Is it dry? Yes, but for how long?

Thanks to a new service at NIWA we can now get some of their cool climate data plots for a site much closer to home than previously.  Up until recently the nearest climate station that I could get plots of rainfall from was at Whangaparaoa. However the climate out on the peninsular is slightly different than on Waiheke thanks to the positioning of the Waitakere Ranges.

NIWA process their various climate stations around the country into a tidy grid of virtual climate stations each about 5km apart. This allows us to have a better idea of the real data for Waiheke.

Here is the key plot – for detail of how to get your own see

It shows the accumulated rainfall for this year, compared with last year and the long term average.

This is a live chart so each week you visit it you’ll get the latest information.

Last Year

Take a look at the blue line. Compared to the long term average – the black line it is nearly flat from Dec to May. That was our four month drought. But as you can see it followed an equally dry Oct/Nov broken only by what I recall as a single rain storm at the beginning of December.  We caught up again in May but the total for the year was only about 1000mm compared to the average of 1200mm.

This Year

Follow the red line, and look at the red bars which show monthly total rainfall for each month. August/September were wetter than average while again Oct/Nov have been dry.  If we don’t get a burst of rain in December then we are back in the same situation as last year.

El Niño, La Niña

One thing is different – The state of the El Niño Southern_Oscillation.  This irregular fluctuation in the boundary between the cooler drier south polar air and the warmer wetter equatorial air is one of the main causes of annual variation in our climate.

From NIWA’s latest climate outlook: A moderate to strong La Niña is well-established in the tropical Pacific, and may strengthen further through the rest of 2010.  La Niña conditions are likely to continue through to autumn of 2011. In the North Island, rainfall is likely to be normal or above normal, with above normal soil moisture levels and stream flows in the east,

The basic rule to remember is: El Niño = Drier, La Niña = Wetter (for NZ North island at least)

So it could go either way – we may see a return to wetter weather and an average year in total, or we could miss out on a couple of crucial storms and have more drought than last year.   This is one issue about climate change that you need to bear in mind – things can change in either direction – what rising CO2 levels really mean is more energy in the atmosphere and more volatility in the climate.  Drier drys and wetter wets and extreme events more often.

Note: I am not a climate scientist or a meteorologist I am just reading the graph as I see it.

Soil Moisture

Here is a soil moisture plot from the same source. I’ll leave you to interpret it. but basically if there are red bars along the bottom your plants probably need watering.

For Waiheke weather see:

2 thoughts on “Is it dry? Yes, but for how long?”

  1. 18th Dec – notice how the rainfall over the last few days is mounting up – about 25mm. However still not as much yet as December last year.

  2. 1st feb 2011 – wow over 320 mm of rain in Jan. look how that graph now goes over the top 95% percentile. That will be the wettest waiheke january for some time.

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