RAINFALL

I'll try to keep this updated as the Wet season progresses for anyone curious about rainfall on the Mitchell Plateau. The first proper storms in Broome usually appear early/mid December so the rain gauge up here should get a little more action then hopefully, with most rain falling Jan - Mar. Average annual rainfall in the area is supposed to be around 1500mm - the highest rainfall in north-western Australia. The average Wet season rainfall is 1,416mm.

Nov 16: 3mm

Nov 19: 1mm

Nov 25: 6.5mm

Nov 26: 12mm

Nov 27: 1.5mm

Total for Nov: 24mm

You can see in the chart below, pulled from an old Department of Conservation document, November is well below the recorded average of 127mm, according to an old weather station that operated at the nearby airstrip until 1986. Plenty of time hopefully to make up the shortfall. 

Dec 1: 6mm

Dec 2: 48mm

Dec 8: 15mm

Dec 11: 17mm

Dec 12: 7mm

Dec 13: 15mm

Dec 14: 24mm

Dec 17: 18mm

Dec 18: 2mm

Dec 22: 37mm

Dec 23: 2mm

Dec 31: 21mm

 

Total for Dec: 212mm

Despite the last week of December being very dry, New Year's Eve brought a welcome 21mm, which puts our December monthly rainfall 30mm over the monthly average of 182mm. January is supposed to be closer to 400mm. Let's hope it delivers.

Jan 2: 6mm

Jan 4: 3mm

Jan 5: 44mm

Jan 6: 179mm

Jan 7: 107mm

Jan 8: 40mm

Jan 10: 40mm

Jan 11: 13mm

Jan 12: 5mm

Jan 13: 2mm

Jan 15: 10mm

Jan 17: 3mm

Jan 19: 22mm

Jan 20: 54mm

Jan 25: 52mm

Jan 26: 1mm

Total for Jan: 581mm

It was quite a dry end to the month but thanks to Cyclone Blake the monthly total is 202mm above the average. Average rainfall for Nov-Jan is usually 688mm and we are now sitting on 817mm. However, with Feb & Mar being high rainfall months the Wet season total could still go either way. We're now over half way towards the goal of 1,416mm.

Feb 4: 55mm

Feb 5: 25mm

Feb 7: 8mm

Feb 11: 1mm

Feb 17: 11mm

Feb 19: 15mm

Feb 21: 31mm

Feb 27: 11mm

Feb 28: 59mm

Feb 29: 112mm
 

Total for Feb: 327mm

Ex tropical cyclone Esther delivered some good rains and a lot of the Kimberley got the soaking that we desperately needed. Technically February ended up being 40mm below the recorded average, but with January being 200mm over we're still hitting our Wet season targets for overall average rainfall. The average for Nov - Feb is 1,055mm. We are now sitting comfortably on 1,144mm. By all normal measures the Wet season seems to be delivering the goods this year.   

Mar 1: 62mm

Mar 2: 14mm

Mar 3: 10mm

Mar 14: 7mm

Mar 25: 15mm

 

Total for Mar: 108mm 

In terms of rainfall March turned out to be a major disappointment. Except for the tail-end of ex tropical cyclone Esther, which delivered 86mm in the first 3 days of the month, we had a total of 22mm in the remaining 28 days of March. Overall that's 212mm short of what we needed to hit the monthly average. As things stand we are 123mm short of where we need to be in an average Wet season on the Mitchell Plateau. Considering the 2018-2019 Wet season was so far below average we really needed LOTS more. April is typically a dry month in the Kimberley but with the Wet season starting late this year there's a possibility we could get lucky and get something in the next few weeks. Fingers crossed.  

Apr 4: 1mm

Apr 6: 12mm

Apr 8: 10mm

Apr 9: 31mm

Apr 10: 4mm

Apr 11: 7mm

Total for April: 65mm

Wet Season Total: Nov 1 - Apr 30: 1,317mm

 

1,317mm puts us about 100mm below the Mitchell Plateau average (Nov-Apr) of 1,416mm - or 90% of the average Wet season rainfall. With last year being so dry we could certainly have used a lot more but, all things considered, it was essentially a standard Wet season here in the north-west.

 

It's worth noting that the average is based on weather observations from 1970 - 1986, which are the only accurate rainfall records for the area. I'd be curious to know, with a warming climate and changing weather patterns, if 1,416mm is still an accurate average for the previous 10 years. Despite being slightly below average this year it is still the highest rainfall in north-western Australia.

 

What has really struck me about the Wet season is just how dependent this rainfall is on large, slow-moving tropical lows, as opposed to isolated local storms. For example, ex tropical cyclone Blake brought 423mm of rain in 6 days. And ex tropical cyclone Esther brought 268 in 6 days. That's almost half of our Wet season rainfall in 2 storms - or 12 days - and almost as much rain as Melbourne gets in 12 months. It starts to explain why our Wet seasons can be very hit or miss, depending on those tropical lows and how they track across the Kimberley.

 

Nov: 24mm. Average: 127mm

Dec: 212mm. Average: 182mm

Jan: 581mm. Average: 379mm

Feb: 327mm. Average 367mm

Mar: 108mm. Average 320mm

Apr: 65mm. Average 41mm.

 

Total: 1,317mm. Average (Nov-Apr): 1,416mm.

©  Gary Annett Photography 2020

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