Blizzard of 2015 – Monday Morning Update

Really no reason to change our thoughts from overnight. The job we have today is to try and figure out where the heaviest snow will fall within the state. Currently we are running with 15″-30″ statewide.

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This graphic is confusing but let me do my best to explain. Time is on the x-axis and height is on the y-axis. Current time is on the right side of the screen and as you move left time advances. The color is relative humidity through the atmosphere (purple is supersaturated with respect to ice) while the pink lines indicate where temperatures are between -12C and -18C. Why do we care? We look for strong lift through -12C and -18C because that’s where snowflake production is most efficient. High snow:liquid ratios and heavy snow is favored where this occurs. This cross section off the GFS for New Haven is about as impressive as I have ever seen in the area. Wow. This also shows the potential for a heavy burst of snow on Tuesday afternoon after the main burst Tuesday morning.

The issue now is where does the heaviest banding setup? Who gets the jackpot from this storm? At this point we’re thinking western Connecticut as the most likely location and we will pin down the details more by this afternoon.

Blizzard of 2015 – Sunday Update

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It’s a beauty from a meteorologist’s perspective and a beast from a normal person’s perspective. The Blizzard of 2015 will be quite a storm across the region. A couple questions I want to answer right off the bat which have come up today.

  • 15″-30″ – why such a big range?
    • Most of us will get somewhere between 15″ and 20″ of snow from this storm. That said, there will likely be a band of heavier snow of between 20″ and 30″. At this point there is very little skill in trying to figure out where in the state that band will be. When we have a better idea we’ll indicate it on the snowfall map. Additionally, there’s not a tremendous amount of difference in how you should prepare for 18″ of snow and how you should prepare for 30″.
  • Where the hell did this storm come from? You said it wouldn’t be a big deal on Thursday!
    • Yup, things changed in a big way. This is one of the few storms in recent memory that wasn’t well modeled beyond 96 hours. The European model on Friday night that came out indicating the potential for a major snowstorm lead the way and by midday Saturday all of our computer models were on board. It’s a testament to how far computer modeling and weather forecasting has come in the last decade – when I started looking at weather models and forecasting in the mid 90s seeing a storm appears out of nowhere 48 hours out was a regular occurrence! That almost never happens in 2015.
  • Will this storm be as bad as the Blizzard of 2013?
    • Maybe, but probably not. The February 2013 blizzard was a 2 or 3 time a century kind of storm. The heaviest band of snow set up in the most populated part of Connecticut (Bridgeport/New Haven/Hartford) which made the storms impact seem that much worse! While some places could conceivably see 30″ of snow – the odds of Bridgeport, New Haven, and Hartford getting there from the same storm are quite low.
  • You’re giving this storm a 9 out of 10 on your impact scale, why not a 10?
    • 2 reasons. 1978 and 1888.
  • The National Weather Service is predicting 24″-36″ for us how come you guys are so much lower?
    • We’ve seen that forecast and while it certainly may verify in some areas we expect those kinds of totals to be much more localized then they’re showing. 24.0″ is also the record for biggest snowstorm at BDL and 20.0″ is the second biggest snowstorm on record for Bridgeport. Setting 24″ as the lowest bound for a snowfall forecast in this area is a very, very, very tough bar to reach.

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The track of this storm is a classic and that’s why we’re thinking it will be a blockbuster. Many of our biggest storms have featured a subtle, but detectable, counter clockwise loop just southeast of Connecticut as they deepen and stall. This one is modeled to do that.

One of the features that I find most useful in forecasting where the heaviest band of snow will set up is tracking where the low pressure systems above our heads at 850mb and 700mb track (that’s between 4,000ft and 9500ft up or so). To the northwest of these lows that’s where the heaviest snow will set up due to a process known as frontogenesis. This produces a narrow band of intense lift that slopes toward the cold air with height.

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It’s important to get those lows close to, but not west of, Montauk Point to ensure the heaviest banding sets up over Connecticut. Near and east of the mid level low track there are all sorts of issues that develop including the dreaded “dry slot” that is almost as painful for snow geeks as the sound of sleet pinging on your window.

As the storm wraps up winds will pick up as well. The combination of heavy snow and strong winds has lead to the issuance of a Blizzard Warning. While blizzard criteria is exceedingly difficult to reach (sustained winds >35 mph and visibility <1/4 mile) we should get close. Our computer models also show the potential for damaging wind gusts – possibly over 60 mph.

B8O6Ap5CQAAoJ1qThe GFS model is not quite as robust as the European with wind speeds but it still is indicating the potential for 60 or 65 mph wind gusts in southeastern Connecticut especially.

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In this profile you can see a wind speed of 66 knots about 2,000 feet above the ground – and a profile that’s favorable for a good portion of this to mix down to the ground. We’ll have to see how this develops through the night and into tomorrow. Power outages are certainly a possibility.

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Hopefully you’ll be able to hunker down and enjoy the storm. We’ll have you covered on NBC and of course on Facebook, Twitter, and basically everywhere.

Blizzard on the Way

This storm is shaping up to be a beauty. A classic New England snowstorm that will produce gusty winds, heavy snow, and possibly more than a foot of accumulation.

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The storm will pass near 40N/70W – what we refer to as “The Benchmark” and will feature a cold Canadian high pressure to the north. This type of setup implies there is the potential for over a foot of snow.

The worst of the storm will likely be Monday night and Tuesday morning. Our computer models show the potential for wind gusts over 60 mph in southeastern Connecticut during the height of the storm.

bufkitprofileYou can see winds of 63 knots (over 70mph) at the top of the “mixed layer” on this forecast sounding for Groton. That implies winds approaching that level could be mixed down during the storm.

This one will be big – we’ll be able to get more specific with  numbers and timing after the midday suite of computer guidance.

 

Not Terribly Enthused

You’ve probably heard something about a storm coming toward New England on Saturday. For me, this one has been full of red flags and problems. So why is that? Let’s start out with the Euro depiction of the storm Saturday afternoon.

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What’s missing from this picture? A high pressure! A cold Canadian high is a prerequisite for almost all major I-95 snow events. There are a couple reasons for this. One is obvious and the other may not be so obvious.

The obvious reason you want a cold high pressure banked to the north of New England is that it provides a steady stream of cold and dry air into the storm. This ensures that the precipitation will be in the form of snow even in the coastal plain.

The less obvious reason is that the cold high to the north and warm Gulf Stream off of the east coast produces a sharp temperature gradient (large difference in temperature over a short distance). The stronger the temperature gradient (aka baroclinicity) the stronger the storm may get. Also, as warm moist air from the over the ocean rides up and over the cold, dry, and dense air near the surface you get a blossoming precipitation shield well north of the low. This is known as isentropic upglide.

The stronger the temperature gradient the stronger the isentropic upglide can be. This schematic from NWS in Louisville shows the process nicely.

So, where does that leave us? This storm will struggle for many areas. Marginal cold air will result is borderline temperature profiles between rain, snow, and sleet. Additionally, the lack of strong isentropic ascent north of the low will cause the precipitation shield to be quite compact.

As opposed to seeing a regionwide snow event we’ll likely see a narrow band of very heavy, wet snow. Whoever can get into the narrow band of heavy snow will get hit pretty good by this storm. Others seeing drips of rain and mangled snowflakes will wonder what all the fuss is about.

Sunday’s Big Mess

I-95 Sunday Morning in Stamford

I-95 Sunday Morning in Stamford

It’s not an exaggeration to say Sunday morning’s ice event was a disaster on highways across the state. Around 8 a.m. I-95 was effectively impassable from Greenwich to Stamford as freezing rain resulted in countless accidents, stranded cars, dozens of injuries.

In New Haven an 88-year old woman was killed in one accident on North Frontage Road. There were a total of 40 accidents in the city with most resulting in at least minor injuries according to New Haven police. In New London, 6 people were injured in a 22 car pile-up just prior to the Gold Star Bridge on I-95. On highways across the state the State Police responded to 216 accidents with injuries occurring in 28 of them. There were countless other accidents on town roads across Connecticut with many more injuries.

The forecast for this event was decent. It wasn’t great but it certainly wasn’t bad. The worst of the icing occurred just prior to 9 a.m. in Fairfield County. In Bridgeport only 0.01″ of freezing rain was reported through 8:52 a.m. and just over the border at the White Plains Airport next to Greenwich 0.06″ of freezing rain fell through 8:56 a.m.

This minor amount of freezing rain was all it took to turn the Connecticut Turnpike into a skating rink. Our computer models showed this pretty well with some signs of light precipitation breaking out with low level cold hanging tough. Experience told us that the cold air would likely not be dislodged as quickly as the models were indicating so that lead us to a forecast of freezing rain at the onset. Here’s the high-resolution NAM forecast sounding for 7 a.m. Sunday – this forecast was based on a computer model that rain Saturday evening – 12 hours prior to the event.

bufkitprofileBy this point we’ve gone from something the models hinted at (plus experience telling us that the cold air would likely hang on a bit longer) to something our higher resolution computer models were explicitly showing. In addition, pavement temperatures by Sunday morning were near 20 degrees – cold enough to cause major issues with temperatures near freezing.

So what went wrong? To be honest I’m not sure. With freezing rain in the forecast we seemingly did “our jobs” in the weather department but at the end of the day that didn’t matter much. Roads were a mess, a number of people wound up in hospitals, and auto body shops saw a sudden surge in business! Were the roads not pretreated or treated fast enough? Was there a breakdown in communication between local/state DOT and their weather forecast provider?  I don’t know.

This brings me to my last point about the state of weather warnings and advisories we use from the National Weather Service. Sunday morning’s icing was arguably more dangerous and impactful than the majority of snowstorms we get that meet “winter storm warning” criteria. In fact, I would argue, that Sunday morning’s ice event was far more dangerous than many severe thunderstorm and tornado warning events in Connecticut are. The last tornado fatality in Connecticut was in 1989 (how many tornado warnings have been issued since? 100?) while in the last 20 years the nearly 3 dozen actual tornado touchdowns have resulted in only 4 injuries according to Storm Data published by the National Weather Service.

I believe the warning/advisory/watch system used by the National Weather Service and us here in local media is pretty close to broken. That said, I don’t know the answer to how we should fix it but I think we need to take a long and hard look at how and why warnings are issued and try to come up with a better system that can keep people safer.