Nth Island convective period 27 Feb - 2nd March

NZstorm · Unread post by **NZstorm** » Wed 01/03/2017 12:08

Todays primary convergence line according to gfs at 4pm.

During this convective episode the thunderstorms have all been south of Hamilton, over the higher terrain.

Auckland will get showers today but i don't expect thunder.

Manukau heads obs · Wed 01/03/2017 14:13

a good sea breeze has developed here

jamie · Unread post by **jamie** » Wed 01/03/2017 14:25

Convergence running on the western side of the Waikato river here in North Waikato. Showers building nicely. Hot and clear on the eastern side

dogmelon · Unread post by **dogmelon** » Wed 01/03/2017 15:44

Look at the Bop radar loop. Is that the front of the sea breeze traversing the Mamaku Range?

jamie · Unread post by **jamie** » Wed 01/03/2017 16:42

Just watched a nice funnel cloud not far from home. Couldn't pull over to take a photo and by the time I did it died.

Otherwise nothing to write home about yet.

spwill · Unread post by **spwill** » Wed 01/03/2017 17:19

Photo of the Auckland convergence line which is NE of here.

David · Unread post by **David** » Wed 01/03/2017 17:33

Heavy rain now in Howick.

NZstorm · Unread post by **NZstorm** » Wed 01/03/2017 18:01

Some low topped heavy showers in the Auckland area.

David · Unread post by **David** » Wed 01/03/2017 18:04

20mm in the last 30 minutes!

spwill · Unread post by **spwill** » Wed 01/03/2017 18:08

David wrote:20mm in the last 30 minutes!

Wow, torrential rain at Howick, not a drop here today so far.

Manukau heads obs · Wed 01/03/2017 18:50

Just happen to be in the Mt Wellington area..torrential rain..very narrow band..

Nev · Unread post by **Nev** » Wed 01/03/2017 18:52

That's amazing rainfall David, and still going…
I see MS have also issued a Severe T-Storm Watch for that area not long ago…

MetService Severe T-Storm Watch Map - Mar 1, 6.15pm.png

dogmelon · Unread post by **dogmelon** » Wed 01/03/2017 19:07

dogmelon wrote:Look at the Bop radar loop. Is that the front of the sea breeze traversing the Mamaku Range?

Yes dogmelon, it looks that way. However, unless you're in the New Zealand Weather Forum clique you don't get acknowledged, let alone an answer.

jamie · Unread post by **jamie** » Wed 01/03/2017 19:23

Haha chill out dogmelon. I saw your comment but didn't understand it. I thought the main wind was always NE. The NE has been pushed back by the westerly sea breeze hence we are now seeing the convergence in eastern Waikato. But until now the winds were not meeting at the mamaku ranges as far as I could tell. But maybe I interpreted your comment wrong?

NZstorm · Unread post by **NZstorm** » Wed 01/03/2017 19:41

dogmelon wrote:
dogmelon wrote:Look at the Bop radar loop. Is that the front of the sea breeze traversing the Mamaku Range?
Yes dogmelon, it looks that way. However, unless you're in the New Zealand Weather Forum clique you don't get acknowledged, let alone an answer.

The wind is a sea breeze enhanced but it is also a general wind change to a more persistent SW for the coming days.

NZstorm · Unread post by **NZstorm** » Wed 01/03/2017 19:49

Whenuapai sounding today showing very moist unstable air upto about 3.5km then some strong capping.

The lower topped clouds can be efficient rain makers in the right conditions.

David · Unread post by **David** » Wed 01/03/2017 20:06

We've had 37mm here, eased to patchy drizzle/light rain since 7pm.

spwill · Unread post by **spwill** » Wed 01/03/2017 20:24

David wrote:We've had 37mm here, eased to patchy drizzle/light rain since 7pm.

Nothing here today, convergence line sitting just NE of here.

David · Unread post by **David** » Wed 01/03/2017 20:32

A weather station in Ardmore recorded 65mm this evening... pretty impressive!

spwill · Unread post by **spwill** » Wed 01/03/2017 21:45

Photo of the convergence line east of here this evening.

spwill · Unread post by **spwill** » Thu 02/03/2017 08:43

Both Auckland Airport and Whangaparaoa received no rain yesterday.

NZstorm · Unread post by **NZstorm** » Thu 02/03/2017 11:58

The gfs sounding for yesterday evening for E Auckland. This highlights the warm stable layer in the mid atmosphere preventing thunderstorms from occurring yesterday. CAPE is marked in yellow.

jamie · Unread post by **jamie** » Thu 02/03/2017 12:24

So what temp would have been needed to break that cap or what sort of rising velocity would the parcel of air required to break through?

Richard · Unread post by **Richard** » Thu 02/03/2017 12:54

spwill wrote:Photo of the convergence line east of here this evening.

dramatic looking cloud

NZstorm · Unread post by **NZstorm** » Fri 03/03/2017 06:53

jamie wrote:So what temp would have been needed to break that cap or what sort of rising velocity would the parcel of air required to break through?

I am not sure of the details but from my experience an big obstruction like this in the atmosphere means no thunderstorms.

Oddly enough some of the heaviest convective rains I have seen in Auckland in the past have come without thunder.

Research has shown that cloud tops have to get colder than -20C for lightning to be a risk. And -30C or colder is a more ideal number.

NZ Weather Forum