Last Thursday to Saturday, Macquarie Island received the highest ever recorded rainfall (in something like 65 years). Our Bureau of Meteorology (BOM) senior observer Keon Stevenson provides the following story:
On the 15 January the deep low pressure system that produced significant rainfall over Tasmania drifted towards Macquarie Island from the northeast. We were expecting significant rainfalls here and we had a competition as to who could guess the correct amount over a 36 hour period. After checking the various predictive weather models, the NOAA (USA) model was predicting around 90 mm of rain to which most of us were very skeptical. The European Centre deterministic model was going for more! However, as the NOAA model was spot on for our last rainfall event of 23 mm, there had to be some accuracy and belief there.
Light rain began in the afternoon on 15 January around 1700 hours and increased to heavy rainfall into the evening and the following morning. Rainfall is officially read from 0900 to 0900 over a 24 hour period, and at 0900 on the 16th we recorded 42.2 mm in our rain gauge. This was reported as the second most rainfall in history of a 24 hour reporting period!
The rain was very heavy and consistent between 0900 to midday on the 16 January when the low was very close to Macca — 26.2 mm fell during that three hour period. The rain eased slightly and we had continuous moderate rain for another 12 hours. Mean sea level pressure on the island got as low as 960.3 hpa just after 1500 hours.
To 0900 on 17 January we received 63.4 mm, which is a new record over a 24 hour reporting period. The previous 24 hour record of 52.8 mm was recorded on 14 March 2001. So, over a period of about 36 hours we received a total of 105.6 mm in our tipping bucket rain gauge (primary instrument). During that morning we also discovered landslides and collapses of the coastal escarpment slopes around the Razorback, Gadgets Gully and down at Sandy Bay as reported by the Spirit of Enderby via VHF radio. Unfortunately the landslides filled our small water supply dam at Gadgets Gully with rocks and dirt, and damaged our water supply piping to station, which took the next three days to fix.
Oh yeah, Scotty guessed the closest rainfall figure of 75 mm!