bluewave

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.

The most memorable storm that winter closer to NYC was the 12-30 event which broke the slump we were in since after the 95-96 winter. Data for December 30, 2000 through December 30, 2000 Click column heading to sort ascending, click again to sort descending. NY PORT JERVIS COOP 16.8 NY DOBBS FERRY-ARDSLEY COOP 14.0 NJ NEWARK LIBERTY INTL AP WBAN 13.9 NY MINEOLA COOP 13.6 CT DANBURY COOP 13.4 NY LAGUARDIA AIRPORT WBAN 13.3 CT STAMFORD 5 N COOP 13.0 NJ HARRISON COOP 12.8 NY NEW YORK AVE V BROOKLYN COOP 12.7 NY NY CITY CENTRAL PARK WBAN 12.0 NY JFK INTERNATIONAL AIRPORT WBAN 10.3 CT IGOR I SIKORSKY MEMORIAL AIRPORT WBAN 10.0 Data for January 20, 2001 through January 21, 2001 Click column heading to sort ascending, click again to sort descending. NY WEST POINT COOP 7.5 NY GARDNERVILLE COOP 7.3 NJ WANAQUE RAYMOND DAM COOP 7.0 NY WALDEN 1 ESE COOP 7.0 NY PORT JERVIS COOP 6.7 NJ CHARLOTTEBURG RESERVOIR COOP 6.5 NY SEA CLIFF COOP 6.5 CT DANBURY COOP 6.3 NY NY CITY CENTRAL PARK WBAN 6.0 NJ ESSEX FELLS SERVICE BLDG COOP 6.0 NJ GREENWOOD LAKE COOP 6.0 NY JFK INTERNATIONAL AIRPORT WBAN 6.0 CT IGOR I SIKORSKY MEMORIAL AIRPORT WBAN 6.0 NY WESTCHESTER CO AP WBAN 6.0 CT JEWETT CITY COOP 6.0 Data for February 22, 2001 through February 23, 2001 Click column heading to sort ascending, click again to sort descending. NJ CANOE BROOK COOP 6.5 NJ CRANFORD COOP 6.2 NJ PLAINFIELD COOP 6.0 NY LAGUARDIA AIRPORT WBAN 6.0 NJ HARRISON COOP 6.0 NY NY CITY CENTRAL PARK WBAN 5.8 NJ NEWARK LIBERTY INTL AP WBAN 5.7 Data for March 5, 2001 through March 6, 2001 Click column heading to sort ascending, click again to sort descending. NY RIVERHEAD RESEARCH FARM COOP 14.5 CT DANBURY COOP 14.3 CT IGOR I SIKORSKY MEMORIAL AIRPORT WBAN 13.5 NY BRIDGEHAMPTON COOP 13.3 NY WEST POINT COOP 13.0 CT JEWETT CITY COOP 10.0 NY WALDEN 1 ESE COOP 9.0 CT ANSONIA 1 NW COOP 9.0 CT NORWICH PUBLIC UTILITY PLANT COOP 8.5 CT GROTON COOP 7.5 NY ISLIP-LI MACARTHUR AP WBAN 7.0 NY DOBBS FERRY-ARDSLEY COOP 6.5 NY MINEOLA COOP 6.2 NJ NEWARK LIBERTY INTL AP WBAN 6.1 NJ GREENWOOD LAKE COOP 6.0 CT STAMFORD 5 N COOP 6.0

Remember that NYC doesn’t always jackpot when we have an active KU BM storm track regime. Sometimes the coastal storm tracks are inside the BM like December 2020 favoring the interior like BGM. Other times coastal storm tracks are just wide of the BM favoring Suffolk County like in January 2022. And other times we get more of a goldilocks track like in January 2016 with the jackpot in the middle near NYC. So the common denominator for all NESIS snowstorms is generally someone around the region getting a 10”+ snowfall max. This type of major coastal snowstorm track has become a prerequisite for NYC to reach within a few inches of the longer term mean in the 24” to 25” range. All the seasons since 93-94 with near to above this range featured KU NESIS snowstorms. From the 1960s to the 1980s NYC could get to within a few inches of the 24-25” snowfall range with numerous smaller to moderate events and no major KUs. But obviously the much higher years such as 77-78 featured major KU events. So there were multiple ways to get close to the 24-25” range.

We had the -EPO +PNA which was able suppress the Southeast Ridge.

-PNA -AO intervals back in the much colder era didn’t regularly feature a Southeast Ridge linking up with the -AO Greenland blocks. This is more of a recent occurrence during the 2020s. Notice back in the 1950 to 1970 era when we had frequent -PNA and -AO patterns there was usually a trough in the East. My guess is this recent alteration of that past pattern is related to our much warmer climate including land areas, SSTs, and a faster Pacific Jet. I complied 15 separate such months from that era as a comparison. 1950 to 1970 colder era winter -PNA -AO patterns across 15 different months

The Southeast Ridge wouldn’t have linked up with a -4 to -5 -AO block in that much colder climate era.