WeatherWatch.co.nz says that despite the main bulk of rain easing in Auckland and Northland this morning coastal flooding is likely to return again tonight as the centre of the storm tracks by.
The centre of the low isn’t expected to reach Auckland until around midnight – at the same time as hightide.
Head weather analyst Philip Duncan says it’s not just the rain that causes flooding. “The sea is such a huge area of water that heavy rain on the land hardly affects it. However with a deep low, such as the one north of New Zealand, we have what is called a ‘storm surge’ near the centre and that may should cause more problems tonight”.
Follow WeatherWatch.co.nz on Facebook – for Breaking Weather News on your Facebook wall. Simply click here to Like us
Mr Duncan says a storm surge is created when low air pressure near the centre of the low allows water to rise up in a dome shape over an area roughly the same size as the low’s centre. “It’s a bit like a vacuum cleaner in the sky lifting up the water. It can have a significant effect on low lying areas”.
“Coupled with the storm surge we also have the strong to gale force winds which will tonight strengthen further ahead of the centre – driving more water up”.
High tide tonight in Auckland is expected to be 10cms lower than it was late this morning but WeatherWatch.co.nz says the storm surge will counteract that.
Mr Duncan says Auckland and those around the Firth of Thames will be at a high risk of storm surge flooding, as will eastern and northern parts of Northland and Coromandel Peninsula.
WeatherWatch.co.nz says the centre of the low is expected to cross directly over Auckland around midnight with the air pressure around 986hPa according to the MetService chart.
The air pressure in Auckland is currently around 995hPa. It’s the air pressure gradient between the centre of the low (986hPa) and Aucland (995hPa) that is creating the strengthening winds over the upper North Island this afternoon.
on 23/01/2011 4:44am
we have had lots of rain overnight and non stop throughout the day our water tank which is fairly big was completely empty for the past 3-4 weeks and it is now half full over the period of rain lastnight and today, hopefully it will be full by the time this rain has stoped
on 23/01/2011 3:14am
Lots of rain, 100mm ? Overnite in town but calm cloudy and warming with very high humidity now. no wind and rivers reasonable. What can we expect tonite?
on 23/01/2011 3:49am
More rain Robert, but hopefully starting to ease a little overnight. The centre of the low will cross East Cape tomorrow afternoon. MetService still have a rain warning in place:
Heavy Rain Warning, Areas Affected: Gisborne and Hawkes Bay Periods of heavy rain are expected to continue until early Monday. From midday Sunday to 3am Monday, a further 100 to 180mm is expected to accumulate. Heaviest rain will be in the ranges, but 50mm is possible about coastal areas
on 23/01/2011 3:07am
You talk about Auckland (and the closest Auckland holiday destinations) but you don’t really talk about the rest of the country… a bit biased if you ask me.
on 23/01/2011 3:31am
Well we can’t make the storm move into other areas! But I understand your point.
Our focus today has been on those most affected. If we start getting reports of damage/flooding further south you can be sure we will be covering it, but on a day like this our resources are fairly limited to the main area of concern.
Where are you from?
on 23/01/2011 3:41am
I’m in Whakatane. We’ve got lots of action here in the Eastern Bay… slips, road closures, flooding in Edgecumbe, Awakeri, Te Teko, Whakatane etc. It’s been pretty badly affected too. Our river catchment areas have received quite a lot of rain and we’ve got a civil defence team monitoring our rivers. They’ve had to spill water from the matahina dam onto farmland (some has been protected by stopbanks though). It’ll be interesting to see what happens when the waters make it to the coastal areas – hopefully not around high tide (midnight)!
on 23/01/2011 3:47am
Hi there – thanks very much for the update, much appreciated.