Happy Summer Solstice No Matter What Your Calendar Says

Well this week we have already exposed the "moon illusion" in the sky and now I have to warn you about the home calendar that has June 21st as the first day of summer. Many folks are confused by this and I even found 2 calendars today that have the first day of summer on June 21st, including one in the weather office! What do you believe? Well, you have to trust in me that this year June 20th is the first day of summer and not the 21st. Why all the confusion on the date this year? Well even though most of the time summer begins on June 21st, that is NOT the case during a leap year. Yes, you've got it. Since 2008 is a leap year summer begins today on June 20th at 7:59 p.m. I already have the pots and pans ready! This tradition of banging pots and pans on the solstice began when I was young in Hyattsville, Maryland on West Park Drive. I have carried it on to this day. Yes weather people can be strange and I am no exception. Now for some unusual facts you may not have thought about.

We have come a long way since our shortest day of last year which was December 22, 2007. We only had 9 hours and 17 minutes of daylight with a sunrise at 8:07 a.m. and a sunset at 5:24 p.m. Today we have a whopping 15 hours and 4 minutes of daylight with a sunrise at 6:17 a.m. and a sunset at 9:21 p.m. Now you know how I like to dig deeper for facts you might enjoy. If you add in the "nautical" twilight we receive this time of year we have over 17 and a half hours of daylight. Our nautical sunrise is at 5:02 a.m. and a nautical sunset will be at 10:37 p.m. What is nautical sunset? First we better distinguish between twilight, civil twilight, and nautical twilight. You better get an extra cup of coffee this morning for this.

Twilight: Before sunrise and again after sunset there there is natural light provided by the upper atmosphere, which does receive direct sunlight and reflects part of it toward the Earth's surface. Some outdoor activities may be conducted without artificial lighting. The major determinants of the amount of natural light during twilight are related of course to the local weather and state of the atmosphere.

Civil twilight: It is defined to begin in the morning, and to end in the evening when the center of the Sun is geometrically 6 degrees below the horizon. This is the limit at which twilight illumination is sufficient, under good weather conditions, for terrestrial objects to be clearly distinguished; at the beginning of morning civil twilight, or end of evening civil twilight, the horizon is clearly defined and the brightest stars are visible under good atmospheric conditions in the absence of moonlight or other illumination. In the morning before the beginning of civil twilight and in the evening after the end of civil twilight, artificial illumination is normally required to carry on ordinary outdoor activities. Complete darkness, however, ends sometime prior to the beginning of morning civil twilight and begins sometime after the end of evening civil twilight. Do you have all this?

Nautical twilight: is defined to begin in the morning, and to end in the evening, when the center of the sun is geometrically 12 degrees below the horizon. At the beginning or end of nautical twilight, under good atmospheric conditions and in the absence of other illumination, general outlines of ground objects may be distinguishable, but detailed outdoor operations are not possible, and the horizon is indistinct. So you see our nautical sunset time above is not until 10:37 p.m. I think Lafayette should be called the LAND OF THE MIDNIGHT SUN. :)

So enjoy the longest day of the year which will be the first Friday in 10 weeks that we should stay dry here in Lafayette. Now that I wrote this we are doomed. I did warn folks that you cannot totally rule out a pop up thunderstorm this time of year since the summer marks the heart of our thunderstorm season. Even last night we picked up a pop-up thunderstorm near Carmel. Now this weekend I do have a chance of thunderstorms in the forecast. But I am still optimistic about more man-made fireworks than nature's fireworks at the Taste of Tippecanoe. The main course should be full of great music and food with just a side-order of pulse thunderstorms, but no supercells are expected. I will be back to explain why and the difference between them. In the meantime, here is a little appetizer or two. The yellow-shaded areas are where you do not want to be at 6 p.m. on Saturday. Notice Lafayette looks pretty good!

The supercell index for Saturday at 9 p.m. looks even more promising as the bigger, stronger thunderstorms that develop in Illinois should drop into southern Indiana.
This is because most of your lift in the atmosphere will be where the hot scorching weather in the southwest meets clashes with cooler air and higher upper-level winds. You can see on the map below this would favor the areas of heaviest rain well to our south and southwest. It will be Missouri and southern Illinois and Indiana that will have the heavier rain.

So here at home we are looking good for the Fireworks show! Any thunderstorms we do have should not last long and not everybody will see rain. Do not cancel those plans, that is for sure. I will have your thunderstorm time-line coming up here shortly and talk about a type of thunderstorm a few of us will see this weekend that is much different than what we were used to in the Spring. Tune in to find out more. Have a great day!