Weather

Lower Derwent 28-day rainfall forecast

Sun Mon Tue Wed Thu Fri Sat
    17
 
 
18
Low
 
19
 
 
20
Low
 
21
Low
 
22
Med
 
23
Low
 
24
Low
 
25
Low
 
26
Low
 
27
Low
 
28
Low
 
29
Low
 
30
Low
 
31
 
 
1
 
Jan
2
 
 
3
Low
 
4
 
 
5
Low
 
6
Low
 
7
Med
 
8
 
 
9
Low
 
10
Med
 
11
Med
 
12
 
 
13
 
 
         

Chance of rainfall somewhere within district

Nil
<25%
Low
25-50%
Medium
50-75%
High
≥75%

Issue Notes

Issued 16 Dec 2019

The hemispheric long wave pattern has been relatively slow moving in recent weeks. There are five main troughs. Currently the most significant troughs are near the longitudes of South Africa, the Indian Ocean, New Zealand, the southeast Pacific, and the Atlantic Ocean. Summary: Over southern and eastern Australia the cold front events with potential to bring widespread rain are now expected about 21 December to 25 December, 9 January to 13 January, and 15 January to 19 January. Rain events originating in the tropics and moving south are possible about 24 December to 28 December, and 30 December to 3 January. Over Western Australia the strongest cold fronts should occur about 21 December to 25 December, and 16 January to 20 January.

Forecast Explanation

This forecast is produced by a multi-model ensemble consisting of dynamical atmospheric models, which are forced by the latest observed atmosphere, ocean, land and ice conditions. The models are designed to simulate features of the real atmosphere, including the daily movement of long and short wave patterns in the Southern Hemisphere.

The future probability of rain in each district is estimated using output from the multi-model ensemble, combined with historical information about the difference between the model forecasts and observed rainfall.

In this deterministic framework the skill of the forecast tends to decrease with time, however the forecasts are updated daily to provide the latest estimates of rainfall probability out to 28 days.