Rare "Storm Warning" for WA Coast - Perth

Perth forecast for the 24th of May, 2020
It's not often that we see so many "brown"* arrows in a forecast. Whilst us weather junkies and extreme weather lovers will follow this with great interest, it's also time to be aware of the damage this storm will bring.
Be Prepared!
Tie down loose items in your yard.
Have a torch. Charge your devices.
Be prepared for power outages.
2020-05-24 - Perth WA Storm Forecast
2020-05-24 - Perth WA Storm Forecast

The BoM have issued a "Storm Force" warning for the WA Coast today; a very rare weather event. Tonight Perth will be in the grips of a major storm the likes we haven't seen for some time.

"Storm" doesn't just mean thunder and lightning, in meteorology each word has an exact definition. And when you see a "Storm" warning, it's serious business - damaging winds are on the way.

The table below shows the potential gust you could expect for different forecast average wind speeds and associated wind warning category.

Average wind speed (knots) Gust strength that should be planned for (knots) Wind Warning thresholds
10 14
15 21
20 28
26 36 Strong wind warning issued
34 48 Gale force warning issued
48 67 Storm force warning issued
64 90 Hurricane force warning issued

Clearly, we are talking average wind of 48 knots (90Kmh) and gusts of 67 knots. Akin to the driving your house down the freeway and speeding - 120+ kmh. There are going to be lots of powerful wind bullets.

Add to these damaging winds, is the timing of the passage of this storm. The strongest winds arrive during the the night; emergency crews won't be getting much sleep, and no doubt, are already in a state of preparation for the inevitable damage. Trees down, power lost.

WA and Perth residents should be in a state of preparation: charge all your devices, know where a torch is, know where some warm clothes are. Secure loose items in your yard. Anything not tied down can become a projectile.

A quick synoptic chart primer / technical dive for those interested:

Synoptic Charts.
1) Simple idea #1: Wind blows in the direction of the lines ("Isobars")
2) Simple idea #2: The closer the lines are, the stronger the wind
The "Isobars" join areas of equal pressure.
Pressure is measured in "Pascals", much like Weight is in "Grams"
The charts use "Hecto" pascals - Hecto means "100x", much like "Kilo" means "1000x"
Thus the number 1031 on the chart means "1031 Hectopascals" or "hPa"
(Hecto means "100", much like "Kilo" in Kilogram means "1000")
Perhaps you can see the centre of the storm is 991 hPa., while the calm "H" area is 1031 hPa.
This is where you can use the "hPa" graph on the PERTH LIVE WEATHER page - using the current live hPa reading on the Pressure chart will give you an indication of where we are in the transition of the storm.
Tropical Low and Cold Front combine for a powerful weather event

* The Brown Arrows:

10 or so years ago, whilst chatting over a few beers, we were discussing the red/yellow/green arrows, and came up with the idea brown arrows for Gale force winds.

As a kitesurfer/windsurfer, these are really exciting winds to be out in, and can be a lot of fun. But .. there are times when just maybe, things get a ittle (or a lot) out of control - a gust is a bit stronger than you expected, and your heart rate rises, adrenaline kicks in, and you're fearing for your safety. Which in these sports, can be half the fun.

And thus the "brown" arrows and the term "smelly shorts weather" were coined, to indicate powerful winds they might make you .. well .. fill your dacks. :-)