Chinook Winds Can Be Phenomenal and Dangerous January 11, 2010

Eating Snow Can Be a Problem Unless Your Name is Chinook

Winds that flow over the top of mountains will often come down the leeward side the range.  When the airflow moves from the higher elevation to lower, there is compressional warming.    If you compress air, it heats up and when it expands it cools. That is why oxygen under pressure comes out cold when released.    In the American West,  such a downslope wind is referred to a Chinook Wind.  The word Chinook means “Snow Eater” because Native Americans had noticed that when a warm wind blew down the mountains, the snow would disappear.  That would be from rapid sublimation, or the snow turning directly to vapor as a result of the influx of warm, dry air.  It is said that in places on the Eastern Slope of the Rockies, Chinook Winds are so common that houses have sliding wooden shutters to protect windows from flying debris.  Flying debris?  Are the winds that strong?  Yes…sometimes they are that strong.

Chinook Arch

On this date in 1972, The National Center for Atmospheric Research in Boulder, Colorado recorded a wind gust of 144 mph.  That is nearly category 5 hurricane strength.  South of Boulder at Rocky Flats, winds gusted to 105 mph and 90 mph gusts greeted downtown Boulder.  Stapleton Airport in Denver reported gusts to 53 mph on January 11, 1972 and 47 mph the following day.   In Boulder, more than 25 mobile homes were destroyed…some by wind and others by fire that erupted after they were overturned. 

Chinook Arch

Buildings suffered major damage, car windows were blown out, traffic lights blown away and trees, power lines and utility poles were down.  Some 75 families had to leave their apartment building due to severe structural damage.   Flying debris caused much of the damage, much as one might expect in severe weather or a hurricane.  Industrial complexes, government and private offices were evacuted out of fear of the results of flying matter and broken glass.  15 airplanes were damaged and hanger damage reported at Jefferson County Airport.   In Boulder, the damage added up to 2 million dollars and total reports for damage in the area came to about $25 million. 

Wild Pac NW Temp Swings-Daily Swings Jan 1972 Ft. Nelson BC

 So, what about the “snow eater” part.  In Denver, temperatures climbed to the mid 50′s.  It is not unusual for temperatures to rise 20 to 40 degrees in a matter of minutes.  The winds typically come from the northwest or west with the mountain crest sporting the “chinook arch.”  At the outset of a chinook, temperatures can vary wildly as warm air mixes with cold.  So, one spot may feel a 30 degree temperature rise in 15 minutes only to feel the rush of much colder air before the warming begins again.  In the Black Hills of South Dakota,  the town of Spearfish in 1943 experienced a 49 degree rise in temperature in just 2 minutes.  90 minutes after that, the mercury dropped 58 degrees in less than a half hour.  The low for the time frame was -4 F and a high of 54 F.  The system in 1972 was not isolated as on January 15, 1972 there was a 103 degree rise in temperature in 24 hours in Loma, Montana where the mercury went from 54 below zero to 49 degrees above zero.   Here are some other significant temperature rises:  Granville, ND on Feb. 21,1918 went from -33F to 50F in 12 hours, Fort Assiniboine, MT rose from -5 F to 37F in 15 minutes, Dec. 1 1896 folks in Kipp, MT  felt the mercury rise of 34 degrees in just two minutes and a total daily rise of 80 degrees and 30 inches of snow disappeared in half a day. 

The United States is not the only place to get this type of phenomena, but North America is the only place where they are called Chinook.  Elsewhere, they are known as Foehn Winds, but Chinook is much more fun.  There is some notion that the term Chinook derived from people of a region in the Columbia River Valley, the Chinooks, who first reported the winds to the white settlers.  But I like the Snow Eater story better.

National Snow Cover Still 59% of USA

Weather Bottom Line:  The Monday snow was pretty lame.  Not enough moisture.  Now, some folks may get above freezing on Tuesday afternoon as the clouds break but I suspect that the official end of the below freezing temperatures will be on Wednesday afternoon or maybe even midday.   The long wave pattern is finally changing and the cold air will retreat back into Canada.  That will mark about 12.5 days since we were above freezing in Louisville, one of the longest stretches on record, though I believe the longest such freezing streak runs to 17 days.   It’s going to be short of my early prognastication in late 2009 that we wouldn’t get above freezing until the 15th, but the 13th is close enough…or long enough.  Now, we get to the 40′s Wed through Friday.  There is still that big low that will develop in the Gulf.  The southern branch of the jet stream will swing down out of the southwest into Texas and a low will form. It will then eject into the SE US.  The jury is still out but at this time, most modeling data does not drag down cold air sufficiently to give us snow…but we’ll see.

2012: Doomsday Just 3 Years Away; Winter Begins Today, 1/2 Nation Under Snow December 21, 2009

El Triunfo de la muerte(1562)-Man has envisioned the Apocalypse (and been wrong) for centuries

Click Image to See how Fitz Destroys the World!

Is the End of the World 3 years from today in 2012?  The big hit movie that is out called 2012 claims that the end of the world will be upon us exactly 3 years from today.  There have been many end of the world movies over the years.  I like the Koko the Clown animated short that shows Koko unsuccessfully keeping the world from destruction from the actions of Fitz the Dog…click the photo to the right for the film…it’s great.  No, in 2012,  there will be huge floods, a big planet crashing into the earth and the sun will burn us to a crisp among other things.  This is all based on the Mayan calendar that ends on December 21, 2012. There’s even at least one website dedicated to helping you survive 2012.  But, according to the National Geographic, it’s all nonsense.  They point out that the Mayans had a long calendar that lasted 1,872,000 days or over 5125 years.  But, according to the experts, the Mayan calendar does not mark the end of all time, but instead marks the time when the calendar simply rolls over to another enormous cycle. 

I Like Koko's Version of the End Better

Now, the movie has sparked fear around the globe with reports of people threatening suicide to avoid the trauma of the impending doom.  Some women are said to have decided that they would kill their children and then commit suicide to spare the family from the fate of an apocalyptic world.  So much anxiety has been brought forth that NASA dedicated an entire webpage to try and aleviate fears.  However, back in 2006, NASA reported predictions that the current cycle of solar activity will peak soon.  A lead scientist predicted that it would be in…2012.  But others think its 2010 or 2011.  It is supposed to be the biggest burst of solar activity in 50 years.  Many people think that climate change is connected to solar activity, so this should add to the debate. 

Who knows what will happen 3 years from now…we don’t even know what’s going to  happen this year except that one thing is for certain…

December 21, 2009 is the start of Winter, or the Winter Solstice. It starts at 17:47 UTC or 17:47 Z.  That is 12:47 pm EST.  That is when the earth is positioned such that the sun shines directly over 23.5 degree south latitude, which is the Tropic of Capricorn.  Actually, I think its 23 degrees and 27 minutes south latitude.   The day is the longest in the Southern Hemisphere and the shortest of the Northern Hemisphere.  So, why is it the beginning of winter in the Northern Hemisphere?  It’s because the earth’s atmosphere has lots of water vapor.  What has that got to do with anything?  Well, the heat capacitance of water is rather high so it takes a while for it to warm up and cool down.  Think of a pot of water. When you add heat to the stove, the water doesn’t boil immediately, it takes awhile to heat up.  When you remove the heat, it doesn’t cool right away but takes awhile to return to room temperature.  Same with the earth.  When the radition of the sun is decreased, it takes awhile for that part of the earth to cool down.  From this point forth, the Northern Hemisphere will start receiving a more concentrated dose of solar radiation, but it will take a few months for the atmosphere to react.  Hence, spring does not come until around March 21 when the sun’s radiation is generally perpendicular to the equator.  NASA explains fully the seasons.

Heat Index Chart

The same principal holds for weather conditions with regard to geography or local atmospheric conditions.  In the desert, it is not uncommon for there to be a 40 degree difference in day and night temperatures.  But, along the coastal regions, there can be as little as a 5 degree difference between daily highs and lows.  That is because in the desert, it is dry and along the coast there is an abundance of humidity levels, or moisture content in the air.  That is why it is pretty tough for temperatures along the coast to hit 95 degrees or higher.  It does happen but there has to be perfect conditions.  People who talk about a place like New Orleans claims it gets to 95 degrees with 95% humidity.  That is simply not pragmatically possible.  But, what is quite frequent in New Orleans is a temperature of say 88 degrees with 60% humidity.  The chart on the left indicates that would create a heat index of 95 degrees.   Oh, it does happen from time to time in the middle east, particularly in the Persian Gulf.  I think Ethiopia has the record highest dewpoint at 94 degrees.  To make my point, if it were 115 degrees and the dewpoint was 94, the relative humidity would be about 54%. 

Now, one should not confuse the solstice with the perihelion.  The earth rotates about the sun, not in a circle, but instead in an eliptical orbit.  The earth tilts on it’s axis at about 23.5 degrees and when it is near its closest, or the perihelion, it is tilted away from the sun.  It’s seems counterintuitive for residents in the Northern Hemisphere, which is most of humanity, but the earth is closest to the sun not long after the winter solstice.  The earth’s perihelion is around January 3 of each year, which one in Chicago would call the dead of winter.   The aphelion is when the earth is about 152 million kilometers from the sun, or about 7 million kilometers more than it is at the perihelion.  You have a different reason to celebrate the 4th of July now that you know that July 4 is the earth’s aphelion.  I’ve always reasoned that nature shows its wisdom in this process.   See, when the earth is at its closest, the landmass of the southern hemisphere is tilted toward the sun…the region of the earth that has far less landmass than the northern hemisphere.  Perhaps we would suffer extreme global warming if the majority of landmass were closest to the sun when the tilt was toward the sun.  True perfection, this planet of ours.

Click on Image for 2 week animation of snow depth

Weather Dunce

Weather Bottom Line:  To begin Winter, the lower 48 of the United States has about a 52% snow cover.  Louisville got a bit of a dusting late Sunday night.  I typically do what weather guys do which is follow the Jackson Browne methodology and  “forget about the losses and exaggerate the wins.  But, I will break with tradition and tell you that I was a dunce.  I did not see this little snow event.  My guess is that it’s not because it wasn’t there and was a “surprise” as newscasters like to say when a forecast doesn’t come about.  No, I believe that it was probably right there in the data and I simply missed it.  I was a dunce.  But, I am confident of victory regarding Christmas.  It will not be a White Christmas.  The big storm coming out of the southwest will pass to our west.  We will have rain with steadily rising temperatures as we go through the week.  As I had mentioned the other day, there was a weird push of cold air with the low remaining somewhat stationary to our northwest, which I believe is an indication that the low is going into it’s dying stage and we have an occlusion developing.  But, I don’t think that will result in any significant snow and if anything does come about, it would be in the form of a dusting for Friday.  But, after warming above seasonal levels by midweek, we go back below seasonal temperatures for next weekend.