Rainbow to the West

My mother sent me this picture this morning. It's not often you see a rainbow to the west!

A radar image at 13:05 UTC

Double Rainbow

Photo Credit: to Kylee Thurston. Thanks for the amazing picture!

Double Rainbow in Spanish Fork as seen from near the 1-15/US-6 interchange

Gusty winds in Provo Right Now!

Wow! Look at the 52 mph wind gust on BYU campus! I can confirm that observation. My apartment is only a few blocks south of the Eyring Science Center. The trees were bending quite a bit, and a group of those college kids in the parking lot out back were using bed sheets as sails for their skateboards. Also in

The radar showed some widespread rain, and we had a rainbow to prove it was raining, but there were only a few drops on my window.

Short Rainbow

Double rainbow spotted in Springville, Utah on June 11, 2015

This rainbow looks rather short. Why is this?
Rainbows would actually be complete circles if the light were not intercepted by the earth surface (maybe you've seen complete circle rainbows when you look at the sprinklers that water your lawn). The center of the rainbow circle is in the line of sight between the sun at your back and your eye. Rainbows will look short if the sun is high in the sky because more of the rainbow light is intercepted by the surface. When the sun is low in the sky less of the rainbow light is intercepted by the ground and you see more of the full rainbow.

An attempt to illustrate this phenomenon is shown:

Short Rainbow

Tall Rainbow

Summer Storms and Rainbows

Summer thunderstorms are always the highlight of this time of year. We have had a lot of moisture this last week. Even though the season is turning into fall the sun is still strong enough to kick-start some afternoon thunderstorms. Yesterday's storm was exciting. I was sitting inside when all of a sudden the winds picked up around 7:00 PM (19:00). This was a gust front associated with a thunderstorm that had just passed through Payson. (Maybe someday I'll write about gust fronts). The winds settled down a little bit and we had a brief downpour of rain--about a quarter of an inch. There was some lightning and thunder, too. While this was a fun to watch, it got rather chilly very quick. You can see in the charts below that the temperature following the gust front decreased quickly--about 20 degrees in 20 minutes.

Here is a link to my weather station during this time: Link. (For current conditions click "current conditions" on the right side panel.)

Today's storm was a little calmer. There was even a beautiful rainbow in the backyard. Looking a little closer, I saw two rainbows!

(c) BKB

(b) BKB

The brightest rainbow is the "primary bow." Rainbows are caused by light being refracted and reflected in raindrops. Sunlight looks white, but it actually consists of all the wavelengths of light. When that light travels through a water droplet, the different wavelengths of light are separated. When thousands of water droplets refract the light, we see a rainbow. The inside of the primary bow is always violet. As you move outward the colors go as followed: indigo, blue, green, yellow, orange, and red on the outside.

(c) BKB

The second bow is called, (you guessed it) the "secondary bow." The colors in the secondary bow are reversed, with red on the inside and violet on the outside. This is because this bow is caused by a double reflection inside the drop. You may have notice that the colors are more faint. This is because not all the light is reflected off the water droplet. For each reflection, some light passes through and never reaches your eye. The double reflection for the secondary bow thus looses more light than a single reflection.