NOAA National Weather Service Weather Forecast Office

WEATHER CURRENTS
National Weather Service, Chicago

Spring 2006  Volume 4 Issue 1

Serving the people of north central and northeast Illinois, northwest Indiana, and the boaters of Lake Michigan

Remembering the Lemont Tornado of 1976
By Christopher Gitro, Meteorologist Intern

One day will be remembered by many people living in the DuPage and Cook County areas during the early summer of 1976.  The date would be June 13 and the day began as any normal day would in the Chicago Metro area.  The region had been experiencing a very warm period with a high of 94 degrees being observed the previous day.  With afternoon temperatures hovering in the lower to middle 80’s, little would be known that in just a few minutes after 400 PM, sudden chaos was about to strike southern DuPage and southwestern Cook Counties.

A strong tornado developed across the Lemont area at 418 PM, just north of downtown.  From this point, the tornado began taking a rather erratic track, first heading southeast through the eastern sections of town.  The tornado grew more ferocious during this time, causing extensive damage at the Hillcrest Subdivision.  From there the storm began heading in a northerly direction, and then northwest where it ripped the roof off an Argonne National Laboratory reactor.  The tornado then crossed I-55 where it inflicted more damage on homes before finally dissipating.  In the storms wake, 2 lives were lost while 23 people were injured.  The total track of the tornado was 8 miles long with a width of up to 800 yards.  Total damage approached 13 million dollars.  After all the damage was surveyed, the final rating of the tornado was an F-4 on the Fujita Scale, meaning winds ranged from 207 – 260 mph.    Of particular interest with this tornado was the fact that two satellite anticyclonic (clockwise rotating) tornadoes were produced.  In addition, the total time on the ground neared one hour, however the total distance traveled was only about 8 miles.  Further research of the storm indicated that the storm was nearly stationary for a period in the tornado’s lifecycle, ultimately contributing to such the short distance traveled. 

Hardware and software upgrades at the NWS Romeoville Office
By Christopher Gitro, Meteorologist Intern

On April 3rd, the latest software upgrade to the AWIPS system will be completed.  This software will allow additional products to be available and offer other enhancements.  As part of this software installation the basic Linux operating system will be upgraded. 

Other changes are on the way for our WSR-88D radar.  During the middle of May, updates will be made to our Open RDA (ORDA) and RPG.  These updates will take the radar off line for approximately 1 week beginning the week of May 15th.  The ORDA is the main controlling configuration of the radar while the RPG creates radar products based on data supplied by the ORDA.  Reflectivity and velocity images made available via our website are examples of products created by the RPG.  This process is simply a continuation of the upgrades our radar has received since it became operational in the early 1990’s.  After the update is complete, more radar products will be available for our interpretation during hazardous weather events and the radar hardware will be easier to upgrade in the future.

New technology will help the staff at the National Weather Service office in Romeoville to look at rain and snow systems and thunderstorms in a better and more efficient way.  This upgrade is a part of a nationwide upgrade of the Doppler radar system. Some operational impacts of ORDA include;

• Improvements in calibration
• Improved sensitivity in long pulse
• New clutter suppression technique
• Mesocyclone Detection Algorithm
• Storm Cell Identification and Tracking Algorithm
• Precipitation Algorithm Improvements

If a major severe weather outbreak is anticipated during the scheduled week in May, the outage will be postponed.

Drought Conditions Continue
By Tim Halbach, Meteorologist Intern and Bill Morris, Service Hydrologist

Drought conditions have persisted over northern Illinois and northwestern Indiana since March of 2005. Current indications would suggest the likelihood that drought will persist through the upcoming summer.  With a weak La Niña in place and forecasted to continue through the summer, dry conditions will be possible again this summer.  Even though precipitation at the start of 2006 has been above normal, most of the region was around 10 to 12 inches below normal in 2005, so several months of above normal precipitation will be needed to help end the drought.  Last summer, there was sufficient subsoil moisture available for most crops. However, most of that moisture has been depleted and may be cause for concern for agricultural activities this growing season.   Normally at this point in the spring season, the ground is saturated from a combination of snow melt and rainfall. With the warm winter and lack of snow cover, this moisture isn’t available this year.  Over the short term, an active weather pattern will help to mitigate some of the drought conditions, but the test will be whether above average precipitation can be sustained through the critical summer growing season.

Severe Weather Reminder
By Jim Allsopp, Warning Coordination Meteorologist

Its severe weather season again. Time to put away the snow shovels and begin thinking about severe weather preparedness. Last year, much of northern Illinois was experiencing drought, with very little severe weather activity. However there were large destructive tornadoes at nearby Stoughton, Wisconsin on August 18, Evansville, Indiana on November 5, and near Des Moines Iowa on November 16. On March 12 of this year tornadoes struck downstate at Springfield.

F3 Tornado at Stoughton, WI Aug 18, 2005

Radar display from NWS Lincoln, IL of tornado producing supercell bearing down on Springfield March 12, 2006

Its only a matter of when, not if, a significant tornado strikes this area. Preparedness, education and advanced warning are the keys to surviving a severe weather disaster.  Keep these safety rules in mind;

Tornado Safety Rules

In homes, go to the basement and get under the stairway or under a heavy piece of furniture. If there is no basement go to a small interior room on the lowest floor, such as a closet, bathroom or hallway. Stay away from windows.  

In schools, hospitals, nursing homes, public buildings, go to small interior rooms or halls on the lowest floor. Stay away from windows. Avoid large rooms such as gymnasiums or auditoriums.

In high rise buildings, go to small interior rooms or halls. Stay away from windows.

In mobile homes and vehicles, make plans to go to a nearby substantial structure when the tornado watch is issued, before the storm hits. If a tornado is approaching and there is not time to get to a place of safety, get out and lie flat on the ground in a low spot or ditch. Nationwide, about 40% of tornado deaths occur in mobile homes.   

Lightning Safety Rules

 Plan ahead and avoid dangerous lightning situations. Check the latest forecast before going outdoors for extended periods. Watch for storms and seek shelter indoors when storms approach.

In a home or building, avoid using the telephone or electrical appliances. Do not take a shower. Metal pipes can conduct electricity.

You are safe from lightning in an enclosed vehicle.

Lightning is attracted to tall objects. If caught outdoors and no shelter is available, find a low spot away from trees, poles and fences. Standing out in the open is dangerous. If you are in the woods, seek shelter in a low area in a clump of smaller trees or brush rather than near lone tall trees.

If you are swimming or boating, get out of the water immediately.

Lightning Safety Precautions for Youth Athletics;

Before the Game

• Check the forecast and be aware of the potential for thunderstorms.

During the Game

• Have a portable NOAA Weather Radio to receive severe weather watches, warnings and forecasts.
• If there is a threat of thunderstorms, designate a lightning spotter. (Not the coach or referee)
• Pay much more attention to the lightning threat than to the rain threat.
• If lightning threatens, suspend play and seek shelter in a building or hard-top vehicle with the windows up.

Guidelines for Suspending Play

• Flash to Bang Method - Count the number of seconds from the flash of lightning until you hear the bang of the thunder. Divide by 5 to determine the distance of the lightning flash in miles.
• 30-30 Rule - Using the Flash to Bang method, if thunder occurs within 30 seconds of the lightning it is less than 6 miles away - close enough to be a threat. Stop play and get to shelter. Stay indoors until 30 minutes after the last lightning or thunder.

Lightning Safety

• Avoid being near or under tall objects such as tall trees and power poles.
• Avoid being out in the open where you are the tallest object.
• Do not be on or near water.
• Do not be near or touching metal objects such as a chain link fence or metal vehicle (it doesn’t matter if you are wearing metal cleats or rubber soles).
• Picnic shelters, gazebos, baseball dugouts, tents and awnings will keep you dry but do NOT offer protection from lightning.
• Go inside a substantial building or hard-top vehicle with the windows up. Avoid using electrical appliances, telephones or plumbing.
• If caught out in the open and your hair stands on end, there is a tingling on your arms or back of your neck, or you hear buzzing - get down low in a crouching position and cover your head with your arms.

Flash Flood Safety Rules

If you live or work near a stream, creek, drainage ditch, or low lying flood prone area, get to higher ground if water rises rapidly or if a flash flood warning is issued for your area.

Do not let children play in or near flooded areas or storm drains.

Do not drive through flooded roads, especially if water is moving rapidly. You may not know the depth of the water and the road bed may be washed out under the water. Two feet of moving water can cause a vehicle to become buoyant and out of control.

Stay “Weather Aware” to Prevent a Boating Emergency
By Tim Seeley, Meteorologist

The longer days and warmer temperatures of Spring fill recreational boaters with anticipation of  the fun and relaxation to be found on the water.

One of the greatest dangers on Lake Michigan is the weather. Springtime is usually a mix of pleasant mild conditions and unsettled, even violent, weather. Sometimes the transition from mild to wild occurs in a very short period of time. To keep your outing on Lake Michigan safe and prevent you from being caught off guard, you must stay aware of the  current and forecast conditions for the Lake.

Before heading out on the water, check to see what’s going on right now and what the forecast is for later on. Hourly roundups of weather observations from on Lake Michigan as well as along and near the shores are available in the Marine section of the NWS Chicago web page. Forecasts for the Nearshore Waters (within 5 nautical miles from shore) and Open Waters (beyond 5 nautical miles from shore) of the Lake can also be found there. This information is also broadcast on NOAA Weather Radio stations KWO-39 Sears Tower at 162.55 MHz,  KZZ-81 Lockport at 162.425 MHz, and KXI-86 Crystal Lake at 162.00 MHz.

Recently added to the NWS Chicago Marine web page are forecasts of winds and waves on Lake Michigan in a graphical format, an example which is shown below:

Once under way, monitor Channel 16 for significant weather from the NWS relayed through the U.S. Coast Guard.  You should also regularly tune in to the Sears Tower or Crystal Lake broadcasts, especially when changes in the weather were forecast or the sky appears to be turning for the worse.  The latest forecasts, statements and any warning will be broadcast on these NOAA Weather Radio stations.

While on the water always know where the closest safe harbor to your position is in case you need to immediately head to safety.  If thunderstorms or rapid, gusty wind shifts are forecast you should keep close to shore so that you can return to safety quickly.  The NWS issues statements to give advance notice of rapidly changing weather conditions to affect Lake Michigan when possible, and will issue warnings if there is an ongoing or imminent threat to mariners.

 Thunderstorms can move very quickly and reach Lake Michigan from several miles inland in a matter of minutes. If it is impossible to get out of the way of the violent weather then take all necessary precautions to ensure the safety of all aboard. Everyone should be wearing their PFD and head below deck if possible. Sailboats should lower their sails. Stay away from ungrounded metal objects in case of a lightning strike. Steer the bow at a 45 degree angle into the waves to prevent being swamped.

Remember, keep your outings on Lake Michigan safe and prevent yourself from being caught in a situation you’d rather not be in.  Know your limits, your craft’s limits, and always keep aware of the weather.
           

Below are definitions of terms that are used in NWS text products and broadcasts:

Amatuer Radio News
By Bill Wilson, Meteorologist

The National Weather Service Service Ham Team has a new Antenna array. Last year, we installed new antennas for 2 meters on our tower and replaced all our Coaxial cable to our radios. At the top of the tower is a commercial grade omni directional antenna and just below it is a dual 13 element yagi. The yagi is mounted with a rotator. We have two antennas for the 70 cm band and a 10 to 80 meter band dipole. Our range has improved significantly to where we can communicate with 2 meter repeaters in the far northwest and far southern counties of our County Warning Area. This will be an improved communication between the county emergency managers, amateur radio spotter networks and the National Weather Service Ham Team.

The National Weather Service Ham Team has received a club call sign, KC9IZH. We will be using this call sign until we receive our vanity call sign. Look for the announcement of the new vanity call sign in a later issue of this newsletter.

The National Weather Service Ham Team Echolink net will be on Tuesday night at 7 pm CDT. The net is a forum for County emergency managers, and Amateur Radio Spotters to discuss issues concerning severe weather communications and we pass information our radio and severe weather operations. Radio Frequency communications is the primary mode that the Ham Team operates and Echolink is our additional mode of communications during severe weather.