Wind chill.  These two words will be heard plenty over the next couples days in the midst of the latest outbreak of Arctic air (surprisingly, the La Crosse area 26 days with overnight lows below zero during an average winter; last night was just the first).  As you may know, wind chill is an apparent temperature.  If you go outside when the temperature is 5° with no breeze, and later go out when the temperature is 5° with a 10 m.p.h. breeze, the later time is going to “feel” a lot colder, despite the temperature being the same.

The reason for “feeling” colder lies in the role of that constant breeze or a stiff wind.   Moisture in your skin will evaporate when exposed to a breeze.  The evaporation process creates a cooling effect, which is why a fan or a breeze feels refreshing on a hot summer day.  That same breeze does not feel nice at all during the winter because of the same effect.

We may be "feeling" a wind chill of -10° to -25° over the next few days.

Here’s a chart showing how large of an impact just a light breeze has on how frigid temperatures feel.  Wednesday night through Friday will be especially nasty, as winds stay steady between 15 and 20 mph.  Advisories will be in effect for this time period because frostbite can set in within 10 minutes with wind chill that cold.  Here’s a link on our website about frostbite for tips on how to ward off the dangerous condition, especially for parents with little kids.

Try to stay warm!  Relief arrives this weekend with temperatures in the 30′s.  -News 19 Meteorologist Alex Kirchner

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A typical Midwestern winter had to start at some part, right?

Up until January 12th, I’m sure plenty of snowmobiles, sleds, and skis were collecting dust instead of powder.

Figure 1: 4.3″ of snow fell last month, which was 7″ below average, and at least 20″ behind the previous 4 Decembers.

December had an average high temperature of 35° and a whopping 4.3″ (Fig. 1) of snow for the entire month.  This month has had two record-setting 53° days, an average high of 41° until Tuesday, and just a trace of snow through Jan. 11th.

Why has this winter been so mild and relatively snow-free, despite predictions in November saying the opposite?

Let’s start with La Niña, which is influencing our weather right now. La Niña may sound familiar, as last winter was a La Niña winter. We were definitely wetter than average, especially last December.

During a La Niña event, cooler than average waters occur in the Pacific near South America (Fig. 2).  The jet stream that drives our weather gets its strength from the temperature contrast between the Equator and the North Pole, and when that contrast is weakened by a cooler Pacific, the jet sinks south.  In turn, weather patterns in North America are affected by the altered path of the polar jet (Fig. 3).

Figure 3: Usual impacts of La Niña on U.S. winters

We’ve been anything but cooler and wetter than average, so far.  Here’s the next step:  another disturbance called the Madden-Julien Oscillation (MJO) has come into play this winter (see how complex weather can be!).  I won’t bore you with the details, but the MJO can modify the jet stream further, and push it north into Canada.

Figure 4: The MJO alters the jet stream, and keeps precipitation and cold air north of the Midwest.

This matches the pattern we where in for the start of this winter (Fig. 4), with the polar jet keeping cold Arctic air bottled up in Canada (keeping us warmer than average), and keeping the main storm track north of the Midwest (less chances for snow).

Looking ahead, now that there is a decent amount of snow pack after Thursday’s storm, temperatures will stay colder than where we’ve been lately for a while (snow reflects sunlight, so the sun cannot heat up the air as easily and temperatures stay colder).

Figure 5: The CPC's forecast for the next 3 months

The Climate Prediction Center is predicting temperatures to stay near or slightly above average for the rest of winter, which may be MJO’s doing.  La Niña will still be playing a role this winter.  The CPC also has above average chances for precipitation for the Midwest (Fig. 5).  I guess that means we may have a chance at a true winter full of snow after all!  Stay tuned!

News 19 Meteorologist Alex Kirchner

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The News 19 Forecast Team traveled to the Kickapoo Area School District in Viola, WI last Thursday, September 22nd, kicking off the 2011/2012 Weather Academy season!  With a new curriculum and freshened graphics, we’re looking forward to taking weather education to a whole new level.

Weather Academy is an education program that teaches area school children about weather processes.  They also learn the always important safety procedures during hazardous weather events.  250 students attended the afternoon assembly, accompanied by their grandparents and staff.  (Grandparents’ Day)  The assembly was followed by an in-school open house, where the kids drew Weather Windows for the Daybreak show, saw neat experiments, and practiced their forecast presentation skills in front of the Junior Weather Wall.  Overall, it was a very positive experience for the children, grandparents, staff and the forecast team!

Including Kickapoo Elementary, we will travel to six schools this school year for Weather Academy.  The schedule is as follows:

• Kickapoo Elementary – 9/22/2011
• Summit Environmental School (Summit Elementary, La Crosse) – 10/13/2011
• St. Patrick’s Catholic School (Onalaska) – 12/1/2011
• Blair-Taylor Elementary – 1/26/2012
• Sand Lake Elementary – 4/5/2012
• Seneca Elementary (Eastman, WI) – 5/3/2012

We look forward to the rest of the school year and the opportunity to help area children learn more about how the atmosphere works!

If you would like Weather Academy to come to your school, contact the forecast team at news19.weather@wxow.com.

Until next time, see you on the air!

News 19 Meteorologist Nick Grunseth

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As a meteorologist, hearing and speaking “weather lingo” has become a part of my daily life.  Just ask my wife!  On a day when severe weather is possible, I flip some proverbial switch that launches me into full weather nerd mode.  When she asks when the storms will hit, I’ll tell her when, but only after I explain how the increasing instability, appropriate wind shear, wet-bulb zero heights near 8,000 AGL and plentiful moisture will make it a busy day at the weather office.   At first, she used to tell me to “tone it down.”  Now, she flips her proverbial filter switch, picks up her book, reads a few pages, and waits for the punch-line.  Smart woman.    But when it comes to expecting precipitation, there’s one term I don’t mention very often around her, or even with my family and friends: “percent chance.”

When it comes to forecasting precipitation, knowing the “percent chance” of an upcoming event is important to many people.  However, some people who put faith in this number mistakenly interpret the true definition of “percent chance” in weather terms.  If I go out on the street and ask people what it means if there’s a 30% chance of rain today, a majority will probably say it means 30% of the area will receive rain, while the other 70% will stay dry.  Some may also state ”looking at this date over the past 100 years, it rained 30 of those days.”  While it’s a good try, both of these understandings are false.

The percent chance of precipitation is also known as the probability of precipitation. (POP)  The National Weather Service has been using POPs for decades, assigning them to daily forecasts.  Basically, when a meteorologist says “there’s a 30% chance of rain today,” it means there’s a 30% chance any random point in a given area will experience measurable precipitation.   And the number isn’t just pulled out of the air.  (Pun intended, of course!)  The number 30 is determined by forecasters and computer models.   It means three out of ten times when conditions were similar in the past, it rained.  So yes, the higher the percentage, the more likely it’s going to rain or snow, but it all depends on the size and history of your forecast area.

So why the confusion?  A large part of the problem is the lack of explanation by broadcasters and internet resources.  You’ll rarely hear from a broadcaster what percent chance means; or, worse yet, the broadcast does not correctly understand the whole concept.  On internet forecast pages with percent chance listed, there’s usually no written statement next to the forecast, explaining it’s probability rather than coverage area.  The lack of explanation, combined with human nature’s urge to jump to conclusions, can lead to a misunderstanding of what the meteorologist or broadcaster is trying to relay.

The WXOW News 19 forecast team frequently displays the precipitation risk, but not the exact chance of precipitation.  You’ll hear mentions of “slight, moderate, and likely.”  You will also hear and see the terms “isolated, scattered, hit and miss, widespread,” etc.

I have many friends and colleagues that live by percent chance.  That’s perfectly fine and I don’t shun them.  Their forecasts have a lot of good, quality information too.  A POP is there to provide the meteorologist an understanding of what the atmospheric setup is like.  In my personal opinion, the reason that specific number does not make it to air is because I feel avoiding an exact percent chance as much as possible provides you, the viewer, a better idea what the weather will be like.  Remember the whole area thing?  News 19′s viewing area is far different compared to other media outlets.  It’s also not fair to write on a graphic “50%,” when that chance exists closer to Prairie du Chien compared to the “10%” that would exist in La Crosse.  Second, it can be very confusing!  I am a big fan of taking the complexity of numbers and equations and making a forecast that’s easy to understand.  More or less, you’re just trying to find out if it will rain or not, right?  So why make your experience of understanding the weather forecast similar to writing a college mid-term?  No thanks!

Thanks for reading, and feel free to post with comments or questions!

News 19 Meteorologist Nick Grunseth

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Hi everyone;

We have seen our share of tornado pics, video and scenes of natural disasters this year right here in the United States, but a weekend occurrence has caught my eye and attention. A volcano in Chile erupted over the weekend. Photographers have caught an unbelievable array of stunning images of the Puyehue volcano. Here’s a sample:

For more pictures and the story details use this link.

You’ll be amazed at the images!

Dan Breeden

News 19 Chief Meteorologist

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There have been plenty of mentions of the letters ‘E F’ followed by a number lately to describe how strong a tornado is, like the EF-2 tornado that struck La Crosse on Sunday, or the EF-5 tornado that devastated Joplin, MO.  Besides a ’5′ sounding like a stronger tornado that a ’1′ or ’2′, what do the numbers mean?

The ‘Enhanced Fujita scale’, or EF scale, is the system used to rate the strength of a tornado.  Professor Tetsuya Fujita, partnering with Allen Pearson, came up with the scale in 1971.  The scale uses the amount of damage caused by the tornado as an indicator of its strength, rather than its size.  A tornado could be over a mile wide, but if its winds are relatively weak, or it goes through a dirt field and does not hit anything, it really was not a strong tornado, was it?   Compare that to a smaller tornado fifty yards wide, but with strong winds that can demolish houses.

The ‘Enhanced’ portion of the EF scale was implemented in 2007 after a team of meteorologists and wind engineers updated the strength indicators of the scale.  Here’s a chart with the older Fujita scale, and the Enhanced Fajita scale:

Courtesy: Storm Prediction Center, National Weather Service

The National Weather Service sends out damage survey teams after a possible tornado goes through, and based on amount of damage (for example, when looking at a house roof, are there a few shingles blow off, or is part or all of the roof missing?), the survey team can derive how strong the winds were (based off of wind experiments engineers and meteorologists conduct), and from there, can derive a tornado’s strength.  If the winds were estimated to be around 100 mph, the tornado would be considered an EF-1.  Here’s a chart with the older Fujita scale, but a good description of the damage done by each type of tornado:

Courtesy: www.tornadoproject.com

Thankfully, the tornadoes that went through the Coulee Region were on the lower end of the scale, and no one was seriously injured or killed.  Any tornado is dangerous, so always be prepared or alert when severe weather threatens. 

Feel free to pass on any questions or concerns.  I would love to help!

News 19 Meteorologist Alex Kirchner

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Ever since I arrived at WXOW-TV in late 2009, I have heard from countless people, some of them life-long residents, why La Crosse lives in a secure, protective bubble when it comes to severe weather.  Here’s one of many sayings:

“La Crosse will never be struck by a tornado.  It’s not possible.  Don’t you know where three rivers meet, a tornado can’t form?”

A show of hands: how many of you have heard this before?  You’re not alone.  Another show of hands, and be honest: how many of you believed this myth?  If so, don’t feel bad.  This is a good learning experience! 

Many of us have heard the tall tales of the rivers and the bluffs acting like a barrier to keep tornadoes away.  But on May 22, La Crosse received a rude awakening.  It is not safe from tornadoes; rather, it’s just as vulnerable as any other community in Wisconsin or Minnesota.

To our life-long residents’ credit, this is the first tornado in La Crosse in 45 years, and many were young or may not remember that far back.  The last time La Crosse was in this postition was July 10, 1966.  An F1 tornado touched down at the airport, flipping planes and a car.  Minor damage was reported.  A stronger, F2 tornado touched down in southeast La Crosse five years earlier, May 1961.  This twister did considerable damage to garages, homes, vehicles, and anything else in it’s path.  Thankfully, with both these events, no fatalities were reported.

So what does science say about the myth?  For decades, meteorologists have attempted to dispel this myth and others using scientific proof.  For instance, did you know that the top of a typical severe thunderstorm in the Midwest stretches ten miles above the ground?  In a tornadic situation, the rotation is not from the base of the cloud to the ground; rather, the violently rotating column of air extends all the way to the top of the storm.  Logically thinking: a ten mile tall storm or a 700 foot bluff – who do you think wins?

And what about that river theory?  Well, there’s no scientific evidence that points to tornadoes avoiding rivers.  There’s no magical pressure or temperature difference that will keep the tornadoes away (unfortunately), because once again, the storm is so huge, comparing it to the Mississippi is like comparing a RC car to a semi.  I just doesn’t work out logically.

Thankfully, in the end, no one was killed or seriously injured from the May 22nd storms.  But many of us learned more about how weather works.  Just remember: it doesn’t matter where you are or what geographical features you may have around you.  There’s always a chance a tornado could tear through your community.  Always be prepared and keep it tuned.  We will work hard to keep you safe!

If you have any questions or comments, feel free to leave them!  I would be more than happy to answer!

News 19 Meteorologist Nick Grunseth

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Hello Everyone;

In this weird weather year of 2011, the La Crosse stats just keep piling up. After the first 4 months of the year(no surprise here, I’m sure) the precipitation numbers indicate 2011(9.84 inches) ranks ninth in the wettest start to a year.

2008 with 11.21 inches ranks 4^th. And in the top spot you have to go all the way back to 1945 which recorded 11.77 inches.

Incidently,  Rochester’s 2011 ranks 6^th with 9.03 inches.

Lastly, it’s a little scary to see all the reports of severe weather and tornadoes around the country this spring. Let’s hope that trend reverses in the coming months.

Until next time…

Dan Breeden

News 19 Chief Meteorologist

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Hi Everyone;

It was a day to remember for the News 19 Forecast Team. We went into continuous coverage mode for the latest severe weather outbreak. We were continuously on the air for one hour and 32 minutes; not the record, but a marathon session nonetheless.

It started several days earlier as the computer guidance available pointed to the development of a strong low pressure area that would move in and draw warm moist air into the region. Saturday night a warm front moving north produced heavy rain producing thunderstorms, leaving us in the warm sector of the system. Heat, humidity and the right combination of wind shear and instability gave us the makings of the severe outbreak.

The storm’s cold front provided the trigger for the supercell rotating thunderstorms and it looked as if tornadoes would be possible. Doppler radar indicated relatively weak circulation as they moved through the immediate area and tornadoes didn’t quite spin up for the WXOW viewing area. The area east and northeast of here in central and northeastern parts of the state were more favorable, and indeed, did see a couple of twisters.

We went on the air as the storms moved into Southeast MN, and radar indicated impressive rainfall and hail signatures. Here’s a look at radar reflectivity as large hail and damaging winds moved into the Caledonia vicinity.

The next image shows the storm approaching La Crosse moving between 60 and 70 miles per hour. The southern end of the storm produced the worst of the conditions with hail over 3 inches in diameter in some instances.

The storm continued at a breakneck pace as it moved into western La Crosse County and then Monroe County. Here’s another look as it moved east. The V-shaped radar echo is a common severe weather signature. This storm was in this configuration for a long time, and as it moved into Juneau County and a more favorable environment, it produced 2 tornadoes at one point producing EF2 damage on the Enhanced Fujita Scale, near Arkdale, WI. A funnel cloud was spotted near Oakdale in Monroe County prior to producing the tornadoes.

Here are a few pics of hail from the path of the storm.

Thanks to all who sent in the pics of your severe weather experience.

Dan Breeden

News 19 Chief Meteorologist

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Hi Everyone;

As we play the waiting game for the 2011 version of Spring Flooding, one can’t help but think back to other big floods of note. In this case you don’t have to think back very far. Just last September heavy rains fell and rivers rose, including the Zumbro, Black, and Trempealeau Rivers. They all hit record or near record levels. Even the Mississippi rose to about 1.4 feet above flood stage.

Think now back to June of 2008, record floods from very heavy thunderstorms. Those rains concentrated on areas southeast of La Crosse so the Mississippi there was spared, but the Kickapoo and others were not. Major damage occurred. Here’s a graph of the river levels:

The river exceeded the record stage by almost a foot.

Let’s go back another year. Ouch! How about the Flooding of August 18-20, 2007. Flood waters ravaged Southeast Minnesota and Western Wisconsin. Here’s a look:

Okay those are from thunderstorms, let’s check on spring snow melt related flooding: April and May of 2001 come to mind. La Crosse crested at 16.41 That’s almost 4 and a half feet about flood stage, and it is the 3rd highest crest on record!

But, you have to go back to 1965 to find the grandaddy of all spring floods. A large part of the Northside of La Crosse was inundated, as the water rose to the all time record level of 17.90 feet at the La Crosse gauge on April 21st.

Somehow those old black and white photos add to the legend of that weather event. I think if you were to ask people from around here, the Spring Flood of 1965 might just be the most famous(infamous?) of all La Crosse weather events. For more info follow this link.

Until next time.

Dan Breeden

News 19 Chief Meteorologist

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