The next SKYWARN meeting is 15-Jul @ 7:00 PM, the third Tuesday of the month.
About 27 members attended the 17-Jun meeting. Topics discussed included:
- The table top exercise planned for the June meeting is delayed until July.
- The Owatonna Peoples Press wants to do a "ride-along" with a spotter during an activation.
- Bumper stickers and magnetic signs are available through Dave KCØUVY. Clothing items availble through Court Sports.
- Marv NØFJP provided a summary of Automatic Position Reporting System (APRS) and how it could help during an activation.
- Some spotters questioned why an activation notifcation did not go out on 11-Jun. There were several reasons, but one of the needs is to update the City Watch list to makethe calls. Chris G offered to help get the list updated.
- New Speedtech Skymate windmeters were purchased by a grant through CERT. A plan needs to be establishede for the storage and use. Spotters wishing to have their own can buy them from Cabelas for under $100.
- Dale WBØPKG showed off his home made anemometer. A demonstration by Dave KCØUVY is captured at below left. The
plans can be downloaded.
- Dave KCØUVY shared his experience chasing storms on 07-Jun through IA. One of his pictures of a wall cloud is below right.
- Marv NØFJP shared his chasing experience on 11-Jun before the storm system hit Steele County.
Steele Coutny SKYWARN was activated on Wed, 11-Jun. Steele County was in a Tornado Watch area as cells as high as 45K approached with some midlevel rotation. This system produced numerous tornados in IA earlier in the day. Dale WBØPKG activated the EOC around 8:30p and Craig A. began making phone calls. Four people staffed the EOC with 9 spotters in the field and 3 staffing the EOC.
From Minnesota WeatherTalk
In the April Newsletter, we discussed the difference between the equinox and equilux. the summer solstice is the longest day of the year and occurs around 22-Jun each year. How long the day is depends on where you are at. Along the northern most shore of Lake of the Woods daylength on the summer solstice can be about 16 hours and 20 minutes. Along the Iowa border it will be around 15 hours and 25 minutes, a difference of 55 minutes.
Highs and Lows
From USA Today
Water pressure is higher at the bottom of the ocean than at the surface. Since air molecules have mass, the force (Weight) of the air molecules is higher at the bottom of the pile than at the top. The weight of all of those air molecules compress the air near the earth. Air pressure is the actual force of air molecules spreading across the earth. The question arises on how the different zones of high pressure and low pressure come about. This graphic helps show how converging and diverging winds can cause the development of high and low pressure areas.
Light vs. Sound
Because light is an electromagnetic wave it travels at the speed of light in the vacuum of space. Sound waves, however, need a medium in which to travel and typically weaken with distance. Just as the human voice has its limits, sound waves from thunder can be dampened by the atmosphere. The typical range of thunder is about 15 miles. The distance to lightning can be estimated by counting one mile for each five seconds between a lightning flash and the sound of thunder.
From Minnesota WeatherTalk
Maximum temperature values of 100 degrees F or greater are rare in the Twin Cities anyway. They occur historically only once every 3-4 years in the Twin Cities. The last occurrence we had was July 31, 2006 (101 degrees F at MSP), and the last summer with multiple occurrences was 1988. The frequency of days with 90 degrees F or higher in the Twin Cities is trending downward. In the early and middle part of the 20th Century it was about 20 days per year. In the most recent 30 years of record it is only about 13 days per year.
Hot Air Balloon Research
From Science Daily
Three hot-air balloons dropped asphalt shingles, lumber, sticks, leaves and pine needles onto a north Alabama landfill. Similar to the types of debris thrown into the air by tornados that touch the ground, scientists hope the resulting Doppler radar data can be used to recognize tornado debris. If computers can be programmed to recognize debris in the radar data, it could add a level of urgency and precision to warnings when tornadoes do occur.
Clouds form when air is cooled to its dewpoint or the temperature it reaches saturation. Air can reach saturation in a number of ways. The most common way is through lifting. As a bubble or parcel of air rises it moves into an area of lower pressure (pressure decreases with height). As this occurs the parcel expands, which takes heat away from the parcel. So as air rises it cools. Since cold air can hold less water vapor than warm air, some of the vapor will condense onto tiny clay and salt particles called condensation nuclei. The reverse is also true. As air sinks it encounters increasing pressure so it is squeezed inward, adding heat to the parcel so it warms as it sinks. Warm air can hold more water vapor than cold air, so clouds tend to evaporate as air sinks.
Parkersburg, IA Tornado Fallout
From KAAL TV
Strange things fell from the sky in Prairie Du Chien, WI hours after the tornado that struck northeast Iowa in late May. It was debris from Parkersburg, about 125 miles away. The local police department was collecting pictures, checks that contain personal account information, and things like pages from a yearbook. The items were returned to officials in Parkersburg so residents could claim them.
Midland WR-100 Programming
During the WX Radio programming events, a question was asked about the connector jack labeled "PC" on the back of the radio. Midland advises the jack is for factory use only to load the operating software and trouble shooting.
On a related note, the Marquette, MI NWS web site discusses reception of NWS broadcasts. It also includes a description on several types of external antennas that can be made and used.
From Popular Mechanics
America's current system for detecting tornadoes—about 120 Next Generation Radar, or NEXRAD, devices tracking a storm's direction and velocity—has been the backbone of weather prediction since the early 1990s. The radars are tilted upward from the Earth half a degree. When you look 40 or 50 miles out, radar beams are more than one-half mile high, missing the bottom third of the troposphere where severe weather often begins to form. A complete NEXRAD scan takes 5 to 6 minutes to complete.
The Collaborative Adaptive Sensing of the Atmosphere (CASA) network could be in place by 2013. CASA radars are gap-filling radars set up to probe nearby clouds in areas where the NEXRAD radars don't see. Completing a scan in 1 minute, the information is transmitted through a system dubbed Distributed Collaborative Adaptive Sensing (DCAS). The first testbed is a network of four nodes in the middle of Tornado Alley in southwestern Oklahoma, along with other sites in Houston and Mayaguez, Puerto Rico.
Astronomy Picture of the Day
For those with an interest in astronomy, check out the Astronomy Picture of the Day. Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer. The archive has pictures dating back to June, 1995. The folks behind it estimate they've served up over 100 million space-related photos since that mid-1990s start.
How High Is that Cloud?
Mention has been made many times about the inability of the Chanhassen radar to see activity at lower altitudes in Steele County. If you want to get a feel for how high is up, look at the commercial aircraft flying north to the Minnapolis-St. Paul airport. Commercial aircraft often pass over Steele County, depending on the landing patterns being used. On typical flights, commercial aircraft fly at over 30,000 feet and start descending about Waterloo, IA and crosses into MN around 25,000 feet. As the planes continues to descend over Steele County for landing at MSP, the typical altitude is 10,000 feet to 15,000 feet.
Word For The Month
From Minnesota WeatherTalk
An HP Supercell is a high-precipitation supercell thunderstorm where the intense precipitation and often times shafts of hail obscure the view of storm spotters who are looking for rotation to visually identify tornadoes. Unlike most classic supercells, the region of rotation in many HP storms develops in the front-flank region of the storm (i.e., usually in the eastern portion). HP storms more often produce extreme and prolonged straight-line wind events, serious flash flooding, and very large damaging hail events.