bluewave

The kicker trough out West was a little stronger this run so everything shifted east from 0z. Need to weaken that feature in future runs for a stronger Rockies Ridge and Southeast Ridge. But the Pacific has been acting as the spoiler in recent years. So it will be something to watch over the next few days. New run Old run

It’s been a mixed story this winter. On one hand we had the extreme Southeast Ridge suppression back in January. But this month so far with all the events except the one that produced the significant snow near DC the gradient has been shifting further north. This weekend the AIFS forecast originally had the low sliding to our south but it turned into a big cutter. The other common denominator has been that the models have been underestimating the strength of the Northern Stream of the Pacific Jet. So we have been getting the consistent cutter, hugger, and suppressed Southern Stream storm tracks. This is going to be the first test case for an East Coast low this winter so far. So we don’t have much of a sample size of events to draw on for individual model performance. You can look at the upper low on the GFS coming into the West acting as a kicker low. But this feature is weaker on the CMC and Euro. That piece of energy could be a big key to the forecast. I am not sure it’s currently getting sampled very well since it still back over the Pacific. We could probably use a special NOAA flight this weekend since the Pacific has been consistently acting as the spoiler for us. I would really like to see this pattern relax at least once this winter to finally allow something approximating a benchmark track to return after being absent for years.

With a little luck the stronger Rockies Ridge, Southeast Ridge, and sharper trough on the Euro and Canadian verifies so this can get pulled in closer to the coast by the bowling ball upper low.

While there are some differences in the sensible weather so far, this La Niña February is more along the lines of the February 2021 La Niña. That one featured a record Arctic outbreak down the Plains. But this one won’t be quite as intense. There was also a -5 -AO block that month. Plus we are on track for February being our snowiest month of the winter.

The changes in the wavelengths has made the correlation less over time.

This is why I am mostly focused on the magnitude of the 500 mb height anomalies. While the raw indices can be informative, the actual 500 mb anomalies tell a more complete story. Since you can view them and see how they combine with the height anomalies in other regions rather than in isolation. But when the raw indices like the AO get down into the -4 or -5 and lower range, they are often accompanied by corresponding 500 mb anomalies in the +400 to +500 meter range like we are currently seeing. But sometimes the orientation of the wavelengths can lead to the PNA raw index not lining up exactly with the 500mb look. These more variable and amplified wavelengths are probably why the AO and NAO have fallen out of sync in recent years. This weekend is a great example of the -NAO not matching the -AO magnitude. In the old days the blocking wouldn’t have been as squeezed into the AO sector and we would have saw a stronger -NAO also.

JFK would have had close to 23” like Malverne did in the December 1947 blizzard. Data for December 26, 1947 through December 27, 1947 Click column heading to sort ascending, click again to sort descending. NY BEDFORD HILLS COOP 32.0 NY WARWICK COOP 31.0 NJ RUTHERFORD COOP 29.6 NJ RINGWOOD COOP 29.0 NJ GREENWOOD LAKE COOP 28.8 NY BABYLON COOP 28.5 NY SCARSDALE COOP 28.2 NY DOBBS FERRY-ARDSLEY COOP 28.1 NJ WANAQUE RAYMOND DAM COOP 28.0 NJ RIDGEFIELD COOP 27.0 NY EASTCHESTER COOP 27.0 NY NY CITY CENTRAL PARK WBAN 26.4 NJ JERSEY CITY COOP 26.2 NJ ELIZABETH COOP 26.0 NJ WESTFIELD COOP 26.0 NJ NEWARK LIBERTY INTL AP WBAN 26.0 NJ LITTLE FALLS COOP 26.0 NJ MIDLAND PARK COOP 26.0 CT GREENWICH COOP 26.0 NY WORLD TRADE CENTER WBAN 25.8 NY PLEASANTVILLE COOP 25.5 NY OSSINING SING SING COOP 25.0 NY CARMEL COOP 25.0 NY WEST POINT COOP 24.8 NJ PATERSON COOP 24.0 NY MINEOLA COOP 24.0 NJ PLAINFIELD COOP 23.0 NY HEMPSTEAD MALVERNE COOP 23.0 NY LAGUARDIA AIRPORT WBAN 22.8 CT DANBURY COOP 21.5 NJ CHARLOTTEBURG RESERVOIR COOP 21.0 NY YORKTOWN HEIGHTS COOP 20.5 NY PATCHOGUE 2 N COOP 20.0 NY PORT JERVIS COOP 19.0 CT BRIDGEPORT COOP 19.0 CT COLCHESTER 2 W COOP 18.0 CT NORWALK COOP 16.0 NY SETAUKET STRONG COOP 15.0 CT WATERBURY ANACONDA COOP 15.0 CT WATERBURY CITY HALL COOP 15.0

It would reinforce the point I have been making that we need BM KU snowstorms to reach average to above average seasonal snowfall near the coast since the 1990s.

The warmest SSTs on record for February in the Gulf can work to our advantage with set up. Stronger convection and cyclogenesis early on can help to boost the 500 mb heights along the East Coast. Leading to a closer storm track to the benchmark.

This is one time when a stronger transient Southeast Ridge can work to our advantage and help to lessen the influence of the faster Pacific Jet and shortwave coming into the West Coast. It’s definitely a fragile set up where small changes can cause a shift. But at least at this early stage represents the best chance this winter for a heavier snowfall event. New run slightly stronger transient Southeast Ridge and closer EPS mean to the coast Old run a little weaker with more suppressed storm track

In the colder era with colder SSTs too the east an amplifying system would not cause the Southeast Ridge to flex. Those were the composites I posted earlier in this thread. Probably a warm water feedback process becoming more common. This is why strong -PNAs in the old days used to have a Southeast Trough more often and not a Southeast Ridge.

I think you are mistaking the description of the pattern as complaints. We were bound to have a colder than normal winter eventually after 9 warmer to record warm winters. Even the summers had 3 colder ones out of the last 15. So 12 warmer summers out of 15 is less impressive than 9 out of 10 warmer than average winters.

This has been one of those cases where the 500mb anomalies have varied from the CPC official PNA index. Most of us on this forum would consider it a -PNA pattern when there is a deep trough sitting over Seattle. It really pumped the Southeast Ridge forcing the gradient further north than NYC wanted to see.

Tell that to New Orleans.

The block is very close to where it was for the other 15 times when the -AO reached -4.8 and lower going back to 1969. So it’s not too far north. The greatest difference is that there was no Southeast Ridge in the other dates. So suppression would have been a risk in the old days and not an intense cutter. 15 date composite since 1969 with -AO of -4.8 or lower

This weekend will be our first cutter dropping under 970 mb with a -5 -AO. So the Southeast Ridge got so strong that it prevented the low from sliding to our south like in the past. Should at least be gusts over 50 mph and possibly 60 mph by Monday. Near record 5.5 sigma 500 mb block around Greenland

This is only the 2nd time since 1950 that NYC translated such a low seasonal snowfall total by 02-12 into 20 to 25 days of 1” snowcover. This extension of 12.0” to 21 days has been very impressive. Only rivaled by 80-81 which had 21 days with 10.8”. But 80-81 had a 4.9” event in January while the biggest snow this season to date in NYC has been only 3.0”. So a great job of making so many small snow events last so long on the ground. 2-12-25……21 days..….12.0” 2-12-21……20 days…..33.8” 2-12-15……24 days…..23.5” 2-12-09……21 days…..19.3” 2-12-05….. 20 days…..18.3” 2-12-01…….21 days…..25.4” 2-12-88…….25 days….18.5” 2-12-85…….22 days…..23.9” 2-12-81……..21 days …..10.8” 2-12-78…….21 days……38.6” 2-12-65……22 days……18.8” 2–12-58……22 days……20.8”

May 2020 which tied the all-time heaviest late season snowfall following a string of long range model forecast snowstorms that didn’t work out. That was our latest record snowfall following a disappointing winter when models kept advertising the big one in the long range. Spots had more snow in May than in February that year.

All the past 6 year snowfall period slumps across our local stations occurred in a colder era. So it was easier to achieve near to above 50” snowfall to break the droughts. But we haven’t been cold enough since the 15-16 super El Niño for such high snowfall totals in NYC. Even this winter being colder than the last several have run into p-type issues near the coast. So combined with the less favorable tracks and not having enough cold ahead of the storms will be challenging to get enough cold next 3 winters and an active BM storm track to reach 50” near NYC. Remember even in 20-21 NYC couldn’t make it to 50” due to mixing issues and warmth around some of the storm tracks. In a colder climate that would have been an easy 50” year. So the next 3 winters will decide if the 6 year slump through 23-24 will become a 10 year one when this season ends and becomes the 7th year in the series.

The significant metric at JFK has been the 6 year running mean snowfall from 18-19 to 23-24. It was near the bottom of the list since they started keeping snowfall records there. That’s why the period around the 20th and the next few years are so important. Past instances with similar 6 season slumps all experienced big rebounds in the following years. In fact the reason the 6 year slumps didn’t become 10 year slumps near or under 15”was there there was a quick rebound to near 50” in the following seasons. So we need a major snowstorm around the 20th and a near 50” season next few years to turn things around. But it will a big challenge to expect repeats of 76-77, 77-78, 93-94, 95-96, 02-03, 03-04, and 04-05 in the much warmer mid to late 2020s climate. I will update the new 7 year running mean once this winter ends. Then we’ll have the next 3 seasons to try and avoid the lowest 10 year running mean of 18.0” set in 1993. Lowest 6 year snowfall means JFK 2024….14.3” 2002…13.0” 1993….14.7” 1975….14.7”

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.