Topic: Dorrigo rainfall for 2009 - Is it a near record for the town in 100 years?

[Harley Pearman]

Dorrigo rainfall for 2009 - Is it a near record for the town in 100 years?

Over recent days when analysing the North Coast rain events and rainfall for the latest rain event to hit the region, I came across a storey on Weatherzone from Saturday June 20, 2009 titled "No respite for drenched NSW North Coast" in which it is stated that:-

"Dorrigo just inland from Coffs Harbour is now up to 2,607 mm for the year over 1,000 mm above the long term average. The town now only needs 300 mm to record its wettest year in over 100 years".

I have tried to find out the accuracy of this and note some anomalies on what I have found to date.

There are a few rain gauges in the locality but it appears from what I can find is that Station Number 59140 located on Old Coramba Road seems to be the main station for the town. This station is located at Latitude 30.3458 degrees South and 152.7189 degrees East.

Old Coramba Road starts just off the Waterfall Way east of town (Not sure of the specific location of the weather station in relation to the township).

There is another rain gauge site Number 559015 but this is not used as the main weather station for the town.

On Weatherzone specific for this weather station (Old Coramba Road), it is stated that records and data from the site commenced only in 1996. Hence there are only records for a little more than a decade at this station.

Since that time average yearly rainfall is stated as:-

- Mean rainfall 1,842.9 mm.
- Median rainfall 1,676.2 mm.

As at 23/6/2009, this station had recorded 2,690.6 mm over 84 days thanks to the big rain events from February to June 2009. It has been a wet year and the rainfall is significantly well above the average at this station.

Looking further into this, there may have been 4,153 mm recorded in 1950 at the Dorrigo Post Office (I have tried to find details of where that came from because that is only stated in a weather forum from New Zealand so I do not know the accuracy of it).

I have read that in June 1950, 1,400 mm fell at Dorrigo especially from weeks 2 to 4.
The Gunghalin Weather Centre states that Dorrigo has an average annual rainfall of 2,004 mm which is different to the actual weather station.

This has lead me to raise some questions on the accuracy of the statement and where did the figure come from given that the weather station on Old Coramba Road has only been in existence since 1996 and certainly not for 100 years. Based on what I can find to date, it seems that it might be the wettest year or near wettest year since records commenced in 1996 as recorded at this station.

Any feedback from readers would be appreciated. Thank you.

Harley Pearman

[Richary]

I am not sure of the records but last night or the night before NBN news reported that Dorrigo had about 4600mm of rain so far this year, the yearly average is 4100mm.

Not sure how accurate this information is (given that it is commercial TV) but just some local input while up here.

[Michael Bath]

Hi Harley, unfortunately many of the news reports by Weatherzone are based on limited datasets which fail to include previous sites in the same general location.  Your post reminded me that I had data for Dorrigo Post Office and it's now available online from this link - the site number is 059013:

http://www.bom.gov.au/climate/data/weather-data.shtml

Which gives you this dataset:

http://www.bom.gov.au/jsp/ncc/cdio/weatherData/av?p_nccObsCode=139&p_display_type=dataFile&p_stn_num=059013

Sure enough, 1950 had 4153.3mm of rain with 1417.3mm in June. Getting into the 3,000s for a year is not common but the 4000+ is a stand-out.

MB

[Harley Pearman]

Thank you for clarifying this. I suspected that there were some anomalies.

Anyway for interest, the Dorrigo Old Coramba Road Weather Station has now recorded 2,694.7 mm to 26 June 2009 over 87 days. Assuming that it does not rain for the rest of the month, that figure would finish at 1,529 mm above the average for the first six months of the year. Still quite wet.

I will monitor this station to see how much falls by the end of the year.

Harley Pearman