1st Snow on Dec 9th--What About the Other Snowless Decembers of the Past?

Finally our first real, widespread snow and its already December 9th. Most people have finished putting up Christmas lights.

A far cry from last December when we had snow on the ground almost everyday with the average high temperature well below freezing. 

3 inches of snow in Sharon Center, Medina County

How does this overall "winter-less" pattern compare with the least snowiest Decembers going back to the late 1960s? First, here are the least snowiest Decembers in chronological order:

1965: 1.2"
1967: 2.8"
1971: 1.9"
1978: 2.5"
1986: 1.1"
1994: 1.0"
2001: 3.7"

The answers to our pattern lie in the winds aloft. They establish the direction the storms along with the propensity for storm development in certain locations. Often times, these "locations" or dips in the wind field are established/enhanced by the warmer/cooler ocean temperatures. These ocean/atmosphere connections are felt "down stream" here in Ohio as either a cold or warm pattern.

Below is the first year: 1965. The map on the left shows where the HIGHS and LOWS are located. The right map shows the COOL and WARM pool in the Pacific and Atlantic and their positions. Notice the HIGH near the WARM POOL in the PACIFIC and the HIGH over the great lakes. In between lies the WESTERN trough where the LOWS reside. This HIGH kept warmer than normal air over OHIO and the snow amounts small.

Now 1967, 1971, 1978, 1986, 1994 and 2001. Notice that the PACIFIC HIGH is near the WARM POOL in each year and the WESTERN trough sits ahead of it. Also, notice the LOW in the ATLANTIC in varying degrees each of these Decembers. For OHIO, the same RIDGE we have overhead this year suppressed the COLD and SNOW in these past years.

When we average all of these years, we come up with this composite picture. Notice once again, the HIGH over OHIO.  

November this year, featured the strong PACIFIC HIGH which drove COLD AIR into the WESTERN TROUGH which kept the OHIO RIDGE in place keeping us mild and wet. Look at the similarities between  this past November picture below to the Decembers above.  Scary isn't it?

 Now look at the first week of December through the 7th. The HIGH has shifted north into ALASKA shifting the WESTERN TROUGH east into CANADA and the CENTRAL US which has drove the OHIO RIDGE well east.

Does this still mean December will stay below normal in snowfall or are we anticipating a shift to a colder pattern? I have a good feeling that this December will feature more short-lived cold shots and off/on snow. Will it be as snow less as the Decembers above?  Given these pattern shifts and the ATLANTIC shifting cooler, we can expect weather that is more winter-like. Meanwhile, I'm off to cut down a Christmas tree!

Dec 7th Snowcover Last 5 Years: Which Year is the Winner?

Our first lake effect event begins Friday.  So far, hardly a flake has fallen this year. Has this year's snowfall country wide more or less than in recent years?  Here are the numbers with these excellent snow maps from the National Snow Analysis site. from this year back to 2007. Last year and this year are dead-even. Notice the snow this year is west whereas last year, it was east.

Ocean Temperature Changes & Our Early Winter Pattern

One basic element of long term weather trends lies in the changing ocean surface temperatures.  The effects of these ocean temperature changes are very apparent here in North America where we are surrounded by the Atlantic, Pacific and the Arctic to the north.

My last post looked at how different the last 3 Decembers have been when comparing the different indices located over the oceans. What about the changes in the oceans comparing, say last December to the current levels?

Let's break down last December in two parts. The colors show the warmer and colder locations compared to the average. I indicated these "cool and warm" pools with a "C" and a "W". Notice how they changed from the beginning of the month to the end of the month.

Now look at this year. The Atlantic cold pool shifted more north toward Greenland. The temps off of the SE coast are a bit warmer. The warm pool from last year in the western Atlantic (driven by the strong arctic levels) shifted west into the Caribbean, Gulf of Mexico and New England waters. The cool pool in the Pacific is cooler near Alaska while the classic La Nina "cool" signature between Hawaii and Mexico is now more extensive and cooler.

How did the storm tracks differ over the US last December to the current setup?  The ripples in the flow over the US and Ohio brought small snows and repeat cold air shots throughout the month last December.

This year, the Bermuda High in the Atlantic is now situated near the Southeast Coast. The Pacific Ocean high northeast of Hawaii is also more north this year. Both of these Highs have shifted the trough out west. So any strong front (the "L" over the middle of the US) that tries to make it into Ohio gets squashed. 

The temps in Cleveland last December were very cold.  The "blue/purple" bulls-eye over the central US highlights much below temperatures. We had three separate stretches of 20 degree high temperatures. The first was 4 days, the second was 8 followed by a 5 day stretch at the end of the month. Snowdays at Progressive Field were cold and snowy. I cut down my Christmas tree in a blinding snowstorm!

The temperatures finishing out November this year were slightly above normal in Cleveland. Absent were the strong fronts necessary in driving cold air south 

All of these maps are just more illustrations of how the tiny changes in the oceans can alter the weather patterns across Ohio. Given this current pattern that features no significant drivers of arctic cold, I highly doubt we will see a long stretch of cold temperatures like last December. More details on the prospects of short-lived lake effect snow next Monday.

Were the last 3 Decembers All that Similar?

Since early November when our winter weather outlook came out, we emphasized how variable this winter would be. We really didn't see this winter having long stretches of arctic cold like the last 2 or 3 winters.  The variables for this winter just didn't match up like the winter of 2010-11 or 2009-10 or even 2008-09.  Similarities do exist for sure but the differences can't be ignored which I believe will be significant players.



What are those differences?  The three that top our list are the PNA INDEX (Pacific-North American Index), the AO (Arctic Oscillation), the NAO (North Atlantic Oscillation) and La Nina or El Nino.  Don't fret over the technical specifics of each index.  Just realize that each one originating from different locations (Arctic, North Atlantic and the Pacific) has the capability of influencing storm tracks and intensity over northern Ohio.  Long term trends are great but can we see day-to-day details within these indices?

Look at the daily plots for the AO, NAO and PNA for each of the last 3 Decembers: First 2008, 2009 then finally 2010. Notice the fluidity of each of the last December's daily index levels.

What about the ever-popular El Nino/La Nina which gets all of the publicity?  The daily changes are significant when you look at the changes in the pressure patterns over the tropical Pacific (the SOI Index). Never mind the geeky "SOI", just know that it changed a great deal from December to December. Each pressure variation alters the jet stream over North America and the Great Lakes. Even the La Nina of 2008 and 2010 were very different.  This year's La Nina is also very different.

How did this relate to high temperatures? Below is the daily high temperature graph for December 2008, 09 and 10. Last year was consistently cold yet 2009 and 2008 had a lot of ups and downs with only limited cold shots.


What about December snows?  Not much in the last 3 winters.

So the variability of the Arctic, North Atlantic and Pacific/La Nina/El Nino can have effects on our Cleveland weather day to day. Comparing last December to this December or 2009 to 2011 isn't as easy as it seems when you look at the how these elements change on a daily basis. Some of these elements one year can produce more snow and cold in Cuyahoga county and in other years, the frequency of cold is far less in Akron and Mansfield. A look back to the previous year doesn't always work in giving us insight on the current forecast.

Will this December be as changeable as year's past.  Will we have a December like 2010 with continuous cold?  Will this December feature cold shots with some milder breaks?  I will address that in the next post.

Meanwhile, I'll be cutting down my Christmas tree in the mud followed by stringing lights on my house in shorts!

Comparing NOV/EARLY DEC 2009 vs 2010 vs 2011

Comparisons are always tricky. Go ahead and pick the data and sure enough, you can find some correlation or causal relationship to the current weather situation.  The operative word here is "CAUSAL". Is the information or data giving you an accurate snapshot of what is driving the current weather? In other words, is there a direct cause and effect relationship?

The index we look at as a direct measure of the strength of the arctic air to the north is the ARCTIC OSCILLATION.  Pressure differences over the arctic and temperatures high in the atmosphere can make the arctic air more or less changeable for us living around the Great Lakes. If the AO index is negative, the arctic air becomes unstable and has a tendency to drive southward. If its positive, its stays locked up in the higher latitudes of the arctic.

Look at 2009 from the fall into early December.  Notice how the AO was strongly negative into late November and early December.  We had 20 of the 31 days in December with highs in the 20s and 30s!!!

Now look at 2010, same ultra-low negative AO index reading. We had 28 of 31 days in December with highs in the 20s and 30s!!!

Look at the early December snow from last year:

Why is this year so different? Check out the AO index recently.  Its been strongly POSITIVE with no big signals that it will drop sharply negative. While this isn't the ONLY measure of a potential cold air shifts into Northern Ohio, it is a strong one.  So if you are going out to any one of the many Christmas farms in Medina County to cut down your tree, the chances of their being a prolonged snowfall are much less than in the last 2 winters. 

Colder Air Still Coming after Thanksgiving? You Bet!

I love the science of weather and the patterns that govern it. While some of my posts can get a bit scientifically technical, my aim is to describe in the most simplistic terms what we look at in formulating our forecasts both in the short and long term. Knowing the forecast is one thing.  Yet developing a basic understanding in how and why we come up with our forecasts is quite another beast. That's why I like to describe elements of the weather on the air. Its fun for me and hopefully informative for you. I liken it to a great meal: Eating the savory food is great. Being able to understand the recipe and recreate it later is even better!  Remember that I not only give you the meat and potatoes, I give you the recipe too!

Which brings me to the pattern changes in the upcoming week. Last Wednesday, I hinted at some colder air and snow for the Sunday after Thanksgiving. Here's what I said.

It still seems like that is a good possibility. But the colder pattern is slowing in its evolution. In other words, the low doesn't seem to want to establish itself over the Great Lakes as fast as it did last week. Here is Sunday evening...the following map is Monday

The squeezing of the LOW from the west and the east has me concerned that it might either, weaken or hold off longer until Tuesday. Either way, this is the ingredient for cold air and waves of either rain and/or snow!!!

That was the "meat and potatoes". Now the recipe:  Why the change in the overall pattern?

Normally we would look to the Arctic's behavior to see potential cold air outbreaks. In this early winter season (2011-12), the arctic shows no signs of heading into what we call "negative territory".  So we have to find another driver of this pattern shift.  That driver might be the highly variable Pacific Ocean/Northern Hemisphere pressure patterns. The area we look at is here:

 When this area is "negative", the snow and cold stay out west and the eastern US stays milder and snow free. When it turns "positive", the cold and snow shift east and the milder air shifts west as seen below.

The pattern has been strongly "negative" which has driven the milder air northward into northern Ohio. Temps in Westlake made it close to 70 a week ago. Norwalk hit a high of 65. Even in Akron, temps were well into the upper 60s. My kids were outside in t-shirts!  It happens in November.

It look like this pattern might shift "positive" in early December. Does this mean lots of cold air? Does this mean more snow? I think a little of both. IF this pattern gets "locked in" for a week or two, we can surely expect a handful of lake effect snow events and perhaps a general snow with temps below normal.

We are still holding on to the notion that this winter will have breaks in any cold period perhaps more than in the last several years. So when it gets cold, we don't anticipate it lasting weeks on end!

Hopefully for skiers, Brandywine will open before Christmas and the hills at Virginia Kendall Park in the Cuyahoga Valley will be primed for sledding.

2011 Thanksgiving Weekend Snowstorm?

We have often compared this upcoming winter to the winters of the early 1950s.  Those were La Nina winters. See my post from a few weeks ago. That this, the factors (Atlantic & Pacific Ocean temperature trends/temperatures) that were present then are somewhat present today among other factors too technical to mention.

The years that we found to match up well are 1950, 1954, 1955, 2008, 2010.  Aside from some differences in the Atlantic Ocean temps in the 60s and 70s, you can throw 1964 and 1976 in there too mainly due to the strong influences of the arctic in those years especially in the mid 1970s. If you recall the Blizzard of 1978, BOTH OF THEM, you know what I mean!

Heading into Thanksgiving week, my dad reminds me of the Great Snowstorm of 1950.  One of the most memorable snowstorms in Northeastern Ohio history. He was 5 years old at the time but he remembers it like it was yesterday growing up near St. Stevens Church in Cleveland's west side. Downtown Cleveland and Akron got hit with 25 inches of snow. Geneva 33 inches! Temps dropped from 38 at midnight to 14 in less than 12hours on Friday the 24th.

The classic Ohio State-Michigan football game was scheduled for that Saturday afternoon in Columbus, Temps that morning were in the single digits; winds were 40 mph.  The final score: 9 to 3.  Only 27 total yards!

I bring all of this up now because I noticed something "scary" on the maps for Thanksgiving weekend.  Here is the map for Friday the 25th. Not much to show.  Fairly quiet pattern.

Now look at Saturday the 26th. Notice the low developing just to the west.

Now look at Sunday the 27th.  WOW!  A monster storm over the Great Lakes and Cleveland!  Again, its more than a week away but scary nonetheless. What is even scarier is when we compare the 1950 snowstorm to next week's map:

Look at 2 days before the storm in 1950. Very quiet...

Now look at the day before the storm developed over the Great Lakes. Looks eerily like the map for next Saturday.

Now for the main storm day in 1950, Saturday during the Ohio State Michigan game in Columbus.

Looks almost exactly like the map for Thanksgiving weekend of this year!

Yeah, yeah, I know its more than week out and alot can change. But given the years (1950, 54, 55, etc) which we used in our comparison for this year's winter outlook, it bares watching. So if you are flying out Sunday the 27th, keep an eye on the 8day forecast. If this maps continue to show this storm early next week, it could paralyze air traffic from Cincinnati to New York!