September 211 Newsletter

The next SKYWARN meeting is 20-Sep @ 7:00 PM, the third Tuesday of the month.

MN Storm Chasing Convention
The 2012 MN Storm Chasing Convention has been announced. It will be held in Plymouth on 14-Jan. The scheduled keynote speaker is Reed Timmer. A catered lunch is included in the $35 ticket price. A 23-Aug posting on the web site indicates tickets are almost sold out.

OSCAR License Class
The Technician License Class is now scheduled to begin on 14-Feb-2012. The same format will be used as previous years. Six classes on Tuesday and Thursday nights, one review night, and the VE Session on 08-Mar. Dale WBPKG and Tom NUW will be the lead instructors, with the excellent support from several OSCAR members. Anyone that has an interest can send a note to OSCAR for e-mail notifications. Check the OSCAR web site for more information.

New MN Records From Multiple Sources
Minnesota experienced several new records the past couple of months. Record dewpoints brought warm minimum temperatures at night and high Heat Index Values during the day. At Minneapolis, the record dew point is now 82 degrees. Moorhead now has the highest dew point recorded in the state at 88 degrees at the same time establishing a new record Heat Index Value of 134 degrees for the state.

Weather Underground provides a synopsis of all-time high dewpoint measurements in the USA and the world. NOAA mapped out where 2,700 daily maximum temperatures were set in July. Another 6,000 records are mapped for the highest minimum temperatures. You can view these maps at...

Climate Normals Calculation From Multiple Sources
Climate conditions have been measured and recorded for many years. Normals include various statistics such as monthly average precipitation, temperature, and Heating and Cooling Degree Days. Current climate "normals" are based on data from 1961 to 1990. The World Meteorological Organization (WMO) recommends recalculation of climate normals every decade. The National Oceanic and Atmospheric Administration-National Climatic Data Center (NOAA-NCDC) will soon provide new climate normals for the most recent three decades, 1981-2010. It should be recognized that any reference to "normal" in the past may change with the new data set. For example, the normal annual precipitation in Waseca will change from 34.72 inches to 35.72 inches (about 3%).

Changes in the calculation of "normal" may be real changes in the climate. Some statistics may be affected over time by other environmmental changes. A growing city may become hotter because of a Heat Island Effect. Larger building or trees may affect wind patterns around the weather stations.

Equinox From Multiple Sources
We have two days each year when there are 12 hours between sunrise and sunset at the equator, called the Equinox. The Vernal (spring) Equinox was on 20-Mar and the Autumnal (fall) Equinox will be 23-Sep. The next Vernal Equinox will be on 20-Mar-2012. There are 183 days between the 2011 Vernal and Autumnal equinox. There will be 177 days between the 2011 Autumnal Equinox and 2012 Vernal Equinox. We know the earth does not follows an elipitcal orbit around the sun. As the Earth gets closer to the Sun, the gravitational pull of the Sun makes the Earth move a little faster. The difference in the number of days between the Equinox is caused by the changing speed of the Earth around the Sun.

Eyewall Replacement Cycle From Multiple Sources
Hurricanes are made up of organized bands of thunderstorms and heavy rain that spiral inward toward a calm center. One of the signs of hurricane intensity is the size of the eye. As the hurricane intensity increases, the eye becomes smaller. High intensity hurricanes (over 100mph winds) often have two eye walls. They can be identified by looking at satellite imagery. They appear as two concentric rings of enhanced convection. The outer eyewall is generally almost circular and concentric with the inner eyewall.

When a hurricane is being tracked, the intensity of the storm often decreases and increases as it moves. This is one way the storm intensifies. The Eyewall replacement cycle is a process of building-decaying-replacing the eyewall. Thunderstorms along the outer eyewall are pulled in, robbing the inner wall of the moisture needed to sustain the intensity. The result is the hurricane intensity decreases. The inner eyewall is eventually replaced by the thunderstorms, forming a new inner eyewall. The hurricane intensity starts to increase again.

Developing Tornado Video CNN
This video posted on CNN ireports was underneath a tornado as it formed. This also provides an example as to why spotters should always be looking around them. While looking in one direction, other developing tornadoes form in the area.

Soil Moisture From Multiple Sources
A long standing theory exists that soil moisture have an impact on precipitation. Researchers recently demonstrated that evaporation from the land surface is able to modify summertime rainfall. Interestingly, the research suggests soil evaporation may affect the frequency of rainfall, but not the quantity of rain. The higher evaporation increases the probability of afternoon rainfall east of the Mississippi and in Mexico. In the western U.S., however, the dryness absorbs that may evaporate. The result is additional moisture does not increase the frequency of rain.

Lightning Photography From PC World
Watching nature's lightshow can be a breathtaking experience -- capturing it on camera is even more special. But in order to do so, you need to have the right camera, the right shooting location, the right camera settings, and the right post-processing technique. It takes a lot of patience (and luck) and plenty of patience in order to capture brilliant lightning bolts, but it can be one of the most rewarding types of photography. Check out this "how to".

Term For the Month From Multiple Sources
This term has various connotations, but in meteorology it is commonly used in many states (along with the term swelter) to refer to hot and humid conditions, where the air feels "close" or even "oppressive." Forecasters may use the term when they expect high dew points, or combinations of high temperature and high humidity. It is used frequently in the tropical latitudes, but certainly was appropriate for Minnesota this week with record high dewpoints and Heat Index values over 100 degrees F. Under such conditions themo-regulation (stability of body temperature) for humans and animals becomes a challenge.

Copyright 2011
All Rights Reserved
Steele County SKYWARN
Owatonna, MN