bluewave

We were able to get that one cold air drain down the Hudson Valley on December 22nd with the strong Arctic high and NNW flow missing the Great Lakes. Climatological Data for NY CITY CENTRAL PARK, NY - December 2024 Click column heading to sort ascending, click again to sort descending. Sum 1351 1020 - - 824 0 4.53 2.8 - Average 43.6 32.9 38.2 -0.9 - - - - 0.3 Normal 44.3 33.8 39.1 - 804 0 4.38 4.9 2024-12-01 38 27 32.5 -10.7 32 0 0.00 0.0 0 2024-12-02 39 29 34.0 -8.9 31 0 0.00 0.0 0 2024-12-03 42 32 37.0 -5.6 28 0 T T 0 2024-12-04 42 30 36.0 -6.3 29 0 0.01 T 0 2024-12-05 40 31 35.5 -6.5 29 0 0.09 T 0 2024-12-06 34 30 32.0 -9.7 33 0 0.00 0.0 0 2024-12-07 41 31 36.0 -5.4 29 0 0.00 0.0 0 2024-12-08 55 38 46.5 5.4 18 0 0.00 0.0 0 2024-12-09 51 44 47.5 6.6 17 0 0.18 0.0 0 2024-12-10 50 44 47.0 6.4 18 0 0.26 0.0 0 2024-12-11 60 41 50.5 10.2 14 0 0.85 0.0 0 2024-12-12 41 29 35.0 -5.0 30 0 0.00 0.0 0 2024-12-13 33 27 30.0 -9.7 35 0 0.00 0.0 0 2024-12-14 34 26 30.0 -9.5 35 0 0.00 0.0 0 2024-12-15 41 28 34.5 -4.7 30 0 0.06 0.0 0 2024-12-16 52 38 45.0 6.1 20 0 0.91 0.0 0 2024-12-17 59 49 54.0 15.4 11 0 0.02 0.0 0 2024-12-18 53 42 47.5 9.1 17 0 0.32 0.0 0 2024-12-19 45 37 41.0 2.9 24 0 0.05 0.0 0 2024-12-20 37 33 35.0 -2.9 30 0 0.04 T 0 2024-12-21 33 19 26.0 -11.6 39 0 0.15 1.8 2 2024-12-22 21 13 17.0 -20.4 48 0 0.00 0.0 1 2024-12-23 31 13 22.0 -15.1 43 0 0.00 0.0 1 2024-12-24 39 28 33.5 -3.4 31 0 0.10 1.0 1 2024-12-25 35 28 31.5 -5.2 33 0 0.00 0.0 1 2024-12-26 36 24 30.0 -6.4 35 0 0.00 0.0 1 2024-12-27 44 26 35.0 -1.2 30 0 0.00 0.0 1 2024-12-28 54 40 47.0 11.0 18 0 0.56 0.0 0 2024-12-29 60 50 55.0 19.2 10 0 0.16 0.0 0 2024-12-30 58 49 53.5 17.9 11 0 0.37 0.0 0 2024-12-31 53 44 48.5 13.1 16 0 0.40 0.0 0

The lack of snow cover, warmer lakes, and the delayed Hudson Bay freeze-up will alter the Arctic outbreak next week. The airmass will significantly modify crossing the Great Lakes. The big story for us will be the wind chill factor with the strong winds. While the actual temperatures will be a little below average here, the area south of the Great Lakes will see the coldest temperatures. That -20 departure back on December 22 will probably stand as the coldest we see for a while.

This decade so far is producing a different type of reversion to the mean. The average so far in Boston is reverting to what NYC used to get. NYC is reverting to the old Washington DC mean. So a northward shift of the snowfall climate zones last 5 winters. Hopefully, we can see this storm track pattern relax some next 4 winters. Otherwise the 2020s will finish as our lowest snowfall decade.

Governments should never have the power to regulate the free and open of exchange of information. The issue here isn’t the models but the way the information is packaged. First, operational model skill begins to degrade past the 120 to 168 hr period. This is why ensembles have been created when going beyond a week. They do a good job of showing us what type of long wave or 500mb patterns we can expect. The individual short waves and storms usually don’t come into focus until we get to 120 hrs or less. I am not sure why the modeling centers have decided to make the less reliable OP runs beyond a week available. Since the ensembles are the way to go longer range and allow some broad outlines to become known. When you understand the model biases, then more clues are made available since they can tell you what the models are missing. But anyone posting a long range OP run snowfall totals or hurricane tracks has to realize these solutions are very low probability. So perhaps the NWS can communicate to the modeling centers that these OP types of runs longer range should probably be kept in house at the modeling centers. Since I am sure they don’t appreciate the calls from media and others about these images of long range snowstorms and hurricanes posted to social media which probably won’t verify as shown in the OP runs.

This has been the issue since 18-19 with the very fast Northern Stream of the Pacific Jet. The 3 primary storm tracks have been cuttter, hugger, and suppressed Southern Stream. This is one of the main reasons NYC average snowfall during the 2020s so far has dipped under 20”. So even when we get these marginally colder intervals it’s been a challenge to get a big KU event. We even had these KUs in warm patterns from 15-16 and 17-18. But benchmark storm tracks have been few and far between.The interesting thing about NYC snowfall is that they generally need KUs for normal to above normal snowfall. Getting to average with a series of small to moderate events in a general warmer climate is tougher. Maybe in the colder era we could count on a bunch of light to moderate events to add up to normal.

I am describing the actual pattern. So it’s the pattern which has been biased warm. Never realized that describing temperature patterns and the repeating model bias trends required trigger warmings. You are probably a younger guy who doesn’t remember what actual cold Januaries were like in the past.

The is the same pattern of the models underestimating the Pacific Jet beyond 10 days. Notice how much lower the heights will be over the EPAC and WNA than the earlier runs for mid-January. Very hard to sustain a -EPO during the winter after 13-14 and 14-15. New run Old run

Yeah, a continuation of the long range model forecasts backing off the cold a bit from earlier runs. While the original run wasn’t that cold, the new run has less for us. With the similar strongest cold departures going west and south. The long range runs and especially the GEFS are beginning to show the La Niña seasonal shift to more -PNA by mid to late January. Very difficult to sustain a +PNA during a La Niña event. New run Old run

These set ups in recent years have been a delicate balancing act. The original runs had no system out front so this storm was free to run to the Lakes and had P-Type issues for NYC. Then models started suddenly showing a new system developing off the East Coast over this weekend. The first response was then full suppression. Then the transient Southeast Ride with more wave spacing started showing up. The storm track pattern since 18-19 with the exception of 20-21 and Jan 22 have really made us work hard for every inch of snow.

All we need is a slightly stronger transient Southeast Ridge separating the two systems on Sunday for NYC to go from a C-2” to 2-4”type event. New run Old run

The mid-level lapse rates in NJ really mean business.

While the ensembles may be smoothing things out too much, all 3 OP runs try to show a transient Southeast Ridge in 10 days.

My guess is that NYC will see several days with highs over 32° from the 6th to 16th.

10-11 was our last chance to surpass 95-96 when Newark got 60” in only 33 days. But the pattern reversed too quickly after January. We were one of the few spots from DC to Boston that didn’t set a new seasonal snowfall record during the 2010 to 2018 record KU era.

But 2016 was warmer than those 3 years with a better snowfall outcome due to the great STJ pattern.

I hear what you are saying. But storm tracks in January during the last decade have been more important than average temperatures for snow. Provided that the NYC monthly average doesn’t get above 40°. NYC January average temperatures and snowfall since 2015 2024….37.0°….2.3” 2023….43.5°….T 2022….30.3°….15.3” 2021….34.8°….2.1” 2020….39.1°….2.3” 2019…..32.5°….1.1” 2018….31.7°….11.2” 2017….38.0°…7.9” 2016….34.5°…27.9” 2015….29.9°….16.9”

From 69-70 to 92-93 NYC had 12 seasons when the snowfall was within 5” of average. Beginning in 93-94 to 22-23 there were only 3 seasons within 5” or normal. So our seasons have become all or nothing in the last 30 years with most seasons well above or well below average. As the climate continues to warm with these challenging storm tracks for snow, the below average snowfall seasons eventually win out. So unless we see a marked improvement in the cutter, hugger, and suppressed southern stream storm track pattern by 2030, the NYC long term average will eventually drop to below 20”.

Doesn’t look like any -20 departures like we saw back on 12-22 at least through the next two weeks.

Close to the global daily all-time high temperature for December 29th. The previous record for this date was set last year. So the global temperatures continue to exceed expectations.

Continuation of the December and multiyear theme. Long range guidance has been too strong with the 500 mb heights and -EPO near Alaska. So as we get closer models show lower heights there. So if they are beginning to show more of a +EPO long range, then the +EPO could verify even stronger in the longer range. Same way the -EPO forecast verified weaker.

The warmer December than forecast allowed Lander, Wyoming to go +11.3° for December. The extreme winter warmth across parts of the CONUS regions has been unprecedented since 15-16. Before this period, having near to above a +10 monthly departure for a U.S. climate station would be a rare to uncommon event. We can remember the double digit departure months occurring much less frequently in the past. January 2006 in the Upper Midwest and March 2012 come to mind. Now these very high monthly winter departures have been happening yearly with multiple months in the same winter recording such departures. We have had a remarkable 12 winter months across varying ENSO states since December 2015 meeting this criteria for one or more climate stations. It’s even more impressive to see these monthly temperature departures occurring in the warmest climate normals period. Dec…2015….NYC….+13.3 JAN…2017….BTV…..+11.0 FEB….2017….ORD….+10.3 FEB…..2018…ATL….+10.6 FEB….2019…MGM….+10.5 JAN….2020…YAM….+9.8 DEC….2021….DFW….+13.2 JAN….2023….DXR….+12.3 FEB….2023…..SSI…..+9.8 DEC….2023….INL…..+15.8 FEB…..2024….FAR…..+17.5 DEC….2024…..LND…..+11.3

A neg nao would not be an issue with a great STJ pattern like we had in 2016 with the super El Niño. A La Niña dominant Northern Stream makes the 50/50 an issue. On top of the generalized faster Pacific Jet since 18-19.

Most of the time it’s cold enough to snow here in January. Some of our snowiest Januaries were warmer than average. But our big issue since the 18-19 has been the overpowering Northern Stream of the Pacific Jet. So it makes it harder to get heavy snows here with the cutter, hugger, and suppressed Southern Stream storm tracks. I would gladly take a warmer January like 2016 and 2017 if we had a primary benchmark storm track instead with the multiple KU events those years. Hopefully, we can get the fast Pacific flow with so many shortwaves close together to relax enough for at least one 4”+ or 6”+ event in NYC before the +PNA -AO eventually fades. But as we have seen even during some colder intervals this time of year there is no guarantee. Since the suppressed southern stream issue is showing up in the modeling wit the fast Pacific flow with multiple embedded shortwaves plus the 50/50 confluence. This is a situation where a dominant STJ would probably be of more benefit.

Same issue across North America and the entire Northern Hemisphere. https://www.star.nesdis.noaa.gov/smcd/emb/snow/HTML/snow_extent_monitor.html

Same situation as we have seen in recent years with the coldest departures going to our west or south. The delayed freeze-up on Hudson Bay and strong blocking there is keeping nearby Canada very mild. You can see the milder temperatures relative to the means working down into Northern Maine.