bluewave

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.

We would need for the diving PV to get out near the benchmark like in February 1978 to make people happy. The alternative is it gets stuck over land like January 1978 and we are on the warm side for much of the precipitation. Either way, it should get really cold behind the storm. http://greatlakes.salsite.com/maps/jan2427_1978_500_loop.gif http://greatlakes.salsite.com/maps/feb58_1978_500_loop.gif

This would be a new 500 mb amplitude record if it wound up verifying. The OP Euro has a near record PV just to our SW at -5.8 SD. The block at the pole is also in near record territory at +6.5 SD.

NYC hasn’t had 1”+ of snow in the week leading up to Christmas since 2008 and 2009. Time Series Summary for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Ending Date Total Snowfall Dec 19 to Dec 25 Missing Count 2021-12-25 0.2 0 2020-12-25 T 0 2019-12-25 0.0 0 2018-12-25 T 0 2017-12-25 T 0 2016-12-25 0.0 0 2015-12-25 0.0 0 2014-12-25 T 0 2013-12-25 T 0 2012-12-25 T 0 2011-12-25 0.0 0 2010-12-25 0.0 0 2009-12-25 10.9 0 2008-12-25 4.7 0

If suppression does turn out to be an issue after Christmas, then this December would be one of the low NYC low snowfall outliers for the AO dipping below -3 since 2000. December -3 or lower daily values since 2000 and NYC snowfall 12-11-22….-4.2378……? 12-28-20….-3.197……..10.5” 12-8-12…….-3.902……0.4” 12-18-10……-5.265…..20.1” 12-21-09……-5.2821….12.4” 12-05-05……-3.569….9.7” 12-28-01…….-3.293….T 12-29-00……-4.688….13.4”

The big block pulling back to Siberia could allow more of a Western Trough like the OP or one in the Plains like the EPS. While we would avoid the big OP warm up before Christmas on the EPS, still have to deal with that Great Lakes primary low. Any secondary development near the coast would probably favor the interior like we are seeing for Friday. Need a slower retrogression of the block back into the WPO domain to keep the heights up along the West Coast. Too fast an EPO rise could allow the PV to dig more out West.

The record SSTs in December 2020 along with the 500 mb pattern probably caused us to miss the 40” jackpot which ended up in Binghamton. The low was too tucked in for those amounts near the coast. But the historic January 2016 blizzard was able to feed off those same record SSTs. So the colder readings a month later plus the flatter SE Ridge and BM track worked to our advantage.

It’s pretty much the same thing every December. Late November models start showing a great pattern in early December. Then the first NYC 4-6”+ snowstorm gets pushed back into mid-December. Other years like this one gets pushed back to late December. In reality, NYC has only had a few 4”+ snows between December 1-10. Some years like last, the late December snow got pushed back to early January. But at least it eventually arrived. NYC Dec 1-10 snows over 4” since 2000 Maximum 2-Day Total Snowfall for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Rank Value Ending Date Missing Days 1 14.0 2003-12-06 0 0 0 2 6.0 2002-12-06 0 - 0 3 5.8 2005-12-10 0 0 4 4.6 2017-12-10 0 0