Weather Halo draws Saint John eyes skyward

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God set the rainbow in the sky following the flood, according to the Book of Genesis.

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Cindy Wilson/Telegraph-Journal

A rare halo around the sun with the Cathedral of the Immaculate Conception in the foreground. The halo is formed by ice crystals refracting sunlight.

A circle around the sun, like the one over Saint John for the past couple of days, usually signifies a storm coming, according to common weather lore.

Except that, in this case, the halo has more to do with rain on its way to Newfoundland, according Environment Canada meteorologist Claude Côté in Fredericton.

Ice crystals in cirrus or cirrostratus clouds cause both halos and "sun dogs," says Environment Canada senior climatologist David Phillips in Toronto.

These thin clouds high in the atmosphere veil the sun. The sun shines through like a lamp through a sheer curtain, but the ice crystals refract the light - bending the rays just like in a high school science experiment with a prism.

If the crystals are aligned in one direction, the refracted light will form sun dogs on either side of the yellow orb. These are sometimes called false suns, Phillips said.

With the ice crystals not in any particular formation, the light bends in a diffuse way to form a big circle, sometimes with rainbow-like colours around the outside edge - such as happened over Saint John this week.

"It's called a halo around the sun "¦ it's often a very good sign of getting some precipitation," Phillips said.

However, Environment Canada does not forecast rain on New Brunswick until the weekend.

These clouds, possibly 10 kilometres above the earth, travel on the jetstream, Côté said, usually coming ahead of a weather disturbance.

Generally, a halo or sun dog gives 24 hours or less warning of bad weather coming; this time, however, the disturbance was 120 kilometres south of Halifax on Tuesday afternoon, headed for Newfoundland, said Côté.

"It's a sign that there's going to be weather somewhere," Phillips said.

However, the St. John River will get a couple of days to spill more floodwater into the Bay of Fundy before we get more rain.

In past ages people paid attention to the sky, Phillips said. Farmers, fishermen and sailors with no Environment Canada weather forecasts depended on these signs.

"A halo around the sun or moon will bring rain upon you soon," according to one bit of folklore cited by Phillips. Or, "When the sun is in its house, it will rain soon.-The bigger and brighter the ring, the nearer the wet.-The circle of the moon never filled a pond, but a circle of a sun wets a shepherd."

Halos do not often make a complete ring around the sun that people can see, which makes the one over Saint John a rarity - if it is still there today. Côté could not see the halo in Fredericton.