Archive for December, 2011

2011 Recap: Precipitation
December 31, 2011

By Meteorologist Mike Skurko

2011 will go down as the wettest year on record in the Pioneer Valley…records that date back to 1905 at Bradley Int’l.  We saw a total of 69.23 inches of precipitation this year, which is well above our average total of 46.21 inches.

The most memorable rainstorm cam from Tropical Storm Irene in late August, which brought 5.2 inches of rain to Bradley (and closer to 10 inches of rain for parts of Franklin County).  Perhaps this storm ultimately put 2011 into the record books.  Without it, our yearly total would have only been 64.03 inches…which would have lost out to 1972 for the all-time record by about a 1/2 inch.

Here are a couple more factoids:

– 9 out of 12 months had above average precipitation…May, July, and November were the only below normal

– 46% of our average yearly precipitation fell solely in August and September this year…21.32 inches just in those two months

– No monthly rainfall records were set, but 2 were set for snowfall…54.3 inches in January and 12.3 inches in October

– Bradley reported 84.5 inches of snow for the calendar year, well above the yearly average of 49 inches

– The greatest single-day snowfall at Bradley was 24.0 inches on January 12th


2011 Recap: Temperatures
December 30, 2011

By Meteorologist Mike Skurko

This year was a battle between a very cold start to the year, followed by an unusually warm finish.  In the end, it was our very mild months of November and December that tipped the scales…ultimately causing 2011 to go in the record books with above average temperatures.

January, February, and March of 2011 finished out with temperatures 1.9 degrees below average…which is statistically significant spread out over a three-month period.  A milder spring and summer helped get those numbers back on track.  By the end of August, our mean temperature (both highs and lows compared to normal) was at a dead-even zero…neither above nor below average.

Still, our high temperatures for the year were fractionally below normal all the way through October.  The big change came in November and December, when high temperatures astonishingly finished out nearly 6.5 degrees above average.  It was this very mild stretch that ultimately kept our yearly average temperatures above average, capping off 2011 as a relatively warm year:

Highs: +0.95 degrees above average, Lows: +1.53 degrees above average, Mean: +1.24 degrees above average

A few other little tidbits…

– We hit 90 degrees on 15 occasions, one shy of the normal amount of 90 degree days per year.

– We dropped below zero 5 times this year, while a typical year only sees that happen 4 times.

– Our hottest day of the year was 103 degrees on July 22nd…the new all-time record at Bradley Int’l.

– Our coldest night of the year was -7 degrees back on January 24th (nowhere close to the all-time record of -26 degrees in 1961)

2011 in review
December 29, 2011

By Meteorologist Mike Skurko

Visit our facebook page at cbs3springfield to vote on how you believe the final recap numbers will come in for western Massachusetts in 2011.  We will have the recap posted on New Year’s Eve.

Wind chills made easy
December 28, 2011

By Meteorologist Mike Skurko

When it comes to determining wind chills, this complex calculation below is used to quantify the effects of temperature (T) and wind speed (W)

Wind Chill = 35.74 + 0.6215*T – 35.75*(W^0.16) + 0.4275*T*(W^016)

Perhaps a simpler method to come up with an easy-to-remember ballpark figure is the “15-15 Rule” (you will not find that rule in a book…it’s a title I made up myself).  The 15-15 rule means that a 15 degree temperature and a 15 mph wind will create a wind chill of zero degrees!  Pretty simple, right?

Using this as a ballpark estimate, you can figure out slightly more accurate wind chills based on the forecast you see.  For example, if the forecast calls for temperatures in the single digits along with a 15 mph wind, you’ll know that those wind chills will be slightly below zero.  If the temperature was 15 degrees, but the winds were only at about 5 to 10 mph, then the wind chills must be above zero.

Tonight’s forecast calls for overnight lows in the middle-teens (around 15 degrees) with winds at about 15 – 20 mph.  Both of those factors are very close to the “15-15 Rule” and would produce a wind chill near zero degrees.  Below is the complete chart from the National Weather Service for various temperatures and wind speeds:

Winter arrives one day later
December 20, 2011

By Meteorologist Mike Skurko

Typically the Winter Solstice occurs on December 21, but this year it is holding off until December 22 on the East Coast (12:30AM EST to be exact).  This “delay” in the first day of winter occurs about once every 4 years…the last time it happened was in 2007, and the next time it will happen will be in 2015.  The reason behind this is similar as to why we have a leap year every 4 years.

Our calendar has 365 days in a normal year, with 366 days in a leap year.  The leap year is to help balance out the length of an actual year of approximately 365.2422 days.  In reality, a year is slightly longer than our standard 365 days, so every 4 years we must add an extra day to the calendar to correct it.  Most of you already knew that…and that also highly contributes to why the solstice is a day later about every 4 years.

However, this 365.2422 days is an AVERAGE  as the very specific length of one year varies due to two other  forces.  The gravitational pull among other planets can slightly alter this length of time, as well as the subtle changes in the earth’s wobble (which affects the shifting of the Earth’s axis…something that is very important to defining the solstice).

Occasionally, all of these exterior forces can align in such a way that it more drastically alters the winter solstice date.  In 1903, the winter solstice occurred on December 23…and that is not expected to happen again until 2303!

10-to-1 Rule
December 19, 2011

By Meteorologist Mike Skurko

The system we are expecting for Wednesday has produced the above rain/snow totals for western Massachusetts.  While this is primarily a rain event, those totals might initially speak otherwise.  For example, 0.9 inches of snow is expected very early Wednesday morning in Pittsfield, but only 0.4 inches of rain is expected the rest of the day.  However, a look at the properties of rain and snow can explain why most of the precipitation will still be rain in Pittsfield.

Snow forecasting applies a rule known as the 10-to-1 ratio.  Because snowflakes contain much less water than a regular raindrop, the amount of water to produce 10 inches of snow would also produce about 1 inch of rain.  Dividing the snowfall by 10 will give you the “liquid water equivalent.”  A storm that only produces 2 inches of snow would only produce about 0.2 inches of rain water.  This ratio can vary, becoming as little as 5-to-1 (a very wet snow) or as large as 30-to-1 (fluffy lake-effect snow).

In the case for Pittsfield on Wednesday, 0.9 inches of snow would only contain 0.09 inches of actual rainwater if you apply the 10-to-1 rule.  This is significantly less than the 4-tenths of an inch of rain expected for the day.

Ocean effect snow
December 18, 2011

By Meteorologist Mike Skurko

Out along the Cape this morning, 2.5 inches of snow accumulated in Wellfleet and Truro from a phenomenon known as ocean effect snow. While not as common as lake effect snow across the Great Lakes region, it is driven by the same fundamental processes.

Lake effect, or ocean effect, snow can be created when a cold airmass moves over a warmer body of water, which creates an unstable atmosphere. [It is the same fundamental instability that a cold front creates when cutting into a warm, humid airmass in the summertime and triggers thunderstorms.] Specifically, a temperature difference of at least 13 degrees Celsius (23.4 degrees Fahrenheit) between the lake water and the air at about 5000 feet is needed for this instability.

Moisture from the lake will be used with that created instability to condense into clouds. These storm clouds will get pushed by the winds, and eventually push the clouds over land. Frictional forces of the rougher land compared to the smoother water start to kick in, and cause the cloud movement to slow down and pile up, depositing the snow on the downwind side of the lake. For example, a wind from west-to-east will create the lake effect snow on the eastern side of the lake.

In the case of the ocean effect snow last night, the frigid airmass interacted with the warmer ocean water just north of Cape Cod. Northerly and northeasterly winds eventually pushed these clouds onto shore and deposited the snow.  The picture below comes from a National Weather Service spotter in Wellfleet, MA.  This was taken at about 5PM today, so some settling/packing of the snow has occurred.

Snowflake Shapes
December 17, 2011

By Meteorologist Mike Skurko

Some light snow showers in the Berkshires earlier today gave us these nice photos of individual snowflakes from our viewers in Goshen, MA.   These snowflakes are known as dendrites, which come from the Greek word “dendron” which means “tree”.  A close look at the edges of these types of snowflakes and you’ll see how they branch out and form jagged edges, rather than smoother sides of a basic shape like a hexagon (those types of snowflakes are known as plates).

Both of these types of snowflakes have six sides, as that is the natural pattern formed by bonding hydrogen and oxygen to make the water droplets that form the snowflakes.  Extensive research has found that certain shapes of snowflakes correspond with certain temperatures.  This morning, the temperatures in the Berkshires were near 30 degrees, and you can see that the flakes photographed by our viewers match the temperatures to produce those dendrite shapes on the graph below:

There is a saying that no two snowflakes are alike.  The reason for this is the different environments snowflakes form in, as well as the random collision with other snowflakes in the atmosphere and how that alters their shape.  While the chemistry and physics of how a snowflake gets its exact shape is not well understood (i.e. why that tree-like effect happens on some snowflakes and not others), it is proposed that two snowflakes created and closely monitored in identical conditions in a lab would theoretically produce an identical shape.

Just last year  Dr. Kenneth Libbrecht, a professor of physics at Caltech and a top researcher and publisher of books and photographs of snowflakes, successfully found a snowflake that identically matched a photograph of another snowflake from 1963!

Football kicking and air pressure
December 11, 2011

By Meteorologist Mike Skurko

Earlier today, the Denver Broncos made an incredible 59-yard field goal to force overtime against the Chicago Bears.  Our anchor Chris Stewart (a lifelong Bears fan) blamed the field goal on the thin air in Denver.  He is absolutely right…thin air allows footballs to be kicked further than at other stadiums around the NFL.

The reason is simple…the high altitude of Denver puts it at a lower air pressure than other cities around the league.  A lower air pressure means there are less air molecules to resist the motion of the ball, and thus creates less drag for a kicked football.

I haven’t found any studies computing the exact math for this for a football, but there have been studies for baseball at Coors Field in Denver.  The thin air at Coors Field allows a baseball to travel about 10 percent further than many other stadiums around the league.  The thinner air does not create as much resistance for a baseball to cut through after its hit, and the same can be said about a football after it has been kicked.  In fact, of the three longest field goals in NFL history (all 63 yards), two of them were made in Denver.  Perhaps that 59-yard field goal in Denver today would have only been made from 55 yards at another stadium.

Now the effects of thin air can be offset by the detrimental effects of cold air on a football.  A cold football will naturally become under-inflated, as temperature is directly proportional to pressure.  You’ve probably noticed this effect on an unusually cold morning…it will deflate your car tires just a little bit.  Trying to kick a cold football (i.e. trying to kick an under-inflated football) will not transfer energy from the kicker’s foot to the football as efficiently.

We’ve all tried bouncing an under-inflated basketball or volleyball…it doesn’t bounce back as high.  This is because there is not as much energy transfer between the ground and the ball due to the lower pressure.  Similarly, it is harder to hit a baseball or golf ball as far in colder weather because the energy transfer between the ball and the object is not as efficient.  Baseballs hit 400 feet in warm weather may only travel 385 feet in cold weather.  A 300-yard drive in June might only travel 290 yards in November.

Probability of a White Christmas
December 8, 2011

By Meteorologist Mike Skurko

Driving down route 5 in West Springfield the other day, I heard Burl Ives “Have a Holly Jolly Christmas” on the radio.  The line “I don’t know if there’ll be snow, but have a cup of cheer” got me wondering…it’s too early to tell if we will indeed have a white Christmas, but what we do know is our historical odds of having one.

There are many popular definitions of a white Christmas, such as snow anytime on Christmas Day or snow on the ground when we wake up Christmas morning.  The one that is deemed “official” by the National Weather Service is a snow depth of at least one inch observed anytime on Christmas Day.  This means either the snow can already be on the ground, and/or the snow can accumulate at least an inch anytime during the day.  A few flurries to provide a dusting on the grass would not cut it though.

Here is a map of the statistical odds of a White Christmas all across the country, based on a historical analysis of decades worth of December 25ths:

If you can’t see it close enough, the breakdown for western Massachusetts is:

highest elevations in the Berkshires: 76-90%

the rest of Berkshire County, Franklin County, and the hilltowns: 61-75%

city areas (Springfield, Holyoke, Northampton): 51-60%