Graupel

April 21, 2015: If you happened to be out early this morning, you may have seen what looked like little balls of styrofoam falling from the sky.

A look at graupel from South Beloit this morning, courtesy of Suzan Laws

A look at graupel from South Beloit this morning, courtesy of Suzan Laws

These little balls of ice are called “graupel”, and they are similar to hail and sleet. We had conditions ideal enough to form these little pellets of ice.  Here’s how we get those:

 

Graupel starts out as snow crystals

Graupel starts out as snow crystals

Basically, the upper atmosphere has to be pretty cold.  Cold enough to create snow crystals.

The snow crystals fall through supercooled water droplets. The droplets freeze on to the snow crystals.

The snow crystals fall through supercooled water droplets. The droplets freeze on to the snow crystals.

As the snow crystals fall through the clouds and toward the ground, they fall through a layer of supercooled water drops. “Supercooled” means the water is at a temperature below water’s freezing point. Water needs to have some structure on which an ice crystal can form; if the water is “pure” and without dust, etc. for the ice to form onto, it will stay as a liquid.

Round balls of ice form as the freezing water droplets build up.

Round balls of ice form as the freezing water droplets build up.

So, as the snow crystals fall through this area of supercooled water droplets, the water droplets form ice on the snow crystals as the crystals come in contact with them.  This ice builds up to the point where the snow crystals are covered and resemble “pellets” or “balls” of ice.

The balls of ice or graupel fall to the surface after the ice builds up enough.

The balls of ice or graupel fall to the surface after the ice builds up enough.

This all falls to the surface, resembling bouncing balls of styrofoam as they fall. How do you tell the difference between graupel and sleet, hail, etc.? Graupel is brittle and falls apart easily.  Graupel is also pretty small, especially compared to hail.

We usually do not see graupel except in thunderstorms, or when the atmosphere is below freezing in a deep layer, similar to the cold conditions we had today.

-Alex

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This post was written by Alex Kirchner on April 21, 2015
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A Look Back 48 Years Ago and 11 Days Ago

We are 11 days removed from the EF-4 tornado that ripped through north central Illinois, beginning in Franklin Grove, stretching 43.5 miles through Flagg and into Fairdale. While locals and non-locals are pitching in on the effort of recovery for residents affected by 7 tornadoes on April 9th 2015, many are also remembering the devastation from a tornado that struck the Stateline nearly 48 years ago.

On April 21st, 1967 the city of Belvidere experienced a deadly tornado, with eerily similar damage to the EF-4 tornado on April 9th 2015, but this one was twelve times as deadly.

Let’s flash back to meteorology in the 1900’s. Right after World War 11, the weather community started the use of radars, which were around for about 30 years by the time the Belvidere Tornado occured.
4-9 radar imageIn 1948, less than 20 years before the 1967 tornado, Robert C. Miller and E. J. Fawbush correctly predicted the first tornado in Oklahoma.  10-15 years before the Belvidere Tornado, computers ran their first models of the atmosphere. Just 5 years before the deadly tornado hit Boone County, Keith Browning and Frank Ludlam published a detailed study of a supercell storm, the first one of it’s kind. In fact, it wasn’t until a few years after the Belvidere tornado that Dr. Tetsuya Theodore Fujita invented the “Fujita Scale.”

Are you catching my drift here? While the foundation and structure of much of meteorology was founded, knowledge and awareness was minimal on the atmosphere during the early and mid 20th century. This is a key contributor to the saved lives and safety of many Stateliners on April 9th 2015.

The tornado that devastated Boone County 48 years ago was rated an “F-4″ on the Fujita Scale. According to the Fujita Scale, an F-4 tornado *estimates wind speeds between 207 and 260 mph, and typical damage includes well-constructed houses leveled, weak foundation structures blown away, and cars thrown. We now know that the Fujita Scale could over-estimate wind speeds, which is why we now use the Enhanced Fujita Scale (another educational advancement).

Still, the damage we see in photos of the Belvidere Tornado in 1967 grimly mimic the photos being posted from Fairdale within the past 11 days.

According to Jim Allsopp, Warning Coordination Meteorologist at the National Weather Service, the Belvidere Tornado first struck just before 4PM 2 miles southeast of Cherry Valley. It went on to destroy 300 new cars and 100 employee cars at the Chrysler Plant, which was only a fraction of the damage it would go on to create. The tornado moved on to the southeast side of Belvidere, where 127 homes were destroyed and hundreds more were damaged.

At the time, Belvidere High School had just dismissed students onto buses filled with elementary school students. 12 buses were rolled over and children were flung into muddy fields.
belvtor2

 

In 2011, Ken Anderson (left) told WREX, “My bus (#30) was moved 100 yards by the tornado. I was wedged under a seat, my shirt soaked red with blood. I saw one, little body half buried in the mud. That memory, an 11 year old should never witness. In this picture, I am on the left (shirt tail out). That concerned look on my face marked the end of my childhood.” At Belvidere High School, 13 people were killed and another 300 were injured, which was just a little more than half of the havoc caused that day.

 

 

 

Dale Marks also vividly remembers April 21st 1967, “They tell me I was lucky. I only had both legs and pelvis broken. Our bus was just on the north side of the school. I think there were five people killed on my bus.’
belvtor1The Belvidere Tornado of 1967 went on to kill a total of 24 people and injure another 500.
To read Jim Allsopp’s full synopsis of the event, click here. To read all of the survivor comments from 2011, click here.

 

 

The Belvidere Tornado of 1967 was an F-4 and was up to 1/2 mile wide. It traveled 25-28 miles on the ground.
fairdale1The tornado that hit Fairdale (left) eleven days ago was an EF-4 that was nearly 1/2 mile wide. It traveled 30 miles on the ground.
But, what about the fatalities and injuries? During the 1967 F-4, 24 people were killed and another 500 were injured. During the 2015 EF-4, 2 people were killed and 22 were injured.

 

 

 

 

 

 

Education and awareness are saving people’s lives.

The Storm Prediction Center was able to put out the risk of severe weather nearly a week ahead of the April 9th event. The Chicago National Weather Service was able to implement watches and warnings with ample time to get to safety before these tornadoes struck communities. In fact, Ogle County Sheriff Brian Van Vickle stated, “I don’t think you could’ve asked for better warning.” Local TV meteorologists were able to give in depth explanations on air and online about WHY that Thursday could end with severe weather. We all could do this because of advancements in the world of meteorology.
4-9 radar image 2

In my opinion, the most important thing meteorologists can do is continue to explain to you WHY we could see dangerous weather, WHY we saw dangerous weather, or WHY we ended up not seeing dangerous weather. We’re living in a world with Google at our fingertips, with politics overlapping into sciences, and with education being pushed on everyone. We have been raised and trained to ask questions. Why would you believe something just because someone told you? You have the right to question. I think it’s our job to explain to you why it’s a threat, not just the fact that it’s a threat.

In my opinion, one of the most important things we as a community can learn from both of these deadly tornadoes, is the importance of heeding warnings and continuing to educate yourselves and listening to “the why” instead of chalking it up to “sensationalism,” “hype,” and even “TV ratings.”

Because awareness and education is one of the biggest contributing factors in the difference in death and injuries during severe weather.

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Posted under event, history, news, safety, science, severe weather, statistics, tornado, weather, weather geek

This post was written by Morgan Kolkmeyer on April 20, 2015
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Tornado Timeline

April 16, 2015: A week ago, severe weather slammed the Stateline, with a total of 7 confirmed tornadoes in our area alone (11 total throughout Illinois). The National Weather Service has completed their damage survey, so here’s a final look at where and when each tornado touched down.

The paths of each tornado from last week's outbreak. Courtesy: National Weather Service

The paths of each tornado from last week’s outbreak. Courtesy: National Weather Service

6:37 pm: EF-0 Cherry Valley tornado touches down. The tornado is on the ground for 3 minutes, with winds at 65 mph. The tornado travels nearly 3 miles.

6:39 pm: EF-4 tornado forms near Franklin Grove. With winds up to 200 mph, the tornado travels 30 miles into southern Ogle Co., and is on the ground for 40 minutes.

7:05 pm: EF-0 tornado touches down in eastern Ogle Co., east of Lindenwood. This is one of the EF-4’s satellite tornadoes. The twister is on the ground for 3 minutes, and travels nearly 2 miles.  Winds reach 65 mph.

7:15 pm: EF-1 tornado forms between Kirkland and Belvidere. Winds hit 110 mph as the tornado travels almost 4 miles.  This is the second satellite tornado from the EF-4 storm, and lasts 6 minutes.

7:24 pm: EF-0 tornado touches down shortly after the EF-4 lifted. This tornado formed south of Belvidere, and lasted 1 minute. Winds reached 85 mph.

7:25 pm: EF-1 tornado hits I-90 and the Summerfield Zoo. This tornado formed from the same storm that created the EF-4, and touched down after the EF-4 lifted. Winds reached 110 mph as the tornado was on the ground for 6 minutes.

7:50 pm: EF-0 tornado forms southeast of Harvard in McHenry Co. The tornado had winds near 90 mph, traveled 1/3 of a mile, and lasted 1 minute.

There are still plenty of ways to help out the tornado victims.  Check with the Red Cross and the Salvation Army to see how you can help.

-Alex

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This post was written by Alex Kirchner on April 16, 2015
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Quiet Weather

April 15, 2015: If you’ve enjoyed the weather we’ve had so far this week (little rain, lots of sunshine with a few clouds, middle 60’s to 70°), then you are in luck: we should see this stretch of weather end until the weekend.

Satellite and radar imagery from Wednesday evening.

Satellite and radar imagery from Wednesday evening.

Here’s why: see where the jet stream is? The main polar jet is well up into Canada. Along with allowing the above average warmth into the Stateline, the “steering winds” for any weather systems is staying well to the north as well. Under the ridge over the Midwest, we shouldn’t see anything get moved in until the weekend.

The pattern breaks down by Friday night, so the weekend will featuring a little more variety than what we’ve had so far this week. Enjoy the sunshine and warm weather!

-Alex

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This post was written by Alex Kirchner on April 15, 2015
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Record dry air (nearby)

April 14, 2015: Did the air feel really dry today to you? It did in Chicago today, where the dry air tied a record at O’Hare airport.  The relative humidity dropped to 13%, which tied April 8, 1971, April 11, 1956, and May 10, 1934 for the driest relative humidity on record for Chicago. For reference, the human body generally feels comfortable at 45% relative humidity, so 13% is very dry!

Relative humidity readings at 4 pm today

Relative humidity readings at 4 pm today

If you are wondering what or how we figure out the relative humidity of the air, here’s a crash course (get ready for a lot of science!): humidity describes how much water vapor is in the air. We can measure this with absolute humidity, which is the mass of water vapor divided by the mass of dry air at a certain temperature. The hotter the air, the more water vapor it can hold, and so the value for absolute humidity is higher.

To get to relative humidity, we use the ratio of the current absolute humidity to the highest possible absolute humidity at that temperature. At 100% relative humidity, the air is completely saturated and can’t hold any more water, usually creating rainfall as the moisture falls out of the air.

An area of high pressure results in downward movement in the atmosphere. This dries the air out, and is why we don't usually have clouds or active weather under high pressure.

An area of high pressure results in downward movement in the atmosphere. This dries the air out, and is why we don’t usually have clouds or active weather under high pressure.

Why did the air feel so dry today? We did have an area of high pressure right overhead, which may have contributed to the dry conditions. High pressure promotes downward movement in the atmosphere, which counteracts what you may have learned in elementary school about the water cycle- instead of the air rising, then cooling and condensing into clouds, downward moving air dries out.  This is one of the reasons why the air was so dry today.

-Alex

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Posted under event, record weather, science, weather

This post was written by Alex Kirchner on April 14, 2015
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What is a satellite tornado?

April 13, 2015: You’ve likely heard or read about this term since the April 9th tornado outbreak in the Stateline: satellite tornado.  So, what is it?

A satellite tornado refers to a tornado that forms within the same severe thunderstorm of a much larger, more intense tornado.  The smaller tornado orbits around the larger tornado, much like a satellite does around a larger body in space.  The tornadoes are completely separate from the primary, massive tornado. The cause of satellite tornadoes is unknown at this time; however, if conditions were ideal enough to produce a large, violent tornado, then it seems reasonable that secondary tornadoes could form too.

Approximate paths of the EF-4 tornado and two satellite tornadoes

Approximate paths of the EF-4 tornado and two satellite tornadoes

So far, at least two tornadoes have been identified by the National Weather Service as being satellite tornadoes to the massive, devastating EF-4 tornado that hit near Rochelle, Ashton, and Fairdale on April 9th.  One was a weak EF-0 tornado that touched down briefly east of Lindenwood and I-39. The second was an EF-1 tornado that formed northwest of Kirkland, then moved to just north of the Boone Co. line.

The NWS is still investigating the damage from last week’s tornado outbreak, and more tornadoes may be identified, as well as additional tornadoes designated as satellites of the violent EF-4. This information may change a little, so we will keep the updates coming as we get them.

-Alex

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Posted under science, severe weather, tornado, weather

This post was written by Alex Kirchner on April 13, 2015
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Looking back on April 9th, 2015

Last Thursday was our first taste of severe weather for the season and it was a very eventful day. The event started with a deepening, fast moving low pressure system. This low pressure system was the driving force for converging and gusty surface winds that evening. There was a strong frontal boundary difference making way for backing winds near the boundary helping rotation. The surface was very moist with dew-points observed at Rochelle and Sterling reaching 66° at one point. This became a perfect setup for a large and dangerous tornado.

The night began with some scattered strong thunderstorms, but no Tornado Warnings were issued until 6:09 PM and that is when storms started to fire up all across the Northern Illinois region.

TOR Timeline 9th

The first Tornado warning was for a radar signature of rotation just south of Cherry Valley. Soon after at 6:35 PM was the first issued Tornado Warning for a large wedge tornado near Ashton. Finally all tornado warnings had expired around 7:45 PM.

So far throughout the state of Illinois there have been 8 confirmed tornadoes. Four of these tornadoes were confirmed in the Stateline.

tornadoes april 9th

The strongest tornado being an EF-4 that tracked across Lee, Ogle, and DeKalb counties. This was the first EF-4 tornado on record in the Northern Illinois region since the community of Washington was struck by one in November of 2013. Wind speeds associated with this EF-4 Tornado were around 180-200 mph. This was the major tornado produced with this storm. There have been 2 fatalities confirmed with this tornado and more than 20 people injured. Structures in the small town of Fairdale, IL have been almost completely swept away.

The EF-4 was not the only tornado in the Stateline that was destructive. An EF-1 tornado with wind speeds up to 110 mph roared through areas just south of Belvidere. This EF-1 tornado first touched down near Flora Road where it impacted a zoo.  Two zoo animals died as a result of the damage caused by the tornado.

Then there were the two EF-0 tornadoes that were south of Cherry Valley and just south of Lindenwood that had little to no damage associated with them.

Here is a graphic posted by the National Weather Service in Chicago of the tracks of the four tornadoes.

nws tor tracks

This photo can be found on their Facebook and I have posted the link below. Also, surveying has not been completed all the way yet by the National Weather Service and when they come out with their newest information we will be sure to pass that along to all of you!

– Nick Jansen

National Weather Service Facebook post:

https://www.facebook.com/NWSChicago/photos/a.170461579677551.41001.164132806977095/900816173308751/?type=1&theater

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This post was written by Alex Kirchner on April 11, 2015
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Rochelle Tornado Rating

April 10, 2015: The National Weather Service sent out damage survey teams to determine how many and how strong the tornadoes were that struck the Stateline Thursday evening. Today, they were able to put together a preliminary rating on the Rochelle tornado.  This was the massive wedge-shaped tornado that cause an unbelievable amount of damage outside of Rochelle, in Ashton, and in Fairdale. Turns out, that massive tornado was one of the strongest on the ratings scale.

The Rochelle tornado has been confirmed as an EF-4 tornado, preliminarily. The NWS survey team will conduct an aerial survey before the final confirmation.  This will help determine the tornado’s path, how long the tornado was on the ground, and if there were any additional tornadoes spawned from this massive twister (the NWS found evidence of at least one additional tornado).

The preliminary ranking and possible track of the Rochelle tornado

The preliminary ranking and possible track of the Rochelle tornado

The team estimates that the tornado was up to a half mile wide, with maximum wind speeds estimated between 180 and 200 mph. These winds speeds are able to level homes, which we unfortunately saw plenty of across the affected areas in Ogle, DeKalb, and Boone Counties. The survey so far sees this as a long track tornado, on the ground continuously for over 20 miles!

An EF-4 is considered a very violent tornado, and rated as one of the strongest tornadoes possible. In fact, had the winds been a little faster, this could have been an EF-5.

The EF-scale, which rates tornadoes based off of damage and wind speed

The EF-scale, which rates tornadoes based off of damage and wind speed

So why does the rating for a tornado come out after the tornado has struck? First of all, it is hard to determine a tornado’s size and strength based only off of the radar, or by photos or video evidence.  It is also extremely dangerous to be anywhere near a tornado, so its best to wait until the threat has disappeared. Analyzing the destructive power of the tornado helps determine the wind speeds more accurately, leading to the ranking for the tornado. This is why the National Weather Service conducts these investigations afterward.

The process for rating a tornado with the National Weather Service

The process for rating a tornado with the National Weather Service

The Rochelle tornado was not the only one of the day- there was at least one other tornado near Cherry Valley earlier in the evening, plus the possibility of other tornadoes developing near or with the Rochelle tornado. The National Weather Service will continue investigating this weekend, and will have rankings on the other twisters in the coming days.

-Alex

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Posted under severe weather, tornado, weather

This post was written by Alex Kirchner on April 10, 2015
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Today’s Severe Weather Thoughts

I want to give a detailed description of my thoughts on the potential for severe weather on Thursday. If you’d like to skip over the “why,” scroll to the bottom of this article. I’ve listed my thoughts on the timing and threat.

Showers and thunderstorms started to develop overnight Wednesday into Thursday morning. A cluster of non severe thunderstorms passed through the Stateline early this morning between 3AM and 7AM, with heavy rain as the main threat. Now, we’ve got a break in the heavy rain and thunderstorms this morning. We’ll likely see another round of non severe thunderstorms and showers pass through in the late morning and early afternoon.

4-9 threattracker

 

The threat of severe thunderstorms doesn’t come in until we head into the mid afternoon and into the evening. However, there are some question marks.
One of the biggest reasons has to do with something meteorologists refer to as instability, which is one of the key ingredients to produce a severe thunderstorm. Have you ever noticed that most thunderstorms occur in the late afternoon? That’s because of daytime heating. All day long, the sun heats up the surface and creates a big difference between the temperature around us and the temperature in the mid levels of the atmosphere. This helps to create more instability. Overnight, there is no sunshine to warm the surface, therefore instability is limited. This is one reason why the threat of severe thunderstorms overnight and early this morning was very minor.
Cloud cover is going to stick around early and late Thursday morning. The thick clouds will limit the amount of sun allowed to heat the surface, which will also limit the amount of instability in the atmosphere. This is the big question mark- will the clouds break in the afternoon, before thunderstorms devlop? IF they do, we run a higher risk of seeing severe thunderstorms. As of this morning, much guidances suggests clouds will start breaking after the lunch hour, which will allow the sun to help increase instability and raise the potential for thunderstorms to turn severe as we head into the mid afternoon through the evening.

The other ingredients we look for as necessary for severe development look to be in place. This includes a strong southerly surface wind, that changes direction as you go up into the atmosphere. Dewpoints reaching the low to middle 60’s combined with an incoming cold front will aid in development of scattered thunderstorms.

4-9 whats the threat

 

 

 

 

 

 

 

I think the biggest threat today will be damaging winds, followed by large hail. I expect discrete thunderstorms to turn severe in the mid afternoon, lasting into the evening. There’s also a risk for a few isolated tornadoes to occur across and near the Stateline.

4-9 know your safe place

 

 

 

 

 

 

 

It is important to know your safe place today, whether you are at home, in school, at work, or driving.

4-9 be prepared

 

 

 

 

 

 

 

Be sure to have your NOAA Weather Radio working today and do not rely solely on outdoor warning sirens.

Chief Meteorologist Alex Kirchner, 13 Weather Authority’s Nick Jansen and myself will be in through the afternoon and evening to track the thunderstorms and update you on the risk for severe thunderstorms.

-Morgan

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This post was written by Morgan Kolkmeyer on April 9, 2015
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Thursday’s Severe Threat

The threat for severe thunderstorms still exists on Thursday.

Before we get there, we see the development of showers and thunderstorms overnight on Wednesday, producing a quarter to a half inch of rainfall. As of right now, these thunderstorms do not look to have the capabilities of turning severe. Same story as we head into early Thursday morning. Scattered showers and possibly thunderstorms can occur. The chance of these posing a severe threat is low, but I DO NOT want to rule out the chance completely.

4-8-15 timing

 

 

 

 

 

 

 

The Storm Prediction Center has much of Illinois (including the Stateline) under an enhanced risk for severe thunderstorms.

4-8-15 spc convective outlook

 

 

 

 

 

 

 

We start to see the potential for these to turn severe as we head into the early afternoon. As of right now, it looks like thunderstorms will continue to develop and pose a severe threat between 1PM and 6PM on Thursday.

If these t’storms turn severe, the possible threats include damaging winds, large hail, and isolated tornadoes. Now is the time to start thinking of your safe place at home, work, and school. Please remember, tornado sirens are for outdoor warnings within ear’s reach. A NOAA Weather Radio is a great way to receive weather alerts indoors.

4-8-15 expect

 

 

 

 

 

 

 

 

In the hours ahead, key ingredients to producing severe thunderstorms can change quickly. We will continue to analyze new information throughout the day. Chief Meteorologist Alex Kirchner will have the latest on 13 News at 5, 6 and 10 tonight, to let you know if the timing or the threat for these storms changes.
Keep up with us on Facebook at www.facebook.com/13wxauthority and online at wrex.com/weather for the latest information.

 

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Posted under rain, science, severe weather, tornado, weather, Wind

This post was written by Morgan Kolkmeyer on April 8, 2015
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