Low Pressure System(s), 8th-11th of May

[Tornado Tim]

Looks like Northland and possibly Auckland could get a chance of thunder as the cold front moves through.

Quite active convection 400ks North West of the Cape moving ever so slightly towards SE.
A north to northeast flow should gradually increase tommorow as the high pressure slides to the east.

Sat Image courtesy of Weatherzone AU

[NZstorm]

Looking like a low level jet there tomorrow which should help any thunderstorms up north to be squally.

925mb 2000ft wind chart for midday tomorrow.

[NZstorm]

The front looks like it will cross the North Island only slowly over the next 36hours with good rain. There is still some thundery activity near the top of Northland this morning. Some upper level warming coming in later today will likely dampen the thunder activity on the front. The upper level air is cooling off again tomorrow so maybe Auckland could catch some thunder Wednesday if there is still some forcing in our area.

[Tornado Tim]

A mild overnight low of 10.4°C, had a light shower this morning. 0.4mm worth.

The convection and lightning activity looks great just off the cape.
Sat Image courtesy of Weatherzone AU

[Tornado Tim]

Latest NASA Terra looks quite good with CB's developing well on the northern end of the occluded front and moving south.

[NZstorm]

Looks like thunder will be on the cards for Auckland and Waikato tomorrow afternoon. Just have to see whether the convergence is there, the 00Z gfs shows some.

[Manukau heads obs]

nice dollop of rain here 2 nite, 28mm so far...might be one more burst yet...

[David]

Raining very nicely here all evening, up to 20mm now

[CHCH Weather Chaser]

I see David your station at 22:11 has a rain rate of 125.2mm/h!! Nice!

[David]

I see David your station at 22:11 has a rain rate of 125.2mm/h!! Nice!

Yup it got torrential for a moment there... another 11.5mm since my last post 45 mins ago

Interesting - in the last 7 hrs we've had more rain than for all of April

[CHCH Weather Chaser]

wow! The GFS has completely flopped for here now with very little rain on the cards today now! Massive change!

Expect the watch for Canterbury to be lifted this morning.

[jamie]

35.6mm so far for here and still raining nicely

[Manukau heads obs]

lovely rain, 37mm total here
just what the doctor ordered
stopped here now

[Nev]

50.5mm here in the 15 hrs to 6am this morn (double my Apr total). Relatively warm too, with temps between 19.6C just after midday yesterday and 14.2C this morn. I see MS recorded NE gusts to 89 km/h at Whangaparaoa early yesterday evening.

[David]

54mm total here and 56mm at the Shelly Park station on the other side of Howick.

[ricky]

The main band of Rain moved just to the East of here, so Grey Lynn missed out on some of that.. Still a few decent Showers overnight but only 30mm total here.

[David]

Just noticed an interesting baro spike on my graphs... there was a NNW change around 5am and the baro dropped 2hPa in 15 minutes, then rose 2hPa again in the following 15 minutes!

[Tornado Tim]

The cold front actually arrived just after midnight here, with the temp drop and baro surge.
Storm Rain was actually 51.4mm comprised of 24mm that fell yesterday and 27.4mm that has fallen today so far.

The convection on the occluded front east of Northland seems to have waned a bit in lightning activity now, however there more of a distant area of convection pre the front that is very active.

[CHCH Weather Chaser]

Cloudy day here today with little wind. No rain around the area. I see Metservice are saying Persistant rain for the Canterbury Plains. Thats well off the mark to be honest!

[Richard]

Yes another one of there bob each way forecasts,Persistent rain for the Canterbury Plains but only 1-3mm rainfall totals .

Been no rain here also.

[snowstormwatcher]

Only been light drizzle here with 5mm since it started late last night. 8 degrees currently.

[David]

The cold front actually arrived just after midnight here, with the temp drop and baro surge.
Storm Rain was actually 51.4mm comprised of 24mm that fell yesterday and 27.4mm that has fallen today so far.

Looking at your graph it got pretty heavy for you at one stage - what was the maximum 1hr rainfall? Looks at least 15mm but hard to tell exactly.

[Tornado Tim]

Looking at your graph it got pretty heavy for you at one stage - what was the maximum 1hr rainfall? Looks at least 15mm but hard to tell exactly.

It got very heavy around 9 past midnight, with 1.6mm accumulating in the gauge in 1 min then another 1.4mm in the following minute.

From 11.40 PM 8th May - 12.40 AM 9th May (1 hour period) 19.60mm of rainfall fell, however this was nothing when you compare it to the 26th of Jan 2010 when 74.2mm fell in the hour (you where at my house with Ricky chasing at the time )

[Tornado Tim]

Done a little rainfall research for this event in the Waikato area:

Matangi: 50.8mm
Hamilton AWS*: 46.20mm
Ruakura EWS*: 43.40mm
Horsham Downs: 36.20mm
Matamata*: 0.0mm** I suspect the equipment wasnt recording at the time

Readings above are at the 9 AM reset time and cover 8th and 9th of May, 2012
*Data collected by Niwa's Cliflo

[Tornado Tim]

Towering cumulus going up fairly fast down to my south. Showers developing around Hamilton atm....