Moon Monday Night

I received several emails this morning regarding the moon and the 'strange ring' around it Monday night.  I didn't get a chance to see it for myself as I was sound asleep once night came, but what you saw was a moon dog - otherwise known as a halo around the moon.  Have you ever heard of a sundog?  It's the same principle.  Let me explain...

If you looked overhead yesterday afternoon you may have noticed a cloud shield moving in from the east.  That was actually from Sandy which at the time was still out in the Atlantic Ocean!  These higher altitude clouds, known as cirrus/cirrostratus clouds, can extend well out in advance of an approaching storm system and despite them covering up the entire sky are often times transparent.   Cirrus clouds are made up of thousands of tiny ice crystals because they form at a height that is well below freezing.  The 'halo' is formed by the refraction, or splitting of light, and also by reflection from the light of the moon.  Now, the ice crystals have to be positioned just right with respect to eye in order to be able to see the halo but when you do it's a pretty neat phenomenon. 

There's an old weather saying, "Ring around the moon means rain soon".  There is actually some truth behind this because cirrus clouds can form a couple days in advance of an approaching warm front because the air ahead of the front is lifted at a slower rate than air ahead of a cold front allowing the cirrus clouds to form.