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Nerd mode: every forecast, readouts, filters and range & bearing for weather enthusiasts

This week’s weatherPerth, Australia

Rain is likely in Perth on Tuesday

Nearly all of NOAA’s 31 GEFS forecasts bring measurable rain to Perth Tue 8 a.m.–2 p.m. GMT+8.

NOAA GEFS, 31 forecasts · Mon 28 Sep 18Z run · updated Tues., Sept. 29, 7:03 a.m. GMT+8 · times are Perth’s (GMT+8)

See it on the globe For warnings, follow your national weather service.

Quick answers

Will it rain in Perth this week?
The best chances of measurable rain: Tuesday (nearly all forecasts, 8 a.m.–2 p.m.); Wednesday (nearly all forecasts, 8 a.m.–2 p.m.); Monday, Oct. 5 (7 in 10 forecasts, 8 a.m.–2 p.m.). Drier: Thu, Fri, Sat, Sun (fewer than 2 in 10 forecasts in any six hours). Times are GMT+8.
How much rain will Perth get this week?
By Tues., Oct. 6, 2 a.m. GMT+8 (the end of the forecast), the middle forecast has 5.4 mm of rain and melted snow, counting from Tue 8 a.m. Fewer than 1 in 10 forecasts bring 13 mm in total.
How windy will it get in Perth?
No strong gusts: fewer than 1 in 10 forecasts have gusts over 48 km/h at any of the six-hourly times. The middle forecast’s strongest gust is 36 km/h, Fri 2 a.m. Checked every six hours, so a brief peak can fall between.
How warm or cold will it be in Perth?
At the six-hourly times, the middle forecast runs from 10°C (Thu 2 a.m.) to 22°C (Fri 2 p.m.) GMT+8. The day’s real high and low can fall between those times.
Are any storms heading for Perth?
No storm Stormlines tracks has 1 in 10 forecasts passing its centre within 160 kilometres of Perth this week.

Chance of rain, six hours at a time

Tue 8 a.m.–2 p.m.: nearly all forecasts with measurable rain; middle forecast 0.8 mmTue 2–8 p.m.: 5 in 10 forecasts with measurable rain; middle forecast almost noneTue 8 p.m.–2 a.m.: 5 in 10 forecasts with measurable rain; middle forecast 0.3 mmWed 2–8 a.m.: 9 in 10 forecasts with measurable rain; middle forecast 0.5 mmWed 8 a.m.–2 p.m.: nearly all forecasts with measurable rain; middle forecast 2.0 mmWed 2–8 p.m.: 1 in 10 forecasts with measurable rain; middle forecast almost noneWed 8 p.m.–2 a.m.: fewer than 1 in 10 forecasts with measurable rain; middle forecast almost noneThu 2–8 a.m.: 1 in 10 forecasts with measurable rain; middle forecast almost noneThu 8 a.m.–2 p.m.: fewer than 1 in 10 forecasts with measurable rain; middle forecast almost noneThu 2–8 p.m.: fewer than 1 in 10 forecasts with measurable rain; middle forecast almost noneThu 8 p.m.–2 a.m.: fewer than 1 in 10 forecasts with measurable rain; middle forecast almost noneFri 2–8 a.m.: fewer than 1 in 10 forecasts with measurable rain; middle forecast almost noneFri 8 a.m.–2 p.m.: fewer than 1 in 10 forecasts with measurable rain; middle forecast almost noneFri 2–8 p.m.: 1 in 10 forecasts with measurable rain; middle forecast almost noneFri 8 p.m.–2 a.m.: fewer than 1 in 10 forecasts with measurable rain; middle forecast almost noneSat 2–8 a.m.: fewer than 1 in 10 forecasts with measurable rain; middle forecast almost noneSat 8 a.m.–2 p.m.: fewer than 1 in 10 forecasts with measurable rain; middle forecast almost noneSat 2–8 p.m.: fewer than 1 in 10 forecasts with measurable rain; middle forecast almost noneSat 8 p.m.–2 a.m.: fewer than 1 in 10 forecasts with measurable rain; middle forecast almost noneSun 2–8 a.m.: fewer than 1 in 10 forecasts with measurable rain; middle forecast almost noneSun 8 a.m.–2 p.m.: fewer than 1 in 10 forecasts with measurable rain; middle forecast almost noneSun 2–8 p.m.: fewer than 1 in 10 forecasts with measurable rain; middle forecast almost noneSun 8 p.m.–2 a.m.: fewer than 1 in 10 forecasts with measurable rain; middle forecast almost noneMon 2–8 a.m.: 3 in 10 forecasts with measurable rain; middle forecast almost noneMon 8 a.m.–2 p.m.: 7 in 10 forecasts with measurable rain; middle forecast 0.3 mmMon 2–8 p.m.: 4 in 10 forecasts with measurable rain; middle forecast almost noneMon 8 p.m.–2 a.m.: 2 in 10 forecasts with measurable rain; middle forecast almost none

Each bar is the share of the 31 forecasts with measurable rain or melted snow in that six hours; the darker the bar, the more forecasts agree. Local days, GMT+8.

The week, day by day

DayChance of rain2.5 mm or moreTotal by day’s endStrongest gustTemperature
Tue 29 (rest of day)nearly all<1 in 101.5 mm · <1 in 1021 km/h13°C–17°C
Wed 30nearly all3 in 104.2 mm · <1 in 1028 km/h12°C–17°C
Thu 11 in 10<1 in 104.4 mm · <1 in 1027 km/h10°C–19°C
Fri 21 in 10<1 in 104.4 mm · <1 in 1036 km/h11°C–22°C
Sat 3<1 in 10<1 in 104.4 mm · <1 in 1025 km/h12°C–22°C
Sun 4<1 in 10<1 in 104.4 mm · <1 in 1023 km/h13°C–19°C
Mon 57 in 101 in 105.4 mm · <1 in 1032 km/h13°C–18°C
Tue 6 (part)–––11 km/h12°C

Chances are the highest in any six hours of the day. “Total by day’s end” is the middle forecast’s running total since Tue 8 a.m., and the share of forecasts with 13 mm or more by then; totals aren’t added up day by day, because the middle forecast of each day isn’t the same forecast. Gusts and temperatures are read every six hours.

Storms near Perth

No storm Stormlines tracks has 1 in 10 forecasts passing its centre near Perth this week. Every storm we’re tracking →

About these numbers

They come from one source, NOAA’s Global Ensemble Forecast System (GEFS): 31 runs of the same model, each started slightly differently, read at Perth’s coordinates on a grid about 55 km (35 miles) apart. “8 in 10 forecasts” means 8 in 10 of those runs. Nothing is adjusted for local effects such as coasts, lakes, hills or city heat, so the numbers can differ from your local official forecast, especially for snow and showers.

“Measurable rain” counts rain or melted snow in a six-hour period. Not an official forecast: follow your national weather service for warnings and decisions. How the forecasts are read: how to read the maps and the glossary.

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