If a low which undergoes explosive cyclogenesis, meaning it deepens very rapidly is a short time, exceeding a certain amount in 24 hours it can be defined as a 'bomb' low.
There is a low approaching New Zealand on Wednesday which meets this criteria and it is expected to bring damaging winds to exposed parts of the South Island and lower North Island, and extremely heavy rain to the South Island west coast later Wednesday.
This low brings extremely large accumulations of rain, up to 300mm in 24 hours for some of the ranges, which could cause widespread flooding, slips and damage to roads. Rivers and streams will rise rapidly, including those in Canterbury that feed from the Alps.This event will especially impact anyone in the mountains, river users, tourists and those traveling on the roads.
As the low moves off the country to the east on Thursday it drags up an unseasonably cold southwest flow from the south causing overnight temperatures on Thursday and Friday to plummet back to single digits, with some areas dropping to 4 degrees.
I've extended the date range of this thread's title, as it looks like it will affect most of the country for a few days (before the next system arrives on the weekend). Also included the rest of that facebook quote, which was cut off mid-sentence?…
Yes, been a while since we've had a 'weather-bomb' cross NZ, or 'Bomb Low' as described by MS. Looks to pass over the south of NZ on Wednesday night, with severe NW gales expected for much of the South Island and lower North Island. The associated front is also expected to bring heavy rain to the West Coast later Wednesday, then move up the North Island on Thursday.
Interesting period of weather coming up, the coming gales is just a extension of the prolonged period many areas have already experienced over the last week, apart from Saturday morning its been none stop wind.
The latest EC models are showing back to their initial prognosis of a significant low moving over the country this WE so maybe an extension further in the date for this event, or another title?
All models showing these systems moving quickly to the east.
More to come next week, perhaps?
Well I am on the West Coast We've had 170mm of rain so far this month at Runanga and only one day when it hasn't rained.Another trough going through as I write this.Next 36 hours likely to get interesting.Many tourists here currently
NZ Thunderstorm Soc wrote:The latest EC models are showing back to their initial prognosis of a significant low moving over the country this WE so maybe an extension further in the date for this event, or another title?
All models showing these systems moving quickly to the east.
More to come next week, perhaps?
John, our possible and rare 'bomb low' is expected to cross the country on Wednesday night, while the other potentially deep low isn't expected to cross the country until at least Sunday - both probably only 2-3 day events. So wouldn't it make more sense to have 2 separate threads for 2 quite separate and potentially significant events to avoid having yet another long rolling thread?
The term "bomb" has a formal definition in meteorology, referring to explosive cyclogenesis at a rate of more than 24hPa of surface pressure lowering at a low centre in 24 hours, however the term has been badly misused in NZ media since around the time a classic bomb low in the winter of 2008 caused a lot of damage in central and northern NZ.
They are talking severe gales of 150kmh in exposed parts of Canterbury in the latest weather warning this morning, could end up being the most significant wind even for central Canterbury since the September 2013 event
harleyb wrote:The term "bomb" has a formal definition in meteorology, referring to explosive cyclogenesis at a rate of more than 24hPa of surface pressure lowering at a low centre in 24 hours, however the term has been badly misused in NZ media since around the time a classic bomb low in the winter of 2008 caused a lot of damage in central and northern NZ.
Yes I think most of us here are in agreement and aware on that front- which is why I was careful to ensure the Metservice quote was attached, this is their prediction not the media this time
NZ Thunderstorm Soc wrote:The latest EC models are showing back to their initial prognosis of a significant low moving over the country this WE so maybe an extension further in the date for this event, or another title?
All models showing these systems moving quickly to the east.
More to come next week, perhaps?
John, our possible and rare 'bomb low' is expected to cross the country on Wednesday night, while the other potentially deep low isn't expected to cross the country until at least Sunday - both probably only 2-3 day events. So wouldn't it make more sense to have 2 separate threads for 2 quite separate and potentially significant events to avoid having yet another long rolling thread?
Talk about calm before the storm,cant even see a leaf moving on the trees, what a lovely change from the last weeks weather, though i dont see this lasting long.
Avalanche wrote:Are there any charts available that show the winds increasing to 160km gusts at or near ground level. Thanks appreciate any guidance regards to this.
Not gusts, but here's 2 more generic GFS 10m mean-wind charts (in knots) for 1am and 7am tomorrow…
the coming gales is just a extension of the prolonged period many areas have already experienced over the last week, apart from Saturday morning its been none stop wind.
