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Lower Derwent 28-day Rainfall Forecast

Sun
Mon
Tue
Wed
Thu
Fri
Sat
21
low
22
low
23
med
24
med
25
low
26
med
27
med
28
29
low
30
med
31
low
Aug 1
med
2
low
3
low
4
5
low
6
med
7
high
8
low
9
med
10
med
11
med
12
13
med
14
high
15
low
16
med
17
low
Chance of rainfall within district
nil
< 25%
low
25% to 50%
med
50% to 75%
high
≥ 75%

Issue Notes

The hemispheric long wave pattern has remained stable in recent weeks. There are five main troughs. Currently the most significant troughs are near the longitudes of the southwest Indian Ocean, Western Australia, New Zealand, the south 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 8 August to 12 August, 12 August to 16 August, and 21 August to 25 August. Rain events originating in the tropics and moving south are possible about 17 July to 21 July.
Over Western Australia the strongest cold fronts should occur about 30 July to 3 August, 5 August to 9 August, and 9 August to 13 August.

Issued Jul 19

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.

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