Good evening from Southern Connecticut Weather!
Thank goodness for that final burst inland.
At this point yesterday, I was quietly beginning to resign myself to a bust. That term gets thrown around, but I'll explain what it really should mean later. The storm was a touch too slow coming together, and mixing held on for what felt like an eternity in SE CT. However, as I wrote on Facebook, you cannot declare victory or failure until all the data is in.
This is a review of our final forecast.
Thank goodness for that final burst inland.
At this point yesterday, I was quietly beginning to resign myself to a bust. That term gets thrown around, but I'll explain what it really should mean later. The storm was a touch too slow coming together, and mixing held on for what felt like an eternity in SE CT. However, as I wrote on Facebook, you cannot declare victory or failure until all the data is in.
This is a review of our final forecast.
Above: the verification map of our snowfall forecast. As a reminder, we take the reports published by the National Weather Service offices from Albany, Boston, and New York to fill in the map, and approximate locations because obviously the map isn't to scale. To the greatest extent possible, we try to include all reports, and throw out obviously erroneous ones--such as people reporting snow before the storm is over.
Defining "Bust"
Alright, so let's just start at the top. What is a bust? That gets thrown around a lot during these events. We define a bust as a result that drastically departs from a forecast. Getting 2.5" of snow when your floor is 4" is a miss, not a bust. Getting 1" when your floor is 4" is a bust. I know that's subjective, but if every time a backyard is marginally off in snowfall it's a bust there's no reason to write a forecast. I note that because if you look closely, you see that some towns had quite a bit of difference over just a few miles.
Snowfall is highly localized. Your location, elevation, and even measuring style make the difference in your final total. There's a huge difference between measuring on your driveway and in your grass (don't do either). There's a difference between the top of the hill in your town and measuring in the town center. That's why there are snowfall ranges, to account for that incredibly local variation.
What we see above overall is mostly a miss, and that'll be reflected in the grading below. It's not a disaster though, with the exception of SE CT, which...my goodness that was awful. One day our friends down there will get real snow again. Unfortunately yesterday was not that day.
The Forecast
Let's take a quick look at what happened. First, the original forecast of 4-8" in hindsight would've been best for the majority of the state. There was never any contemplation of taking the forecast totals down in SE CT, but there should have been. There are other spots in southern and coastal CT, like Shelton and Lyme that have consistently underperformed over time. Just something interesting that may be reflected in future forecasts.
Simply put, the storm came together slightly slower than anticipated. The banding appeared, did not get organized until it was east of the state, in large part in my opinion because of the speed at which the storm was moving.
Let's look at the radar at 8pm--prime time for heavier snow in our forecast.
Defining "Bust"
Alright, so let's just start at the top. What is a bust? That gets thrown around a lot during these events. We define a bust as a result that drastically departs from a forecast. Getting 2.5" of snow when your floor is 4" is a miss, not a bust. Getting 1" when your floor is 4" is a bust. I know that's subjective, but if every time a backyard is marginally off in snowfall it's a bust there's no reason to write a forecast. I note that because if you look closely, you see that some towns had quite a bit of difference over just a few miles.
Snowfall is highly localized. Your location, elevation, and even measuring style make the difference in your final total. There's a huge difference between measuring on your driveway and in your grass (don't do either). There's a difference between the top of the hill in your town and measuring in the town center. That's why there are snowfall ranges, to account for that incredibly local variation.
What we see above overall is mostly a miss, and that'll be reflected in the grading below. It's not a disaster though, with the exception of SE CT, which...my goodness that was awful. One day our friends down there will get real snow again. Unfortunately yesterday was not that day.
The Forecast
Let's take a quick look at what happened. First, the original forecast of 4-8" in hindsight would've been best for the majority of the state. There was never any contemplation of taking the forecast totals down in SE CT, but there should have been. There are other spots in southern and coastal CT, like Shelton and Lyme that have consistently underperformed over time. Just something interesting that may be reflected in future forecasts.
Simply put, the storm came together slightly slower than anticipated. The banding appeared, did not get organized until it was east of the state, in large part in my opinion because of the speed at which the storm was moving.
Let's look at the radar at 8pm--prime time for heavier snow in our forecast.
Above I circled the banding. There's moderate to heavy snow happening in these bands, but the bands are narrow and not consolidated. What does that mean? Look at Stamford--lighter precipitation. West Hartford--lighter precipitation. Far SE CT? Something is falling from the sky but it's so light you can't pull down the cold air as efficiently that's just over your head. With a more consolidated precipitation shield, you have more uniform snowfall.
But there's a second piece to this.
But there's a second piece to this.
We talked about having higher ratio snow at some point during the storm, and that was a great call. This was honestly a bit of a surprise however, and it made the snow forecast mostly respectable. Once the storm started to pull away, it did organize nicely enough for us to take advantage of better dynamics at the end. Between about 11pm and 2am, we saw moderate to heavy snow develop and slowly move across the state. With the entire state well below freezing by then, we saw excellent snow growth and that allowed some places, particularly in central and eastern CT pile up accumulation.
Many were saved from an outright bust at the end.
Timing
Timing worked out very well. Here's what we said:
While the individual models have bounced back an forth a little, there's not much change in my mind. I still think we see the onset of light snow and/or mixed precipitation between approximately 2pm-6pm on Sunday from SW to NE. The heaviest is likely to occur after sunset in a period between about 7pm and 1am, followed by tapering off between 3-5am.
Precipitation started right on time, the heaviest occurred between 7pm and 1am, and the snow was gone between 3-5am. Spot on.
Grade: A
Wind/Power Outages
This was an easy part of the exam. It wasn't a terribly wind storm. We did not have power outage issues. We were right about the inland snow being more powdery. Gusts didn't exceed expectations.
Grade: A
Snow Accumulation
Alright, here's where people really care. I wish that we kept the forecast to 4-8", but even then, the shoreline was going to be in trouble. Fortunately, interior CT carried us here. The overwhelming majority of locations below 5" were within an inch of the floor. A miss, not a bust. Central and part of eastern CT did well.
The shoreline zone however, that was bad for most. In SE CT it was horrific. Objectively. Exceedingly few got close to the floor of 4", and in SE CT folks have a right to complain--very good snowfall reporters reported less than an inch near the shoreline. That's really terrible for a storm that ended up being cold in the end, especially considering that the Gulf Coast is likely to see many times that amount over the next few days. I digress however.
This wasn't our best work. Grading the zones interior CT receives a B- while the coastal zone is an easy F with SE CT busting and the rest of the coast being a pretty bad miss. The average leads to a D+, which is double weighted because again, here is where people really care. I'm arbitrarily dropping it to a D because I didn't respect the decade of coastal futility enough.
Grade: D
Impact
Impact is a little tricky given the shoreline miss/bust. I do think this was still a moderate impact event, as roads did deteriorate, but it's hard to say we nailed it given what happened in SE CT.
Grade: B
Final Grade
Overall, we weigh snowfall 2x because we don't want to game the grading. Every other part of the forecast was really good, but we know what people care about and what's hardest to predict.
Final Grade: C+
As always, please like, share, and interact with us on our social media--on Facebook to share our discussions, and follow us on Twitter @southernctwx to retweet our posts. Hit the buttons below to join.
Thank you for reading SCW.
-DB
Many were saved from an outright bust at the end.
Timing
Timing worked out very well. Here's what we said:
While the individual models have bounced back an forth a little, there's not much change in my mind. I still think we see the onset of light snow and/or mixed precipitation between approximately 2pm-6pm on Sunday from SW to NE. The heaviest is likely to occur after sunset in a period between about 7pm and 1am, followed by tapering off between 3-5am.
Precipitation started right on time, the heaviest occurred between 7pm and 1am, and the snow was gone between 3-5am. Spot on.
Grade: A
Wind/Power Outages
This was an easy part of the exam. It wasn't a terribly wind storm. We did not have power outage issues. We were right about the inland snow being more powdery. Gusts didn't exceed expectations.
Grade: A
Snow Accumulation
Alright, here's where people really care. I wish that we kept the forecast to 4-8", but even then, the shoreline was going to be in trouble. Fortunately, interior CT carried us here. The overwhelming majority of locations below 5" were within an inch of the floor. A miss, not a bust. Central and part of eastern CT did well.
The shoreline zone however, that was bad for most. In SE CT it was horrific. Objectively. Exceedingly few got close to the floor of 4", and in SE CT folks have a right to complain--very good snowfall reporters reported less than an inch near the shoreline. That's really terrible for a storm that ended up being cold in the end, especially considering that the Gulf Coast is likely to see many times that amount over the next few days. I digress however.
This wasn't our best work. Grading the zones interior CT receives a B- while the coastal zone is an easy F with SE CT busting and the rest of the coast being a pretty bad miss. The average leads to a D+, which is double weighted because again, here is where people really care. I'm arbitrarily dropping it to a D because I didn't respect the decade of coastal futility enough.
Grade: D
Impact
Impact is a little tricky given the shoreline miss/bust. I do think this was still a moderate impact event, as roads did deteriorate, but it's hard to say we nailed it given what happened in SE CT.
Grade: B
Final Grade
Overall, we weigh snowfall 2x because we don't want to game the grading. Every other part of the forecast was really good, but we know what people care about and what's hardest to predict.
Final Grade: C+
As always, please like, share, and interact with us on our social media--on Facebook to share our discussions, and follow us on Twitter @southernctwx to retweet our posts. Hit the buttons below to join.
Thank you for reading SCW.
-DB
