July 212 Newsletter

The next SKYWARN meeting is 17-Jul @ 6:30 PM, the third Tuesday of the month.

Note the time change for the 17-Jul SKYWARN meeting.

800MHz Radio Training
Kevin Sedivy of the Owatonna Fire Department will provide a 800 Mhz radio training class for our volunteers on Tuesday, 17-Jul @ 7PM. This is the regularly scheduled meeting time for SKYWARN. All volunteers including those from CERT, SKYWARN, and Amateur Radio are encouraged to attend the event so that we can train as many volunteers as possible.

Volunteers are required to complete online training prior to the 17-Jul training session. The four courses should take a total of a couple of hours to complete. The material covers the ARMER radio system and interoperability. Print out a copy of your completion certificate after completing each module. Bring the certificates to the training session as proof of the completed training. Instructions to access the online training can be downloaded here.

MN Scanner Law
A recent local incident serves as a reminder for all about the "MN Scanner Law". Basically, it is illegal to have any radio equipment in your motor vehicle capable of receiving "any police emergency frequency". Amateur Radio operators have an exemption, but "shall present the license to a peace officer on request". One interpretation of the law is that if someone without an Amateur Radio license might be issued a ticket while operating your vehicle with a radio installed. Keep a copy of your Amateur Radio license readilly available while operating your motor vehicle.

Full Thunder Moon From Multiple Sources
The full moon in July is often referred to as the Full Thunder Moon. Other names may include Full Buck Moon and Full Hay Moon. The reference to thunder references the quantity of the noisy weather element. Full Buck Moon indicates the time of year when the buck deer's antlers grow.

The moon has a special day on 20-Jul, the anniversary when humans first walked on the moon in 1969.

Weather Image Age From Multiple Sources
During SKYWARN Spotter training, mention is made that it takes five minutes for the data for a NEXRAD image to be collected and displayed. We always need to remember the NEXRAD image is at least five minutes old. It may not be obvious the image may not contain new information from each ground site each time the image is updated.

Federal Aviation Administration (FAA) investigations of a couple of weather related accidents suggest the image delay may have been a contributing factor. A FAA Safety Alert reminds pilots that NEXRAD imagery tells what the weather WAS. The actual weather conditions could be up to 15 to 20 minutes OLDER than the age indicated on the display.

Dual Polarization Radar
The February Newsletter provided a story about the upgrade of NWS radar to dual polarization. The NWS posted a YouTube video explaining a little more about what the benefits will be. It is a fun video that spoofs some television advertisements.

Cloud Weight From Multiple Sources
How much a cloud weighs is a heavy calculation. It is based on a variety of things, such as how big is the cloud and the humidity in the cloud. The amlunt of moisture in the cloud is based on the temperature and altitude (pressure). Updraft winds may overcome gravity and hold moisture in the cloud. Dry air has a density of about 0.0628/cubic feet (lb/ft3) and the density of the actual cloud droplets is about 0.0626 lb/ft3. If a cloud happens to have a volume of 1 cubic kilometer, the moisture in the cloud would be over 2 billion pounds.

One estimate of the volume of water in the atmosphere at any one time is about 3,100 cubic miles. This would cover the ground to a depth 1 inch if it all fell down at once.

Energy Stealing Wind Turbines? From Multiple Sources
Wind turbines are routinely touted as being a renewable energy source. Some researchers claim converting wind energy to electrical energy affects how much energy can be harvested from the sun. Only a fraction of the solar energy reaching Earth can be exploited to generate usable energy. Some of the solar energy drives the winds and ocean currents. Most of the remaining solar energy is dissipated as heat. The concern is if the conversion of wind energy into useful (e.g .electrical) energy could outpace the ability of solar energy from the sun to replenish the winds.

Energy Balance From Multiple Sources
As the effects of global warming are studied, new theories are developed. One effect of climate chnage is an increase in rainfall. One new theory is the the increase in rain will reduce the energy in the atmosphere. Raindrops generally slow down as they fall due to friction with the atmosphere. The energy of the slowing raindrop is transferred to the atmosphere in the form of heat. The extra heat in the atmosphere results in higher cloud tops because the water vapor will need to go higher before it reaches the required temperture to condense into rain. Can you see this cycle going on and on? The other potential change is the reduced energy will result in weaker winds.

Term For The Month From Multiple Sources
Accumulated Cyclone Energy
The Accumulated Cyclone Energy (ACE) index is a calculation of the energy of individual tropical cyclones. Kinetic energy is proportional to the square of velocity. The accumulated energy is calculated by summing the square of the wind velocity every six hours. The ACE becomes a larger number with higher wind speeds and/or longer duration of winds over 35 knots.

An ACE is also calculated for the storm season by adding together the energy for the entire tropical cyclone season. Another variation of ACE is the calculation for the period when the system is a hurricane. This variation is called the Hurricane Destruction Potential (HDP), which is ACE but only calculated for the time where the system is a hurricane.

Copyright 2012
All Rights Reserved
Steele County SKYWARN
Owatonna, MN