Rain on the way

NZstorm · Unread post by **NZstorm** » Wed 08/10/2003 21:13

The trough approaching the country could produce some very heavy rainfall over the North Island by the weekend. The trough will get an injection of very moist air from the north thus regions such as Coromandal that are exposed to the north should get alot of rain.

Manukau heads obs · Thu 09/10/2003 08:38

the ground has hardly dried out after the last lot!
as long as its warm rain....
with all this cloudy cool weather, there has not been much grass growth down on the farm

Michael · Unread post by **Michael** » Thu 09/10/2003 11:30

be typical

CbFan · Unread post by **CbFan** » Thu 09/10/2003 15:20

We got in early up here! 61mm in the four hours 0900 - 1300 today (9/10) at Matauri Bay. Most arriving in the space of half an hour of torrential downpour with microbursty winds exceeding 55km/Hr. Lots of water on the ground with extensive surface flooding and streams in the immediate vicinity rising in excess of 1.5m almost instantly. Event didn't hit Kaeo or Kerikeri. Here's hoping for more of the same

Chris Raine · Unread post by **Chris Raine** » Thu 09/10/2003 15:29

There must have been some cold air left behind from last weekend's efforts in Southland. The Tasman sea front gave us moderate rain from about 0500-1200 hours,but around Central Southland - Ohai, Hokanui Area snow on the hills is down to 250 meters and looking very thick above 400 meters. Temp was 1.8 degrees in Lumsden at 1300 NZDT.

Manukau heads obs · Thu 09/10/2003 15:38

hey cb fan, thats alot of rain
it will be cool if you can rig it to get your data into the net !

warmed up here now finally....still less than you would expect for a NE, but its still not coming from very far north, still coming around the high, i guess

tich · Unread post by **tich** » Thu 09/10/2003 16:17

No rain yet in Chch; still warm, though cloudy. However, it looks like rain at the Ashburton river mouth on the 1PM radar. What a sharp range in temperatures for Central Otago at 1PM - 15C at Tara Hills, while only 3.9C in Queenstown! MetService has lowered the forecast snow level in Otago and Southland to 500 metres, but as Chris Raine's post says, it's falling to even lower levels in inland Southland.

NZstorm · Unread post by **NZstorm** » Thu 09/10/2003 17:18

Today's midday freezing level at Invercargill was around the 500m level which is extremely low....no wonder snow to 500m or lower. But unlike last weekend the upper air is less cold. The 500mb(5500metre) temperature is minus 23 today....it was minus38C on Sunday. Hence, this freezing level will be rising during the afternoon as daytime heating warms up the lower layers. And upper air will be very stable with that warmer higher atmosphere, so i don't ecpect deep cb's with todays front.

That was a real deluge up north. We had a brief heavy gusty shower here early this morning. The intensity of the rain suprised me but it did
not last.

Good potential for further heavy rain into the weekend which should turn thundery.

tich · Unread post by **tich** » Thu 09/10/2003 18:45

Today's midday freezing level at Invercargill was around the 500m level which is extremely low....no wonder snow to 500m or lower. But unlike last weekend the upper air is less cold. The 500mb(5500metre) temperature is minus 23 today....it was minus38C on Sunday. Hence, this freezing level will be rising during the afternoon as daytime heating warms up the lower layers.

You're right, it has got warmer in Southland this afternoon - the 4PM obs show inland Southland (Lumsden I guess), back up to 9C. Still cloudy and dry in Chch, but the barometer has just gone up, with a falling temperature and a fresh southerly change. The 4PM radar shows the rain reaching about Ashburton - this front (?) must be moving quite slowly over Canterbury. But it's certainly cooler behind the change - Timaru down to 8.9C at 4PM. (but nothing like Southland)

NZ Thunderstorm Soc · Thu 09/10/2003 19:08

Yeah! bloody boring here today.
...hope the rest of summer is not like this

JohnGaul
NZTS

Michael · Unread post by **Michael** » Thu 09/10/2003 19:36

NZ Thunderstorm Soc wrote:Yeah! bloody boring here today.
...hope the rest of summer is not like this

JohnGaul
NZTS

Sure is Rain Rain Rain more of the Sh#$@in' stuff

NZstorm · Unread post by **NZstorm** » Thu 09/10/2003 19:53

Yes Michael, todays front will still be hanging around tomorrow...so more rain to come. The front should weaken a little in my opinion. And this weekends rainfall/thunderstorms hinges on there being a good influx of high dewpoint air from the north. Have to see what happens. Dewpoint at Kermedecs is currently a dry 10C, Norfolk Island 12C. Hopefully they will be alot higher tomorrow.

Dean. · Unread post by **Dean.** » Thu 09/10/2003 20:53

Showery here since 4.30pm,temperature 9 degrees.Warm 20 degrees before the change today.
Another southeasterly system forecast for Sunday/Monday looks interesting.

NZ Thunderstorm Soc · Thu 09/10/2003 21:23

Michael wrote:
NZ Thunderstorm Soc wrote:Yeah! bloody boring here today.
...hope the rest of summer is not like this

JohnGaul
NZTS
Sure is Rain Rain Rain more of the Sh#$@in' stuff

Sorry, I don't know what you mean???

?

JohnGaul
NZTS

tich · Unread post by **tich** » Fri 10/10/2003 09:31

Yesterday afternoon's front seems to have disintegrated over North Canterbury - there's been no rain that I've noticed in central Chch. It cleared up partially for a time in the evening, but then clouded over again. Dry but overcast this morning, with little wind. However I think I'll be on the safe side and take an umbrella if going out for a long period.

Manukau heads obs · Fri 10/10/2003 12:01

muky pea soap low cloud and drizzle here....yukky weather
as this new low develops, it should clear this frontal remains away hopefully

tich · Unread post by **tich** » Fri 10/10/2003 14:37

A dull, overcast day in Chch. Some brief rain in early afternoon.

Thunder · Unread post by **Thunder** » Fri 10/10/2003 16:54

I'm guesing that there will be thunder potential on Sunday in northern parts of the North Island and on Monday thunder is likely in quite a few places North Island wise, especially the central plateau towards Hawkes bay (RH levels up high could make thunderstorms weaker if they are still the way they are forecast by then) and the Waikato could be of interest during the afternoon, also the Auckland area just after midday. Things could change quickly though by Monday.

If what I've said happens I'll be extatic! BUT! I'm a novice once again so well see.

Of course, as allways there's b#gg!r all potential for thunder down here in the near future!

Cheers
Aaron Wilkinson

NZstorm · Unread post by **NZstorm** » Fri 10/10/2003 17:56

Fair prediction Aaron.

We will have to wait and see where the frontal cloud sheet is on Sunday.
Really need to see this clearing so as to get the surface heating and resultant instability showers/thunderstorms. I don't see there being sufficient forcing in the front for thunder so hopefully it clears out quickly to allow thermal destabilisation to occur.

As for Monday, looks good at this stage for thunderstorms over Waikato/Auckland....provided the low doesn't shift away to quickly.

High humidity will increase the thunder risk.

Manukau heads obs · Fri 10/10/2003 18:17

the murk finally has cleared here now

i will get any photos of good lookign cb clouds up for you araon, to drool over, LOL

NZstorm · Unread post by **NZstorm** » Fri 10/10/2003 20:51

Two surface observations that have relevance to NZ's weather in the coming days. Bitterly cold in the south seas ( Maquarie Island).

And the dewpiont temperature at Norfolk Island has lifted to 17C. This is quite moist air heading south from the tropics now.

Updated: 6:00 PM EST on October 10, 2003
Observed at Macquarie Island, Australia
Temperature 31 Â°F / -1 Â°C
Windchill 18 Â°F / -8 Â°C
Humidity 77%
Dew Point 24 Â°F / -4 Â°C
Wind West at 21 mph / 33.8 km/h
Wind Gust -
Pressure 29.85 in / 1011 hPa
Conditions Light Snow Showers

Norfolk Island.
2003.10.10 0700 UTC
Wind from the ENE (070 degrees) at 8 MPH (7 KT)
Visibility greater than 7 mile(s)
Sky conditions mostly cloudy
Temperature 64 F (18 C)
Dew Point 62 F (17 C)
Relative Humidity 93%
Pressure (altimeter) 30.00 in. Hg (1016 hPa)

tich · Unread post by **tich** » Fri 10/10/2003 22:17

Two surface observations that have relevance to NZ's weather in the coming days. Bitterly cold in the south seas ( Maquarie Island).

And the dewpiont temperature at Norfolk Island has lifted to 17C. This is quite moist air heading south from the tropics now.

Could get very interesting if these 2 airmasses collide. MetService extended severe weather outlook is going for possibility of heavy rain from Kaikoura to Malborough on Monday, with snow to about 500 metres further south on the same day. Here in Canterbury, long-range forecasts have recently been predicting snow to low levels for Monday. It wouldn't be unprecedented - low level warm advection snowstorms in the South Island have occured well into spring, on one occasion inland Canterbury experienced a severe snowstorm in mid November! (1967)

Thunder · Unread post by **Thunder** » Sat 11/10/2003 00:11

Hi Steven W

Yes I agree high humidity is good for thunderstorms in the lower layers (lower 200mb) but up high I thought it actually helps if it is not as humid (still things can develop if it is at 70%). I learnt this from this link here:

http://downunderchase.com/storminfo/sto ... ide04.html

Here's an extract:

There's another important aspect of severe thunderstorms - that is upper level moisture. It might seem odd, but in the mid-high levels (eg, above 700mb), you don't want much moisture! In fact, the drier the better! There are several reasons, but one of them is that dry air means that waste anvil cirrus, and the edges of storms will evaporate. That provides cooling of the air around it and also means that cloud is unlikely to develop around the storms. Cloud will block out the sun and therefore block out heat! So it's good to have low levels of moisture if possible in the upper levels. Anything below 70% is reasonable, below 50% not bad and below 30% even better - especially at the 500 and 300mb levels (probably the more critical levels to have dry air at). Dry air in the mid levels also increases the chances of microburst activity which is often severe.

That AVN thing suggests that the RH levels will be high up in the high levels hence I said it might depend on the RH levels up high in the central plateau to Hawkes Bay area.

Just looked at the models again and it is looking better over the Auckland / Waikato area as you say Steven for Monday (especially the Waikato), should be good! Not so much the central plateau to hawkes bay area any more.

Might I add I totally agree with you Steven W about how the AVN thing is continental forecasting, my first thought was when using this program was that how does a little place in America know what's going on down here in NZ! I'm not sure but it might be of some worth. A guy I know in Oz called Dave Ellem uses it and it has worked resonably well for him, so yeah......

Yes that sheet cloud will need to move it for unstable conditions to develope more.

Can't wait for your pics Brian! If the Cb's come! Mayby Steven you might also have some pics!
Also, If your going to get frames for pictures of your favourite weather etc just go to The Warhouse, it cost me 7 bucks ($6.99) for a nice frame that has glass! They seem to be of reasonable quality and look fine.

Might I add I just edited to include "Go the AB's!"

Cheers
Aaron Wilkinson

NZstorm · Unread post by **NZstorm** » Sat 11/10/2003 09:12

Some excellent notes there Aaron,

The AVN model would work well in Australia. Continental areas can produce some big instability numbers like LI -6, CAPE 3000.
Some of those thunderstorms in New South Wales can be very powerful.

Slight chance of afternoon buildups/cb over inland Otago/Southland today.

Thunder · Unread post by **Thunder** » Sat 11/10/2003 13:13

Ahhh, is that what you mean about continental areas (doh!)

Do you mean that Oz is nice and big and since that land is big it can heat up well and produce those figures like you say and those figures are a bit easier to forecast, where as NZ is small and skinny and has a big mountain range going up the middel of the country so things can be sort of "unpredictable" and harder to forecast. Is that what you mean? If so, I see.

Cheers
Aaron Wilkinson