sydney we had a Thunderstorm every year on Melbourne Cup Day and I see a Storm is forecast for them today.

Thunder · Unread post by **Thunder** » Tue 02/11/2004 17:06

Ah, not enough moisture depth, to shallow. Depending on how things go we'll see.

Wellingtons sounding on the other hand shows better moisture depth which looks like it has resulted in some shower activity in the lower North Island, there's even a couple of strikes on Ricky's detector. That could change by the time you read this?

Below is the metservice strike map. A few strikes just SW of Lake Taupo.

TonyT · Unread post by **TonyT** » Tue 02/11/2004 18:29

Aaron J Wilkinson wrote:Could be some buildups with localised rain on the plains today. It looks to be potentially unstable to around 7000m on the plains but I'm not too sure on what the temp is like inland. On Sunday I did note that Darfield got up to 24C when we were at 20/21 like it is today. I allready note Cu on the plains, will be interesting to watch.

http://www.escootersnz.com/fastpage/ima ... 021104.jpg

The NW sprung up here around 11am, and got quite gusty by midday, and its been so ever since. Temp peaked around 27 degrees late morning, around 24 most of the afternoon.

GreggWard · Unread post by **GreggWard** » Tue 02/11/2004 18:41

Some nice cloud build-ups over the north and eastern ranges of the Manawatu today.

NZstorm · Unread post by **NZstorm** » Tue 02/11/2004 18:44

Fine day but with a showers after 4pm where I was working near Bombay (south of Auckland).

Thunder · Unread post by **Thunder** » Tue 02/11/2004 20:17

Interesting regarding the NW Tony, it was ENE all day until about 4 / 5pm when it went SE for a bit before going to the NW. I'm guessing that only just a little bit up in the atmosphere it would've been NW though.

Understandable those few small thunderstorms that poped up this afternoon just SW of lake Taupo. Things would've been unstable to around 9300m (300mb), possibly still is at the moment. Skew T's are cool!! I just wish they did one for Chch. Do they?? Anyone?? And if they do, why aren't soundings published?

I noted on the program called "A Queens Tour" with John Campble last night (sp?), they were on the west coast of the SI and they were looking at some guy releasing a weather balloon, they have some little weather company over there or something? Does anyone know what it's called and if they are releasing weather balloons over there, how come they don't publish the results / skew t's? Thanks.

TonyT · Unread post by **TonyT** » Tue 02/11/2004 21:26

Aaron J Wilkinson wrote:Interesting regarding the NW Tony, it was ENE all day until about 4 / 5pm when it went SE for a bit before going to the NW. I'm guessing that only just a little bit up in the atmosphere it would've been NW though.

You've hit on two quite common occurances there - first, Christchurch is often the last place on the Plains to get the NW - there are many days in the year when its NW in Amberley but NE in Chch. In fact I would go so far as to say it would be a toss up for which is the prevailing wind direction in Amberley, NE or NW. Many locals would say NW. Second, there is often a short period of light SE in Chch just before a NW'er arrives - sometimes said to be a bounce back or reflection of the NW breeze off the Port Hills and over the city.

Aaron J Wilkinson wrote:Skew T's are cool!! I just wish they did one for Chch. Do they?? Anyone?? And if they do, why aren't soundings published?

MetService used to do twice daily soundings from Chch Airport but stopped a few years ago as a cost cutting measure. They found they could model the upper atmosphere over NZ with just the three soundings (Invercargill, Paraparaumu and Kaitaia). All the historical data is in the NAtional Climate Database if you ever need to look it up. They do still do 6 hourly wind ascents and I think that data is on their web site - but it wont tell you the lower layer stability though

The interesting thing was, when MetService stopped the Chch soundings they put a note in their annual report to the government (and tax payers) to say that they now had the facility to release balloons from Christchurch "on demand", as if this was a wonderful new feature, neglecting to mention that they used to be twice daily!

The READY site has a neat function which will plot a sounding for you from the model data, and you can animate it over the lifecycle of the model, so you can see the predicted changes in stability over the next few days or week.

Aaron J Wilkinson wrote:I noted on the program called "A Queens Tour" with John Campble last night (sp?), they were on the west coast of the SI and they were looking at some guy releasing a weather balloon, they have some little weather company over there or something? Does anyone know what it's called and if they are releasing weather balloons over there, how come they don't publish the results / skew t's? Thanks.

Same story - the balloons are small ones tracked for wind only, and again the data is on the MetService site. I think MetService contract out the work to the guys who used to work for them.

Manukau heads obs · Tue 02/11/2004 22:01

araon, here is a good site for updated every 10 seconds data for CHCH
http://www.zl3gp.co.nz/wxlive/

Thunder · Unread post by **Thunder** » Wed 03/11/2004 00:38

You've hit on two quite common occurances there - first, Christchurch is often the last place on the Plains to get the NW - there are many days in the year when its NW in Amberley but NE in Chch. In fact I would go so far as to say it would be a toss up for which is the prevailing wind direction in Amberley, NE or NW. Many locals would say NW. Second, there is often a short period of light SE in Chch just before a NW'er arrives - sometimes said to be a bounce back or reflection of the NW breeze off the Port Hills and over the city.

Thanks, good info there. Yeah, the NE over Chch today looked to be a very low level thing.

MetService used to do twice daily soundings from Chch Airport but stopped a few years ago as a cost cutting measure. They found they could model the upper atmosphere over NZ with just the three soundings (Invercargill, Paraparaumu and Kaitaia). All the historical data is in the NAtional Climate Database if you ever need to look it up. They do still do 6 hourly wind ascents and I think that data is on their web site - but it wont tell you the lower layer stability though The interesting thing was, when MetService stopped the Chch soundings they put a note in their annual report to the government (and tax payers) to say that they now had the facility to release balloons from Christchurch "on demand", as if this was a wonderful new feature, neglecting to mention that they used to be twice daily!

The READY site has a neat function which will plot a sounding for you from the model data, and you can animate it over the lifecycle of the model, so you can see the predicted changes in stability over the next few days or week.

Well at least I know what's happening here now. I had an inkling they did balloon asents from Rakaia but atleast it's good to know what's going on. Now, which skew t represents Chch better, Invercargill or Wellington. Wellington is closer but it doesn't have a huge mountain range blocking off weather from the west but in Chch we do. Invercargill could become more usefull in the wind arena. Upper temps I guess could be an average of the two, maybe slightly leaning more towards Wellington's upper temp. I guess something like that?? Different weather situations will produce certain results and I'll learn from that and what the skew t's say.

Thanks for that weather site in Chch Brian. What would be usefull would be a station in Inland Canterbury. Actually, I think there's a station at Rangiora areodrome using Brian's software. That area is sort of Inland but not that far in. I'm guessing metservice have inland stations but you'll only be able to get them through metnet?

Regarding that READY system and it's soundings, yes I've seen them but they don't have the Parcel Lapse Rate (PLR) line on them, you know, that line that starts at the bottom generally at the surface dewpoint and temp and then it branches together and curves upwards towars the top. Depending on where the line is it can give you an idea on how unstable the atmosphere is or stable as the case may be. The more area between it and the temp line (providing it's right of the temp line), the more CAPE there is etc, that line! I don't know how to plot it correctly, or is it easier than I think?? Otherwise yes it looks handy and seems to do ok compared to the actuall soundings at NZNV (?), NZPP (?) and NZWP (NZAA for the GFS thing).

Manukau heads obs · Wed 03/11/2004 06:56

actauly i cant take the credit for the macromedia flash software, thats another author (Julian Best)

NZstorm · Unread post by **NZstorm** » Wed 03/11/2004 07:24

The Invercargill sounding is fairly representative for Canterbury for convection forecasting. Most of Canterbury's weather comes up from that direction rather than from Wellington. But the Wellington sounding could be handy sometimes.

Up untill about 10 years ago, northern soundings where taken at kaitaia. Archive for NZWP only goes back to about 1995.

Still a bit low level instability over NZWP today, so perhaps more late afternoon showers today. Cu tops to about 3000m.

Weather looks boring for the forseeable future.

Thunder · Unread post by **Thunder** » Wed 03/11/2004 09:36

There's an archive???!!!

Has anyone looked at my sat animations!! Go to the photo thread thing. Enjoy!

TonyT · Unread post by **TonyT** » Wed 03/11/2004 09:44

Aaron J Wilkinson wrote:Well at least I know what's happening here now. I had an inkling they did balloon asents from Rakaia but atleast it's good to know what's going on.

What would be usefull would be a station in Inland Canterbury.

I think Metservice has some 'low level' upper level winds on its site from Rakaia, which are generated by the radar. Its not a balloon ascent.

I dont know of any on-line stations in inland Canty, I guess lack of good internet access is a bit of a hinderance. There is the fire weather data on the NRFA site, but thats only once per day at 1pm.