Understanding lake conditions
1. Sea breeze
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At the lake a sea breeze may develop on a warm/hot day, particularly when there is a clear sky over the inland. It usually leads to a steady wind for sailing, because the wind from the sea is not disturbed.
The course for racing can be set in the middle of the lake, taking care not to set the gybe mark or layline below the red marker.
2. Westerlies
Winds from NNW to SSW usually result in very gusty and shifty conditions, because wind from the land is disturbed by hills etc..
The course for racing should be set far to the east, because the western area of the lake will be in the lee from the land with often no wind.
3. Thunderstorms
This one is easy: If you hear thunder get off the water!
Don't wait for the race management to abandon the race, don't just beat the boat in front and don't just finish this leg. Don't get caught on the water in a thunderstorm.
Lightning can strike several kilometres away from storm clouds (see "A bolt from the blue").
There are other days to enjoy sailing.
4. Highs and Lows
The image shows a low between K'gari (Fraser Island) and New Caledonia, and a high between Australia and New Zealand in January 2022.
Air rises under a low, decreasing the pressure near the surface of the earth. Air is pushed downwards under a high, increasing the pressure near the surface.
Fair weather can be expected with a high (happy weather) and rain with a low (lousy weather).
Near the earth's surface air moves into the low, gets deflected left in the Southern Hemishphere (see Coriolis effect), resulting in clockwise wind (e.g. cyclones). It moves outwards from the high, left deflection, resulting in counter clockwise wind.
5. Radar Chaff
A strange looking radar image may be chaff.