H5 Clouds: Cirrostratus (Cs) increasing but below 45° elevation
Cirrostratus progressively invading the sky and generally becoming denser, but the continuous veil does not reach 45° above the horizon.
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Notes: The next four classifications (H5-H8) are of the same cloud type. The only difference is the amount of the celestial dome that is covered by the cloud, whether the cloud is increasing or decreasing across the sky, and must be the predominate high-level cloud. The reason is cirrostratus a good precursor of precipitation and if it is increasing then precipitation may occur within 12 to 24 hours.
For the H5 classification, the main characteristic is cirrostratus invading the sky progressively but with its continuous part still less than 45° above the horizon. Cirrostratus not completely covering the sky may be straight-edged and clear-cut. However it is more common to see an irregular border.
