Thursday, May 21, 2009

Parkersburg...One Year Later

Memorial Day has more significance in Parkersburg, Iowa this year. It will be one year ago to the day that the little town in Butler County was nearly wiped off the map by an EF 05 tornado.

6 People were killed in Parkersburg...3 more died in the New Hartford area.

The town was changed forever...but rebirth of homes and connections between family and friends in the area is amazing. It is a testament to the community and to the caring of those who were there day one and again through the last 365 days.

Parkersburg now looks like a new housing development in any suburb Iowa. The big trees that lined the streets are gone. Now there are new sprouts and saplings. There are new and bigger homes in the place where only foundations remained after the tornado last May 25th.

The numbers are amazing. 282 homes were damaged or destroyed. The cost estimate so far is around $37 million.

This weekend Parkersburg will pay tribute to those who were killed and to those who survived. Memorial Day weekend has special meaning for those folks in north central Iowa.

The National Weather Service in Johnston has a pdf poster of the track and timeline of the May 25, 2008 tornado. You can see it and find out more about the events this weekend.

Have a safe weekend.


Thursday, May 14, 2009

Doppler Ground Clutter

There are many viewers who have asked about the junk that is around the center of Doppler radars. It looks like precipitation...but is always there....even on a clear night.

Here is a general explanation of ground clutter around the radar and anomalous propagation.

Ground clutter is a pattern of radar echoes from fixed targets around the radar. An example is the red and orange spots that are always around the Mega Doppler. There are farm buildings and grain silos near the radar site that always show up as red or orange spots that do not move in the center of our radar display. We built Mega Doppler outside of the metro so we would not the interference of buildings downtown. Ground clutter can hide or disrupt precipitation echoes near the radar antenna.

Anomalous propagation (A.P.) occurs with temperature or moisture gradients near the radar that cause part of the radar to bend abnormally. The beam of the radar can be turned into the ground or can bend upward. Both types of A.P. can make it look like there are large areas of rain or snow falling right around the radar. A.P. is most often visible at night with high amounts of moisture. Yellow and green are the most common colors that show up on the Doppler during anomalous propagation. The false returns are most common during nighttime hours when cooler temperatures and more moisture is pumped into the atmosphere adding to the bending of the radar beam.

We manipulate the power and tilt of Mega Doppler to eliminate most of the ground clutter and A.P.


A viewer from Ankeny noticed that it is really difficult to see storms on radar when they move over the northern edge of Ankeny. This is a portion of the email I sent to our Ankeny viewer... it will help explain why being close to the radar does not keep you safer in storms.

The issue with Ankeny is the growth of the area to the north of town since our radar was installed at Alleman. That area...just like so many in central Iowa... has expanded so much in the last several years. Many housing courses...etc have moved very close to the radar site. This has created an issue for those who live under the dome of ground clutter that will always be a part of any Doppler radar location.

I mentioned in the earlier email we purposely put the radar site away from the downtown area of Des Moines. Since the installation of our Doppler... Ankeny and Des Moines have nearly joined at the south...and Ankeny has really expanded to the north. Alleman has expanded right under the dome of silence around the radar site.

We use this site because Alleman is one of the highest points of the central Iowa area. It is where our TV towers are we own the property.

We try to eliminate as much ground clutter and Anomalous Propagation as possible... but if you are right under the radar site... there is really nothing we can do about those permanent returns of buildings and bending of the radar very close to the radar.

In the event of a very close storm over the our radar... you can cross-section the storm with the National Weather Service Doppler that is located over by Camp Dodge in Johnston.

You will notice they have more ground clutter than we do on a clear day... they put their radar into a "clear air" mode that really increases the junk around the center of the Doppler.... but during a storm that is right over Ankeny... this could help.

Keep that NOAA all-hazard weather radio in your home and in a place that will wake you up if the storms move through when your family is sleeping. You can even register to win a weather radio from Channel 13 by going to

Tornado Alley

Is Iowa really in tornado alley? It is a great and very common question we get at the Channel 13 weather office.

It is true. The most severe weather in the country typically has a target over Oklahoma to Kansas to Missouri and Nebraska and Iowa. We get the big storms because we are located where the dry and cool air collects and meets with the warm and humid air. It is the ingredients that are needed for tornado cake...and we are sometimes the frosting on that severe offering from Mother Nature.

Last night Kirksville, Missouri was the end zone for tornado touchdowns. 3 people lost their lives in that northern area of the Show-Me state.

The Weather Channel has some amazing video from a storm chaser that was in the middle of that tornado. The link above is to the storm story of Kirksville.

It is amazing to see the chaser...named "Tornado Tim"... sit in his car and have huge debris thrown on to his car. His windshield wiper was snapped off.

We have great weather today... another chance for strong to severe storms. Those storms should not hit until later in the day. The weekend is still looking fabulous.

Have a great one... living in tornado alley.