bluewave

The first example of this cutter, hugger, and suppressed Southern Stream storm track became evident during the 18-19 DJF period when we only had a single snow squall at the end of January even with the cold pattern in January. All our snow that year was one SWFE in November and a brief period in early March where areas further north did OK. Then this was followed by disappointing 19-20 season. The overpowering Northern Stream of the Pacific Jet began to become a big factor. While the BM KU tracks made a return for 20-21, even in that season there were some notable differences. The December event tracked very close to ACY so BGM got the 40” jackpot. Then the damaging flood cutter on Christmas. The early February event was the only traditional BM KU of this decade where points west to NYC and LI cashed in together. The BM tracks in 2022 were shifted further east so Suffolk did great and areas further west were left out. Of the best results. December 2022 featured the best December AO blocking since 2010 but we didn’t get another Boxing Day Blizzard with 30” around Newark. The hostile Pacific ran the table and even the MJO 8 and -AO pattern in March couldn’t produce. Then in 23-24 we got the one week window in February with the record STJ and the Northern Stream briefly relaxing. Mostly Central Jersey was favored for the best results. Then we had the great -EPO and +PNA from this December into January being joined by the -AO and colder than average temperatures. Very little snowfall to show for it over those two months vs past La Niña mismatch with 10-20”+ in NYC for similar past patterns. One of the most extreme Southern Stream suppression events of all-time with the Gulf Coast getting the record snows. Now this February we have been getting hugger tracks with front end thumps and then mixed precipitation closer to the coast. So while the retrogression pattern following the big -AO block forecast for mid-February has produced KU BM tracks in the past, it’s very uncertain if the storm track will cooperate this time around. Hopefully, we can out something together during that retrogression interval around or after the 20th. While it’s always possible we could see a better March this year than the last 5, I wouldn’t want to have to rely on March if this pattern continues to underperform. Not seeing the big SSW signal like in 2018 and strat coupling which lead to the 30” March on LI and locked in -AO for the whole month. Since it looks like the -AO will start weakening later in February as it retrogrades back into +PNA.

This time around we are still contending with the much faster Northern Stream of the Pacific Jet since 18-19. That winter had the great STJ to go with KB block retrograde back across the North Pole. So we are still dealing with the cutter, hugger, and suppressed Southern Stream storm tracks which make 30” snowstorms in NYC harder to come by.

That KB block shifted the whole pattern across the Northern Hemisphere this month. It’s forecast to retrograde back to near the North Pole over the next week. Notice how this is causing the global temperatures to finally drop below the record levels.

The KB block is definitely the reason we saw the shift on model forecasts for February. The wave break which just occurred with the record low east of Hudson Bay wasn’t forecast very well back in late January. So this record block is forecast to retrograde back into the AO region.

We are just following model forecasts which have improved greatly since the 70s and 80s. Then we take into account what the recent model biases have been. But no matter how much long range model forecasts improve, a 10 to 15 day forecast is always going to have some errors due to the nature of modeling. We live very close to where continental air masses interact with the Gulf Stream to our Southeast. So my guess is that this is one reason snowfall details usually have to wait with snowfall until the short term. Models just can’t pin down snowfall details over a 240 or 360 hr forecast period. So the best we can do is identify patterns would could potentially produce snow. It’s even harder with a rapid succession of systems like we are getting this month. Most 360 hr surprises in the 2020s have been toward warmer and less snowy as the time period approached. So this near record block forecast for mid-February wasn’t showing up on the models back on January 30th. But the general 500 mb longwave pattern will turn out to be correct. It’s always the nuisances and details within a pattern will vary. So while we can get excited about snowfall potential in a general pattern, it’s always going to come down to the shorter range details as to how much snow we get. Old 360 hr forecast had correct longwave 500 mb pattern but missed the record block near Greenland and the North Pole New forecast Old forecast

The record KB block driving the Siberian Airmass SE along with the record SSTs near Japan.

2002-2003 was the last time that all of our climate sites had all 3 winter months with a negative temperature departure. But that was during a much colder climate normals period. So it’s easier to get a cold departure now with the much warmer normals. Since a cold departure now like during December would have been warm using the older climate normals period. Some of our stations had 3 in a row during 09-10 and others like Newark didn’t. This winter JFK finished above average back in December and Newark just managed a slight negative departure of -0.1. So nothing like the magnitude experienced in 2002-2003.

That was based on the modeling at the end of last week before the -AO block started showing up. The first week of February so far has indeed been warmer than average and followed the La Niña script. But the wave break with the record low east of Hudson Bay shifted the whole pattern going forward. Models still have the -AO block peaking next week and gradually weakening later in the month as the block retrogrades back into +PNA.

This looks like the first 5 SD 500 mb block near Greenland during the winter since February 2021. So the million dollar question is whether our best snowfall opportunities will occur prior to and around the peak in mid-February or after. Back in 2021 when the AO went -5 the best snows came in before the block and not after it peaked. This is pretty much unknowable at this point. But at the very least the magnitude of the block now argues for a colder than average February. Before the models started showing the block they were going for +1 to +2 pattern in the means for February. So this could be the first winter since 2002-2003 with all 3 winter months having a cold departure. We are now pretty much assured of having our first colder winter here since 2014-2015. Regardless of the snowfall outcome, this block will be impressive even if doesn’t couple with the stratosphere. So more of a bottom up event. Longer range the models have the AO block weakening in later February and giving way to more of +PNA which is pretty rare for a La Niña February. 5 SD 500 mb anomaly one of the most impressive of 2020s so far

It’s a new 500 mb record for this time of year. Mika Rantanen ‪@mikarantane.bsky.social‬ Follow That is a huge blocking predicted to form over NW Russia. Record-breaking in intensity (for the time of the year), with 500 hPa levels half a kilometre higher than normal. It's like a stone in a river that directs the warm, moist air flow from the North Atlantic towards the Arctic. ALT ALT February 4, 2025 at 8:36 AM Everybody can

New lowest extent record for 2-5 by 500k.

Arctic sea ice thickness and extent at record low levels for this time of year.

This month could be the end of the drought here as the Euro seasonal is wet right through the summer. https://charts.ecmwf.int/products/seasonal_system5_standard_rain?area=GLOB&base_time=202502010000&stats=tsum&valid_time=202506040000

We always get very active patterns around the time of these Arctic warming events.

The 1st half of February has been much more productive since 2010. Individual events and the highest snowfall totals 2022 Jan 28-29….Islip….24.7 2021 Jan 31-Feb 2....Blomingdale, NJ.....26.1 2020 Dec 16-17 East Tremont, NY....12.4 2019 Mar 3-4...Monroe, CT....12.0 2018 Nov 15....Mount Hope, NY.......18.3 Mar 21-22...Patchogue, NY......20.1 Mar 13...Southampton,NY.....18.3 Mar 8....New Farfield, CT..........26.8 Mar 2...Monroe, NY.................14.0 Jan 4...Islip, NY.......................15.8 2017 Mar 14...Montgomery, NY.......23.5 Feb 9...Selden, NY...................16.0 Jan 7...Orient, NY....................12.5 2016 Feb 5...Setauket, NY................12.0 Jan 23..JFK,NY.........................30.5 2015 Feb 2..New Faifield, CT............12.0 Jan 26-27....Orient,NY.............28.5 2014 Feb 13-14...Roselle, NJ............16.7 Jan 21-22....Centerreach,NY....14.0 Jan 2-3......Lindenhurst, NY.....12.5 2013 Mar 8....Harriman,NY..............15.0 Feb 8....Upton, NY..................30.9 2012 Nov 7-8.....Monroe, CT..........13.5 Jan 21......North Haven, CT....12.0 2011 Oct 29.....Harriman, NY.........16.0 Jan 26-27...NYC................... 19.0 Jan 11-12.......Meriden, CT....29.0 2010 Feb 25-26...Mount Hope, NY...27.5 Dec 26........Elizabeth, NJ........31.8 Feb. 10.....Sound Beach, NY....16.2 2009 Dec 19-20....Upton, NY..........26.3

Yeah, the period around the 11-12th may be the best chance for someone in the OKX forecast zones to record a 12”+ total. Statistically February 1 through 15th has featured the highest concentration of 12”+ max events in the OKX forecast zones during the winter since 2010. But the positioning of the gradient and storm track will be key. Roughly 2 week snowfall periods for the 2010's and number of 12"+ snowstorms Oct 29-Nov 15.....3 Nov 16-Nov 30....0 Dec 1- Dec 15.....0 Dec 16-Dec 31....3 Jan1-Jan 15.......4 Jan16-Jan 31.....5 Feb 1-Feb 15.....6 Feb 16-Feb 28...1 Mar 1- Mar 15....6 Mar 16-Mar 31...1 Apr 1-Apr 16.....0

February 2021 was the last time we had a higher number of days in a calendar month with measurable snowfall in NYC. Time Series Summary for NY CITY CENTRAL PARK, NY - Month of Feb Click column heading to sort ascending, click again to sort descending. 1 1964 11 0 - 1920 11 0 2 1926 10 0 3 1962 9 0 - 1924 9 0 - 1923 9 0 - 1916 9 0 4 2021 8 0 - 2014 8 0 - 1936 8 0 - 1914 8 0 5 2015 7 0 - 1994 7 0 - 1972 7 0 - 1950 7 0 - 1883 7 0 - 1879 7 0

We don’t get many successful gradient patterns around here like in 2014 and 1994. So I am not sure yet where the gradient will settle for next week after the next two storms. Those years were much colder than this winter has been. It’s always a challenge when the Southeast Ridge is battling a -AO block over the top. 30 miles can make the difference from the I-78 corridor into NYC between a great pattern and a disappointing one.

February 11-12 will be the make of break moment for the entire winter so far around NYC Metro. That 0z OP Euro was similar to the multi day KU event at the same time around 2-11-94 with that gradient. So getting the gradient to settle just in the right spot will key here to getting a more memorable storm around NYC. It’s why we need these big KU events for normal to above normal seasonal snowfall. But we really have to take the next few storms first to see what the actual track will be. Since the exact wave spacing and gradient location left in the wake of the previous storms will determine whether we can get something really special or not. Just 30 miles can mean everything for a spot like NYC.

Classic case of hydroclimate volatility which makes accurate long range precipitation forecasting very challenging in the new climate. https://weatherwest.com/archives/43181 Hydroclimate volatility broadly refers to unusually rapid and/or high magnitude swings between unusually wet and dry conditions (or vice versa) relative to what is typical for a given location and season. Such rapid transitions can often generate hazards that are distinct from their constituent wet and dry extremes (e.g., floods and droughts), meaning that hydroclimate volatility can yield overall societal and ecological risks that are “greater than the sum of their parts.”

Yeah, they just exceeded that old record set back in 2022.

Today is a great example of how much of a change can occur with an ensemble mean from 360 hrs to 240hrs. The biggest change at day 10 is the much deeper trough digging into the West around Valentine’s Day. So any speculation based on the present 360 hr run is going to look different when it gets to 240 then 120 and 0 hrs. This is why you want to maximize opportunities closer in since you don’t know what the pattern is going to look like from day 10 and beyond. New run Old run

This is the first time we had a gradient pattern in the 2020s with the SE Ridge battling blocking over the top.

I agree. The risk with gradients is that we get mixed precipitation events when the systems really amped like the next few. Then if a system is too weak the confluence to the north can be too strong leading to suppression. What we want next week is a goldilocks scenario right in the middle.