bluewave

I think it’s the record warm pool in the Western Atlantic causing more ridging there than we used to get. But notice how the day 8-10 forecast can’t detect it. We see it start to show up around day 5-7. So it makes looking at these ensembles beyond a week a low skill proposition. New run Old run

This is probably the first time in December that we could get a 974 mb Great Lakes cutter following a few days after a -4 AO and +PNA. So my guess is that the warming climate is causing wavelength changes that would have produced a KU event in the past. Just goes to show how past analogs from a colder era don’t work anymore.

Maybe if we are lucky a big cutter before Christmas can finally pull the trough into the East. That could leave the door open later in the month for a colder storm track. But I am hesitant to buy into a significant snow threat from more than 5 days out with how the models have been in full pushback mode since late November.

The models have changed quite a bit from what they were showing last weekend. So we could get out of December without much snow. But I still think the AO dipping under -4 this month will give us more blocking opportunities JFM.

The warm up around the solstice is an actual annual occurrence now. We have had 11 consecutive years going over 55° in NYC which has never happened before. Contrast that with the first 2 weeks of the month which hasn’t seen the big maximum temperature increase. But I couldn’t tell you why the timing within about 5 days of the solstice has been so reliable for these warm ups.

Yeah, it reversed right after the Boxing Day Blizzard. Just an amazing run of Decembers from 2000-2010. While we have an occasional snowy December like 2020, the snowfall is way down and the temperatures up since the 11-12 non winter. December snowfall has been only 30% of the previous decade or so. Monthly Total Snowfall for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Year Dec Season Mean 2.8 2.8 2022 T T 2021 0.2 0.2 2020 10.5 10.5 2019 2.5 2.5 2018 T T 2017 7.7 7.7 2016 3.2 3.2 2015 T T 2014 1.0 1.0 2013 8.6 8.6 2012 0.4 0.4 2011 0.0 0.0 Monthly Total Snowfall for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Year Dec Season Mean 8.9 8.9 2010 20.1 20.1 2009 12.4 12.4 2008 6.0 6.0 2007 2.9 2.9 2006 0.0 0.0 2005 9.7 9.7 2004 3.0 3.0 2003 19.8 19.8 2002 11.0 11.0 2001 T T 2000 13.4 13.4

Yeah, the Euro lost the southern stream low that was phasing in yesterday. It was that low that was keeping the baroclinic zone close to the coast. Now, it’s too northern stream dominant and the warm pool and ridge is really flexing east of New England. It could also be another reminder how we can’t seem to avoid the big warm up around the solstice.

If the storm wraps up too much and tracks over or west of NYC, then the coldest temperatures will miss to our SW.

We’ll see. The GFS has been struggling the most with the ridge. Remember last weekend when the storm today was forecast by the GFS to get suppressed to South Carolina? That’s why we rely so much on the Euro,EPS, GEM, and GEPS for longer range forecasts. GFS too suppressed with SE Ridge and storm from last weekend New runs closer to what the CMC and Euro were showing

The problem with the block is that it’s forecast to link up with the ridge to our east and become too south based. That’s why so many GEPS and EPS along with the 0z OPs track over or west of NYC. Seems like anytime the ridge can build over the record warm pool it does.

Yeah, the GEPS usually has a cold bias beyond a few days and the storm track is even further west than the EPS clusters and means.

The storm track coming right over or just west of NYC is a concern since that warm pool and ridge east of New England is continuing to be a factor. The PNA actually is pretty good with a nice ridge out West. So this looks more like and issue with the ridge to our east causing the low to come too far west for big snows near the coast.

Yeah, the weaker cluster is the one to the west with fewer lows. The most populated clusters track right over us or near the BM. Several lows in the 950s to 970s is unusual for this far out. So a high impact storm signal either way.

Looks like a cluster going west of us. Another tracking right over And still more near or just east of the BM. The one common denominator is most of them are sub 980mb.

The capture is too late this run for a really big one for us but at least the storm signal is there.

Don’t think it has ever happened with a snowstorm before beyond 7 days. But warmer systems have worked out at day 8-9. Also Hurricane Sandy. But the big signal off all the guidance is some type of high impact storm is possible before the holidays with P-Types and track to be determined later.The really good ones like Boxing Day were all modeled pretty far offshore at this range. https://www.wpc.ncep.noaa.gov/winter_storm_summaries/event_reviews/2010/December25_27_2010_Blizzard.pdf Eight days prior to the storm, only a few members were as far south and none west of the observed 500 mb heights as all forecasts indicated the likelihood that the East Coast trough was much broader than observed and farther east, indicating virtually no likelihood of a significant storm moving up along the Atlantic coast. On days 7 and 6, there are more members that come close to the actual pattern, but the majority of ensemble model members continue to point to the higher probability of a storm track to be well east of the East Coast and probabilistic forecasts would have very low odds of a significant storm.

Yeah, the GFS,CMC, and UKMET at 12z are all widely different with the PNA at 144 hrs. The GFS has the classic snowstorm 500 mb look from over a week out. Our big snowstorms at this range are usually suppressed way to the south on the GFS. The CMC is also struggling with the PV and southern stream so it squashes it south. The UKMET digs the PV into the Rockies so it would probably be warmer if it ran out a few more days. So we await the Euro to see what it comes up with next.

Yeah, we would want to see runs cutting the low of to our SW like the 12z CMC and 0z Euro disappear over the next several days to have a shot a significant snow at the coast from this one. But it all depends on how much the cutoff digs before turning the corner. While the cluster scenario can be more helpful, the means need to start backing off a bit so we have some room for them to come NW under 120 hrs and not be too warm.

We would need a lost and found scenario where the next several runs start backing off the amplitude only to come back in later runs.

The ECMWF has a product called cluster scenario. This breaks down the EPS members into clusters. So it gives more details than just a mean that combines everything. I believe some of the mets in the New England forum have been posting these. Unfortunately, the free site doesn’t have the zoomed in NA chart but the whole NH. It’s more helpful than an ensemble mean. https://charts.ecmwf.int/products/cluster_plot_legA?base_time=202212150000&cluster=192_240&parameter=500

I am not sure if the EPS is further east due to the smoothing out of the various TPV locations. The members like the OP that dig more to the SW over the Tennessee Valley are warmer with less snow. The colder members that plow more across the Ohio Valley have a BM Miller B with more snow. Notice the ridge poking into New England from the east on the OP.

It’s pretty variable on Long Island for which combination or sequence ENSO states produces the most snow. Time Series Summary for ISLIP-LI MACARTHUR AP, NY - Oct through Sep Click column heading to sort ascending, click again to sort descending. Rank Season Total Snowfall Missing Count 1 1995-1996 77.1 La Niña after El Niño 2 1977-1978 68.0 El Niño after El Niño 3 2017-2018 65.9 La Niña after La Niña 4 2014-2015 63.7 El Niño after neutral - 2013-2014 63.7 neutral after neutral 5 2004-2005 58.8 El Niño after neutral 6 2010-2011 55.3 La Niña after El Nino 7 2002-2003 54.6 El Nino after neutral 8 2009-2010 53.8 El Nino after La Niña 9 1966-1967 50.8 La Niña after El Niño 10 2012-2013 46.9 neutral after La Nina

https://xmacis.rcc-acis.org

Yeah, the rising PNA and record block over the pole is the storm signal. But the snowfall forecast for the coast will come down to the exact TPV track. If the TPV cuts off to our SW like the Euro, we will have less snow. But the CMC track across the BM would be snowier.

This will be one event when it’s tough to use ensemble means since there are several areas of low pressure. The Euro has a Miller B and an attempted phase of a southern stream low. So the mean is trying to smooth out too many different low positions. The one thing we know is that the 22-24th will have the highest tides of the month with the new moon. So coastal flooding could be an issue if the low cuts off to our SW. The only thing that I can say about the EPS mean is that an unusually high number of members have lows under 980 mb from 8-10 days out. This would mean that this could be a very intense storm with high winds and heavy precipitation. We almost never see so many deep lows on an ensemble mean this far out.