The Weather Expert

A rainbow around the sun?

     Did you see it?  Well it wasn't exactly a rainbow but rather a halo. A 22 degree halo to be precise.  It is a fairly common occurance but it is not always so bright. Ice crystals are the cause.  They are what make up the high, thin cirrus clouds we often see.  As these ice crystals slowly fall, they align themselves like tiny prisms that break the white light from the sun into the colors of the spectrum.

     In many parts of the country this can often mean that rain or snow is headed your way but it is so dry in the west that more often than not, there is no impending storm.

     You will find this halo around the sun usually in the middle part of the day when the sun is high in the sky.  The angle formed from the sun to you to the outer edge of the halo is 22 and a half degrees.  Read more about halos here. 

     Thanks to Maria Thompson and David Gaskill for sending photos of the halo on Saturday, 5/16.  If you have halo photos or any other interesting weather photos, please email them to me at sdorval@todays6.com .

A spectacular site

     As I returned from dinner this evening I saw a bright rainbow in the eastern sky.   In fact it was a double rainbow.  Every time I see one it reminds me of a meteorology proffessor I knew at Penn State University.  He would look at the weather charts and determine whether or not the next day would be a good day for "rainbow chasing".  While that was a bit too crazy for me, I understand what he was looking for in the depths of those weather charts.

     In a nutshell rainbows are formed when sunlight passing through raindrops is spread into the colors of the spectrum. So if you want to find one you need raindrops and sunshine at the same time. This type of weather is not very common but it does happen from time to time.  If you have those two elements be sure to look for your rainbow in the opposite direction from the sun.

     They are always a great photo op because the light from the typically setting or sometimes rising sun is very soft and is reflected very nicely from the rain clouds above.

     Did you know that the higher the sun is in the sky, the lower the arc of the bow?  It is more rare to see a midday rainbow but if you do it will be a much lower arc.

     I hope you had a chance to see this brilliant spectacle of nature.  If you were able to shoot some pictures, feel free to send them to me and I may show them on the air.

El Nino or La Nina - What's good for Idaho?

     If you had asked me what the long range forecast for the winter was going to be when I became a meteorologist in 1986, I would have given you my standard answer that would included a nebulous explanation of why a dart board was necessary for my forecast.  Well, the past twenty-one years have brought a great many changes to the complex world of weather prediction.

     So now you want to know if you should bother getting a ski pass for next winter! Well instead of dusting off the "not so trusty" dart board I can turn my attention to the Pacific ocean where once thought to be consistent trade winds are actually deciding whether or not to bless Idaho with a heavy blanket of white gold this winter.

     While that seems far fetched, the truth is in the numbers. Take a look at this graph of Snow Water Content (SWE) from Mores Creek Summit over the last few years. The green line represents what a "normal" year looks like. About 35" of water content in the snow pack before the spring melt.  Skiers will not only fork over the cash for a season pass in year like 2005-06 (represented by the blue curve peaking at 43" SWE) but they may be able to justify new skis at the annual swap.  Unfortunately, this past year is illustrated by the black line... only 25" of water content.

     We used to think it there was no rhyme or reason to which years got more snow and which were precipitation challenged. Now we know that just a subtle pressure change in the Pacific Ocean in July can have dramatic effects in the amount of snow that will blanket Idaho's mountains that winter.  Both 2004-05(in red) and this past year were El Nino years. Not a welcomed visitor for ski areas or farmers.

     Over the next few months, scientists will study the pressure and wind changes in the central Pacific.  The current forecast is for the typical easterlies to continue which will allow a large pool of cooler than average waters in the eastern Pacific to develop.  This usually means above average snow for Idaho's mountains.

     So if you were disappointed in the winter snow pack of 2006-07 don't despair, a much welcomed La Nina could be just what the doctor ordered for 2007-08...stay tuned.

Questions from Kids

     Today I had the chance to speak to thousands of kids across the state.  I was a guest on Dialogue For Kids on PBS. This is a monthly show in which schools throughout the state can interactively participate. Children in Kindergarten through 6th grade were able to ask weather questions via email or a phone call in this afternoon. The half-hour show is available online on the Idaho Public Television website.

Weather Facts

     If YOU have any weather related questions, feel free to ask.