TriPol

I’m not a Met and I don’t play one on TV, however; if we’ve got a chance at sleet, petty good bet that we don’t have 20:1 ratios. We thought this would be suppressed to the south originally, but even with that, we’d get .5 of QPF, which would mean 5-8 inches. Remember, there’s a snowstorm next week after this too. Now we’ve got the chance that maybe either the high pressure isn’t as strong as originally thought, or the low pressure is coming closer to the coast… which will warm the air. Warmer air = lower ratios.

It doesn't look all that impressive.

Right but how many times since then have we had Weenie suicides? Dozens. We're tracking a storm and then it dies. We never talk about those. But March 2001... it's a right of passage if you're going to be a weather weenie, you have to have a shot of scotch in your hand, be half drunk, and talk about it until the cows come home. We've had worse disappointments.

Is it tradition to discuss March 2001 every time there's a winter storm in our backyard? It's almost 25 years. Models have improved a lot since then. Can we let it die?

Go back here: NYC was in the bullseye a week out. Wound up being a record producing snowstorm for NYC.

Predicting where and when thundersnow will happen is difficult, but... this is the setup could give us that. Interestingly enough, the Great Lakes are forecasted to have Snowspouts this weekend.

According to the EPS mean, there is a definite indication of a MAJOR coastal low pressure center near the latitude of the Mid-Atlantic to Southern New England areas. The evidence that the ensemble members are plotting closely together shows that the group appears willing to evolve toward a coastal redevelopment or borrowed coastal system as opposed to working directionally inland. The Normalized Spread of the ensemble members indicates a low degree of spread across the Northeast region as indicated by the region of North and Central New Jersey and a decreasing amount of uncertainty narrowing in New York City. The greatest area of spread, i.e., the west and south of the city, indicates the confidence level for the track is very high. This also indicates mid-level pattern evolution will transfer to the surface of the climate system in an uncomplicated fashion. The ensemble indicates the same path of motion that has been forecasted by the H5 atmosphere since prior to multiple computer models becoming consistent at the H5, including last night's European model update. At this time the only remaining questions are how much water will fall within the axial centerline of maximum impact and when will maximum rainfall occur. This is why we chase storms all winter. Why we stay up until 3 am refreshing, analyzing. All because of storms like this.

Virga really isn’t a concern in a setup like this. Yes, the antecedent air mass is dry, but this is a deep, dynamically forced system with strong large-scale lift. Once precipitation starts, the column moistens very quickly. Virga issues tend to happen with weak forcing, shallow lift, or fast-moving systems trying to overcome dry air. A closed H5 low with sustained ascent overwhelms that problem. You might lose the very first echoes to evaporation, but not the storm itself.

From H5 (500 mb) height, we are looking at exactly the setup that has a high potential (high ceiling) for the NYC area for a major winter weather event. The ECMWF depicts a then fully closed 500mb low in the Northeast with large negative height anomalies and a slow pivoting flow. It represents a true 500 mb closed low, that is no longer open or progressing as a trough. It is vertically coherent, dynamically mature and no longer associated with the fast zonal flow of upper levels. The closed 500mb low will eventually be around for a period of time, not a question mark of how long. A compact and centered cold pool aloft is also critical to snow production efficiency. Closed mid-level lows create steep lapse rates, which in turn create significant lift and space throughout the region to support snow band formation, and through the mesoscale process create the large snowfall totals in NYC. Most storms that produce over 18 inches of snow are not continuous, steady snowfall, rather they are created by the time and conditions that create the most snow through banding.

There is no model showing 6 inches of snow for nyc right now. Nothing. Zero. We can all appreciate your need to stay conservative, but we should also stay reasonable.

I hated that with a passion. Up to a few days prior, I believe we thought we were going to have a pretty decent snowstorm. Not like this, but 6 inches of snow I think? It's been almost 20 years.

I'll wait until Friday to worry about mixing.

This is bigger. The last time we had something like this was 2016. This is a KU storm through and through.

I'm gonna get weenie tagged for this, but... With over 1 inch of precip, temps in the single digits, teens and 20s... I think this is underdone. I think NYC gets 18 to 24 inches if we get over 1 inch of precip. Other factors will, of course, be the wind and the thermal profile, especially how quickly the column cools once rates increase and whether we get sustained banding.

I keep refreshing Pivotal Weather like it’s a lever connected directly to the Euro’s supercomputer. Strangely, the model remains unimpressed by my enthusiasm.

The EURO won't

Not even thinking of mixing on the GFS.

On the GFS, this starts 18z on Sunday and leaves by 12z Tuesday.

BIG HIT on the GFS!

If the 2006 JMA can predict a record-breaking blizzard for NYC 2 weeks in advance... you never say never about any weather model. Though, the chances of the UKie verifying are statistically improbable.

A primary that survives all the way to Erie in this pattern is structurally suspect. It requires the cold dome to retreat faster than the synoptic setup allows. The 1032 mb high to the west is not a paper tiger. It is feeding low-level cold and keeping the boundary pinned south and east. Primaries do not just waltz through that without consequences. Ukie keeping it mostly snow in NYC while dragging the primary to Erie is internally inconsistent. If the primary truly gets that far north and west, the low-level flow into NYC backs too much from the south. You do not get to keep a clean snow profile and a strong inland primary at the same time. One of those has to give. What usually gives is the primary. In reality, with this kind of trough geometry and thickness field, the inland low weakens earlier. Energy transfers near the coast. The inland center becomes a bag of isobars and stops mattering. That is exactly the evolution the GFS, Euro, and most ensembles favor in similar regimes. Ukie has a known bias here. It over-amplifies inland primaries in cold-dominant patterns, especially at this lead time. It often delays or underplays the transfer, then corrects late when the coastal baroclinic zone asserts itself. La la land is not an unfair description.

If we dig any further, we'll truly bring Venezuela up here.

Funny. You're not saying that on the thread.

The density and structure of snowflakes are influenced by wind. Strong winds can cause sheer forces and collision forces that can break up delicate snowflakes and cause damage to them before they fall to the ground. When a snowflake breaks up, it will typically become much smaller and denser than an intact snowflake because the intact snowflake has significant amount of air trapped within it, which enables snowflakes to be stacked on top of each other. When snowflakes are broken up due to wind, they will lose their structure, making it impossible to stack them. Therefore they will not develop the same amount of height per volume of water as intact snowflakes due to density. As a second point, strong winds often contain turbulent airflows and sublimation. Because they contain a high ratio of surface area to mass, smaller fragments of snowflake are more likely to be partially sublimated away or lifted into the upper atmosphere than intact snowflakes. Thus, much of the snowflakes created by strong winds won't reach the ground where we measure snow accumulation. Thus, the end result is a classic example of meteorological misrepresentation. When looking at radar images and the equivalent liquid from the snowfall, they may appear to be large amounts of moisture, but the awash in total in the ground will be relatively small when compared to the amount of snow that fell as part of the event. This is why windy events tend to produce low totals even when the snow continues to fall steadily.

So would we!