With the mess that the original thread has become, decided to take up a few suggestions to start a new thread. Hopefully this one works. Will start with the original post, then add in a couple of more recent posts to get things started.
Original First Post from 12/30/17
Since the Christmas thread where this potential storm has been discussed for a few days has kind of degenerated into bickering by many of us, I think it's time to start a new thread on this. I promise no bold predictions, lol (which I rarely do, but did a couple of days ago). Let's try to keep the bickering to a minimum, myself included.
Anyway, the global models have gone through a real rollercoaster ride the past 2 days. From an unprecedented (in my 20 years of following meteorological numerical models) near consensus on a major winter storm for our area at about 7 days out (48 hours ago) to almost every model being a complete whiff out to sea (and some way out to sea, like Spain, lol) yesterday, to the models generally moving back towards a potential winter storm in last night's and today's model runs.
Without going into all the details, briefly, the range of solutions now is from a near miss for our area, but a major hit for New England (GFS) to a monster snowstorm for the entire region (the UK) with the other models showing a light to moderate hit for us (the Euro and CMC). It is important to note, however, that all of the major models show a major to huge winter storm - the differences lie in where/when the primary coastal low "forms" and where it tracks from there.
The coastal will "form" from a piece of energy associated with the northern branch of the jet stream, "phasing" with a piece of energy associated with the southern branch of the jet stream, in which both players are thousands of miles away in the Pacific Ocean right now. Hence the initial model input conditions are very data sparse, meaning the error bars on the model outputs are still large and will likely remain somewhat large, at least, until these systems are on land in North America 2 days from now, roughly, which will be 2-3 days before the system hits us (probably starting late Wednesday night).
At this point, it's difficult to predict any exact outcome, which is why we won't see specific forecasts for snow, rain or mix until 2-3 days out, but the key take home message is that a major winter storm is possible and you might want to think about whether a winter storm would affect your plans, especially for Thursday. As they say on the weather boards, for now, we track - for myself and many of the pros and enthusiasts on the weather boards, half the fun is in the tracking.
One last comment. Even at 2-3 days out, things sometimes change significantly, with one of the biggest examples being the 12/26/10 Boxing Day Blizzard, where every model was showing out to sea 60 hours before the start of the storm, but almost every model flipped to a major snowstorm late on Christmas Eve, about 48 hours before the event (prompting me to drive home on Christmas night from Charlotte so I could be home for the storm, but that's a story for another time). And there have been famous busts, too, like Jan-15, where the huge snowfall ended up being displaced about 50-75 miles from where it was forecast even as the storm was starting, although from NYC east, the forecast was excellent. Many other major winter storms, however, were much better modeled in the 3-5 day range and even beyond for a few. Forecast accuracy does keep improving: 5-day forecasts now are as accurate as 3-day forecasts were 20-25 years ago.
Ok, one more comment. We will likely continue the sub-32F run until at least next weekend, which would put most of us at 12 days, which is top 10 for most locations for that kind of thing. And it could still stay below 32F for a few more days beyond that and get into the top 5; the record in NYC is 16 days in a row in 1961, which we likely won't quite hit, as the long range forecast is for above 32F by 1/8 or 1/9 (Day 15). Also, a few days (Sunday-Tuesday) are going to be truly cold, perhaps record-breaking. Freakin' 10F at midnight when the ball drops in Times Square - ouch - 3rd coldest ever, but the record is -7F in 1917 (and it was 4F in 1962).
For tracking purposes, the three main weather boards I look at and post on are below, plus there are tons of FB sites and professional media outlets to follow; the 33andrain site is only a year old, but it has become my favorite board with the best pro analysis going on (they do moderate heavily, though, which keeps the clutter down). I like the NWS a lot, so I'll link to them too.
https://www.33andrain.com/topic/790...ter-thread-part-iii-14-threat-disco/?page=154
https://www.americanwx.com/bb/topic/50504-december-2017-discussions-observations-thread/?page=36
http://forums.accuweather.com/index...76d47e24bf&showtopic=33430&st=1180&start=1180
http://www.weather.gov/phi/
Original First Post from 12/30/17
Since the Christmas thread where this potential storm has been discussed for a few days has kind of degenerated into bickering by many of us, I think it's time to start a new thread on this. I promise no bold predictions, lol (which I rarely do, but did a couple of days ago). Let's try to keep the bickering to a minimum, myself included.
Anyway, the global models have gone through a real rollercoaster ride the past 2 days. From an unprecedented (in my 20 years of following meteorological numerical models) near consensus on a major winter storm for our area at about 7 days out (48 hours ago) to almost every model being a complete whiff out to sea (and some way out to sea, like Spain, lol) yesterday, to the models generally moving back towards a potential winter storm in last night's and today's model runs.
Without going into all the details, briefly, the range of solutions now is from a near miss for our area, but a major hit for New England (GFS) to a monster snowstorm for the entire region (the UK) with the other models showing a light to moderate hit for us (the Euro and CMC). It is important to note, however, that all of the major models show a major to huge winter storm - the differences lie in where/when the primary coastal low "forms" and where it tracks from there.
The coastal will "form" from a piece of energy associated with the northern branch of the jet stream, "phasing" with a piece of energy associated with the southern branch of the jet stream, in which both players are thousands of miles away in the Pacific Ocean right now. Hence the initial model input conditions are very data sparse, meaning the error bars on the model outputs are still large and will likely remain somewhat large, at least, until these systems are on land in North America 2 days from now, roughly, which will be 2-3 days before the system hits us (probably starting late Wednesday night).
At this point, it's difficult to predict any exact outcome, which is why we won't see specific forecasts for snow, rain or mix until 2-3 days out, but the key take home message is that a major winter storm is possible and you might want to think about whether a winter storm would affect your plans, especially for Thursday. As they say on the weather boards, for now, we track - for myself and many of the pros and enthusiasts on the weather boards, half the fun is in the tracking.
One last comment. Even at 2-3 days out, things sometimes change significantly, with one of the biggest examples being the 12/26/10 Boxing Day Blizzard, where every model was showing out to sea 60 hours before the start of the storm, but almost every model flipped to a major snowstorm late on Christmas Eve, about 48 hours before the event (prompting me to drive home on Christmas night from Charlotte so I could be home for the storm, but that's a story for another time). And there have been famous busts, too, like Jan-15, where the huge snowfall ended up being displaced about 50-75 miles from where it was forecast even as the storm was starting, although from NYC east, the forecast was excellent. Many other major winter storms, however, were much better modeled in the 3-5 day range and even beyond for a few. Forecast accuracy does keep improving: 5-day forecasts now are as accurate as 3-day forecasts were 20-25 years ago.
Ok, one more comment. We will likely continue the sub-32F run until at least next weekend, which would put most of us at 12 days, which is top 10 for most locations for that kind of thing. And it could still stay below 32F for a few more days beyond that and get into the top 5; the record in NYC is 16 days in a row in 1961, which we likely won't quite hit, as the long range forecast is for above 32F by 1/8 or 1/9 (Day 15). Also, a few days (Sunday-Tuesday) are going to be truly cold, perhaps record-breaking. Freakin' 10F at midnight when the ball drops in Times Square - ouch - 3rd coldest ever, but the record is -7F in 1917 (and it was 4F in 1962).
For tracking purposes, the three main weather boards I look at and post on are below, plus there are tons of FB sites and professional media outlets to follow; the 33andrain site is only a year old, but it has become my favorite board with the best pro analysis going on (they do moderate heavily, though, which keeps the clutter down). I like the NWS a lot, so I'll link to them too.
https://www.33andrain.com/topic/790...ter-thread-part-iii-14-threat-disco/?page=154
https://www.americanwx.com/bb/topic/50504-december-2017-discussions-observations-thread/?page=36
http://forums.accuweather.com/index...76d47e24bf&showtopic=33430&st=1180&start=1180
http://www.weather.gov/phi/
