bluewave

Big windchill factor day with highs below freezing and wind gusts over 40 mph.

This is really cool.

Yeah, it will be interesting to see how low we can get the winter cold departure by January 25th. The EPS and GEFS weeklies want to bring in a milder pattern by the end of January into February. So the winter negative temperature departures around our area may get smaller as February progresses. Having a cold enough departure by then may raise the possibility of our first colder winter here in 10 years. Even if it’s strictly a function of the warmer 91-20 climo and could be warmer than normal against the old 81-10 normals. But you never know for sure since we have seen several late winter La Niña periods overperform expectations and boost the winters above average based on how mild the finish was. Getting 9 warmer winters in a row is so statistically rare that you would think that one of these years we would get a break even if only by a small margin.

It would have been epic if that took a classic BM track instead. Had heavy snow during the day. Then the warm up and rain and big tidal surge which floated away the whole snowpack which was really compacted. The mini icebergs settled to the ground after floating around the streets and froze into cement blocks with the rapidly falling temps and flash freeze next morning.

Maybe the best -EPO of the winter so far if we can get some coupling with the strat.

I just try to be grateful these days for any amount of snow we get here.

Yeah, the CMC would be a happy compromise between the GFS and Euro.

Yeah, that OP run is a big outlier in today’s 12z model suite.

.5 of an inch OTG here just east of HVN briefly down to .5 mile vis.

We really need at least a transient SER in order to not suppress the overrunning zone too far south with colder air in Canada for the first time this winter. Maybe we get a compromise between the GEFS and EPS. A more well defined lead shortwave which cuts and drags in cold air behind. Then hopefully a serviceable baroclinic zone nearby for overrunning potential.

Subtle differences like how much -AO blocking lingers and whether we can hold some Baja ridging will probably determine the mean trough axis location at that time.

Yeah, the GFS is most aggressive with the closing off of the UL so it slows the NS enough for more of a phase. The CMC has a NS open wave so it doesn’t completely capture the low offshore. But most on here would gladly take the CMC run. It seems like when we did get big phases in the past we had better wave spacing that what the models are showing for this.

The key seems to be how fast the Northern Stream UL closes off. The GFS is the most aggressive so it allows a quicker phase. The CMC still has an open wave near the Upper Plains at the same time and isn’t quite as phased. It may come down to a tiny sampling issue as to which model is correct. Probably the closest to something decent we have seen in quite some time. Anything to slow that NS down and close it off quicker in this pattern would be greatly appreciated.

But the -AO blocking threshold is much higher near or over -5 with a solid STJ than with the weaker -3.5 range we see today.

Perhaps a better overrunning scenario across the Northern Tier as we will finally see colder air nearby in Canada instead of all the warmth we have been getting. The other nuances to the pattern will be how much AO blocking remains. Plus can we maintain some hint of ridging near the Baja instead of a trough which has been so frequent in recent years with -PNAs?

Yeah, Canada is finally expected to begin cooling off from all the recent record warmth at least in the western and central regions.

We just tend to do better here when the NS backs off a bit. Most would be happy with a stronger STJ like we got in January 2016. Things just tend to fall into place easier when we have blocking and a strong STJ. Even La a Nina’s like 20-21 did fine with the NS easing up enough.

The issue with the Pacific blocking not being able to hold is more a Northern Stream function of lowering heights out West too much with the added shortwaves in the fast flow becoming kickers. A dominant STJ that is strong enough usually has better wave spacing allowing more amplitude and less suppression. Sometimes suppression can become an issue with El Niños which are too weak like 79-80.

Block amplification issues usually occur with a dominant Northern Stream. Plus this block isn’t that strong. Remember back in 2010 with the record STJ and wall to wall -3 to -5 -AO days how the systems had no trouble eventually coming north after 2-6-10. Pure -AO suppression is rare with a strong enough STJ. It only really happened once on 2-6-10. But that was one of the strongest -AOs on record. This event is much weaker. Then the snows eventually came north so only one system was blocked.

The GEFS generates some impressive Arctic air to our West for a week 2 ensemble mean.

We want a Southeast Ridge since most of the NYC 4”+ snowfalls this time of year have occurred right before or after a 50° day. Very tough to generate snow here with steady below average cold and no warm ups. The cold that starts building out West with the -PNA could be more impressive than what we will see over the next few weeks. So maybe we get a big cutter and a 50° day followed by a cool down and overrunning hugger snowfall event with more Arctic air available in Canada. Canada finally getting getting colder

The EPS took a step toward the GEFS with the return of the Southeast Ridge by around January 20th. So we could see an end to this suppression pattern around then. Could also be our first 50° day since January 1st. New Euro run similar to GEFS Old run New GEFS run

I had an earlier post today which discussed NYC needing KU benchmark storms to reach average to above average seasonal snowfall. The one time this worked since 18-19 for NYC was 20-21 which was the only above average snowfall season last 6 years. So the frequent cutter, hugger, and suppressed Southern Stream storm tracks with the stronger Northern Stream of the Pacific Jet has been working against normal to above normal snowfall in NYC. All we know so far is that this has carried over into December and early January again this year. Too early to tell if it will continue beyond early January and into the next several winters. So we need to take it one step at a time. I am guessing this shift in the Pacific Jet is related to all the record marine heatwaves in the Pacific Basin which have appeared since 18-19. This faster Pacific Jet is also leading to changes in the 500mb patterns. Some of these changes have actually been to the benefit of the mid-Atlantic as we are seeing the next few days. Plus it’s easier for regions with traditionally lower average seasonal snowfall to get close to average with just one or two big snowstorms.

March 2013 to 2019 was the exception rather than the rule in NYC. Monthly Total Snowfall for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Mean 8.4 8.4 2013 7.3 7.3 2014 0.1 0.1 2015 18.6 18.6 2016 0.9 0.9 2017 9.7 9.7 2018 11.6 11.6 2019 10.4 10.4 Monthly Total Snowfall for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Mean 0.1 0.1 2020 T T 2021 T T 2022 0.4 0.4 2023 0.1 0.1 2024 T T

We probably need to lose that low over the Rockies and Plains on the EPS and GEFS mean which is acting as a kicker to have a shot here.