Air Density and the Worm

The Earlybird and the Worm

During winter blankets are appealing, early morning tickles the bones and it’s easy to get lazy than to push boundaries.
Southerly winds commonly blow of a morning, with accompanying blue skies and a visible warm sun.
If sitting outside just after sunrise there’s a noticeable fight in full swing. Cool air, cool earth in one corner and warm sun rays in the other – these hit the earth with the intention of warming. One side of our face feels cool, the other side toasty as the heat and dry air works on our skin.
It’s quite a contrast, yet in the blink of an eye by mid-morning a transformation occurrs and the fight is over.
The cool vanishes and in typical Qld style we take jackets off and enjoy the temperature rise.

Have you ever sat early morning and watched the wind blow through the trees on a hill top but not down low where air is coolest? Picture it, tree tops moving on the hill, birds down low bouncing between branches in a quiet, windless backyard or gully.

The air eventually heats up in these low pockets, but it may take a few hours. Did you know the sun doesn’t heat the air, but the sun must first heat the earth which reflects heat upward that heats the air?
Once the lower air is warmed it becomes less dense and therefore more moveable and the upper level winds ( in this case, Southerly) that have been blowing for hours can now move, drag, pull, shift the warmer air nearer the earth—— and so begins the daily wind down low. Stability, gone.
Watch for it daily ( in fair weather forecasts) as an exercise in training……. and through this understand how we need to sync with these stability windows while they’re in play.

The earlybird gets the worm….

(Today’s low level wind just hit the backyard now at 8:32am and instantly went from 1 to 10 knots. It’ll blow 15 knots within the next half hour.)

Update 8:55am – 17 knots, Southerly. Yuck!

(The ome image included  was taken at 7.26am)

Notes
• By utilising senses and high awareness it’s common to identify the calm, serene stable periods via the crisp sounds from animals (birds) and the distance they can be heard as the wind isn’t drowning the soundwaves, plus sound travels better through dense air.

• Also, on calm days or nights distant sounds will be more likely heard from the direction the higher level winds are travelling from. For example on a calm morning with a southerly wind that yet hasn’t reached low level, sounds from the south will rumble on the horizon, such as an airport or industrial humm. This tells you what’s happening without even leaving your backyard or lifting your head……

• Offshore, the southerly is probably blowing at sea level because there’s no land to cool down overnight and the warm sea has held temperature better and the air density at sea level allows the free flow of air.

• So, yes it’s a common thing to be in a 15knot southerly on a mackerel ground while another fella is fishing a stability window in a creek or harbour and hooking chunky barra……..at the exact same moment in time.

These skills are sharpened through observation and awareness. Even during most 25kn SE wind events the winds are typically lighter just before dawn….

Johnny Mitchell

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