Further Considerations

  • Observers are advised to wear polarising sunglasses while performing observation during the day. This will increase the accuracy of the observation and reduce the potential for eye damage. Sunglasses make the observation of clouds easier, as well as minimising the dazzling effect of bright sunshine. As well very thin clouds are often invisible against a bright blue sky or a haze, except when viewed with such glasses.

  • At night, a viewing point well away from lights is essential, and the eyes must be given sufficient time to adapt to the darkness. This varies with Observers and circumstances, but it may take 5 minutes or longer to obtain adequate night vision for cloud observations.

  • Because of the continual evolution clouds go through it is necessary to keep an almost continuous watch on the sky. "Difficult" clouds can often be identified by recalling their recent history, during which they may have passed through a more easily recognisable phase. The greater difficulties in cloud observations are usually experienced when an observation is made having no knowledge of previous conditions.

  • Always observe the whole sky. Weather phenomena and their associated cloud could be in only one part of the sky such as a thunderstorm east of the aerodrome or conversely, stratus could be obscuring higher stratocumulus if you only look at part of the sky.

  • Before sunset, the Observer should spend a brief period studying and examining the existing cloud structure of the sky. This will assist considerably in the recognition of clouds after sunset. The clouds will not usually undergo significant change after sunset (unless a frontal system is approaching), however cumulus clouds tend to dissipate at sunset, as generally they require daytime heating to form and be maintained.

  • The first observation after sunrise may require revision of cloud heights, amount and types.