Never have we seen a vertical rainbow

Is it an omen?   As a rainbow it must be good.   On the way home from work we were astounded to see near the setting sun a vertical rainbow.  The sky was blue with large long clouds reaching out like fingers beckoning to us and skudding across the sky as if to make an escape.  As they reached their end they would wisp upwards like meringue being whisked into peaks.  We've witnessed a great many aeroplane trails in the sky, both this morning and this evening.  The sunrise was so beautiful as it lifted itself over the mist laden paysage.

My internet research has led me to facts that I never knew before! This article is about photography.

Sunset Rainbows  are special for three reasons.
(1) The sun's rays are nearly horizontal, so the top of the rainbow will be high in the sky.   A sunset rainbow is the widest arc you'll ever see from the ground. Almost half of the full-circle rainbow can become visible....  This means the ends of the arc are nearly vertical as they intersect the horizon. Sometimes only the end segment of the rainbow appears, and if you see a photo of a vertical rainbow at the horizon, you'll know it was made at sunset (or sunrise). With a little geometry work and a sun angle chart, you can tell time using a rainbow at the horizon.

Ireland Sunset Rainbow near The Cliffs of Moher (photo by Shannon Field)

(2) At sunset, the sunlight contains more red hues and less blue (because of atmospheric scattering). This will affect the appearance of the rainbow by emphasizing the red bands and muting the blue bands. The same red tint will apply to anything on the ground illuminated by the sunset. The effect can be quite dramatic.
(3) If you're lucky, you can get a rainbow against sunset clouds. This phenomenon is gorgeous to behold, but photos seem to be few. Be sure to turn around next time you're photographing a sunset, and see if the sky behind holds anything interesting.

With grateful thanks to Photocentric