BOM Seasonal Outlooks- How did they rate?

The Bureau of Meteorology regularly produces seasonal outlook forecasts for the coming 3 months.  These are immensely useful to farmers and graziers, and very interesting to those who check them versus what really happens.  The BOM does a mighty job and this is in no way a criticism of their work.  Rather, it is a reminder that we need to remember how difficult it is to forecast weather and climate.

Here are the Outlooks for summer from November, December, and January:  Firstly, Rainfall (underlining is mine): 

(21 November)  Drier summer favoured in parts of north Queensland

The national outlook for summer (December-February) rainfall shows a moderate shift in the odds favouring a drier than normal season across parts of north Queensland. However, over most of the country the chances of exceeding the seasonal median are close to 50:50, with no strong shifts in the odds pointing to either a wetter or drier than normal summer.

 (21 December) Mixed seasonal rainfall odds for the March quarter

The national outlook for total rainfall over the March quarter (January-March), shows a moderate shift in the odds favouring a drier than normal season through much of Queensland, the northeast half of NSW and southwest WA. In contrast, the odds point to above average falls in a band extending from southern SA across parts of Victoria to northern Tasmania.

The pattern of seasonal rainfall odds across Australia has been heavily influenced by the El Niño pattern of higher than average temperatures across the central to eastern Pacific Ocean. Although weaker, the contribution from above normal Indian Ocean temperatures has reinforced the Pacific influence.

(19 January) Contrasting seasonal rainfall odds for late summer to mid-autumn

The national outlook for total rainfall over late summer to mid-autumn (February to April) shows contrasting odds across the country: below average falls are more likely in northern parts of both Queensland and the NT, whereas a wetter than normal three months is indicated for northwest and central WA.

The pattern of seasonal rainfall odds across Australia has been produced using recent Pacific and Indian Ocean temperature patterns, with the warm Pacific (El Niño) having the greater influence.

Now, temperature:

(21 November) Warmer summer days indicated in northeast and western Australia

The national outlook for summer (December-February) mean maximum temperatures shows a moderate shift in the odds favouring above average values in the west of WA and in a band across northeast and northern Australia.

(21 December) Warmer in the north and west; cooler in the southeast

The national outlook for March quarter (January-March) mean maximum temperatures, shows moderate to strong shifts in the odds favouring above average values in the west of WA and in a broad region covering much of northern and northeast Australia. In contrast, cooler than average daytime temperatures are indicated in the southeast of the country.

The pattern of seasonal temperature odds across Australia is due to higher than average temperatures in both the Pacific (El Niño) and Indian Oceans, with the Pacific influence being dominant.

In contrast, there is a 60 to 70% chance of cooler than normal days averaged across the season over Tasmania, Victoria and southern SA.

 

This due to the Indian Ocean Dipole and the deepening El Nino.

So what happened?

Rainfall, December to February as a percentage of the mean.

And February on its own:

Rain in mm:

Temperatures- remember, the expectation was for higher maxima across north and north east Australia.  Mean maximum Nov- Jan:

And for January itself:

And judging by the rainfall, February should be cool as well!

 A pretty normal Wet season, in fact. And when you have clouds and rain, you have lower temperatures.  Unfortunately, in the tropics you also get humidity.  Lots of it! 

 Mackay’s rainfall for January and February:

January- 327.2  Mean 279.1mm

February- 374.4 Mean 326.4mm

Many rain gauges around the district reported much higher figures.  My total for the year so far is 1226.5mm, or 49 inches in the old money.  There were many way above mine!

 So the reality was much different to any of the outlook summaries, for which many farmers and graziers, as well as fishers, are very grateful. 

 Looks like the Indian Ocean won!

However, the forecast for WA was pretty much spot on.  They could certainly use some rain!