El Nino, La Nina, and.... La Nada????

Odds are you've heard of El Nino and La Nina (the abnormal warming and cooling of the eastern equatorial Pacific waters, respectively), especially if you've been reading my blog.  This past winter, the Pacific Ocean was in a very strong La Nina, which helped to produce the heavy snows and cold winter across the U.S., along with the severe drought conditions over the southern U.S. this year.

Late last winter, the strong La Nina that helped to ravage the nation early last winter finally came to an end and the Equatorial Pacific waters returned to their normal temperatures.  But this presents it's own issues.  Usually, when a La Nina period ends, an El Nino period begins, even if it's just a weak one, and vise versa.  So the waters off the coast of western South America never stay normal for very long.  But this year, we are seeing an unusually long period of near normal water temperatures.  In fact, one scientist, Bill Patzert, a climatologist and oceanographer at NASA's Jet Propulsion Laboratory has coined the term "La Nada" to describe this period of normalcy.

The latest satellite data of Pacific Ocean sea surface heights from the NASA/European Ocean Surface Topography Mission/Jason-2 satellite show near-normal conditions in the equatorial Pacific. The image is based on the average of 10 days of data centered on June 18, 2011. Higher (warmer) than normal sea surface heights are indicated by yellows and reds, while lower (cooler) than normal sea surface heights are depicted in blues and purples. Green indicates near-normal conditions. (Credit: NASA/JPL Ocean Surface Topography Team)

The problem lies in climate forecasting.  A "La Nada" period brings with it a large amount of uncertainty in the forecasts.  Many scientists believe that a "La Nada" period will bring about "normal" weather conditions, however, previous similar "La Nada" periods have delivered unruly jet streams and wild weather swings, going from one extreme to the next.  And we actually saw this!  As the La Nina ended and "La Nada" began, the jet stream was able to swing back and forth across the U.S. wildly and helped to bring the blizzards to the Midwest, South, and Northeast, along with the tornadic storms across the South and Tornado Alley. 

However, some climatologists are wondering if another warm El Nino pattern will soon emerge - which would be great timing for the United States!  If an El Nino pattern were to develop this summer, much needed rains would likely come to the drought and wildfire stricken southern U.S.  Plus, a late summer El Nino pattern also dampens the hurricane season in the Atlantic, which peaks in late August & September.  Thus, it would bring much needed rain to the South along with a mild hurricane season!

Climatologist and Oceanographers will continue to monitor the progress of the "La Nada" and watch for signs of an emerging El Nino or a returning La Nina.  Until then, try to enjoy your summer!

Happy Summer! ... and why so much rain???

Summer has officially arrived to the northern hemisphere!  Summer officially arrive at 12:16 p.m today - while you were probably enjoying a good lunch.  This also means that today is the longest day of the year.

However, it sure didn't feel like summer around the Upper Midwest today.  A strong low pressure system has been influencing the region since Monday evening and will continue to linger through the day on Thursday before finally moving out on Thursday night.  Some of these storms have had heavy rain with them as well.  There is so much moisture available for this storm system that's it's not funny!    Luckily, warmer and drier conditions will return by the weekend.  By why is this storm so powerful?

It actually because of the monsoon that has been going on over southeast Asia and the Philippines.  Energy from the monsoon has managed to follow the jet stream across the Pacific and reform into storms just off the west coast.  As the new storm then moves across the Rocky Mountains, it meets a lot of available moisture in the Mississippi River Valley.  This is due to the flow around an upper level ridge of high pressure over the Southeast U.S. pumping the moisture in from the Gulf of Mexico.  Add to it a slowly moving weather pattern and you get a good soaker.

Many areas in the Upper Midwest are currently seeing floods (along the Missouri River - record flooding... yikes!) while other areas are under flash flood watches.  I got to experience a flash flood indirectly on Sunday morning as over 5 inches of rain in under 3 hours created a flash flood in the valleys around SW Vernon/NW Crawford County.  The resulting flash flood wiped out my Internet and phone connection making it impossible for me to forecast weather.  It also wreaked havoc on the rural road infrastructure in the region.  Not good.

Anyways, let's hope we don't get any more rain for a while.  We've had enough.  There are other areas of the country that need it worse - like Texas, Arizona, New Mexico, and the other drought stricken areas of the Southern U.S.

Until next time, stay dry - and Happy Summer!

What's with all the tornadoes this year?

I've been asked this by many folks this spring.  While the process of tornado formation is rather complicated, you basically (very basically) only need three things to happen.

1.) Warm, moist air riding over cold, dry air.  This basically describes a frontal boundary.  While tornadoes are certainly possible along a warm front, they are more common along a cold frontal boundary.  At a cold front, cold, dry air pushes under warm, moist air and forces it up.  This creates the atmospheric lift needed to form thunderstorms, especially supercell thunderstorms - from which the monstrous EF2 through EF5 tornadoes are born.

2.) Wind shear.  This is basically just a fancy meteorological term for a change in wind direction and speed with height.  For a tornado to form, you need to have wind at the surface moving in a different direction that at upper levels (basically the warm, moist air needs to be going one way and the cold,dry air another) and at different speeds.  This shear creates a rotation in the atmosphere parallel to the ground.

3.) An updraft.  This is provided by the parent thunderstorm from which the tornado forms.  An updraft (or vertically rising column of air) is what feeds a thunderstorm.  When the updraft of the thunderstorm meets the horizontally rotating column of air, the updraft bends the rotation into the vertical.  This creates the rotation of the supercell thunderstorm, and ultimately the tornado.

But why so many this year?  Well, in a way, it's a "perfect storm".  I know, bad pun.  But conditions this spring were perfect for tornado development over the southern and central United States - a set up only seen once in about 30 years!  First, unseasonably warm air over the Gulf of Mexico (caused by warmer than normal water there) moved into the southern and central U.S. early this spring.  Meanwhile, people in the North Central U.S. were experiencing an unseasonably cool spring.  As these two air masses clashed in the southern and central U.S., the jet stream (a rapidly flowing current of air in the upper atmosphere) dipped far to the south, creating insane amounts of wind shear over the area where these two air masses collided.  This allowed the thunderstorms created by the clashing airmasses to grow rapidly and become extremely severe and producing large, long tracked tornadoes.  And unfortunately they passes through large metropolitan areas - thus putting a large amount of people in their paths.

As we moved into late spring, the jet stream lifted back to the north as an upper level ridge formed over the southeastern U.S.  So the southern and central U.S. now has a break from severe weather.  Hopefully this remains quiet around the rest of the nation now.

Red in the morning.....

We've all heard this common saying: "Red sky in the morning, sailor take warning.  Red sky at night, sailor's delight!".  We were taught it as young children by our teachers and parents.  But does this and other common weather folklore actual have some truth behind them?  Below are some of my favorite sayings I've known and an explanation as to whether there is any truth to them or not.  If you have a saying you want me to try to "put to the test", comment below!

"Red sky at morning, sailor take warning.  Red sky at night, sailor's delight."

This lore does have some truth to it.  In the northern hemisphere, weather systems generally move from west to east across the globe.  Thus to have red clouds, the sun must shine on the undersides at either sunrise or sunset when the light from the sun passes through a large amount of atmosphere.  This results in the scattering of most of the shorter wavelengths of the visible spectrum (purple, blue, green) leaving behind the red end of the spectrum.  If the skies are red in the morning, this is because there is clear skies and high pressure to the east, allowing the sun to shine from that direction underneath clouds moving in from the west - typically ahead of a low pressure system bringing a chance for rain.  If the skies are red at night, the sunlight is coming in from clear skies to the west, signaling the approach of clear skies, high pressure, and fair weather.

"If birds fly low, then rain we shall know."

This too holds some truth.  A drop in air pressure will cause the air to become heavier and make it difficult for birds to fly at higher altitudes.  And a drop in pressure signals the approach of a low pressure system, bringing rain to the area.  The birds will also fly low to catch bugs (also flying low due to the heavy air) before the storms move in.

"If a circle forms 'round the moon, 'twill rain or snow soon."

A halo/circle around the moon is caused by light being refracted as it passes through ice crystals in high level clouds.  These high level clouds are often (but not always) a sign of an advancing low pressure system (the high clouds are typically the left over tops of cumulonimbus clouds that got blown away at high altitudes).  While rain or snow may not always follow, the presence of a halo around the moon provides a high probability of wet weather in the near future.

"From twelve 'til two tells what the day will do."

This one has no truth behind it at all.  There have been countless occurrences of nice clear weather in the early afternoon giving way to violent thunderstorms during the evening hours.  Plus, when you look at it, by noon, half the day is over with - so you already know what it has done!

"Clear moon, Frost soon."

This one does hold some truth.  In the fall and spring, a "clear" moon, or clear sky where you can see the moon, allows for perfect radiational cooling (allowing the daytime heat to escape to space).  When radiational cooling happens, overnight temperatures will drop quickly, and can lead to the formation of frost if temperatures get cold enough.  But obviously, this does not hold true for the summertime when overnight lows rarely dip to the freezing point.

"No weather be ill, if the wind is still."

Calm conditions (usually accompanied by clear skies, but not always) usually indicates the dominance of high pressure over the particular area.  Since highs are large areas of sinking air, they discourage the formation of clouds, strong winds, and precipitation.  On the other hand, most people have heard of the saying "the calm before the storm" in which conditions, including winds, go calm just before a large thunderstorm moves through.  Such a storm would be visible to the west though.  One more occasion in which this lore may not hold true:  in the winter time, calm air and clear skies may signal the approach or presence of an Arctic high which is typically accompanied by VERY cold air.  And it is very difficult to imagine temperatures of -30 to -40 F as pleasant.  BRRRRR!

"A cow with its tail to the west makes the weather best, A cow with its tail to the east makes the weather least."

I know this one from being raised on the farm.  Cows prefer not to have the wind blowing in their faces... it does not make them very happy!  So, as a result, they will typically stand with their backs to the wind.  Since west winds typically mean arriving or continuing fair weather (but not always) and east winds signal the approach of arriving or continuing unsettled weather (again, not always), this lore does hold a bit of truth.

How clean is your air?

How clean is the air you're breathing?  That's the quesiton you should ask often as it could impact your health!  This week, May 2 - 6, is Air Quality Awareness Week across the nation.  How clean the air we breathe is extremely important for our day to day lives.  The main trouble makers with air quality are low-atmospheric ozone and particulates (blowing dust particles and other substances).  On days when air quailty is very low (usually occurs when high pressure settles into an area with very light to calm winds), the NWS will actually issue an Air Quality Alert for the affected area and action days may be declared. On action days, the government urges people to cut down on their number of emissions (or how much they pollute the air) by using public transportation (they may even let you ride for free - but you have to check) and other various ways.

One way to check on the quality of the air in your area is to check www.airnow.gov .  This website will show you the current quality of the air you're breathing and also provide you with a forecast for the next day.  To learn more on air quality, I suggest you check out http://www.airquality.noaa.gov/ . 

Water, Water Everywhere!

Another element that can arise from severe thunderstorms is the threat of flash flooding.  Flash flooding typically occurs when an area that has extremely saturated soil receives heavy rains (or even light to moderate rain over a long period of time).  Flash flooding becomes even more dangerous in areas where topography can lead to water moving extremely fast down hill, such as mountain ranges... or the bluffs, ridges, and valleys of our very own Coulee Region.
Flash floods are the number one weather-related killer in the United States.  Flash floods are capable of moving boulders, removing trees, damaging buildings and bridges, and can even change the course of rivers and streams!  One such event happened in August of 2007 here in the Coulee Region.  Parts of La Crosse and Vernon County received between 11 and 15" of rain in about 36 hours.  The result was mudslides, rock slides, rapid rises in creeks and streams, road damage, bridges were wiped out and destroyed, and some creeks even changed course.  While this was considered a 1000 year event, it can happen anywhere and at anytime.

The best advice is that when a flash flood warning is issued for your area, head for higher ground!  Especially if you live along a creek or stream or reside in a valley.  And DO NOT DRIVE THROUGH FLOODED ROADS!  Turn around, don't drown!  The water in a flash flood is moving incredibly fast and you will be swept away before you know it.

Spring and Summer are Severe Thunderstorm Season!

When thunder roars, GO INDOORS!  While this saying is commonly used for lightning safety, it's a good rule of thumb for any thunderstorm, especially severe thunderstorms!  Severe thunderstorms are thunderstorms that meet one or more of the following criteria:  damaging wind gusts in excess of 58 mph, large hail (at least 1" in diameter), or a tornado.  Severe thunderstorms are most common during the hours of 3 p.m. and 9 p.m. between April and September, but in reality, can occur at any time of the day.

The strong wind gusts are the most common threat from severe thunderstorms, and are even more damaging if they are in the form of straight-line winds.  While a tornado would only affect a relatively small region, straight-line winds can affect entire counties and can even blow at hurricane-force!  In the mid to late 90's, La Crosse County was hit with straight-line winds, and the event is still evident today.  If you drive south on HWY 35 out of La Crosse and look closely at the north side of a bluff near Goose Island Park, you'll notice many fallen trees from the event laying west to east.

While not considered a criteria for a severe thunderstorm, lightning almost always accompanies them.  These electrical discharges from the skies can be hotter than the surface of the sun and are extremely deadly!  Lightning, second to flash floods, are one of the major causes for death from thunderstorms.  And you don't have to be under the thunderstorm to get struck.  Lightning can travel for miles away from it's parent thunderstorm.  So basically, when you hear thunder, you are close enough to be struck.  So when thunder roars, go indoors!