Flood Forecasting (continued)

About the time that Allan returned the first dummy run of the newly developed Macleay flood forecasting system was conducted at the Bureau's Central Office from 1 to 3 August 1961 using an actual heavy rain system for which observational material was available. Item 435 in the September 1961 issue of Weather News gives details. Brian Watson performed the hydrological computations whilst Bob Crowder, Des Gaffney and Ross Maine independently produced their three-hourly rainfall forecasts based on synoptic charts and other material usually available in the Sydney Divisional Office. In a forecast issued at 3.40 am the critical river height of 16 feet (approx 4.94 metres) at Kempsey was predicted to occur at noon, when in the chosen situation the river reached that height at 12.15 pm. The peak of the flood at Kempsey was predicted to be 19 feet six inches (about 5.94 metres) at 6 am the following day whereas the actual peak occurred at 9 am and was 19 feet 9 inches (approx 6.05 metres). The results of this trial were most reassuring.

Item 501 in the May 1962 issue of Weather News reported that floods had occurred in the lower Macleay Valley of NSW on the week-end of 7 and 8 April and Len Dwyer was no doubt anxiously waiting for a report of the Bureau's performance. He would have been aware that the Bureau had issued a flood warning at 1 pm on 7 April that the river at Kempsey would break its banks by 3 am on the 8th. The flood peak at Kempsey of 18 feet 2 inches (approx 5.54 metres) occurred at 11 pm on the 8th and was within a few centimetres of the forecast height which had been issued 30 hours earlier.

Len Dwyer would have been delighted with this success. He did not commence sick leave until a week or so later and died in the Heidelberg Repatriation Hospital on 16 May 1962 at the early age of 54.

The flood forecasting system developed by Neil Body with the assistance of Allan Rainbird was a fitting monument to Len Dwyer's vision, initiative and energy, although it was just one of the achievements during his period as Director of Meteorology.

Bureau of Meteorology