Sun halo appears on Grand Cayman

Grand Cayman residents and visitors were treated to a rather uncommon optical phenomenon known as a sun halo in the midday sky on Wednesday. 

The sun halo created a rainbow-like ring around the sun.  

Cayman Islands National Weather Service Meteorologist Kerry Powery said the phenomenon is caused by sunlight refracting through ice crystals in cirrostratus clouds in the upper atmosphere.  

“Cirrostratus clouds are composed of mostly ice crystals and the sun refracts through them in a way that is similar to light going through a prism,” he said. 

The phenomenon is uncommon, but not rare. Although Mr. Powery said he has only seen a sun halo similar to the one seen in Grand Cayman once before – in Barbados about 15 years ago – it’s been known to have happened here previously. 

“But not to the same extent where you could see the colours of the rainbow the way you can with this one,” he said.  

Sun halos are also known as 22˚halos or a sundogs. They occur every year in different places around the world. They can occur at any time of the year, but in this part of the world, they are more common in the fall, winter and spring when the northern jet stream moves south and pulls cold air from the Arctic.  

Because the halos are caused by ice crystals in cirrostratus clouds, which can signify the approach of a weather front, they can sometimes – but not always – mean that rain is coming within a few days. 

Mr. Powery said that there was a upper level trough to the west of Grand Cayman on Wednesday and southwesterly winds, but that “it would take a lot of variables to fall together” in order for Cayman to get any significant rain in the next couple of days. Officially, the National Weather Service only forecasts a 20 per cent chance of rain from today through Sunday. 

However, Cayman’s rainy season traditionally starts mid-to-late May, so significant rainfall will likely start over the next few weeks. 

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