jm1220

Expect rain from this and if it ends up as something more you’ll be happy. If you’re hoping for/expecting a MECS you’re very likely to get disappointed. Maybe not the worst time to check out Hunter Mountain lol.

I didn't see the outputs on that run but I guess the low consolidates sooner and that inverted trough crap which is where most models produce our QPF from goes away. That's the shot we have for more than just wraparound flakes in NYC. Becoming very clear IMO and has been for a couple days that the places to be for this storm are the Helderbergs/N Catskills, Berkshires and Worcester hills. But the NW parts of our subforum do very well also if we can get that slightly quicker consolidation of the storm.

It's the NAM so I wouldn't be concerned. But what looks likely is that we have this inverted trough feature as the storm comes in that might be spinning up this western low appendage, and it screws people near the coast because that inverted trough brings in 40 degree maritime air on strong easterly wind. Another reason we want this offshore low to develop quickly, so the flow can back around to offshore and dynamics can overcome the crap initial airmass. That inverted trough and the too slow development of the low are the main factors that are ruining it near the coast.

GFS is able to pull it off but we need a pretty substantial SW shift in the developing dynamics and upper low track in the other models to be confident of wintry impact in NYC. I’d give it a 10% chance of an advisory event or greater in the city but can’t be written off yet. Don I’m sure has better stats for what the ensembles show. Expect rain and then be thrilled with a better outcome.

Looks very weird since it chases convection east with one low and the other near the coast. Look at the upper air lows vs what it shows at the surface for dynamics that can kick in for any snow. Multiple lows probably mean just a marginal slop fest.

Another way to look at it-the 700mb low and vertical velocity (lift). Notice how it is well placed for New England because these dynamics get going a little too late for NYC. You want to be just NW of the 700mb low to get into the really good/intense banding. Here's 72hr 78hr-at this point we're probably getting some wraparound snow around the closed/stacked upper low but you can see overall the lift is weakening because the low is stacked. We can see clearly how we want this dynamic happening sooner/SW for our subforum. It's the problem we have all the time with these late developing Miller B type lows. But this is the GGEM outcome, GFS was more favorable. And before 72hr we're too warm in the preceding airmass, and we don't get the benefit of strong lift/dynamics to help overcome it unless you're inland and above probably 500-600ft.

Notice here at 72hrs when the low is SE of Montauk, the direction of the 500mb flow. The low is about to mature but the flow is generally out of the SE. That doesn't really allow a mature CCB/comma head to develop and spread snow well west of the low. We want all this to happen sooner. The focus of the moist feed is into New England. Here by 78hr the 500mb low is closed off and there's a mature CCB with moisture being brought west around the closed low. From here the surface low stacks and starts to weaken since there is no longer a way to evacuate air aloft over top of the low. But see how where it closes off is a great spot for interior New England. We want that 75 miles SSW or so. The crashing upper air heights as you can see there also brings cold air down to the surface.

The upper air system on the GGEM is not matured so there is not a mechanism to spread snow/precip well west of the center. Note on the 500mb chart how the flow is from the SSE mainly near the low, and the closed low is well west of it.

This double low thing will hopefully consolidate into one bigger low sooner. Probably comes from a sloppy phase. But yes, nice improvement.

When did it ever start?

Excellent post but if this (likely) doesn't work out I'm just done. If something happens on 3/20-22 great, but unfortunately the calendar ticking later means more has to go right for anything substantial, and time and again "great pattern" gets ruined by some turd. This is another Nina strikes again situation with the northern stream driven system messing things up, lousy/progressive western ridge placement, etc. Exactly why New England/upstate NY often do perfectly fine in well coupled Nina winters but it gets so much harder from this latitude and south. Albany isn't far below normal for snow and Central Park is sitting at 2.3". With this Albany has a shot at hitting 60"+ on the season (has 41.9 now) while NYC sits at the same pathetic 2.3". My money now is on the too late development vs too early it was seeming yesterday and before.

UKMET buries the Berkshires/Albany area into NW CT. Those have been the places consistently hit hard in the modeling. Near the city on this run we have strong easterly flow and maritime air in the 40s for the beginning of the storm, storm bombs in a lousy place (but further west than GGEM), blah blah blah.

On the 5-10% chance this can pan out, the upside is very high if we can somehow get the low to bomb out 75 miles or so S of Montauk. Those crazy UKMET runs are legit in that very off chance. But the GGEM bombing it out S of Nantucket then tracking it near Cape Cod is way too far east for NYC. We also have the usual problem of strong easterly flow maritime air that has to be overcome as the precip (rain) moves in. So what happens is we get moderate rain for a while in the maritime crap airmass (wet snow inland) that changes to heavy snow over SNE where the late bombing low can work. But the low can't bomb/phase too early because then the low will hug the coast and we get rain from a too far west track. So I'm not encouraged. I'll keep an eye on the next few cycles but if no improvement I'm out.

Hope for SNE on that run? Absolutely. For us near the city/coast? We’re completely screwed because of the low bombing too late and east. We need it to bomb early yet not get yanked due north too early-both processes are linked because the phase that bombs the low also yanks it north. Too late means light/moderate rain here and crushing snow from the Catskills to Boston.

Fine by me. I’d want it crazy tucked at this point. It’s always amped at the end of the run.

Short range models do have snow mixing in for a while in N Nassau and much of NYC. In the city I doubt anything sticks but maybe away from the heat island if it can cool to near freezing. I think it’ll be a lot of white rain but it’s good that it’s falling at night. Temp here is still 40 so a ways to go.

And little cabin's roof might collapse when it has 4" of rain soak into it.

The PNA was so horrible that the trough dove into CA and brought storms in. Where the trough is also matters. Other Nina’s have the trough inland over the West, this one was well placed to funnel moisture into CA. The storms were also cold so the snowpack built up. El Niño features the Pineapple Express type storms like today’s which pile up less snow but bring a ton of rain.

The upper low position funneled the precip/snow into SNE and dry slotted most of us. We need the upper low further south to avoid that outcome. I don’t remember 4/1/97 at all, probably for the best. Would’ve been infuriating.

If there is a closed 500mb low there is a good feed of moisture back to the west up to the point the flow backs around to northerly behind the closed low. If the upper air low supports transporting moisture west, it’ll do so. If there’s an open wave trough and it’s too progressive, that doesn’t happen. Jan 1996, 2016, Feb 2003 etc were Gulf origin lows with a huge moisture feed ahead of those lows into a dome of cold air that the moisture overran. That helped create the huge area of snow and it’s another reason you want a large high pressure area for the low to head into. The massive overrunning surface creates a large area of heavy snow.

If snow is really falling that hard it would cool down to 32-33. The air would latently cool quickly from the melting flakes.

Anyone around NYC needs the strong dynamics to work out for there to be any real snow at all. If what hits us is anything less than heavy it’ll likely be rain or white rain. The low has to bomb and heights crash in the right spot. People inland and with elevation have more wiggle room with a more marginal setup.

I could see maybe a Snowicane 2/25/10 scenario happen if the capture/fling north happens in a good spot. Berkshires to the Catskills are probably the prime zone at this point.

The December rule is usually a good one especially in a Nina when we need to do well early. When there’s not at least a half decent Dec event, the rest of the winter almost always sucks. We had the Dec 16, 2020 significant event, Jan 4, 2018 major event etc before those seasons overall were successful. In a Nina we need to score early. Too early to tell for sure about what’ll happen with this Mon into Tue event but I’m not encouraged at least for most of us. We need to draw a flush.

That’s too far east. It’s also captured and tugged N too late, bombs too late because of the issues with the PNA and southern stream gets out too far ahead. We need the dynamics and height falls to happen earlier and further west. We don’t have preexisting cold air to rely on so the dynamics will have to do it. That’s a great run for Boston not us. We get light to at times heavier rain from that look, maybe wraparound snow at the end from the bombed upper low that happens too late. I’m glad to be proven wrong but so much has to go right for us near the coast to do well from this. We need it to bomb early but not so early it flings the low north across our backyard, and in a way that dynamics are maxed.