Monday, March 05, 2012

Too Many Deaths in Friday's Tornado Outbreak


It's still hard to watch the video of the cataclysmic damage in Kentucky, Tennessee and Alabama realizing that lives were lost. A total of 71 tornadoes touched town according to Dr. Greg Forbes of the Weather Channel. As i write this, a confirmed 45 tornadoes from the National Weather Service which will probably rise as damage assessments continue. Here is a nice blog post from "everythingwx" that summerizes the confirmed tornadoes by state




The horror families go through after losing a loved one prematurely to a twister like what happened Friday HAS to be one of the most emotionally draining experience for a human being to endur.  I can't imagine finding the body of an 15 month old as the sun is shining the following day.  My jaw is still on the floor.

After tragic weather, I often look back at the days and hours leading up to event(s) to see if people were warned in a timely manner with appropriate information necessary to make the right decisions to stay out of harm’s way. I don't know the circumstances of these deaths.  I’m not here to judge the specifics. Not enough information is known as I write this. Yet I can't help but think that some of these deaths could have been prevented if 1), the public knew the proper terminology that describes severe weather alerts, 2) the public took the severe weather risks more seriously.

Let's first address storm alert terminology:

SEVERE THUNDERSTORM WATCH means that conditions are FAVORABLE for severe weather. This does not mean that there is a severe storm currently.

SEVERE THUNDERSTORM WARNING means that a severe thunderstorm is occurring or is imminent based on doppler radar information. A severe thunderstorm becomes "severe" after it meets one of two criteria. Hail that is dime size, 0.75 inches in diameter or larger, and/or wind gusts to 58 mph or more.

TORNADO WATCH means that the potential exists for some of the severe thunderstorms to produce a tornado

TORNADO WARNING means that either a tornaado is occurring (on the ground) or the tornado rotation is detected on doppler radar. You should take cover immediately.

All severe storm watches are issued by THE STORM PREDICTION CENTER in Norman, Oklahoma.  All warnings are issued by the respective National Weather Service office covering the specific area. Northeastern Ohio is covered by the NWS office at Cleveland Hopkins Airport.

Friday morning before sunrise, the SPC issued a "moderate risk" then expanded the risk area and upped it to "high risk" which only happens maybe once a year. 



The warnings were out there early on. They were on television, the internet, Facebook and Twitter. Yet people died. 

What can we do?

I think the answer is twofold. First, educate yourself on the differences between a “watch” and a “warning”! This thing called GOOGLE is great. Use it and look up the difference. I just typed in "watch and warning difference". The 5th entry in the list is what you want. I screen captured it so you can see two things: The first is the entry that explains the difference. The second is how long it took me to find the answer circled in red at the top. 0.19 seconds!  We might not have lots of time in our busy lives but we have 0.19 seconds.


If you don't have internet access, talk to your kids. I would bet a nice dinner that your kids know the difference if you don't. This difference is taught in grade school science classes as early as 1st grade in some school programs. It bothers me that many adults have no idea what the difference is between a WATCH and a WARNING. Most third graders know the difference. An adult has ABSOLUTELY no excuse. Your Life; your family’s life is worth your time and effort.

Yet there exists this mentality that quickly diminishes the severity of these warnings.  Maybe it is denial. People think that it won't happen to them. Maybe people today are inundated by information so much so that the "true, lifesaving" information gets lost or watered down in the mix. Just scanning the comments on Facebook and twitter after weather events shows how much negativity the public has toward these warnings during harsh weather.

The meteorologists in the areas hit by the tornado Friday did an exceptional job in getting the necessary information out to their viewers. This saved lives! Facebook and Twitter were lit up with information from credible sources on the tornadoes on ground. Hats off to you all. Severe weather coverage on LIVE tv is a lot harder than it looks.

The bigger question we need to address long term is how do we change the public’s perception of severe weather. A big step in the right direction would be for some television stations to rethink their coverage philosophy. I am lucky enough to work at a station where we DO NOT believe in breaking into a television show unless the weather situation ABSOLUTELY warrants it.  If a TORNADO WARNING is issued, we go LIVE. No questions asked.  Other stations feel the need to "break into programming" during any garden-variety thunderstorm. This "crying wolf" coverage creates a false sense of security.  So when a real event does occur, people think "no big deal. It won't happen here" and continue with their afternoon or evening activities.  Television stations cannot continue to cry wolf! They need to remember that their primary objective is to INFORM THE PUBLIC WITH QUALITY, SEVERE WEATHER INFORMATION as its defined by the National Weather Service and SPC not by management!

Viewers need to WANT TO BELIEVE what they are hearing yet they’re conditioned to doubt that very same information.  Television stations need to remember this and focus on their primary objective. That is to INFORM THE PUBLIC WITH QUALITY, WEATHER SEVERE INFORMATION.  No over hyping and no "crying wolf". Television stations are a conduit of information. Information is power. If that power is used incorrectly, the harm to the public can be irreparable.  I just hope the damage isn't as great as I fear it is.

Friday, March 02, 2012

Friday Severe Storms to Sunday Snow!

We haven't had much of a winter so our awareness of early spring warmth and storms doesn't seems as heightened. This is the time of year where we see huge day to day variations--often times hour to hour--as the winter time jet stream is weakening at the same time the southern jet stream is pushing north.  The southern branch--abnormally strong this winter--is still flexing its muscle with early season severe weather. As the angle of the sunshine shifts north across the Northern Hemisphere as the seasons change, the temperatures differences along warm and cold fronts becomes greater. Even in a mild winter like this year, the southern jet--a bigger player this winter--becomes the focal point for even more atmospheric energy. All of this means severe weather outbreaks will get more numerous.

Here is the current Ohio Valley radar...Ohio Valley Radar


Speaking of severe weather. another outbreak is likely later today as another strong spring-like system will push through Kentucky and Ohio. This system will be stronger than the Wednesday's. Here is the setup:

The warm front will push northeast later this afternoon...

Moisture will increase...the humidity will be noticably higher by mid-afternoon

Air become easier to lift higher in the sky resulting in rapidly building thunderstorms. This is called "The Lifted Index"
The speed at which the air is moving up into the atmosphere will be great at the mid-levels (12,000 feet)
The jet energy as mentioned before is high with the left-front quadrant of the jet moving into western Ohio
Temps rise along the warm front...then drop quickly behind it later tonight...
60+ degree temps late this afternoon
30s late this evening behind the cold front
The composite radars of three computer projections show rain/storms mid to late afternoon...place your eye on northeastern Ohio to get a reference point.



All of these factors have resulted in the Storm Prediction Center placing Ohio under a decent risk for severe weather later today. High wind watch tonight and Saturday with gusts to 50+ followed by snow late Saturday night into Sunday! A little bit of everything over the next 48 hours!

I'll update you through noon. Angelica and Dick will update you later this afternoon and evening!


Wednesday, February 29, 2012

February US Temperatures--More of the Same!

Skiers this winter continue to wait for the other shoe to fall that ushers in cold temps.  It hasn't happened.  Ski clubs are hating this weather as temperatures have been borderline even for artifical snow production.  My flowers have shown their premature heads through the mulch!  Some people have reported their grass has already started to grow...although I am skeptical on that. :)

Temps continue to stay well above normal. Spurts of cold sprinkled in between mild days did nothing to offset the overall trend. Consider that this map is through February 26th with 3 more mild days to go...
As I write this, the 60 degree line is now just a hair north of Cincinnati. Wouldn't be surprised if we hit 63 late today. 
February is now2nd all-time warmest in Cleveland. The top 10 are as follows:

1998  37.1
 2012  34.9 (unofficial)
1984  34.8
1976  34.5
1930  34.2
1954  34.0
1990  34.0
1932  33.8
1949  33.3
2002  33.1

How about March.....will this above normal pattern stay?  Let me just say that the results of this winter's trend forecast humbled me a great deal.  I learned alot. One specific lesson I learned was not to adjust my thinking just because one little piece of data tells a different story. Sometimes bucking the trend doesn't pan out.

Let's wait for the February data to come out.  Perhaps a weakening La Nina, a more variable Arctic and/or North Atlantic. Too many ":what-ifs" right now.

So for all the high school baseball and softball teams waiting to play their first game, this might be another wet start to spring with frequent rainouts and saturated diamonds.

Wednesday, February 22, 2012

This Winter vs Northern Ohio's Mildest Winters

Late last fall, many winter forecasts continuously highlighted the fact that this winter 2011-12 would mirror last winter's La Nina characteristics--more cold and snow. Yes, LA NINA returned. But the cold air didn't  Yet, as we all know, this winter has been anything but a mirror image of last winter. (the reasons why are here) Instead of enduring snow squalls off of Lake Erie with 70 days with snow on the ground, we've had saturated backyards and average temperatures resulting in the 3rd warmest winter since 1895!

Was this winter's MILD LA NINA similar to any of the other top ten mildest winters here in Northeastern Ohio?  Does the tropical Pacific Ocean behave similarly in these milder winters?

To review, the top 10 winters in northern Ohio through January (February is running 3 degrees above normal as of this writing) are below:





Each map below are the average sea surface temperatures from November through January in each of the top 10 years listed above. Sea Surface Temperatures prior to the early 1950s are reconstructions. Notice where the warmer water is distributed in each map. Warmer colors indicate warmer water; colder colors, colder water.  I circled the La Nina/El Nino area in red. The first is the winter of 1931-32 right down the list finishing up with the winter of 1952-53.


Aside from each of these winters showing some signs of El Nino (8 of 10), the tropical Pacific Ocean looks very different in each example with each resulting in very mild winters. The 1949-50 winter's weak La Nina was the only one close!

What can we learn from this winter's LA NINA pattern?  I believe we put too much emphasis on the effects of La Nina as the main driver of our patterns in the eastern US and Northern Ohio during the winter months. Judging by these temperature reconstructions, mainly El Ninos result in mild winters. But in some instances like this winter, the opposite is true. La Nina or El Nino signatures are a great first start but in many instances like this winter, we need to look elsewhere (the Arctic) for the reasons we see flowers popping up in February!  The 2011-12 La Nina winter was a fluke. Will it happen again next year?   Will Lake Erie freeze over next winter? 

Thursday, February 16, 2012

How Does This Year's Snow Stack Up: Jan 1 -Feb 17th

One recent commenter asked about this year's snowfall since January 1st through the current date (February 17th). You ask and you shall receive...here is this year's snowfall compared to the last 5 years from January 1st through February 17th. Obviously, well below last year. Yet 2008, we had even LESS SNOW through. Interesting...


Tuesday, February 14, 2012

Valentine's Day Update: Any Ice on Lake Erie?

Now that the winter weather patterns are becoming more in line with normal Februaries from past winters--more cold and frequent snows--I can't help but look out the newsroom window to survey Lake Erie. Still no sign of any ice along the south shore. 98% of the lake is still open for business.

Environment Canada has a great site that tracks ice concentrations over the Great Lakes and higher latitudes of North America.  So far this winter, overall Great Lakes Ice Cover is at the second lowest level since 1973 when record keeping began.


How about Lake Erie?  2011-12 ice cover is also at the second lowest level since 1973 slightly behind the winter of 1997-98.  This winter:  2.54%   The winter of 1997-98:  2.38%


Here is the actual data is you like numbers!  I highlighted the top 5 lowest Lake Erie ice winters.



What does this all mean? As we've mentioned before, as long as late winter colder periods develops, expect more late season lake effect snows for the rest of February and March.

I'm still projecting between 20 and 25 more inches of snow from Valentine's Day and the end of March!


Friday, February 10, 2012

Where Does This Winter Rank So Far?

I finally checked the numbers from the NCDC (National Climate Data Center) for January across all of Northeastern Ohio. After averaging November and December temperatures and comparing them to all of the winters since the 1895-96 winter, this is where 2011-12 stacks up in the top 10 warmest winters. Each winter's snowfall through January is also included.  Its number 3!

 How about the trends over the last 110+ winters? It seems according to the data that the trend is slightly upward in Northeastern Ohio.

 What does this mean for the rest of winter?

Look at the February temperatures in these winters? Well above normal...

In actuality, the actual temperatures have been even warmer!
How about March in the past years?




Temps stayed above normal in Ohio but they cooled compared to February and January. Notice the below normal temps across the upper Great Plains. A sign of late season colder spells.

If these comparisons are even slightly close to this March, expect temperatures to run closer to normal to slightly above normal which range from 41 on March 1st to 53 on March 31st. As for snow? We will look at those numbers next week.

Wednesday, February 08, 2012

Climate and Weather: Complete Reporting by the Media is Paramount



In recent weeks, several articles have been published that reignite the anthropogenic (man made) Global Warming debate.  Several surveys including one on climate knowledge to lists of scientists who are considered skeptics have made their way online. At roughly the same time, a new website was launched that aims to list all television meteorologists who have made their opinions public against Anthropogenic Global Warming. All of this has run congruent to the abnormally mild winter we've experienced in Cleveland and across most of the US.  

People have started asking me again what I think of these articles and what my stance is on global warming/climate change. While I purposefully steer clear of this polarizing debate, I always try to give answers that describe the meteorological drivers of our weather patterns. Often time after explaining this year's pattern, I quickly get blank stares when I describe the arctic and its behavior this winter even without using fancy science terminology. By no means is this a way of tap-dancing around the question but rather an opportunity to present additional information that might not be known in a comfortable, conversational setting.

Most people don't want to be “taught" subject matter when watching a news program. Viewers become uneasy when the news feels more like school than an informative telecast. Most people cringe at science even more. They want their news simple and easy to understand. Unfortunately, the world of atmospheric science—science in general--is anything but simple. I’ve found that the general public knows the terms "El Nino" or "La Nina" but little else.

How do we combat this lack of basic weather/climate science knowledge?  The answer is easy. Educate your viewers with reporting the COMPLETE story. Yet most media outlets won’t and don’t do it. Why?

As a television meteorologist, you are taught to “know your viewers”. So we have to cater our weather casts to fit what viewers are comfortable with. Most don’t want to know “why is this happening”. They want the “whens” and “how much”. This makes sense. Weather impacts every aspect of their lives in the short term. 

Viewers are impatient. They want quick, “to-the-point” news and weather. Unfortunately, when a major weather events occurs, the media explains the events in a highly, over simplified manner to fit what viewers are used to during ordinary forecast segments. Key elements are either watered down or left out entirely. The “dumbing” down of weather and climate science stories into "easy-to-digest“ bullet points only perpetuates weather and climate science as simple disciplines and fails to accurately AND COMPLETELY present the reasons why our weather and weather patterns behave the way they do. I'm not advocating long, drawn out, convoluted television "seminars" devoted to weather and science just more complete reporting.  Reporters still need to do their due diligence by researching the drivers of these events and include them in stories before defaulting to the "Its Global Warming or Cooling" card. Worst of all, it wouldn't take long to find.  

Here are some examples:

  1. Alabama Tornado Outbreak



The Xenia tornado outbreak in 1974 was also during a La Nina. The link above shows that there may be a link to tornado outbreaks and La Nina episodes in early spring.



2. New York Hurricanes - Irene in 2011 et all

East coast landfall hurricanes occur more when the Atlantic is in its "warm mode". This mode is called the Atlantic Multidecadal Oscillation. Hurricane Irene last year tracked north into New England.


Back in 1938, a category 3 hurricane made landfall near Bellport, New York. The Atlantic was also in its warm mode.

 Historic east coast landfalls compared to the state of the AMO


3. Drought in Texas

Another extreme associated with La Nina. 20 La Nina events over the last 120 years. 19 of those resulted in below normal precipitation in Texas. Look back at 1918 and 1956. Major drought centered in Texas from the Great Plains occurred during a La Nina.




 How about 2011?


For comparison sake, here is the dust bowl drought of 1934

4. Alaska extreme cold

The long term Pacific Ocean cold pattern called the PDO (Pacific Multidecadal Oscillation) has been linked to colder than normal temperature regimes. This study outlines the PDO and other influences like El Nino and La Nina


Here are the January 1971 average temps along the side January 2012 average temperatures. Both of these months occurred during a negative PDO.


The PDO isn’t the only driver but the comparisons are significant. Some links between the cold PDO and the western trough along the west coast reinforcing the ridge which set the stage for the above normal temperatures during the summer of 2011

5. Mild winter across the eastern 2/3 of the US

The Arctic Oscillation and North Atlantic Oscillation has been strongly positive. (NWS Chicago has an excellent write up here.


The last two winters, these indices have been strongly negative. One PhD in atmospheric science recently told me that these oscillations are "stochastic processes".  In other words, they are random pattern shifts that the computer models have a tough time predicting.

My previous blog post on the winter pattern so far


Is this over simplification in weather/climate science reporting more a reflection of today’s impatient,      “Youtube-ified” society?  Probably. Television news is far different than it was 15 or 20 years ago. News is not a ½ hour event like the good old days. News is produced in smaller increments to fit our fast paced lives.  Mobile devices and other information gathering technology further reinforces the need for quick, one to two minute news bits.  But when it comes to complex science topics like weather and climate reporting, this format doesn’t work nor should we force science into this highly compact template.  Let me be clear on this. I am not against Climate Change reporting.  My intention is not to debate climate change. I'm not here to analyze temperature data or to follow the political money trail. I just want COMPLETE REPORTING that isn’t watered down.  

Allow me to get a bit defensive: If someone wants to label me as a member of one of the climate groups that’s routinely talked about as either pro or anti-AGW, go ahead. If you do than you are missing my point entirely. My goal isn't to refute arguments for or against.


My goal of this post is to emphasize better quality and COMPLETE science reporting on weather and climate related stories through some basic research by the media. We serve our viewers better if we abandon the practice of watering down weather/climate science stories and explain the short-term drivers of weather events/trends within the AGW context. Does this mean that we shouldn’t explain AGW? Absolutely not. Yet continual pointing at AGW as the ONLY first order mechanism in the place of other drivers easily obtained through basic research by reporters through credible sources (NWS, NOAA or NCEP) doesn’t do the science or the journalism justice.


Friday, January 27, 2012

Weather and the Human Condition...Meteorologists Can't Win This Battle


Weather predictions have an ingrained psychological component. The weather conditions might say one thing, Yet we will characterize the weather differently depending on who we are and where we live. Just looking outside at the current weather in our corner of the world in Northeastern Ohio can shape our way of thinking even if the overall weather data says otherwise. This winter’s lack of cold, small snow falls  and "milder” stretches are a prime example of how psychology plays a role in how we perceive the weather. First, let’s set the stage meteorologically then we'll examine the psych.

This early winter weather has been stuck in a fall pattern. A ridge of milder air has sat stagnant over the eastern US. The persistent low over the southwest and a general trough with colder air over the western US and Canada hasn’t budged. The persistent southwestlow has spawned many Texas panhandle/southern systems rich with moisture fromthe gulf of Mexico; a pattern that is not indicative of a typical December or January.    The tropical La Nina pattern (cooler Pacific Ocean sea surface temperatures) and an historically strong arctic pattern over the last several winter say Canadian clipper systems would dominate the early winter with frequent 2-4 inch snows.  Unfortunately, that same arctic component—our cold air driver--has stayed conspicuously stable and quiet.

One computer projection since late November has relentlessly pointed at clippers developing in Canada. A quick snow usually accompanies these clippers across northeast Ohio followed by colder air. This year, once we get inside 48 hours of the forecasted clipper event, the computer projection would quickly push the system back north allowing milder conditions to prevail!  Crazy stuff to be sure. In this atypical pattern where computer projections offer little consistent help in forecasting, we more than ever want a forecast that's definitive.  This winter has been anything but definitive.

At the heart of these computer projections are equations that have no exact solutions, just increasingly better approximations. I tell high school students to imagine math without numbers and no calculators. That description usually follows with a look of horror. Any thoughts of a student in the room becoming a mathematics major are immediately wisped out the window.

Yet weather forecasting is just that: An approximation. Throw in a splash of day-to-day randomness and you have a very tough recipe to replicate over increasingly long time periods.  Computers will get faster and faster. The amount of weather data from satellites will increase.  But the equations that are used in these simulations will always yield approximations…ALWAYS! No one wants to hear this but all simulations are highly detailed shades of "grey" of varying degrees. So are the weather forecasts that we present on television each day.

In a Facebook post, I've explained the "approximate" nature of weather forecasts in the context of this early winter wackiness. I hope that most people are receptive to them.  Many are judging by people’s comments. Yet in times like this where weather isn't matching the Decembers and Januaries of the past (snow and cold), the human condition takes over. Our mind gets thrown off. Our preconceived notion of Decembers and Januaries featuring snow and cold have been replaced with rain and milder air. These changes don't sit well. It makes us feel uneasy holding onto these conflicting ideas.  Psychologists call this "Cognitive Dissonance". How many times recently have you had a conversation with someone and they said, “What is the deal with this 'mild' winter…what is going on here?” The uneasiness in the question is palpable.

No one likes to feel uncertain or conflicted.  Weather most times exists in a perpetual "grey" area. It’s this built in randomness that causes frustration and conflict. Most of the time, we grossly underestimate its significance. We all have a built in motivation to reduce conflicting ideas by altering the existing conditions in our mind to create consistency. In the case of understanding the weather, we do this by 1) either believing the weather information which best fits our comfort level or 2) we alter its importance in our mind 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". The problem is that by creating "consistency" through favoring 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. 

For example, I go on the air and say we’ll see rain to wet snow with 1-3 inches of snow by midnight. Many of us are already preconditioned to believe that this snow forecast will either be too much or too little. The reasons can vary from a disbelief in meteorologists in general--some have the "they never get it right!" mentality—to believing “the mild weather will stay” or that "the big snow is coming!"  Regardless, the preconception of inaccuracy is set from the get-go. 

The rain slowly changes over to snow but only for some areas. It takes a few hours of rain/wet snow before finally going to all snow. The new weather conditions highlighting a slower, back and forth transition to rain and snow present new information that favors the preconception of inaccuracy already present in many peoples' minds. I go on the air and explain that there is no well-defined line where rain goes to snow. I explain that it takes a while for cold air to overwhelm the milder air so the rain/wet snow mix would exist for a longer period of time.

Those who are preconditioned to believe that the forecast would be inaccurate dismiss the scientific explanation, ignore the random changes and replace them with their own simplified, non-scientific explanation while criticizing the real explanation from the meteorologist as hogwash. The countless emails and phone calls are strong evidence. All of this stacks the deck confirming their bias that weather forecasts and meteorologists are always wrong.  For a meteorologist, you can't win even if you present objective information to the contrary.

The psychology happens involuntarily: We struggle with the randomness of the changing weather conditions. We feel conflicted.  We feel frustrated.  We dismiss the weather information that we deem unnecessary to ease our conflict.  We might blame Lake Erie.  We often say "Its Cleveland." We criticize. We simplify.  We use “weather myths” to explain weather events. We come to a new conclusion and now believe we fully grasp the nature of the weather. The false interpretation we just created we believe to be very accurate.  We feel much better about ourselves. Case closed.

This inconsistency doesn't mesh well with every one's already highly simplified view of the weather. A crazy, changeable 8day forecast, negative connotations of weather forecasts and forecasters in general, coupled with a lack of general understanding is a highly volatile psychological mixture which further drives more false conclusions and irrational beliefs about the weather. All of which makes people even more uncomfortable and irritable.  The vicious circle is hard to break.

Weather prediction is just as much art and psychology as it is science. We try to tailor the 8day forecast to match the viewers’ perceptions by smoothing out some of the randomness so that it fits nicely on the 8day but it doesn’t always work out. Let’s hope that the weather pattern returns to "normal" soon.  As a television meteorologist, the forecasts daily would become easier to handle.  As a television viewer, the forecast could become easier to digest perhaps quelling some of our cognitive discomfort. 

I realize that shifting the weather back to “normal” won't change perceptions. It won't change the human condition. It probably won't alter beliefs about weather forecasts, meteorologists and weather patterns as much as I wish it would.  I can guarantee this:  Cold weather in early February will make most of us feel more at ease about the winter. That is until the first snow over spring break!

Tuesday, January 24, 2012

Cleveland Snow This Winter vs. Least Snowiest Winters

Temperatures have been well above normal since November 1st.  Snowfall hasn't stuck around for more than 4 or 5 days at a time. The reasons for the mild winter outlined a few weeks back. You can read about it HERE.

So far this winter, we've received:

22.8" through January 25th

How does this winter's seasonal snowfall stack up  through the end of January when compared to the least snowiest winters of years gone by?

This winter is 33rd all-time on the "least snowiest winters by January 31st" list! Here are the top 32 winters on the list working backward from the 2001-2002 winter.

Breaking down the list by decade:


2000s:  1
1990s:  1
1980s:  2
1970s:  4
1960s:  4
1950s:  3
1940s:  4
1930s:  4
1920s:  7
1910s:  3