Archive for January, 2013

Recapping the cold snap
January 27, 2013

By Meteorologist Mike Skurko

Here is the recap of the high and low temperatures this past week for the Springfield area:

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For the last few years, a cold snap of this length has been happening every other January.  The forecasted overnight low in Springfield for tonight is 9 degrees … which would be our 6th consecutive night in the single digits or colder.  Here are the last three cold snaps of at least 6 days in the single digits or colder (all months, not just January):

January 10 – 17, 2009 (8 days)

January 22 – 28, 2011 (7 days)

January 23 – 28, 2013 (6 days) *forecasted*

If this every-other-January pattern continues, I guess we could pencil in for a similar cold snap in January 2015!

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CSI: Training Thunderstorms
January 20, 2013

By Meteorologist Mike Skurko

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If you happened to catch this week’s new episode of CSI: Crime Scene Investigation, one of their characters … a weathergirl named Rainy Days … talked about monitoring the radar for training thunderstorms.  [A little background info on the episode – an anchor was stabbed during a brief power outage in the studio, so the CSIs looked at all of the station’s employees for the possible killer and their motive.]

So let’s take a look at the meteorology of the episode.  Was the science accurate? Here is the transcript from the weather explanation as Rainy is questioned by CSI Finlay:

Rainy: “Paulson told me they wouldn’t need me until the next segment, so I stayed here monitoring the Doppler.”

CSI Finlay: “For the monsoon?”

Rainy: “Monsoons only happen between May and August, technically this was a training.”

CSI Finlay: “A training?”

Rainy: “Two storms hitting at the same time, upping the volume of precipitation, creating a flash flood.”

CSI Finlay: “That’s very impressive.”

Rainy: “Masters in meteorology and atmospheric sciences, and I’ve got the student loans to prove it.”

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The basic definition here is correct … training storms are storm cells that successively move over the same region in a short period of time, creating heavy rainfall totals over isolated areas.  Think of them like the cars of a train … each one moving along the same path in the same direction.

We all know that a heavy thunderstorm (the ominous reds on radar) can produce a quick inch of rainfall.  Now imagine if two, three, four, or five of those red thunderstorm cells kept moving over the same town, one right after the other.  Flash flooding would be a definite result.

Training thunderstorms typically form along stationary fronts.  Most people in western Massachusetts are more familiar with the thunderstorms from cold fronts and squall lines.  They quickly sweep through the region with one bad line of storms, and then conditions quickly quiet down behind the front/line.  Stationary fronts remain in one place, allowing training storms to continue hitting the same spot instead of sweeping out of the area with the exiting front.

While training thunderstorms are usually not quite as severe, their rainfall capabilities are tremendous when these heavy downpours continue to hit the same town over and over again, one storm cell right after another.  Below is a good example of a group of training thunderstorms.  You can imagine that this would be bad news for flash flooding when a situation like this shows up on our Doppler.

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The Green Flash
January 12, 2013

By Meteorologist Mike Skurko

Our last weather blog entry talked about “sun pillars,” and while researching that a little bit I stumbled across some material about “green flashes.”  This is when a quick flash of green light appears at sunset just before the sun drops below the horizon.  The most relevant pop culture reference I could think of was from the movie Pirates of the Caribbean: At World’s End.  Here is a still frame from the movie:

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While rare, the green flash is an actual optical phenomenon caused by the way light scatters and bends in the atmosphere, known as refraction.  You are probably familiar with color prism shown below, which shows the various colors of visible light and how it is refracted into its rainbow of colors.  Incoming sunlight is similarly refracted by the earth’s atmosphere, and bent slightly with the curvature of the earth.

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The frequency of the color green allows it to bend more than reds, oranges, and yellows.  When the sun is just below the horizon, those colors can no longer be seen, but the green is still able to bend with the curvature of the earth.  Therefore, the green light can make it to the observer’s eye, but other colors are blocked (the blues and purples are usually scattered too much in this scenario that they become invisible to the observer).

Because this phenomenon occurs only for a second, and is better seen with some magnification, it is called a “green flash”.  While it does not create a sudden burst of green light that fills the sky as depicted in the movie, you can see a hint of only green in the last second before the sun completely crosses the horizon line.

Here is the best video I could find on youtube depicting an actual green flash in Fiji.  It can also be seen on our Pacific and Atlantic coasts (including the Cape), but this video was the best.  Conditions must be clear for a green flash to be observed (both in cloud cover, as well as dust and smog), and the actual horizon line must be clearly visible (best over the oceans).  The exact way the light is refracted to cause a green flash is very specific, so a green flash doesn’t always appear even if viewing conditions are excellent.

Sun pillars
January 6, 2013

By Meteorologist Mike Skurko

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The photo above was captured by our Springfield skycam around 4:30 this afternoon.  The vertical ray of light is known as a “sun pillar.”  It is caused by sunlight being reflected off of ice crystals near sunrise or sunset.  Flat, plate-like ice crystals commonly associated with cirrostratus clouds cause the unique reflection pattern.   Think of them as tiny little mirrors that are oriented just right to produce that vertical beam of light.

With increasing clouds in the forecast for us tonight, thin cirrostratus clouds are likely to move in ahead of the thicker clouds overnight.  Below are some other pictures of  sun pillars captured from around the world, courtesy of NASA.

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Unusually warm this week, unusually cold the next
January 5, 2013

By Meteorologist Mike Skurko

While this upcoming week will be mild for western Massachusetts, we are looking at another one of those “arctic blasts” coming into the U.S. by the middle of the following week.  Below are images from two long-range computer models.

The line drawn in blue represents the 540-line, which provides a rough estimate of the rain/snow line.  The line drawn in purple represents the 510-line, which is used as the basic border for “arctic air”.  540 and 510 refer to atmospheric thicknesses … the lower the thickness value, the colder the atmospheric profile is.

The first image is for Friday morning, where our high temperatures that day are forecasted to be in the mid-40s in Springfield (normal high for this time of year is mid-30s).  Notice how the rain/snow line stays to our north and the arctic air remains trapped in Canada.

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The second image is for next Friday, January 18, which shows the arctic air invading the northeast.   A few days prior, the models show that 510-line dipping down to Denver, Colorado and the 540-line touching the Mexican border!  It is likely that brutal cold will be the main national weather story that week.

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2012: All-time warmest for the Pioneer Valley
January 1, 2013

By Meteorologist Mike Skurko

Below are the average high temperatures and total precipitation for 2012.  High temperatures were nearly 3 degrees above normal, which is quite an achievement when it’s carried out for 12 months.  The National Weather Service put this as the all-time warmest year on record for the Pioneer Valley, dating back more than 100 years.  While not illustrated below, the average low temperatures were 3.4 degrees above normal as well.

Drought gripped much of the nation, us included.  While November was at an all-time driest, the second-half of the year was an overall improvement in precipitation totals compared to the first-half (I know I was playing golf much earlier than usual this past year thanks to a record-mild and very dry March).

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The season-by-season breakdown of these numbers goes like this … winter was the 2nd warmest, spring tied the all-time warmest, and summer was the 5th warmest.  Autumn was only a half-degree above normal, so it didn’t break any top-10 lists here.

We set 9 new record high temperatures, 2 record low temperatures, and 2 daily snowfall records.  Records broken in 2012 are listed below:

02/29…record daily precipitation…0.59…previously 0.15 in 1968
02/29…record daily snowfall…4.4…previously 0.8 in 2008
03/12…record high…74…previously 69 in 1977
03/18…record high…72…previously 71 in 2011
03/19…record high…79…previously 73 in 2010
03/22…record high…83…previously 75 in 1948
03/23…record high (tied)…75…also set in 1938
March…record warmest…47.1…previously 46.2 in 1945
04/16…record high…92…previously 90 in 2002
Spring…record warmest (tied)…54.3…also set in 2010
06/20…record high…97…previously 96 in 1995
06/21…record high (tied)…96…also set in 1953
07/18…record high…100…previously 99 in 1982
08/15…record daily precipitation…1.33…previously 1.18 in 2004
10/13…record low…27…previously 28 in 1981
11/06…record low…20…previously 21 in 1991
11/08…record daily snowfall…0.9…previously 0.7 in 1910
November…record driest…previously 0.51 in 1976