Friday, January 31, 2014

Don't Believe Snowfall Forecasts A Week Out

This pattern gets very tricky with a slightly southerly flow (WSW to ENW) this weekend and especially over the next week. The probability for more "panhandle snows" is growing.

In this age of the internet where every possible computer model and projection is available 24/7 on hundreds of websites and apps, anyone can post snapshots of these computer outputs especially when a rumor of heavy snow gains steam (next week). The problem with this is twofold. First, most people believe that these neat looking maps mean more accurate forecasts especially farther out.  Secondly, most people treat these snapshots as Gospel and believe that these computer model depictions are actual forecasts. Nothing could be further from the truth. The phrases "could happen" with "mostly likely" to happen become interchangeable. Both phrases couldn't be more different. Wxbrad has an excellent post on this here.

"Could happen" scenarios bubble up from the seeds nestled in a common computer model misconception. Many believe that they provide forecasts. Not true. They are only guides. Nothing more. They come in two forms or outputs. One is called a deterministic solution, the other is an ensemble. A deterministic is ONLY ONE possible outcome with a set of initial conditions. An ensemble is a blend or average of a bunch of deterministic solutions. It smooths out the extremes giving us an average of the multiple outputs. The problem lies within the INITIAL CONDITIONS. Not all weather conditions are known for each geographic point in an area (in this case, northern Ohio). So there are data gaps before the model even runs. So unless you know the weather conditions for each and every point in northern Ohio (say every 50 or 100 feet) the computer output will have gaps. The overall solution will be estimated and smoothed out where these gaps exist.  Imagine the gaps between Cleveland and Westlake or Akron and Medina. Actual solutions for these gaps are not known so the output is approximated.

We learn to use both the ensemble and deterministic in our assessment of each weather pattern and forecast for the area. Computer models are only a guide, an interpretation of the weather scenario, nothing more. We learn the pros, cons and biases inherent in each model and apply them to the current weather situation. Meteorologists deal in "mostly likely" scenarios after taking all of the available data and computer models into account.  WE create forecasts that are "mostly likely" to occur. Look how the computer output (GFS) for snowfall accumulation for next week has changed in both depth and location over the last 3 days.

Be careful of Facebook posts that show solutions more than 5 days out. This is only one possible solution with one set of initial conditions showing a "could happen" scenario. Don't get me wrong. Its fun to speculate. But "Could happen" scenarios are not a healthy way of looking at the weather (just look at the devolution of Facebook comment threads). "Mostly likely" scenarios are safer and work better in the long run.

Trust the meteorologist not the computer.

Thursday, January 30, 2014

Behaviorial Meteorology: Psychology Behind Our Cold Weather Perceptions

Last year I wrote an article on how our perceptions of the weather are shaped by events that have
occurred most recently. This winter's cold weather is a prime example: The last two winters have
been milder in comparison so we are preconditioned to believe that this winter would not only be
worse (which it is) but one of the worse in years and comparable to the harsh winter of the 1970s and
early 1980s. Both are false.
Why do we perceive this winter to be one of the worst ever? Its a classic example of the RECENCY
EFFECT: This is the tendency to think that more recent trends and patterns we observe (which are
more recent in our minds like our recent mild winters) are a very good representation of the
entire period in question. Since the winters of yesteryear are distant memories, we tend to weight
them less than our memories of recent winters. We believe our memories and observations--
recent mild winters--are excellent predictors of what the near future will bring.

How often has someone said to you this past fall "We are due for a bad winter".  Or how about
this: "This winter has to be one of the coldest ever" or "This colder trend recently surely means
that the rest of the spring and summer will be cold?  That is the RECENCY EFFECT at work.
Those frequently uttered sentences above are totally driven by our perceptions.  Our perceptions
make us feel good because they fit our hard-wired biases.  Most of the time, we grossly
underestimate the significance of our biases. The truth is that this winter is ranked...45th coldest! 
The winter pattern rarely has a connection to spring or summer. Hard to believe but its true.

This type of information might run counter to our perceived notions ultimately becoming a source of
frustration and internal conflict.  We have a built in motivation to reduce conflicting ideas by altering the existing conditions in our mind to create consistency. Pick any topic: weather, economics, politics, investing...anything. We all do it. 
In the case of understanding our winter weather or any weather during any season), we do this by 1)  Believing weather information which best fits our preconceived notions 2)  We alter its importance in our mind and/or dismiss the hard, cold facts and data all together or 3) We just plain criticize it. Sometimes, it’s a blend of all three. This inclination to favor information that reinforces our comfort level is called a "Confirmation Bias".  Incidentally, this happens all of the time inside Facebook comment threads.

Watch what happens when the first cold stretch develops in spring. Everyone will be shouting that
"they knew this would happen because of our cold winter." That's classic CONFIRMATION BIAS.
The problem is that as we create "consistency" through favoring our own view of the information,
we create a new false interpretation of the weather which we believe to be true. Rather than
looking objectively at the reasons for the change scientifically (science scares people), most
people tend to use an overly simplified and often inaccurate scientific explanation of the weather
to ultimately confirm their predispositions.

The response "We are due for a bad winter" has virtually no scientific merit.  For events that require object analysis, our own human nature deceives us.  In this case, our biases "cloud"--no pun intended--our judgment of the weather.  By recognizing our own weather biases, we can actively attempt to dampen the effects. As much as it might hurt, trust the data.

Wednesday, January 29, 2014

Northern Ohio Winter Weather Scorecard


We were spoiled over the last 2 winters with little snow and frequent breaks in the cold. This winter has been more typical of winters past: Long stretches of cold, a deep snow cover with periods of extreme cold. How does this winter compare with recent winters? Last 30 winters?

We all perceive the winter to be a certain way depending on how much weight each of us puts on the different parameters. Some use snowfall as the definitive measure of the winter's weather. Others look at the extreme cold (nights below zero) as a better measure. We will look at several winter parameters to determine how they all rank across the board.

1) The average temperature since December 1st:

  4 winters since 2000 were far colder OVERALL! How would you rank this winter so far?... Coldest in years? Do you think it's in the top 10? 
This winter ranks...45TH ALL-TIME!

The average temperatures for the month of January:

This month was far colder...coldest in 5 years YET only 29th coldest all-time!
How about snowfall:  44.9" through the 29th of January with more wet snow to come.

This is the most since 2008-09. Yet we've had 7 winter since the early 1990s with MORE SNOW through the end of January.

Lake Erie ice cover has increased to well above 95% after the most recent arctic outbreak.  
 This is the most since 2011 when we had 97.6%. The years with more ice cover as of January 29th:  2011, 2003, 1997, 1994, 1986, 1982, 1978, 1977

We tend to recall the extremes of a season not the averages. So how to the extremes rank? Here are the number of days in the single digits. 
This year has had the most single digit temperatures since 1994
This year's 27 days at or below freezing is comparable to other colder winters since the early 1980s 

Many, many days with snow on the ground make the winter seem a lot worse. We have 43 days so far. The way we are going, this year will finish out as having the most days with at least an inch of snow since the late 1970s.
15 more days with at least of snow on the ground will break the ALL-TIME record of 57 days!

There's a lot of information here. What we need to take home from all of this winter data is this:   

The winter is no where near the coldest overall (45th coldest). Here is where the psychology comes into play: When evaluating how cold the winter has been thus far, we remember the extremes in both temperature (most in 20 years) and days with snow on the ground (close to the all-time record) not the averages.

Monday, January 27, 2014

Snow Rollers

Lots of people asking what these "snowballs' are rolling around in the backyard. These are called Snow Rollers. They occur when the temperatures are just warm enough (slightly above freezing) so that the snow melts just enough to stick together. The winds have to be at just the right direction and speed (usually light) for the snow to roll and coalesce without falling apart.

Here are a few pictures from Lexington and Medina, Ohio

More snow rollers. This one from Garrettsville, Ohio

Another from Burton, Ohio

Thursday, January 23, 2014

Winter Scorecard...More Snow This Weekend

Its been 3 years (2010-11) since we had a winter this cold (avg temperature since 11/15) with many more weeks to go.  The last winter with more nights below 10 degrees was in 2001.
Our ~38 inches of snow through January 23rd is the highest total since 2009.
Lake Erie ice cover is now at 94% and climbing, the highest level at January 22nd since 1996.

Although we haven't had a huge snowfall, the persistent pattern which features a monster trough across the eastern 1/2 of the continent allows cold air originating from Siberia (which deepens over the heavy snow cover in northern Canada) to drain south on a frequent basis in pockets along with fast moving "Alberta Clipper type" snows to fall across the Great Lakes and northern Ohio. 

The diverging wind field aloft and smaller scale cyclonic winds in the mid levels (rotating energy) within the jet stream are amplifying these clippers as they sag through the middle of the US at the base of this large scale eastern trough.

Instead of straight forward light snowfalls associated with these Clippers, heavier and more widespread snowfalls are increasingly likely especially Saturday. The forecast for Saturday calls for a good 2-4 inches.

Map courtesy: Weatherbell

Friday, January 10, 2014

Free-For All Friday: Polar Vortex, Lake Erie Ice & Winter Stats

I won't belabor the Polar Vortex talk.  Its been played quiet enough everywhere. Check out my last post for my thoughts on its misuse earlier in the week.

First, the Lake Erie ice cover update:

Over the last week, we have DOUBLED the ice cover concentration. January 4th, Lake Erie was at 44%. By January 10th, the number was just south of 90% which is way ahead of last year and slightly ahead of January 2011 and 2001; fairly close to January 1996.  The MODIS high resolution visible satellite image illustrates this increase perfectly. First image is from January 4th, second is from January 9th.

January 4th

January 9th
Back in 2011, I took a photo from the E 55th marina after the lake froze over. Notice the railing in the foreground. Compare that to a photo I took on January 4th after strong winds sprayed the lake water on the shoreline which froze everything on contact including the railing.

 A few more close up photos from along the Cleveland shoreline.

Contrary to what you might think, this winter in northern Ohio hardly cracks the top 40 coldest winters through the first week of January. Remember the hard winters of the early 2000s?

Thursday, January 09, 2014

Weather Reporting Needs To Change: Polar Vortex Edition

Many media outlets in my opinion have incorrectly described the cold air outbreak across the US as the Polar Vortex moving across the US. Some have said that their reasoning was the 500mB heights/trough signature. I think that this 500mB northern hemispheric map shows it best. While the eastern US trough was deep, cold and unlike any outbreak since the early 1990s, other pieces of the PV were easily visible on the 500mB chart around the higher latitudes. Was this piece of the PV over the US the actual main Polar Vortex sliding south from the Arctic or was the piece over northern Asia or the one over Northern Europe the main Polar Vortex?  Or did the main Polar Vortex stay over the North Pole with several pieces breaking off, amplifying and propagating south into lower latitudes dragging down arctic air?  (The correct answer is the latter) But see what I mean?

Call it an argument of semantics. Call it splitting hairs. Call it no big deal. I say it is a VERY big deal.

In a time where basic, objective and accurate science knowledge isn't emphasized in the media; where the US is lagging many other counties in math and science scores; where short phrases and hashtags govern our daily social consciousness; where scary words like "Polar Vortex" gain national and international attention through its instantaneous proliferation through social networks, attention to detail makes a HUGE difference.

I understand that "Flash and Dash" reporting has long since replaced investigative reporting. I get it. I understand that holding the viewer as long as possible is an important driver of a newscast. That's not going away. But we still have a duty to educate the public when its appropriate.  All I ask is for some basic due diligence.  When meteorological phenomena like the "Polar Vortex" directly effects a large chunk of the nation's population, we owe it to the viewers to be as detailed, complete, objective and accurate as possible. Perhaps shelving the flashy reporting model with a more--dare I said it "old school" approach in these instances would serve the viewers better. I'm open to suggestions.

The last paragraph in this blog entry say it all.

Monday, January 06, 2014


Huron, Erie, Sandusky and Ottawa Counties in OHIO under a LEVEL 3 snow emergency. Which means that only emergency vehicles are allowed on the roads.

Temperatures this low are not common in northern Ohio. It only happens a few times every few decades. Here is the cold air trivia for northern Ohio. This is on par with the cold of the late 70s and early 1980s.

The HUGE buckle in the overall jet stream across the North American continent has dumped arctic cold across most of the US and Canada
More than 85 million people are under a WIND CHILL WARNING. This is issued only when wind chills are expected to fall below -40 for more than 3 hours.

Lake Erie lost some ice over the weekend after a season high of 56.7%. Expect some rapid ice growth over the next few days.
Current wind chills are running between -10 and -30. CURRENT WIND CHILLS CAN BE FOUND HERE.


Sunday, January 05, 2014

The Anatomy Of an ARCTIC BLAST: 2014 vs Previous -15 Days

We don't reach -15 or below very often in northern Ohio--only 12 times in 140+ years of record keeping. Signs of arctic cold show themselves in the temperatures above the earth's surface away from surface influences such as concrete.

To be clear, not every instance of below zero nights or days is exactly alike. Several parameters need to be in place for this to occur in northern Ohio: COLD AIR ALOFT (850 mB level - 5000 ft), clear skies and snow cover.  How cold do the 850 mB temperatures have to get to reach, say -15 or lower?  Looking back at the 6 coldest readings in Cleveland history (I also threw in 2009 because that was the last time we fell to -10 or below), the west to east 850 mB temperature profile looked different each time

The 1/19/1994 record low event looked like this at 850 mB. Cold core was north of the Great Lakes.
850 mB temps fell to between -30 to -32
1/23 and 1/24/1963 was a two day event, -17 and -19 respectively. The 850 mB temp profile was this. NCAR reanalysis was used because the grADS site only goes back to 1979. The temperatures are in Kelvin. Cold core north of the Great Lakes.
850 mB temps fell to around -28 converted from Kelvin
1/20 and 1/21/1985 was another two day event, -18 and -17. Notice how the core of the 850 mB cold was centered in the midwest over Iowa, Illinois and northern Missouri before it moved east into Ohio. The 850 temps were some of the coldest on record. Here is the 24 hour breakdown from the grADS site:

850 mB temps fell well below -30
1/21/1984 was similar in surface temperature yet the 850 mB temps never fell below -25. Once again, cold core north of the Great Lakes.

Based on my checking, the coldest 850 mB temperatures EVER were during the 1/16,17/1982 event with a -38!

Yet the surface temperatures never fell below -13 and -17 over the two days.

850 mB temperature fell to a mind blowing -38 Celsius!
The 1977 two day cold blast...temperatures are in Kelvin. -28 was the coldest in northern Ohio.

Finally, 1/16/2009...850 mB fell to at least -23. Cold core was shallow.
 How about the cold on Tuesday? The 850 mB forecast temperature drops to -30. 

Each instance has a different west to east 850 mB profile with different resulting surface temperatures even though   the 850 mB temps might have been similar to past events.

In other words, the 850 mB temps are only part of the story when it comes to predicting arctic cold overnight lows.

Some cold tidbits for Cleveland:

The last time we fell below zero was in 2011
The last time we fell below -10 was in 2009 when we hit -13 (5 nights below zero)
High temperature at or below zero:  14 Times
The last time was 1994:  -3
The coldest high temperature EVER in CLE:   -5 in 1985
Below zero high temperature happened twice in 1982
Below zero high temperature happened 5 Times in 1899
Winter 1976-77 had 28 instances or below zero temperatures (days and nights)