bluewave

I think you guys missed the point of my post within the specific time period of this month so far. The majority of the storms this month had the mixing line near NYC with Southeast Ridge gradient. The storm which just produced the heaviest snows to our south came behind a recent storm which briefly shifted the overrunning gradient zone a little further south. It was a weaker low which couldn’t gain much latitude. The next few much stronger storms will come north again through the weekend eventually pushing the gradient even further north. So this has been a very consistent pattern this month. The storm this weekend will rapidly deepen and drive the gradient down into the mid-Atlantic next week. Then we have another low coming out of the Southeast around the 20th that will be in a tug of war between the tendency of the Southeast Ridge to amplify and the 50/50 low to suppress. We would like to see the low find the benchmark for once this winter before this pattern relaxes later in the month. But we have seen this cutter, hugger, and suppressed Southern Stream storm track play out time and time again since 18-19. So we probably shouldn’t get the hopes up too high for the 20th due to the difficulty of getting a coastal storm just in the right spot near the benchmark. The very fast Northern Stream of the Pacific Jet seems to be driving this persistent storm track pattern. Maybe we can see at least some brief relaxation of this pattern before this winter comes to a close. January was all about suppression with the very strong Northern Stream and near record 50/50 low to our east. It would have been a much better pattern with an undercutting STJ and El Niño as the storm track would probably have been further north with the typical STJ orientation. Then the hugger track has dominated this month with the one suppressed storm near DC last few days.

I moved up to the CT Shoreline near the end of the summer in 2023. The winters are a little colder here with better radiational cooling than the LI South Shore. Plus I still get a nice sea breeze during the summer without too many 90° days.

Yeah, gradient patterns tend to shift further north with heaviest snow totals than models expect around our area especially when there is no strong 50/50 low and confluence. The opposite was true in January when we had the record strong 50/50 low nearby. So the snowfall initially forecast over the Northeast especially on some OP GFS runs went to our south. The model error patterns have been highly predictable.

We don’t live in DC.

Still too high but better than some of the OP GFS runs.

Too much of a cold bias in our area for the EPS snow mean in early February as the mixing line usually verifies further north with gradient patterns.

It’s the lowest seasonal snowfall through 2-12 in over 30 years with an average temperature so far under 35.0°.

This may be the first winter in NYC with 20 days of 1” snowcover and no days of 4” snowcover if we can’t put together a 4”+ event before the season ends.

The amplitude and volatility of the AO, NAO, and other 500 mb patterns has been increasing between deeper lows and higher highs closer together. As the ocean and atmosphere warm the 500mb patterns, jet stream, and storm tracks become more erratic. So we get these odd pairings of features of the like the Southeast Ridge merging with Greenland Blocks which didn’t used to happen in the way we have been seeing in the 2020s.

It’s linking up with the Southeast Ridge which didn’t used to happen with -AOs near -5.

Interesting split with the EPAC going into El Niño mode while the La Niña remains entrenched in the CPAC.

I believe this weekend will be our first cutter under 980mb so close to nearly a -5 -AO. We were talking about blizzards with the -5 -AOs in February 2021, 2010, 1978, and 1969. So the Pacific Jet and Southeast Ridge continue do new things in the 2020s.

The Northern Stream of the Pacific Jet has been unusually fast across the Western Into the Central US so far this month. Pretty much the opposite of what you want to see for a KU event. If this was an El Niño with a STJ a little further south, then we would probably be looking at a 30” February with the blocking. But past La Ninas usually had the Northern Stream weaken with this type blocking. This fast Northern Stream flow leaves more room for cutters, huggers, and suppressed Southern Stream storm track solutions. So we’ll need to see some relaxation of this jet before the blocking fades later this month in order to get at least one heavy snowfall event closer to the coast.

This is the extremely fast and active Pacific Jet loaded with individual shortwaves.

NYC is going to need at least one big 6-12” event before this pattern relaxes near the end of the month in order to make a run on 24” to 25” this season.

What happened since the 1990s was that a greater percentage of snowfall was coming in bigger events. So this masked the decline in the years when we didn’t get big KU events. In a colder and more stable climate we had a wider distribution of snowfall types including smaller, moderate, and major. The data suggests that we aren’t headed back to a 1961 1991 regime with the long term average in the 20s. But a new regime over the next 30 years of under 20 “ since the climate has warmed so much since then From 18-19 to 23-24 NYC only averaged around 15” due to the record warmth and lack of KU events. This season is an interesting case so far. Past cases of this amount of cold and similar long wave 500mb patterns have produced 35” to 50” snowfall seasons for NYC. But the overpowering Pacific Jet has lead to much less so far this season. That wasn’t present with past similar patterns. Going forward my contention has been that NYC will need a heavier snowfall event before this pattern relaxes in late February in order to go over 20”. We need the storm around the 20th to avoid the cutter, hugger, and suppressed Southern Stream storm track pattern which has dominated since 18-19. But we have seen how fast modeled patterns beyond 120hrs have shifted this season to something less favorable than the models were initially showing. So I will say it’s possible we could eventually score a heavier snowstorm around NYC before the end of February boosting the seasonal snow closer to the 24-25” range. But it’s not a guaranteed outcome since it too far out and we have seen how the longer range has disappointed this season so far.

The entire snowfall distribution near the coast has dramatically shifted since the 1990s. I will just use NYC as an example but all the other coastal sites have experienced the same pattern change. So we have 60+ years of data divided into 2 climate normals periods spanning 30 years each. The mid range seasonal snowfall range has greatly diminished and been replaced by all or nothing type years. Meaning well above or well below normal snowfall. This has become an issue as the climate continues the rapid warming since the 1990s. So the risk is that we continue to see this pattern increase going forward leading to the average coastal snowfall falling to around 15” or less from the 2020s into the 2040s. 1960-1961 to 1992-1993 NYC snowfall distribution 19” to 30”……17 seasons Under 15”…..5 seasons Over 31”……4 seasons 1993-1994 to 2023-2024 19” to 30”……4 seasons Under 15”……11 seasons Over 31”……..14 seasons

The difference back in that era was that we didn’t have the persistent have cutter, hugger, and suppressed Southern Stream storm tracks like since 18-19. We would get clippers dropping south of us for snow. Plus we often get coastal tracks near the BM which weren’t KU events but more moderate events. Then there were the KU years sprinkled in but not of the 2010 to 2018 frequency and magnitude. So we had more options for NYC to get to within the 19” to 29” range which was very common. These days we need a major snowstorm or multiple ones for NYC to approach the 24” to 25” range. So there was more variety to get the job done instead of having to rely exclusively on KU NESIS events since the 1990s.

Exactly since it’s the storm track which is necessary to getting NYC close to 25”.

Jan 21, 2001 was a cat 1 KU event due to how extensive the 6-9” area was.

The statistically objective metric is that NYC hasn’t had an average to above average snowfall season in over 30 years without a major coastal snowfall event ranking somewhere on the NESIS KU BM track. Many of these storms had 10”+ and 20”+ amounts somewhere in the OKX forecast zones. There were several winters during the 30 years from the 60s to 90s within around 3” of the long term 24” to 25” range that didn’t have such heavy snowstorms. So in the colder era we were able to break even just on small to moderate events. These days we need major to historic snowstorms to achieve this outcome. So we have fewer ways to do it than in the old days. Since there were several years with and without KUs which go there.

Yeah, the risk around the 20th is the -AO linking up with the Southeast Ridge again. This would result in the low hugging the coast. So the inland regions could really cash in while the coast gets another mixed precipitation event. Still too early to be sure since it’s outside the model reliable range. Just about every other February -AO in the -4 to -5 range had a KU within about a week or so of the occurrence. Like in February 2021, 2010, 1978, and 1969. So it would be very disappointing if we get 3 -AO link ups with the Southeast Ridge. I posted the other day how this has become a frequent occurrence in the 2020s. The last -4 AO link up was only a little over 2 years ago in December 2022. Prior to that we had one near -4 in December 2012. Then before that it was in January 1998. So this has become a much more frequent occurrence. Hopefully, we can find a way to buck the trend around the 20th to avoid the cutter, hugger, and suppressed Southern Stream pattern we have been in since 18-19. 2 Southeast Ridge link ups in near term Third one possible around the 20th

Snowfall can vary quite a bit over short distances. https://www.raymondcmartinjr.com/weather/2001/05-Mar-01.html

It’s in the official monthly climate report for March 2001. https://www.ncei.noaa.gov/pub/orders/IPS/IPS-B4467854-7C53-42F0-88D4-3798355E3BA8.pdf

Every weather event that occurs is in some way influenced by the average global temperatures around the time of the event. You wouldn’t expect the real world weather events to be the same during an ice age as they were during the PETM. So the background climate temperatures during each era sets the parameters or range of possibilities for the individual weather events.