Summer Rain Outlook Update 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).

5 Responses to “Summer Rain Outlook Update December 12 2012”

  1. cementafriend Says:

    Ken, do not know if you take historical events into account. I have a feeling that the present situation is like the period 1973-1977.
    The second half (calender) of 1973 had much higher than average rainfall, then there were floods in Brisbane Jan 1974 (ground saturated high runoff). The second half of 2010 had much higher rainfall than average (in fact Dec 2010 had the highest monthly total in recorded history from 1892- should have been a warning), then floods in Jan 2011. 1976 had well above average rain in the first half year and below average in the second half. This will apply for this year -80% above average in first half and probably 30% below average 2nd half. The low rainfall in the 2nd half of 1976 carried through to low rainfall in the first half of 1977 ( half the average).
    My gut feel is we will get below average rainfall in the first three months of 2013 -maybe 60% of average. Around my way that will mean about 450mm It maybe that there will be some bleats about higher than average temperatures in SE Qld -less clouds.

    I see now (WUWT) that the IPCC are recognising that clouds and the sun affect climate.

  2. handjive Says:

    Living In Coolangatta, we have received a decent drop of rain, much as you have predicted.

    It is extremely humid atm, and the next week up to NYE has more rain in store, for sure.

    Keep up the good work.

    • Ken Stewart Says:

      Thanks. I was going to do another post before Xmas but have better things to do.
      No heavy rain but certainly widespread light stuff with high humidity, so the timings are still right!
      Merry Christmas and Happy New Year to all.
      Ken

  3. cementafriend Says:

    Ken, you were right about the timing of rainfall in Dec. Here it rained 12-14, 18 and 27-30th. I was right about the low amount of rain. in Dec We had about one third of average. I actually expected more based on your forecast. The quantity for the half year was also less than expected at 43% of average and in fact the lowest half year since 1951 (the year total is still above average because of the high amount in the first half).
    We could do with decent rain in the next few months.

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