Low Pressure system 11-12th March, 2012

[Tornado Tim]

Looks like the Low that centered just off the coast of Victoria, Australia will travel south and join up with a low in the Southern Ocean.
This is expected to become a more broad trough of low pressure as it gets closer to New Zealand with a Cold front expected to hit the SW of South Island. The Northern tip of the Cold front is expected to become more active over the central Tasman as SFC Sea temps are expected to be warmer.

As the trough of low pressure approaches the West Coast of the South Island it is expected to redevelop in to more of a low of sorts and cross the midriff of NZ.

There is a possibility of storms for parts of the west coast of the NI on the 12th as a pool of colder air contained on the NW sector of the Low moves further east towards land. A low risk at this stage for Waikato for an evening storm, possibly a moderate risk on the coast as showers/storms form over sea and move onshore in a westerly flow.

Will have to see how the models firm this up later on.

[NZstorm]

Also a thunder risk Sunday evening from Taranaki to upper South Island associated with the front/warm sector moisture. Could be also be a risk over Northland/Auckland Sunday pm but its a long shot atm. See how it looks tomorrow.

[NZstorm]

Could be also be a risk over Northland/Auckland Sunday pm but its a long shot atm. See how it looks tomorrow.

Looks better with atleast isolated thunderstorms possible from Northland to western Waikato Sunday afternoon. We need some daytime heating. The dewpoints will be in the 18-20C range. There will be mid level cloud though.

[Tornado Tim]

isolated thunderstorms possible from Northland to western Waikato Sunday afternoon. We need some daytime heating.

Yes that is certainly the case as the upper air isnt very cold at all, -10 to -12°C. GFS has now brung in more moisture onshore bringing up the SFC CAPE.

[David]

Metservice have a moderate thunderstorm risk for Northland Auckland & Coromandel tonight.
A cloudy humid day here so far with 95% humidity

[Manukau heads obs]

looking better now to the NW on the rain radar and I have picked up a few strikes too now from there

[spwill]

The main shower line to west is looking better now.
Dewpoint above 19C here.

[Tornado Tim]

21.8mm of rain fell here with passage of the front overnight, not bad

[Manukau heads obs]

nearly exact the same amount here, 21.3mm!

[David]

Got 13mm here

[Nev]

16.5mm here and 14.2mm at Grey Lynn.

[Michael]

This is windier than the saturday before last here,the wind hasnt stopped whistling since 11am.At least then it was sunnier.

[David]

This is windier than the saturday before last here,the wind hasnt stopped whistling since 11am.At least then it was sunnier.

I recorded a peak gust of 62 km/h at 6.34pm, which is the same max gust I had from the recent weather bomb

[Michael]

Our windows are buckling and banging going on from the tree.Last week we had more isobars over us when east or SE and they kept telling us strong winds for 3 days,we lucky if we got a gust on 1 occasion 1/2 this speed today.

[Tornado Tim]

Just checked the rain rate figures last night, got very heavy at one stage around 1 AM.
From 00:57 to 01:07 (10 min accumulation time) 7.8mm of rain fell.

[Nev]

This is windier than the saturday before last here,the wind hasnt stopped whistling since 11am.At least then it was sunnier.

I recorded a peak gust of 62 km/h at 6.34pm, which is the same max gust I had from the recent weather bomb

Just for the record though, most places around Akld generally recorded peak gusts on Monday evening about 2/3's lower than those (mainly westerlies) on Mar 3 - most notably, Brian's 115 km/h gusts early that Saturday morn versus 69 km/h on Monday. Below are a few more 'official' readings...

Code: Select all

Akld max gusts (km/h) c/o NIWA - 24 hours to midnight.  
Site              Mar 3    Mar 12
Warkworth           84       63 
Whangaparaoa        98       63 
Albany              70       43  
Whenuapai           80       50 
Musick Pt          101       78 
Lincoln Rd          76       53 
Penrose             59       53 
Pakuranga           56       47 
Mangere             85       62
Auckland Aero       85       58 
Pukekohe            62       51 
Ardmore             81       54 

[Manukau heads obs]

note that westerlies funnel big time here (same at the signal station)...SW I am not much windier than elsewhere

[David]

Thanks Nev - looks like my readings were an exception then