An intense low pressure system originating from the coral sea is forecast to bear down on the Nth Island of New Zealand on Tuesday and Wednesday ( 24th and 25th September 2013)
The low appears to have formed at the apex of a strong intense sub-tropical Jetstream kink and has a fast transition to the mid latitudes toward the Nth New Zealand Island
ACCESS G has intense deepening tonight ( 23rd sept) and central pressure may go as low as 978 hPa on Tuesday and into the early hrs of Wednesday
This system could be as intense as a CAT 2 cyclone in terms of wind intensity and heavy rainfall.
A severe weather warning has been issued
MET SERVICE . New Zealand Weather Bureau
Issued: 3:13pm Monday 23 Sep 2013
Valid from Wednesday 25 September 2013 to Saturday 28 September 2013
A deep subtropical low
is expected to lie over the Far North by midnight Tuesday and should move southeast during Wednesday to lie near East Cape by midnight. On Thursday the low should move towards the Chatham Islands, with the flow over New Zealand turning southwest.
There are currently Warnings and Watches in force for the entire North Island and also Marlborough.
There is a moderate confidence of heavy rain in western Bay of Plenty continuing into early Wednesday morning, and a high confidence of heavy rain in Gisborne continuing into Wednesday morning. Further south, there is a high confidence of heavy rain reaching warning criteria on Wednesday in Hawkes Bay,and a moderate confidence in Wairarapa as well as about the eastern hills of Wellington. In Marlborough and northern Canterbury, there is a high confidence of warning amounts of heavy rain continuing through much of Wednesday,particularly about the Kaikoura Ranges and Marlborough Sounds.
East to southeast gales are expected to affect most of the North Island and upper South Island, and there is a high confidence that these could be severe for a time on Wednesday west of the main North Island ranges from Waikato to Wellington, including Bay of Plenty and the central high country, and also about Gisborne and the Marlborough Sounds. There is a moderate confidence of severe east to southeast gales in Nelson, Buller and northern Westland on Wednesday.
As the low moves away to the southeast on Wednesday, heavy rain may return to Northland, with a low confidence of warning amounts of rain in western areas. Additionally, southwest gales are likely in Auckland, Northland and about the the northern tip of the Coromandel Peninsula on Wednesday, and there is a moderate confidence that these could be severe for a time.
A ridge of high pressure should quickly cross the country late Thursday and early Friday, then a low may approach Fiordland later Friday, with an associated trough bringing a burst of heavy rain to the West Coast. There is a low confidence of warning amounts of heavy rain in Fiordland and southern Westland on Friday and in northern Westland and Buller later Friday and on Saturday.