As we usually do, it's time to take a look at our forecast for the first big winter storm of the season and evaluate ourselves. For those of you new to SCW, we do this to show you what went right, what went wrong, and learn from our mistakes. We are serious about providing you with the best forecast we can craft because we are aware that weather forecasts impact everything from childcare arrangements among families to closing decisions among businesses that must be open to generate income.
No forecast is perfect. No matter the forecaster or computer model, meteorology requires analysis of complex processes in a volatile and often unpredictable atmosphere. There will always be areas of improvement.
Here is our final snow map with an overlay of National Weather Service spotter reports. In line with our forecast, these spotter reports cover the entire storm, Part I and Part II.
Southwest Connecticut Snow Forecast & Impact
Let's start with the incorrect parts of the forecast. The first thing you will notice is the "snow hole" in southwest Connecticut. As I posted yesterday, even from the GOES-E satellite above the Earth, there is a very clear lack of snow along the shoreline.
When crafting the final forecast, I contemplated expanding the 2-4 inch zone along the entire shoreline, but decided against it due to guidance (particularly the European model) that provided SW CT a more robust period of snow during Part II and colder temperatures that would have made accumulation easier.
I should have respected the temperature challenges the shoreline has during early December.
While the overall forecast for timing was good, there was a bit of a whiff for eastern Connecticut on Tuesday morning. Often, these storms shut off precipitation earlier than anticipated. While I did mention that the storm would be slow to depart, snow lasted after 9am. That certainly had an impact on clearing out. This is a bit nitpicky since the forecast was spot on for most, but still something that should be pointed out.
Part II Blowup
Aside from breaking the hearts of snow lovers in SW CT, the thing I regret most about this storm is failing to mention more explicitly the potential positive bust (higher than expected snow) with Part II banding. In fact, I took language out that said significant surprises were likely if banding rotated over certain areas. Ouch. There were spots in northern CT that produced between 5-10 inches of snow because of that banding. This is also a bit nitpicky since no reasonable person would have forecasted 5-10 inches of snow in Part II (even the models didn't have that kind of signal), but still worth highlighting.
What Went Well
With apologies to our friends in SW CT, the impact was about what we predicted in locations away from the shoreline. This was a high impact event for northern CT. This was a moderate impact event for interior sections of our southern four counties. There were widespread delays and cancellations on Monday and Tuesday, and state government was delayed on Tuesday.
Higher Total Zones
Similar to the Part II blowup, no reasonable person would have forecasted upwards of 18 inches in northern Connecticut. But, 18 inches is exactly what happened in at least one spot, and other spots were close.
We were more bullish on higher totals, both in NW CT and in central CT, and when the easy call would have been to slash forecast totals during the long lull (which we forecasted) where many were calling bust, we held firm and ended up being right. We recognized the potential of Part II. In fact, if you look at the snow totals on our map, it probably would have been better to keep some of our northern zone boundaries from the first map.
We fully recognize that this is an IMBY (In My Backyard) business. If we call for 4-8 inches in Greenwich, a lot of people will be unhappy when 8 inches don't fall, and everyone will be (rightfully) upset when there's barely a coating. But messaging matters too. Not all storms are created equally, and I think one of the things that has separated SCW from others is our ability to clearly communicate uncertainty.
Communicating uncertainty is oftentimes seen as making a broadbrush forecast (1-25 inches possible!), but being clear that the northward progression of the mix line is a nowcast, or that the intensity of Part II is uncertain, provides individuals with the tools they need to make informed decisions based on their risk tolerance. When things are a close call, we provide what we think will happen, and if we don't you're always free to push us.
Timing--With the exception of early Tuesday snow in eastern CT lasting longer than anticipated, we were right on target with the start of Part I, the lull, and the start of Part II. A-
Impact--It's hard to give a really high score because of the lack of impact along much of the shoreline, but for most of CT, it was spot on. B
Snow Forecast--This was a really good forecast, but the shortfall in SW CT hurt. The zones worked relatively well and the forecast was fundamentally sound. B+
Messaging--Although frustrating to some I'm sure, I think we effectively communicated the potential and were clear to readers that the lull was irrelevant to the potential that Part II held and eventually realized. A
Final Grade: B+
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