Archive for July, 2012

CBS3 Pinpoint Weather and NESN parternship
July 31, 2012

By Meteorologist Mike Skurko

CBS3 Springfield is proud to announce a new partnership with NESN, getting exclusive behind-the-scenes content and analysis for western Massachusetts for the Boston Red Sox and Bruins.  Along with that, western Massachusetts will receive gameday and postgame forecasts from CBS3 Springfield’s team of meteorologists.

Be sure to look for CBS3 Springfield Pinpoint Weather to provide forecasts for that night’s game at 6 p.m. on NESN’s Red Sox First Pitch, and again on Red Sox GameDay Live.  After the game, we will take a look at the forecast for the upcoming games, whether they’re at Fenway or on the road, during Red Sox Extra Innings Live.

London Olympics weather
July 29, 2012

By Meteorologist Mike Skurko

Getting a glimpse of the start of a beach volleyball match at the London Olympics on tv last night, the announcers noted that the temperature was 55 degrees…hardly beach weather.  That got me thinking about what the weather is typically like in London in the month of July.

Despite the UK’s reputation for nasty, windy, rainy weather…a typical July in London is cool, but pretty dry.  It’s average high and low temperatures in the summer closely resemble those of downtown Seattle, Washington.  London only averages 7 days per year above 86 degrees, and only two days a year hit 90 degrees.  While England is an island, a large part of it’s cooler climate is simply because of it’s position further north.  While Springfield sits at a latitude of 42 degrees north, London is at 51 degrees north…the same latitude as Calgary, Canada.

However, not all of this year’s competition is being held directly in London.  Some of the football matches, including the U.S. Women’s first two preliminary matches, are being held in the city of Glasgow (located about 400 miles north of London…in the blue and white shaded region on the temperature map above).   As far as precipitation, London’s average summer rainfall is only about half of what we typically see from June through August here in the Pioneer Valley.

[Maps courtesy of The Met Office – national weather service of the United Kingdom]

Saturday rainfall totals
July 29, 2012

By Meteorologist Mike Skurko

Here are the rainfall totals from Saturday’s widespread rain across western Massachusetts, which cause numerous reports of flash flooding…involving stuck vehicles and closed roadways through the middle of the day.  East Longmeadow had the highest recorded total in New England, although parts of central Long Island received about 5.5 inches.

To give you an idea how quickly the rain came down at times, Bradley International recorded a total of 1.89 inches of rain on Saturday, with an astonishing 1.53 of that coming down just between 3 and 4 p.m.

FRANKLIN COUNTY
   CHARLEMONT            1.24

HAMPDEN COUNTY
   EAST LONGMEADOW       4.69
   SOUTHWICK             2.50
   BLANDFORD             2.25
   HOLYOKE               2.20
   WEST SPRINGFIELD      2.01
   PALMER                1.98

HAMPSHIRE COUNTY
   BELCHERTOWN           2.80
   WARE                  2.60
   HADLEY                2.54
   GRANBY                2.16
   AMHERST               1.21

Courtesy of the National Weather Service, Taunton, MA

Storm Prediction Center’s “tornado outlook”
July 27, 2012

By Meteorologist Mike Skurko

The anticipation of severe weather across the Northeast caused everybody to have the word “tornado” on their mind.  Even before any of our forecasts first thing in the morning, people were asking about western Massachusetts’ tornado potential.  There were also a number of text messages, emails, and facebook comments coming into our weather team (and I would assume the other tv stations as well) regarding the word “tornado”.  Without having made a forecast for the day…somewhere, somehow the word “tornado” had everybody monitoring the forecast with heightened alarm.

Certainly the events of last year has made western Massachusetts much more weary of severe weather potential.  In fact, just one year ago yesterday we had a tornado warning for western Massachusetts…a storm that ultimately caused the microburst in Wilbraham.  But why did so many people think we ran such a higher risk of getting hit by tornadoes again yesterday?  My theory is that it came from the circulation of a certain “tornado outlook” map from the Storm Prediction Center in Oklahoma.

The Storm Prediction Center (SPC) in Oklahoma,  a branch of NOAA and the National Weather Service, is responsible for issuing all severe thunderstorm and tornado watch boxes across the country (it is up to the local offices to issue the actual warnings).  Along with their outlooks, the SPC also issues the following maps for potential wind damage, hail, and tornadoes for storms throughout the day.  This is a map of the SPC’s “tornado outlook” issued yesterday morning.

Yes, that does seem daunting…Springfield being clipped by the 5% category for tornadoes.  However, there is a HUGE difference between these percentages from the SPC and the percentages we are used to seeing with weather forecasts (such as “30% chance of rain”).  The definition of these tornado percentages issued by the SPC is the “probability of a tornado within 25 miles of a point.”  That is much different than simply a 5% chance of tornadoes, or that 5% of the population within the circled area will get hit by a tornado.

Lets think about that area…within 25 miles of a point.  Remember elementary math…the surface area of a circle is pi times the radius squared.  As shown below, all of the surrounding area in a 25-mile radius from a point would encompass a surface area of 1963 square miles.  To put that in perspective, the combined surface area of Hampden, Hampshire, and Franklin Counties is 1904 square miles.

This means that the SPC’s 5% outlook for tornadoes would equate to just a 5% chance (or a 1-in-20 chance) of one tornado in an area roughly the size of our entire viewing area, minus the Berkshires.  To further put this in perspective, if Franklin, Hampden, and Hampshire Counties were all under the SPC’s 5% risk of a tornado 20 different times throughout the summer, we would still only see one total tornado in western Massachusetts for those 20 days combined.

In the case of the June 1st, 2011 tornado, much of New England was under that 5% tornado risk category.  Below is the archived tornado outlook map from that day:

Statistically speaking, after a tornado touched down on June 1st, we would need to be placed under this 5% category twenty more times before another tornado would actually occur.  Meteorologists and weather enthusiasts across New England know that it is rare for western Massachusetts to be under that 5% category just a couple of times a year, let alone twenty.

Yes, other news sources and websites called for “isolated tornadoes” with yesterday’s storm system…and they have to.  Being under that 5% category still means the SPC believes there is a small chance for an isolated tornado or two to occur.  However, as thoroughly explained above, this “isolated tornado” chance carries a much smaller probability than the simpler, daily forecasts of “isolated showers” or “isolated flurries.”

Hopefully this provides you with a better understanding of how the Storm Prediction Center comes up with its percentages.  When one of their maps is copy and pasted around the web, be aware that their “5% chance of tornadoes” or “30% chance of wind damage” carries a different definition than the standard “30% chance of rain”.  While a tornado watch or warning is still something not to take lightly during these events, 5% of the entire western Massachusetts population will unlikely be hit by a tornado every time this sort of map is issued from the SPC.

Meteorology 101: Sea breezes
July 21, 2012

By Meteorologist Mike Skurko

While on vacation in Myrtle Beach, South Carolina last week…and many folks in western Massachusetts heading to the New England beaches at some point this summer…I thought it would be appropriate to talk about sea breezes.  Why does the wind typically pick up and come in off the water right along the coastline?

Sea breezes are generated by the difference in temperature between the land and water.  During the day, the sun heats up the coastline much faster than it heats up the ocean.  A large body of water takes a lot longer to respond to temperature changes than a land surface, which is why it still feels cool to take a swim on a hot summer day.  Warmer air is less dense, so it will rise and heat up the column of air directly above the land…creating a small area of low pressure at the surface.

 

This warming on land also expands the column of air, which creates a relatively higher pressure aloft (about 3000 to 5000 feet) compared to the same level above the ocean.  To balance this, the wind aloft will start flowing from the high to low pressure.

 

Once that air is over the water again, it cools.  As explained above, warmer air is less dense and will rise…so in this case the cooling air becomes more dense and will sink towards the ocean surface.  Air sinking towards the surface is a definition of a surface high pressure.

 

Just like it does aloft, the wind will blow from the higher pressure to the lower pressure.  At the surface, this means the wind will be blowing in from the water, thus completing the cycle and creating the sea breeze.  As the land continues to warm up more and more during the afternoon, the cycle reinforces itself.  Sometimes it can become so strong that a mini-cold front develops…known as a sea breeze front…that can trigger a line of thunderstorms running parallel to the coast.

Moving closer to the sun
July 5, 2012

By Meteorologist Mike Skurko

After reaching its furthest point from the sun last night, Earth’s orbit will now pull it closer to the sun in the months ahead.  The earth revolves in an elliptical orbit, not a uniform circle, so the distance from the earth to the sun varies over the course of the year.

The closest point to the sun, known as perihelion, occurred in early January and puts it about 91.4 million miles from the sun.  It’s furthest point, aphelion, which occurred at about midnight last night, puts us 94.5 million miles from the sun.  The moon also undergoes a similar elliptical orbit which varies its distance away from us.

So, if you think the hot weather across the country this week is because we’re closer to the sun…that’s a myth.  In actuality we couldn’t be any further from the sun at this time of year.  What controls our warm and cold seasons is the tilt of the earth’s axis, which is pointed nearly 23.5 degrees towards the sun for the northern hemisphere in summer.  In fact, we actually receive about 7% more of the sun’s energy at perihelion…but because we’re tilted away from the sun at that time (winter), we don’t get a warm up from that.

Heat causes road buckling
July 4, 2012

By Meteorologist Mike Skurko

Video courtesy Youtube

You may have seen the viral video of a car going airborne while innocently driving down a road in Wisconsin.  The intense heat across the middle of the country caused highways to buckle in many parts of the state.  This SUV obviously missed, or underestimated, the warning sign and shot straight up into the air…Dukes of Hazard style.

When asphalt heats up, it will expand…just like the air in our atmosphere.  That expansion will put stress on the roadway, and since it can’t be forced downward due to the ground…it will be forced upward where there is no resistance.  The result is a raised, cracked surface that needs immediate attention by road crews.

Buckling isn’t limited to roadways…it can also cause transportation delays for airport runways, train tracks, and subway rails.

Meteorology 101: Derechos
July 3, 2012

By Meteorologist Mike Skurko

The intense line of storms  across the mid-Atlantic on Friday are still making national headlines…due to the ongoing widespread power outages during their excessive heat this week.  (Remember how bad the power outages and tree removal was after our October Nor’easter?)  This storm complex has a name that you probably never heard of before…a derecho (pronounced deh-REY-cho).

A derecho is a long-lasting, fast-moving line of thunderstorms that can produce straight-line wind damage over hundreds of miles.  The criteria for a derecho is a wind damage swath of at least 240 miles (Friday’s storm was more than 700 miles) and wind gusts of at least 58 mph for most of its length.

A derecho is similar to a type of storm you may have heard of before…a bow echo.  Simply put, derechos can be viewed as a bigger, meaner, longer-lasting version of that.  Here is a graphic from the National Weather Service depicting several timeframes of Friday’s derecho, which should give you a good idea what these storms look like.

Notice how the center of the line of storms appears to bend out towards the direction it’s traveling.  That is a classic indication of straight-line wind damage.  Strong flow behind the line of storms will push out the center of the storm, giving it that bow shape and producing the most devastating straight-line winds at the furthest point out.  Here is a schematic of the evolution of a typical bow echo that produces straight-line wind damage.

Winds gusts hit 91 mph in Fort Wayne, Indiana (marked by a purple dot on the map above…right in the center of the “bend” in that bow echo.  Tornadoes are uncommon with derechos, as straight-line winds are unfavorable for tornadic development.  However, they can develop around the north end of the line (see the area marked with a capital “C”) from the cyclonic flow that wraps around this end of the storm.

Derechos only happen a few times a year, most simply due to their large size.  They most commonly occur in heart of severe weather country in the Midwest, but can also occur in western Massachusetts once every couple of years.

June 2012 in review…ending the streak
July 2, 2012

By Meteorologist Mike Skurko

All things considered, this was a rather “average” June across the Pioneer Valley.  Our average high temperature of 79.6 degrees at Bradley International was 0.3 degrees cooler than normal.  Our average low temperature of 57.6 degrees was 0.3 degrees above normal!

This June stopped a warm streak just one month short of an all-time record.  For the last 14 consecutive months…April 2011 to May 2012…high temperatures were above normal.  June stopped that streak just one month shy of a record.

1) 15 months – June 1990 to Aug. 1991

2) 14 months – April 2011 to May 2012

3) 11 months – Jan. 2010 to Nov. 2010

4) 8 months – June 1973 to Jan. 1974

5) 7 months (3 times) – Oct. 1950 – April 1951; Nov. 1952 – May 1953; Oct. 2001 – April 2002

*It is important to note that the “average” numbers used to compile these statistics are the same average mean temperatures for our recent streak.  The average highs and lows are actually tweaked every decade to reflect more recent “normals”…but that’s a weather blog entry for another day.

As for precipitation, we were also close to normal in that category.  Our total rainfall for June 4.22 inches, just 0.13 inches below normal.  Every month in 2012 has had below normal precipitation so far, but this is the first time we’ve been within a half-inch of the average.

New map illuminates world’s historic earthquakes
July 1, 2012

By Meteorologist Mike Skurko

The “Ring of Fire” looks a lot brighter, courtesy of this new map plotting earth’s major earthquakes from 1898 to 2003.  Earthquakes of magnitude 4.0 or greater…more than 203,000 of them…were marked by a greenish-blue color that gets brighter with earthquake intensity.

The result is this stunning map which artfully outlines our planet’s tectonic plates, specifically the zone known as the Ring of Fire…the line of the most numerous and intense earthquakes in the northern and western Pacific Ocean.

The map was created by John Nelson, mapping manager for IDV Solutions.  If you haven’t seen it already, among that company’s many creative charts and maps is a stunning map of 50+ years worth of tornado tracks across the country.