Lightning - Shocking.... isn't it?

So I seem to be on a roll with the bad puns.  Anyways, today's topic is lightning safety.  Lightning is a serious issue during thunderstorms, and you don't have to be directly under a thunderstorm cloud to get struck (did you know that lightning can travel as far as 10 miles away from the cloud?)!  Lightning is often in the presence of heavy rain or hail, strong winds, and even tornadoes, so they are in "good" company. 



Good advice!

Luckily, lightning has a friend.  A friend that gives you advanced warning that it is coming.  Thunder.  A saying presented by the National Weather Service for safety purposes is "When thunder roars, go indoors!"  The point here is, that when you hear thunder, that means that there is a lightning-producing thunderstorm in the vicinity and that you should move indoors for your own safety (not only from lightning, but from other severe weather that may be present as well).  Simply put - if you don't want to get struck by lightning (and who does?), get inside.  And stay there for at least 30 minutes after the storm has ended, since lightning could still strike you as the storm moves away.

But what if I'm inside????  Lightning can't hit me then, right?
Well, I hate to pop your bubble, but it can actually affect you in your home.  Stay off of electrical devices connected to the power grid (telephones, computers, etc.) as lightning can cause a power surge and destroy these devices.  The best idea is to unplug these when a storm moves in.  Also, stay out of the shower/bath.  If lightning strikes nearby your home, it's electrical current can actually follow your home's plumbing!  Not to mention, if your home is struck and manages to catch fire, you'd have just moments to get out due to the fire... and if you come out of the shower/bath, you'd be naked and would likely waste precious time putting clothes on!  So just stay away from water and electrical devices, just to be safe.

Also, the water point brings up another issue.  If you are outside fishing or swimming in a body of water and hear thunder or see lightning, leave immediately!  Water is a perfect conductor for electricity!!!!!

If you are traveling in your vehicle, you can relax if your vehicle has a hard-metal topped roof.  If lightning strikes your vehicle, it will safely pass to the ground beneath you... but it will also likely kill your car's on-board computer, which is a costly repair.  You'll be safe, but you car will be dead.  The best bet is to not travel through a thunderstorm unless absolutely necessary!  Stay home or pull off the road and wait for the storm to pass.

No one wants to get struck by lightning.  So just get inside and play it safe, staying away from water sources and electrical devices.

Wind just blows me away!

Okay.... so that was a bad pun.  But hey, at least it is accurate!  Wind is a crucial part of the atmospheric system... but when it becomes strong, it can make things dangerous!  Strong winds associated with severe thunderstorms are often, I feel, the most neglected factor of the storm by the public.  People think they can handle a little wind.  But what happens when that wind gets too strong?  Things happen.

Straight-line wind damage in Burnett County, WI on July 1st, 2011.
Courtesy of WQOW-Eau Claire, WI.

Strong winds associated with severe thunderstorms can be very destructive, especially when they are
straight-line winds.  Straight-line winds are very powerful because of their non-divergence and can easily topple entire forests (a past event like this is still evident along a few bluffs south of La Crosse, WI) and damage homes. 

The National Weather Service will issue severe thunderstorm warnings for storms that produce winds in excess of 60 mph to alert the public of the danger.  When such a warning is issued, it is advised that you get into a basement or interior hallway and stay away from windows since strong thunderstorm winds can blow in your windows and send glass flying around the room - injuring anyone in the path of the glass.  Strong winds can even topple old or poorly constructed buildings, so choose a study structure to seek shelter in.



Image of a microburst in Australia.

In addition to strong winds produced by thunderstorms, there is another type of strong wind that can cause significant damage to property and the public.  A microburst is a brief, localized, but powerful gust of wind that originates from quickly sinking air.  They can produce damaging straight-line winds at the surface that are similar to tornadoes.  And there are two types of microburst, wet and dry... and you can probably figure out the difference there!  Just like thunderstorm winds, microbursts are also destructive, so you should seek shelter immediately if you are warned about them (although there the time between an issued warning and being able to take cover is still very short!).

So all in all, be careful with the wind.  Sure it can help you rake the yard in the fall (by blowing all your leaves into your neighbor's yard), but it can also be very destructive.  Take the warnings seriously and stay clear of those windows!

Hail hurts!

Most people east of the Rocky Mountains have seen this type of precipitation during a severe
thunderstorm.  Hail, which is a frozen ball of ice, can cause significant damage to property and even cause people their life!  From crop damage to automotive damage and hospital stays, hail can have a dramatic impact on a person's life.

So what do I do?

When large hail (greater than 1" in diameter - this is the stuff that causes the most damage) is indicated by radar in a near by thunderstorm, the local National Weather Service office will issue a severe thunderstorm warning to alert the public.  If this warning is issued for your area, stay inside!  If you have some time before the storm hits, you may be able to get your vehicle inside a structure, but your safety should come first and foremost.  Hail is often accompanied by strong winds, heavy rains, and even tornadoes, so you should take shelter immediately.

The record holder 8" hailstone that fell near
Vivian, South Dakota on July 23, 2010. 
It had a circumference of 18.625" and weighed just shy of 2 lbs!

In addition, if you are outside, seek shelter immediately.  Hail does hurt... especially large hail.  While most hail is often small, it can and have gotten as large as a bowling ball!  Imagine that hitting you on the head over and over!

So just play it safe.  If hail is expected or IS falling in your area.  Stay inside.  You can go outside after the storm has passed to look at and collect some of the hail if you wish.  Just keep in mind..... hail hurts!

Turn Around.... Don't Drown!

If you are one of the many people out there who watch television and radio weather reports or get information directly from the National Weather Service (NWS), you have heard this saying before.  If this saying is new to you, commit it to memory - it could save your life!

"Turn Around, Don't Drown" is the common safety tip for dealing with floods while traveling in a car or on foot.  If the roadway in front of you has water over it (even a small amount), turn around and find a different route.  The water could actually be concealing a huge gap in the roadway created by the moving flood water.  Also, you may have no clue as to how fast the water is moving, and it only takes a few inches or feet (depending the vehicle) of water to float a vehicle.  Which means you could very easily be swept downstream by the rapidly moving flood water.

Okay, so what if I'm not in a vehicle.  What do I do then?
First, I would recommend getting a NOAA Weather Radio that can alert you to the watches, warnings, and advisories that the NWS issues.  They come in portable and non-portable varieties.  These devices issue alerts for floods and flash floods along with information to keep safe.  Secondly, if a watch or advisory is issued for your area, be on the look out for rapidly rising water and take necessary precautions!  Get ready to evacuate if necessary and make arrangements in advance.  However, if a warning is issued and you live in a flood prone area, abandon your home immediately and get to higher ground.  Flash floods can develop in minutes or hours dues to excessive rainfall, a dam or levee failure, or the release of water behind an ice jam - so you may not have much time to evacuate before your escape route is cut off by flood water.

I also want to mention that you should never, ever walk, run, or swim through flood water.  It only takes 6" of fast-moving water to knock you off your feet and the current is often extremely fast.  Again, turn around, don't drown.  And please don't think that you can outrun a flash flood!  Many have sadly tried and have lost their lives because of it!  Just stop, turn around, and find another escape route.

Remember... Turn Around, Don't Drown!

Oh where, oh where did my twister go?

Even though storm chasers are missing tornadoes....
I'm quite positive the public is not!

If you have noticed a lack of tornadoes across the nation so far this spring, you’re not alone.  Many meteorologists and storm chasers have indeed noticed the shortage of twisters across the U.S. so far this spring.  Tornado season usually begins to kick into high gear in March, but this year has been relatively quiet thus far.

If you may recall, last year was quite active.  By early April 2012, there had already been 290 tornadoes (which resulted in 60 tornado-related deaths).  Now fast forward to early April 2013, and the nation has only seen 137 reported tornadoes and, thankfully, only 2 fatalities.  So what is going on?  Why is the amount of tornadoes less than half of what we saw last year?  What changed?

The main reason that is has been so quiet (tornado-wise) thus far is also one of the biggest topics you hear or have talked about among your friends – the colder than normal spring and late winter! The cold air over the central and eastern U.S. can largely be blamed on a stationary high pressure system over Greenland and the North Atlantic which has blocked the normal flow of storm systems across the nation by altering the jet stream.  Normally, the jet stream begins to bring warm, moist air (a critical component for tornadogenesis) from the Gulf of Mexico into the central U.S. this time of year.  But this year, the flow has been the opposite, bringing cool dry air in from the north.

So when will this pattern change?  The process is well underway.  The blocking high pressure system over the North Atlantic has been weakening and warmer temperatures and moist air have moved back in from the Gulf of Mexico in recent days.  As a result, the first significant outbreak of severe weather across the nation could occur early next week as several storm systems slide across the central part of the nation.  The first of these systems will come through the Midwest on Sunday into Monday with the potential for gusty winds and some large hail.  This first system could then set the stage for a much larger severe weather outbreak by Tuesday and Wednesday when a second storm system slides through.

The categorical (left) and probabilistic (right) outlooks for severe weather for Monday, April 8th, 2013.
Courtesy of the Storm Prediction Center.

The severe weather outlook areas for Tuesday, April 9th (in red)
and Wednesday, April 10th, 2013 (in purple).
Courtesy of the Storm Prediction Center.

So what about folks up here in Wisconsin?  Although we can see severe weather and tornadoes now, our tornado season begins to ramp up in late April and continue into August (but they CAN occur anytime of the year, as evidenced by the tornado that hit near Kenosha on January 7th, 2008).  But at least for next week, we should remain safe in the severe weather department (unlike 2011 when the earliest outbreak in WI was on April 10th!).

Just out of curiosity, looking back on the past few years, 2012 was actually a very quiet year for tornadoes in Wisconsin.  According to the National Weather Service, there were only 4 reported tornadoes in Wisconsin in all of 2012 compared to 38 in 2011 and 46 in 2010.  So let's hope for another quiet year in 2013! 

Also, please note that Severe Weather & Tornado Awareness Week in Wisconsin in April 15th through the 19th, with a statewide tornado drill on Thursday, April 18th around 1 p.m. (should severe weather happen on that day, the drill will be postponed until Friday, April 19th).  Next week, I plan on posting regularly informing you how to stay safe in various weather situations, and then during Severe Weather & Tornado Awareness Week, I plan on posting on the various types of severe weather we see!

Hope to see you back here soon!  :)

Cold + Snow in March = Crabby People. Why is it so cold?

If you are like the many people I've heard from in the past week or so, you are very sick of the cold and snow that the area has seen over the past few weeks.  Many people are longing for the warmer and snow-less days of spring that typically begin around this time of year.  However, we have been stuck in a cold and snowy pattern that doesn't seem to let up.  This has led to many crabby people around the region!  And it has left many wondering why.

Negative and positive phases
of the Arctic Oscillation

It all has to do with the Arctic Oscillation (AO).  The AO is an index of sea-level pressure variations north of 20°N latitude and is either given a positive or negative value.  This index is directly related to the degree to which Arctic air can penetrate into the mid-latitudes, where we live here in the Midwest.  When the AO is positive, this symbolizes low pressure in the Arctic.  This allows the mid-latitude jet stream to blow strongly and consistently from west to east in what is known as a zonal or near-zonal flow.  This keeps the cold Arctic air locked into the polar region.  However, when the AO becomes negative, this means that there is high pressure in the polar region, resulting in larger swings of the jet stream (much less zonal) and allows for greater movement of very cold polar air into the mid-latitudes.  These large swings in the jet stream also result in strong storms sliding along the stream which can produce several inches of snow at a time.

Well, right now, the AO is negative.... very negative.  As the chart below shows, the AO is currently at its lowest level of the winter with an index value near -5.5!  This means that the high pressure over the arctic is strong, and is sending plenty of cold air southward into the eastern half of the nation (as you are probably well aware of)!

The Arctic Oscillation Index during the 2012-2013 winter months. The black line is the observed number, while the red lines are the predicted values for the near future.

Luckily, the AO index is predicted to rise dramatically through April 1st, which, if correct, means that the cold air will be retreating back into the polar regions and more spring-like air will move into the region.  Rejoice spring lovers!  Granted, it does not mean a complete reversal of the pattern, but it will mean that the cold conditions we are seeing across the eastern half of the country will ease up.

The April temperature outlook (left) and precipitation outlook (right) released by the Climate Prediction Center on Thursday, March 21st, 2013

And the April outlook released today from the Climate Prediction Center tends to agree.  They are anticipating slightly above average temperatures for the eastern and southern portions of the United States during the month of April, with below normal temperatures along the west coast.  And if you are wondering about precipitation, it appears the Great Lakes is expected to see above normal amounts of precipitation while the coastal areas may see below normal precipitation.

So it appears that the month of April should be near normal temperatures but wet for the Midwest.  So, yes spring lovers.  Rejoice.  Spring is on the way!

 

Time for a bigger rain gauge!

Wait…. What?  We’re in the middle of a drought and you’re talking about getting a bigger rain gauge?  What’s going on here?


The map shows location of selected rain gauges,
with blue (red) triangles depicting sites with
significant increasing (decreasing) trends,
and white circles showing sites
 with little or no change.
(Credit: Adapted from Villarini et al. (2013))

Even with the current drought situation plaguing much of the Midwest, some of you may actually want to consider getting a bigger rain gauge if you enjoy weather-watching.  Why?  Well, heavy rain events are becoming more common!  A study by the University of Iowa recently published in the Journal of Climate suggests that heavy rains have become more frequent in the Upper Midwest over the past 60 years, holding true even with the current drought situation.  The study also found that temperatures over the center of the nation are rising too, which helps to explain the heavy rain issue.  Warmer air can hold more water vapor, and when more water is available in the atmosphere for precipitation, a greater chance for heavy rains exists.

Lead author Gabriele Villarini stated “We have found that there is a tendency toward increasing trends in heavy rainfall in the northern part of the study region, roughly the Upper Mississippi River basin.  We tried to explain these results in light of changes in temperatures.  We found that the northern part of the study region – including Minnesota, Wisconsin, Iowa, and Illinois – is also the area experiencing large increasing trends in temperature, resulting in an increase in atmospheric water vapor.”

However, the current drought that has affected the Midwest is not part of the study.  It has occurred too recently (over the past year or two) while the study focused on rainfall and temperature data from about 1950 to 2010.  Also, it should be noted that the study was not looking at average annual rainfall, but rather just heavy rainfall events.  So while the area may currently be experiencing a deficit in overall rainfall, the area may be in the normal range when it comes to the number of heavy rainfall events/days.

In addition to the rising temperatures adding to the water vapor in the atmosphere, other studies point to changes in irrigation over the Ogallala Aquifer (which runs from Nebraska to northern Texas) as a source of increased water vapor in the atmosphere.  This suggests that human changes in land use, land cover, and agricultural practice also contribute to the increased frequency of heavy rains.

So in our warming atmosphere, you can expect to see more heavy rainfall events across not only the Upper Midwest but possibly the globe as a whole.  This will also increase the frequency and risk of flash flooding in the area as heavy rains quickly flow into area streams, creeks, and rivers before the ground can absorb the moisture (for those of you in the Coulee Region, think back to August of 2007 when parts of the area received over a foot of rain in about 2 days).  Keep this in mind if you live in or plan to move to a flood prone area in the future so you are aware of the risk.  It also raises the importance of early warnings from the National Weather Service and local media.  I will be going over the meanings of the warnings, watches, advisories, etc. that the National Weather Service issues coming up in April during Wisconsin’s Severe Weather Awareness Week (April 15^th – 19^th), so watch for that.  It never gets old going over these important messages since they save lives!