WxWatcher007

It’s in the envelope of possibilities, but man, it’s really on an island right now.

Eastern SNE gets hit good up to Maine. Not much elsewhere. But it is further west from earlier runs.

Oof, yeah that would be a problem.

If the Euro and others are right about the track, there could be some serious coastal erosion.

Yeah, as we get into high-res range, we may see some big totals forecasted. A more organized system meandering west with dynamic bands could create some serious localized flash flood issues.

I started a thread for posterity. This looks like it's going to be pretty impactful.

Since it's becoming increasingly likely that a nor'easter or hybrid storm impacts New England, and possibly significantly, I think it's time for a breakout thread. October is usually when we see these kind of systems in New England, but this year we're seeing it early. For days, there's been a signal across guidance for some type of storm development off the east coast, and the players are starting to appear on the field. A look over the western Atlantic this morning shows an expansive area of disorganized convection. What's notable here is that in a historically quiet season in the Atlantic, where it has been difficult to get convection to fire, despite the generally hostile basin we have a window for a shallow warm core system to develop out of this. As the tropical guy, I'm actually not going to spend too much time over whether this becomes a subtropical storm, because as I noted yesterday, the NHC is highly unlikely to ever designate this, even if it looked ST. Despite not being tagged by the NHC, the guidance does seem to start this out as a warm core system, even if relatively shallow, though the 00z Euro is a bit more aggressive in maintaining a warmer core for longer. While most guidance has kept the storm closer to the coast, the GFS has waffled on whether it scrapes the coast or provides a more solid hit. It's an outlier, so this analysis is based on the current "consensus" across most guidance. Our storm system will gradually take shape, with the convection currently off the coast organizing into a weak low. From there, we see some energy from the tropics--perhaps something that would have been more likely to form in a more favorable Atlantic--get pulled into our developing coastal. From there, we see a faster pace of organization as our low consolidates as it moves up the coast. One thing that I'm interested in seeing is if this tropical feature coming up from the south becomes stronger/more organized. The trend on the Euro recently has been yes, as evidenced by the trend gif I'm posting below. Maybe it doesn't matter in the whole scheme of things because it's unlikely to become a tropical cyclone on its own, but it's of some interest to me. Critically, as energy dives in from the west as well, our newly energized low is blocked from being kicked out to sea, and is forced to hook west and meander until the escape route opens up again. This is where we get to impacts. The first thing to analyze is how strong this could get. Pressure falls are modest, and aside from the latest legacy GFS, most guidance gets the low down into the 985-990mb range. I will note that some of the AI GDM and WNV3 ensembles have stronger lows right up under New England on Sunday and given their general performance that may be something to watch as we get into higher resolution range. Regardless, this is likely to be impactful, especially for coastal areas for a few reasons. First, the pressure gradient between our low and the high to the north will create a persistent flow that likely lasts through the astronomical high tide cycle. That could bring significant coastal flooding. Moderate to major coastal flooding is already predicted for Mid-Atlantic areas. The gradient will also be a wind producer. Each model, regardless of track, has long duration windy conditions, especially in eastern New England. How far inland these winds get will depend on track of course, and how much mixing we can produce with a strong LLJ associated with our storm. These are 925mb winds on the 00z Euro And here's the (wrong) GFS. The wind and coastal flooding may be bad enough, but the biggest question IMO is rainfall. I think with a more substantial warm core system we could see higher totals, as we'd likely see a more organized storm with tropical characteristics like banding. The Euro has hinted at big rainfall totals over a few days in eastern NE, and AI guidance has painted a wider area with modest to significant rainfall. In fact, areas up the New England coast are favored for meaningful rainfall--something that folks haven't seen in a while. Bottom line: this looks like a pretty significant storm that could impact New England. There's still a lot to sort out on exact track and intensity of the system, and how organized it will be when it reaches out latitude. But the signal for something is growing, and an OTS/low impact track seems increasingly unlikely.

GFS twins are big hits especially in eastern NE.

Yeah it’s really interesting. Google DeepMind has been the best in tropical in the Atlantic two years in a row now, and the weathernext has been the top performer overall. The machines really have been good…even going back to their hits last winter…

Nice shot! Burst mode is your friend. A video with a screen grab works nicely too.

Sandy 2.0 is not walking through the door. Let’s ease up here lol. Euro is a good hit, though not especially wet. That said, don’t underestimate long duration winds with sig rain and astronomical high tides. This could be quite impactful with the right track.

What a garbage model right now. With shifts like this 00z will put the center over Springfield. 64.5 here at WXW1 50.4 up at WXW2 with more frost possible tonight. First freeze possible tomorrow night.

GFS buried in Bermuda in 30 minutes?

I'd say having the initial development happen further southwest in warmer waters, which could allow for the low at the start to have more tropical characteristics (deeper warm core, persistent convection closer to the center, banding features). The further north it heads however the more purely baroclinic it's going to be given SSTs, and the capture would just hasten the full transition to a typical extratropical nor'easter. At the end of the day however, the impacts wouldn't be substantively different unless this were leaning tropical and then scooting north imo. All that said, I think it's unlikely to ever be designated, even if it looked good. Recent history shows that the NHC tends to be slow on these. Did you know that October 2021 became Subtropical Storm Wanda? It was designated days after it delivered legitimate C1 wind gusts and damage to the coast. Last September saw a low that was probably subtropical given its appearance in its final hours before "landfall", but it never got designated. Quite a temperature contrast. For the most part, our region is much warmer than normal, but this is what it gets you. Isn't 24C around the usual line for subtropical development?

Total deluge especially ENE areas

Absolutely. A stronger low with a graze track does nothing for most of us. The hook west is key to expanding and extending impacts.

Easy money C5

Walt, it's good to hear from you. I hope all is well. As you know, the signal for something developing off the coast has been there for a few days now, and as we get closer in time I am becoming a touch more bullish. I think the odds are low that we see an officially designated subtropical storm, but I am intrigued by some of the guidance signals between the Google DeepMind, EPS, and Euro/GFS AI. This is a highly uncommon thing for us up in the Mid-Atlantic and New England to see in September, even if it remains non-tropical. Currently I think the impacts are around what you describe. If the Euro suite is to be believed, we would see strong winds, prolonged easterly fetch causing significant coastal flooding, especially if the storm is still potent around astronomical high tides later in the week, and potentially significant rainfall. I'll note that part of southern Connecticut has been inundated recently with rainfall and flash flooding, and although this rain would likely last over days, if it is potent with a tropical tap banding into the state could cause serious issues. This is one to watch IMO. Regardless of official designation.

It may be a tricky setup but it’s not almost a week away. Follow the ensembles and proceed with caution.

Euro deluge

Probably out of time, but it was a good effort lol.

We don’t look at the GFS, but it’s a damn good hit. AI twin is west too.

Yeah I think you’re right based on the latest IR.

IR presentation is still fine--it looks like it's trying again to clear out an eye. I haven't seen satellite estimates come up however, and that may go a long way toward keeping this below hurricane status. Not sure. There's still time but the clock is ticking.

We like.