September 21 Newsletter

The next SKYWARN meeting is 21-Sep @ 7:00 PM, the third Tuesday of the month.

Activation From Dave KCUVY
A brief activation was made on 13-Aug. Approximately 20 members responded to the 6:10 PM call. A storm cell coming in from the west fizzled out as it reached Steele County. Everyone was released at 7:10 PM.

SPX WX Radio Event
SPX in Owatonna offered employees an opportunity to purchase NOAA WX radios at a discount. Steele County SKYWARN volunteers and SPX employees worked together to program 196 radios. The radios were set up on 10-Aug and distributed on 12-Aug, just in time for the storms that night. SKYWARN members included Bill KDDJX, Bob R., Carl KDGVQ, Chris NCPG, Dave KCUVY, Deuel NSL, Marv NFJP, Mike KDDKC,Tim KDDKA, and Tom NUW. We appreciated working with Sharon Jacobson, Marcia Halverson, and a number of SPX employees making this a successful event. Several pictures taken from the event are included in the Archives.

Tornado Response Review
Steele Co. Community Awareness Emergency Response (CAER) is holding an after action review of the 17-Jun tornado event. The review is being held at 7:00PM on 15-Sep at the Community Center (SCFF fairgrounds). All responders, agencies, and local government officials involved in the response and recovery efforts are invited to attend. Contact Chris Gannon by 10-Sep if you wish to participate.

Tornado Summary From Various Sources
The National Weather Service in Chanhassen, MN posted a summary of the 17-Jun tornado events. The NWS reports that 24 of the 25 tornadoes reported within the Chanhassen forecast jurisdiction were videotaped. In total it appears that there were about 40 tornadoes statewide that day. This set the all time single day record for tornadoes in Minnesota. Todd Krause thinks 2010 will exceed the 2001 record of 74 Minnesota tornadoes.

It also appears that MN is now part of Tornado Alley for 2010. Minnesota leads the nation in the number of tornado touchdowns (122) this year. Texas is No. 2 with 87 tornadoes, followed by Kansas (80), Oklahoma (70), Colorado (62) and Wisconsin (59). If the pattern holds, this would be the first year in recorded history that Minnesota leads the nation in tornado touchdowns.

Corn and Humidity From MPR
Late August has turned resulted in some high humidity and air conditioning running. Farmers seem to hoping for a good crop resulting from favorable weather conditions most of the summer. Is there a connection? Corn is an efficient evaporator of soil moisture, and releases that moisture into the surrounding air. The MN State Climatology Office made some comparisons of dew points near corn fields. The brief experiment found dew points between 1 and 5 degrees F higher in the corn on a hot summer day when compared to nearby areas. The unknown is if the higher moisture levels significant enough to cause additional low level moisture to fuel thunderstorms and enhance rainfall.

Car Exhaust and Lightning From New Scientist
During the working week, air pollution rises because of all the vehicles on the road. This effect has been shown to modify rainfall patterns both at the weekend and during the week by creating stronger updrafts of air and bigger clouds. Research suggests weekday pollution can bring lightning as well as rain. Lightning strikes across the US are recorded by the ground-based National Lightning Detection Network. Lightning strikes increased with pollution by as much as 25 per cent during the working week in some locations. In the southeast, moist, muggy air creates low-lying clouds with plenty of space to rise and generate the charge needed for an afternoon thunderstorm. In the heart of big cities with high pollution, the effect is not as pronounced as in the suburbs and rural areas surrounding them.

Whirlwinds and Gustnadoes From USA Today
Small vortexes such as swirling sand and leaves indicate a whirlwind (when dust is picked up, it is called a dust devil). On a cold weather days, you can get whirlwinds as wind forms eddies as it moves around the corners of the building. On calm, sunny days, you can get whirlwinds at interfaces of various ground cover. For example, a pavement playground will heat up much more rapidly than a nearby grassy field. The air over the playground rises rapidly and the air from over the grassy surface moves toward the playground to take the place of the rising air. On occasion, gustnadoes (not technically tornadoes) form that are not attached to a parent thunderstorm. Waterspouts sometimes form from a towering cumulus cloud that may or may not be producing lightning and thunder.

Raindrop Speed From USA Today
When the Golden Knights jump from 12,500 feet, it typically takes 67 seconds for them to fall to 2,000 feet, at which point they deploy their parachutes. The final 2,000 feet is typically covered in 60 to 90 seconds. Raindrops falling on my head do not have the benefit of a parachute, so how long does it take a raindrop to hit the earth from 10,000 feet? A few assumptions are in order, such as how big the raindrop is and its terminal speed. An average-size raindrop is 1 to 2 millimeters in diameter with a terminal velocity of 18.5 feet per second. Unless there some other effect (down-draft, up-lift, wind, etc.), the math comes out to 540 seconds, or almost 9 minutes.

Also, note that falling raindrops are not shaped like typically shown tear drops. Average-sized raindrops tend to look like hamburger buns, as air resistance and surface tension serve to squish the bottom of the drop.

Colorful Skies From USA Today
Clouds can enhance a sunrise, but the clouds themselves are not responsible for the color of the light. In a cloud-free atmosphere, the setting or rising sun will appear to be more of a yellowish-orange compared to the yellowish-white of the midday sun. It is also less intense than the midday sun due to the greater amount of atmosphere it passes through on its way to your eye. Small particles in the atmosphere scatters out more of the blue end of the spectrum, enhancing the orange- and red-enhanced light seen by an observer.

Clouds act like mirrors. They are white when illuminated by white light and are red when they are illuminated by red light. When you put add clouds to the equation, the reddened hues from the sun not only reach your eyes directly, but are also reflected by clouds making for even prettier sunrises and sunsets. Stratospheric clouds resulting from volcanic eruptions (this was widely observed after the eruption of Mount Pinatubo in 1991) can produce absolutely breathtaking sunrises and sunsets.

Learn more about the colors of clouds:
- The Color of Sunrises and Sunsets

PBS Nova
There are many television shows and documentaries relating to storms and tornadoes. PBS has a collection of on-line information that might be of interest.

Term For The Month From Various Sources
Indian Summer
"Indian Summer" is a name dating back to the 18th century. It is generally means a period of sunny, warm weather in autumn, not long before winter. Some references also note that "Indian Summer" does not occur until after the first frost. Because there may not be a warm period after a hard frost, "Indian Summer" may not occur every year, but could also occur multiple times in one year. On the other hand, "Indian Summer" in some parts of the southeast describes the hottest time of the year.

Copyright 2010
All Rights Reserved
Steele County SKYWARN
Owatonna, MN