Auckland Weather and Rain Update

Well it's almost situation normal. It's winter and it's raining.
So I won't do any more blogs about this for a while.
Last time I blogged was Saturday 22nd May. It had started raining hard.
The NZ Herald rain gauges indicated that 197mm had fallen for the 2010 year.
That was just 50% of average rainfall that is recorded for that period.

Since then it has rained a lot.
Today, 15th June, NZ Herald has recorded 367mm.
That means 367-197mm has fallen since 22 May. 170mm in fact.
That's a lot of rain in 3 weeks. Feels like it doesn't it.

According to Granny Herald, average June rainfall to date is 52mm, but we've had 97mm.
That's almost double the average rainfall for June.

Overall for the year, to 15th June, Herald reports average rainfall is 454mm.
We have now had 367mm. That's 80% of average.

Quite a change from a month ago when Auckland was sitting on 35% of average rainfall, and was experiencing the driest four month period on record.

Aucklands Weather - What's happening now?

In case you didn't notice it rained last week.

Over a 24 hours period on Thursday and Friday Auckland recorded 59mm of rain.

This brought its annual rainfall for the whole of 2010 so far to 197mm in total.

So, Auckland received about a third of its entire year's rainfall in one day.

That's a big rain.

Even so, Auckland has still only received about 50% of normal rainfall for this January - May period. And the storage lake's are showing the results.

Check out this page on Watercare's website: http://www.watercare.co.nz/watercare/water-supply/aucklands-water-situation/dam-levels.cfm

You can use it to enter the storage lakes and see how their storage levels have changed over the previous 7 days.

Lower Huia has gone from 55% full to 68%, due to that rain.
Lower Nihotupu has gone from 62% to 70%.
Upper Huia has increased from 53% to 78% of full.
Upper Nihotupu has increased from a low of 23% to 55% of full.
And the Waitakere Dam has gone from 33% to 60% of full.

That's a big increase in good pure, bush catchment collected, stored water.

Has Auckland's Climate Changed?

Auckland's water situation
The time to save is now.
Total rainfall in the last four months has been the lowest in nearly 100 years of records in the Waitakere water supply catchments and the third lowest in nearly 50 years in the Hunua catchments. If this dry spell continues through winter, we could face restrictions next summer.

This information is from Watercare's website today.

Watercare states on its website that lake storage levels are at 55.45% of full.

I know that's low. I well remember the drought and water shortage of 1994. Perhaps Auckland should be taking this a bit more seriously.

Auckland Regional Council Parks staff tell me that this drought - the drought of 2010 - is more severe than the one in 1994. They speak of a drought that happened around 1978 (I was overseas then and did not experience it).

Parks staff have spoken of old Tairare (sp?) trees in the Wenderholm area - with metre girth trunks - that have yellowing leaves and will die now through prolonged lack of water. I am aware of street and cemetery trees in Devonport that have died toward the end of this summer.

Because I am a recreational fisherman, I am in the habit of checking the weather details in the back of the Herald. And as a regular cyclist to work at ARC have become a bit of a junkie for checking rainfall patterns and how accurate the weather forecast is. Generally, I would observe that the NZ Herald forecasts for Auckland and Northland (bach is at Mangawhai Heads) have been very reliable. Up until the end of 2009 that is.

But for most of January, February and even now, the Herald weather forecast for rain has been amazingly incorrect. I can recall that throughout the summer period the forecast for Auckland and Mangawhai was almost always for "rain coming in the next 48 hours". And there was never rain. It was so often forecast, but it never came. Never eventuated.

Like now. The forecast - both on TV and in NZ Herald - has been for rain all day and everyday this week in Auckland. Sure we had 8 mm yesterday (Wednesday), but nothing like the forecast.

These observations make me think that the models or forecasting methods that have been used happily by the Met Office (which supplies information to TVNZ and NZ Herald) till now, cna no longer be relied upon to predict the weather 2 or 3 days ahead any longer. Well. The forecasts have been notoriously incorrect for most of this year - when it comes to predicting rain. So that leads me to wonder what underlying pattern has changed, that is not being picked up by the Met Office. Don't know. Maybe it will all blow over....

Meanwhile I ask you to keep a watch on the rainfall information in NZ Herald. In particular, check out the "Average rainfall to date for 2010" and the actual "Rainfall to date for 2010", and keep an eye on it.

Ever since the end of January - pretty much - the ratio between Actual Rainfall/Average Rainfall has tracked at about 35%. In other words Auckland's rainfall is about a third of the annual average for the Auckland region.

Today's readings listed in the NZ Herald (from Met Office and NIWA) for the 2010 year so far:

Average rainfall = 347mm. Actual rainfall so far this year = 123.6 mm. Ratio = 35.6%

What is especially interesting about this ratio, is that Northland's rainfall ratios - even though Northland has been cited as an area of "severe drought" - have been consistently higher than Auckland's ratio. The data for Whangarei and Kaikohe show ratios of Actual/Average greater than 40%. Today - for example - Whangarei's ratio is at 46%, while Kaikohe's is at 65%.

Auckland has experienced a particularly severe drought for the whole of 2010 so far, which published weather forecasts have failed to foresee. So what has changed? Have weather patterns changed? What should we be doing about this in Auckland?