Archive for December, 2013

Accuweather’s inaccurate 45-day forecasts
December 28, 2013

By Meteorologist Mike Skurko

Nearly the entire meteorological community laughed when AccuWeather debuted 45-day forecasts earlier this year.  The failures of such specific long-range forecasts are now being reported.  I got word of this more than a week ago, but now the results have also been published on The Capital Weather Gang, a nationally-known weather blog maintained by the Washington Post, and garnering more mainstream discussion.

Dr. Jon Nese, a former professor of mine at Penn State University’s meteorology department, as well as a former on-air expert analyst for The Weather Channel, conducted an experiment with his “Introduction to Meteorology” students this past semester.

Students tracked the high temperatures for AccuWeather’s 45-day forecasts for 15 different cities across the country, as well as the climatological normals over the last 30 years (aka the “average high” or “normal high” you see on TV).  Below is a chart created for one of the cities tested … Boston:

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The blue line represents AccuWeather’s daily forecast for Boston’s high temperature throughout the semester, while the red line shows the “normal high” for that day for Boston.  As Dr. Nese’s charts clearly illustrate, the “normal high” is more accurate than AccuWeather’s attempted forecast for anything beyond 8 days out.

Charts very similar to this one appeared for the other 14 cities tested throughout the semester as well.  You can read Dr. Nese’s full report here: Students put AccuWeather long-range forecasts to the test

AccuWeather responded the next day here: AccuWeather defends value in 45-day forecasts

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December snowfall record could stay intact
December 20, 2013

By Meteorologist Mike Skurko

Believe it or not, our two rounds of snow in the last week have pushed the Pioneer Valley a half-inch away from a December snowfall record.  The official record at Bradley International Airport is a total of 12.9 inches set just last year.  So far this month, Bradley has recorded 12.4 inches.  Saturday night’s storm produced 6.7 inches, Tuesday had 4.8 inches, plus a few minor dustings scattered throughout the month.

However, looking at some long-range weather forecasts, it is quite possible we do not set a new record this month.  After this weekend’s rain, there is no new snow in our 7-day forecast through December 27th.  Two popular weather models, the GFS and the Euro, are shown below for Friday, December 27th:

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Both models are in good agreement that a large area of high pressure will be building into the Ohio Valley heading into next weekend, which would keep our weather dry beyond the 7-day forecast.  Our best chance may come just before New Year’s.  The above images are surface maps, whereas this image below is an upper-air computer model, also of Friday, December 27th:

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Notice the orange-colored region in western Canada, just north of Montana.  This is a small trough that will be sweeping through the northern tier states in the final days of December.  This particular computer model puts it into the Northeast by Monday, December 30th.  It’s tough to give precipitation estimates that far in advance, but the overall weather pattern suggests this small trough may be our best chance to pick up that final half-inch of snow to receive a new December record.

White Christmas probabilities
December 18, 2013

By Meteorologist Mike Skurko

For those dreaming of a white Christmas, the scene outside right now seems perfect.  Bradley Int’l has recorded 12.4 inches of snow so far this month, just a half-inch away from a new December record for the Pioneer Valley (which was just set last year).

A white Christmas is officially defined as a snow depth of at least one inch on the ground at any point on Christmas Day.  The Springfield area has historical odds of 50 to 60 percent for that happening, or about once every other year.

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Unfortunately, our recent snow will not all be sticking around for the 25th.  Sunday’s forecast is the biggest obstacle to obtain an official white Christmas.  Temperatures could climb into the 50s on Sunday, and rainfall could exceed one inch, maybe two.  This warmth and steady rain has the potential of washing away most of the snow that we’ve received in recent days.

We’re overdue for snow to be falling on Christmas day as well, as the snow in 2010 and 2012 came a day late on the 26th, and 2011 featured no December snow at all.

Winter weather driving tips from Mass.gov
December 14, 2013

By Meteorologist Mike Skurko

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Mass.gov, the official website of the Commonwealth of Massachusetts, shared these ten winter driving tips.  I know, I know … many of them seem obvious, but it’s always good to re-read stuff like this before the start of each winter.  Keep it fresh in your mind, and you never know … it may prevent an accident and/or an injury in the future.

  1. Ensure your car is road-ready; check the tires, brakes, lights, and windshield wipers.
  2. Keep the gas tank at least half-full. In extremely cold temperatures, condensation can build up in an empty tank which can cause the fuel line to freeze.
  3. Before hitting the road, clear the car’s hood, roof, and all windows and lights of frost and snow.
  4. Pack an emergency road kit in case of a breakdown or accident. It should include an ice scraper, shovel, flashlight, jumper cables, flares, blankets, and a first-aid kit.
  5. Check road conditions before travelling by calling 5-1-1 or by visiting the MassDOT traffic page, which provides real-time views of roads across the Commonwealth.
  6. If possible, postpone travel until roads have been plowed, treated, and cleared.
  7. A highway speed of 65 miles per hour may be safe in dry weather, but can be an invitation for trouble on snow and ice. Speed limits are set for optimal conditions, so adjust your speed to the weather outside.
  8. Always wear a seat belt.
  9. In wintry conditions, motorists should always drive with their headlights on for maximum visibility.
  10. On slippery roads, a vehicle will not be able to stop or turn as quickly as it would on dry pavement, so allow greater distance than usual between yourself and the vehicle ahead of you.

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Two chances of wintry precip coming … second on Monday morning
December 6, 2013

By Meteorologist Mike Skurko

Continuing our weather blog discussion from last night … the Monday morning commute is going to be a slow one across the Northeast.  Accumulating snow and some freezing rain will impact much of southern New England, both the intensity and timing of the storm will likely have bigger impacts across western Massachusetts than the one for us tonight.

Here is a computer model for the projected radar image late Sunday night into Monday morning:

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The blue is snow, while the orange and pink is a wintry mix of snow, rain, and ice.  Unfortunately for Pennsylvania, precip-type computer models are showing this region to encounter a substantial period of freezing rain.  Some of that freezing rain may arrive in western Massachusetts (including downtown Springfield) for the Monday morning commute.  Here is an image for 7 a.m. Monday:

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The top panel showing the probability percentage of rain, while the bottom panel shows the percent chance of freezing rain.  Having used these winter precip-type models for years, these percentages for freezing rain do not get this high for winter events in western Mass often, which is why we are paying close attention to freezing rain having a big impact on the Monday morning commute.  Stay up to date with the forecasts through the weekend.

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Two chances for wintry precip coming … first on Friday night
December 5, 2013

By Meteorologist Mike Skurko

Two rounds of wintry precipitation will impact western Massachusetts in the coming days.  The first is expected late Friday night into early Saturday morning.  The second is expected late Sunday night into early Monday morning.  Right now, it appears these two systems will behave in reverse ways … the first being a Friday rain changing to a mix overnight, the second being an overnight mix changing into a Monday rain.

Details are still developing on the second episode for Monday, and we have to get through the first round of wintry weather Friday night.  Let’s take a look at a few computer models for the first system, beginning with 10 PM Friday night:

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You can see that Friday’s rain will start changing over to a wintry mix late Friday evening.  The 5 PM Friday commute is still expected to be fine (a steady rain, just no snow/ice yet).  As cooler air moves in late at night, this will progressively change the rain over to sleet and snow, first in the hilltowns and Franklin County, then down towards the Springfield area.  Thankfully, it is a quick event, clearing out by sunrise on Saturday and not allowing significant snow to accumulate (although there will still be many slick spots).

Both the National Weather Service and our own Futurecast agree on a minor 1-2 inches for the hilltowns, but nothing more than a brief coating for the downtown Springfield area.

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(Note: Futurecast’s values are rounded off, so a “zero” doesn’t necessarily mean absolutely no snow, but it remains under a half-inch)

Skies clear out Saturday afternoon and Sunday, but then our next system develops out of the south and will deliver widespread rain and snow across the Northeast.  Currently, this appears to be more of a rain-mix event rather than an all-out snowstorm for Springfield, but it may have icy implications on Monday morning’s commute.  More details on that will be posted as we start the weekend.

Model images courtesy Dept. of Meteorology, The Pennsylvania State University

Fall 2013 in review
December 2, 2013

By Meteorologist Mike Skurko

The beginning of December marks the start of meteorological winter … the full months of December, January, and February.  Likewise, meteorological fall is made up of the full months of September, October, and November.  Let’s take a look at the numbers for this past fall season:

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High temperatures were very close to normal for the entire fall season, finishing just four-tenths of a degree below normal.  Precipitation was also below normal, perhaps more than the numbers appear.  This fall finished 2.35″ below the normal amount of rainfall.  It would even be worse if not for the three and a half inches of rain we received the day before Thanksgiving.  Minor drought conditions existed across Southern New England before that rain came:

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There are two reasons why “meteorological seasons” are slightly different than “astronomical seasons”: number one, it makes for easier record keeping when dividing everything up over full months.  Second, these seasons are more closely related regarding their weather.  For example, December 15th is still before the winter solstice, but the average weather for mid-December is much more similar to winter than fall.

Why overpasses and bridges freeze first
December 1, 2013

By Meteorologist Mike Skurko

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This morning’s 70-car pileup on Interstate 290 in Worcester perfectly illustrates how bridges and overpasses freeze before other roads.

Freezing rain is essentially “normal” liquid raindrops that freeze over after landing on the surface.  The air above the surface is just warm enough to support rain.  Even if the reported air temperature is about 30 or 31 degrees, it may be warmer a little bit higher up, and the raindrops don’t have enough time to freeze before they land.  However, once it does hit the surface, these raindrops will then freeze over on objects … trees, sidewalks, and roadways … as they have been sitting at sub-freezing temperatures.

Bridges and overpasses will have ice develop before other roads because they are left exposed to the colder air.  A road that is directly on the ground will be warmed by the earth underneath, so even though the air temperature is 30 degrees, the road may still be above-freezing for quite some time, especially if high temperatures were above freezing for the last few days.

Meanwhile, a bridge or overpass has cold air flowing above AND below it, which cools it much faster.  Imagine a drink sitting in a cooler.  Which cools the drink faster (and keeps it cooler longer): having ice packs touching one side of the drink, or having ice on both sides of the drink?

Even though the air temperature is the same, and the precipitation falling is the same, the bridge/overpass will drop below 32 degrees much faster than all of the other roads.  This can easily catch drivers off-guard, and which is why you see road signs like the one above.

Massachusetts State Police reported that this morning’s accident in Worcester occurred between mile marker 5.6 and 6 on the elevated bridge deck on I-290 around 7 a.m.  Automated weather conditions in Worcester reported at that time were 32 degrees with precipitation.  The elevated bridge deck was obviously still cold enough to support freezing rain compared to the road immediately before and after the overpass.

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