Archive for December, 2012

Summer Rain Outlook Update December 12 2012

December 12, 2012

Progress so far:

So far in December there has definitely not been widespread or heavy rain, so I should stick to forecasting dates when a weather enhancement is more likely rather than how much rain can be expected.  However, the predicted timings line up very well.

graph 12dec12

BOM mentioned instability on the 1st, and a low developed off the coast in the next few days but went south rather than west- northern NSW got this influence.  There were isolated storms about with light rain, and of course the very hot weather around 4th and 5th, with a large change.  So instead of heavy rain we got extreme heat!  Further storms around in the past couple of days- well within the +/- 5 days range.

Outlook for the rest of the year:

It is still very dry, with only coastal showers.  Humidity is building, the monsoon trough has moved south into the Coral and Timor Seas, with cloud streaming down from Indonesia through Western Australia.  The Wet season is getting closer.  We may even have a rain depression or cyclone before the end of the year in North Queensland.

I’m still tipping a major disturbance mid to late December with surges around 18-22 and 26, plus possibly 30 (and probably 2-4 January), all +/- 5 days.  I expect this to bring heavy rain, especially in the week leading up to Christmas- but I’ve been wrong before about rain intensity!

I again mention that rainfall is measured at 9.00 a.m. on the day after it falls.  As well, my method captures the average of 3 day rainfall anomalies across 10 sites in subtropical Queensland.  I do not predict rain for specific locations.

I won’t change my outlook for 2013 for now but there will be some small changes.

SOI 30 day mean (to 12 December) is -2.2 (neutral).

Weekly NINO 3.4 Index (to 9 December) was + 0.37 (neutral).

The Indian Ocean Dipole is currently -0.07 (neutral).