Effective as of 4:00 AM Tuesday April 20 2021
Explanatory notes:
As at 4 AM, Himawari-8 Night Microphysics imagery shows stratus to the east of the hills and there is also smoke haze from prescribed burning lying over the region and aloft. The smoke haze is expected to ease later in the morning with the dissipation of the nocturnal inversion, increased vertical mixing and easterly winds strengthening, however, depending on prescribed burning activities, smoke aloft remains possible. Further smoke haze with visibility reductions possible from this evening and overnight if there are prescribed burns to the southeast with a southeasterly gradient flow and the nocturnal inversion once again developing.
The stratus possibly extends to the metropolitan area in the morning spilling over the Darling Scarp becoming stratocumulus clouds from later in the morning and into the afternoon. Also the slight chance mist and fog (or smog) early today especially over areas with cold air drainage given moist low level air with smoke particles also acting as condensation nuclei, if winds remain sufficiently light under the nocturnal inversion and if radiational cooling isn't too restricted by the smoke aloft and stratus.
The subtropical high pressure ridge strengthens to the south leading to a somewhat easterly gradient flow from Wednesday.
The west coast trough likely deepens off the coast from Thursday with warm air advection. Another upper level trough approaches from the west leading to some high and middle level clouds but conditions are expected to be dry. Warm to hot with the warm air advection and the hot air mass over the region but the decreasing solar insolation as autumn progressing is certainly having its impact.
Possible smoke haze at times depending on prescribed burning activities, air quality and visibility reductions most likely overnight and in the mornings with the nocturnal inversion, most likely until Thursday with the gradient flow shifting to become a more northerly direction from Friday, smoke haze still possible if there are prescribed burns to the north.
The west coast trough likely moves inland at the end of the forecast period with the subtropical ridge lying just slightly north leading to moist onshore flow from Monday afternoon but still some uncertainty this far out.
Tuesday April 20:
City:
12-25 Degrees Celsius
Partly cloudy.Early smoke haze.
Chance of any rain:0%
Amount:Nil.
Perth Metropolitan Area:
Partly cloudy.Smoke haze early then easing from later in the morning.Winds east-southeasterly at 10-20 km/h tending south-southwesterly at 15-30 km/h in the afternoon.
Wednesday April 21:
City:
13-25 Degrees Celsius
Mostly sunny.
Chance of any rain:0%
Amount:Nil.
Perth Metropolitan Area:
Mostly sunny.Possible smoke aloft depending on prescribed burning activites.Winds east-southeasterly at 10-20 km/h.
Thursday April 22:
City:
13-27 Degrees Celsius
Partly cloudy.
Chance of any rain:0%
Amount:Nil.
Perth Metropolitan Area:
Partly cloudy.High clouds.Possible smoke aloft depending on prescribed burning activites.Winds easterly at 15-25 km/h tending southeasterly in the late afternoon and evening.
Friday April 23:
City:
14-29 Degrees Celsius
Partly cloudy.
Chance of any rain:0%
Amount:Nil.
Perth Metropolitan Area:
Partly cloudy.Winds east-northeasterly at 15-25 km/h becoming light from afternoon.
Saturday April 24:
City:
16-31 Degrees Celsius
Partly cloudy.
Chance of any rain:0%
Amount:Nil.
Perth Metropolitan Area:
Partly cloudy.Winds northeasterly at 15-25 km/h becoming light during the afternoon.
Sunday April 25:
City:
15-31 Degrees Celsius
Partly cloudy.
Chance of any rain:0%
Amount:Nil.
Perth Metropolitan Area:
Partly cloudy.Winds northeasterly at 15-25 km/h becoming light during the afternoon.
Monday April 26:
City:
17-31 Degrees Celsius
Partly cloudy.
Chance of any rain:5%
Amount:Nil.
Perth Metropolitan Area:
Partly cloudy.Winds northeasterly at 15-25 km/h shifting northwesterly later during the day.
Charts:
Figure 1.Surface synoptic chart.Image courtesy of the Australian Bureau of Meteorology(BOM).
2.
Figure 2.Key features identified on True Colour RGB satellite image.Satellite image courtesy of the Japanese Meteorological Agency(JMA).
Figure 4:Surface synoptic prognosis.Image courtesy of the Australian Bureau of Meteorology(BOM).
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