bluewave

I don’t think that the models will have a handle on that system until the big storm on Friday gets out of the way.

Beyond identifying model biases day 6-10 and 11-15, it’s a very low skill game to try and guess what happens beyond that range. So we try to use some analogs to fill in the gaps like how low the AO has been in December. One would hope we see more blocking intervals like the list of analogs below. But the sample sizes may never be great enough to account for all the possibilities. December -3 or lower daily values since 2000 and NYC snowfall 12-11-22….-4.2378……? 12-28-20….-3.197……..10.5” 12-8-12…….-3.902……0.4” 12-18-10……-5.265…..20.1” 12-21-09……-5.2821….12.4” 12-05-05……-3.569….9.7” 12-28-01…….-3.293….T 12-29-00……-4.688….13.4”

The tendency to see the -AO block link up with the SE Ridge and become more south based has been a frequent theme. The EPS run last Thursday that had at least a window for a more wintry event didn’t have the linkage. The PNA isn’t much different as the vortex digging into the PACNW hasn’t changed locations from the forecast last week. So the changes leading to the warmer solution look more Atlantic based than Pacific. If we had a stronger +PNA like in December 2020, this probably would have been another potential KU. Verification for today Forecast from last Thursday

The late December warmer correction is another example of the week 2 products running too cold recently. New 240 Old 360

Yeah, a cutter can go 5 miles west of NYC or 500 miles west and still be a big rainstorm on Long Island. So there is more leeway for a long range cutter forecast to work out. But a benchmark snowstorm can’t afford to be 500 miles off and still verify. So cutter tracks can start showing up day 6-10 and still work out for us. But we are lucky if a big snowstorm is correctly modeled by day 5. The big ones usually start out suppressed beyond day 5 and correct west the closer in we get. We briefly had a window last Thursday when the cutter was showing up right along the coast or even to the east. But the one cluster the EPS was showing over the Great Lakes turned out to be right. The ensemble mean SE of MTP would have been perfect from 72 hrs out for a KU. But the big westward correction we often get in the shorter range put the storm to our west. The animation below is the one you want to see for snowstorms in our area.

Then you missed all the posts commenting on how the big cold and snowy pattern was always 11-15 days away on the ensembles since late November. This has been the model bias for the last 90 days .You can find all my previous posts commenting on how it needs to start showing up under 8-10 days to be believable. As to the warm up showing up near the end of the month, it’s now coming into the under 10 day range which is more accurate.

5 days either side of the solstice is the fastest warming part of December. We are on track for the 12th year in a row going above 55° and maybe into the low 60s. Why this happens every year at this specific time would make a nice research paper. The highs during the first 2 weeks of December don’t show such a large increase.

I can still remember Christmas 1980 and 1983 which were the coldest on record going back to the late 1800s. Time Series Summary for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Rank Ending Date Lowest Min Temperature Dec 25 to Dec 25 Missing Count 1 1980-12-25 -1 0 2 1983-12-25 4 0 - 1872-12-25 4 0 3 1914-12-25 11 0 4 1958-12-25 12 0 5 1968-12-25 13 0 - 1948-12-25 13 0 - 1878-12-25 13 0

It all depends of the 500mb pattern. NYC had it’s first subzero reading in February 2016 since 1994 and was in the 60s within a week. Data for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Date Max Temperature Min Temperature 2016-02-12 27 15 2016-02-13 22 6 2016-02-14 15 -1 2016-02-15 35 13 2016-02-16 54 35 2016-02-17 39 35 2016-02-18 36 27 2016-02-19 39 24 2016-02-20 61 39 2016-02-21 55 44 2016-02-22 52 38 2016-02-23 40 35 2016-02-24 60 36 2016-02-25 61 37 2016-02-26 39 27 2016-02-27 41 26 2016-02-28 60 38 2016-02-29 61 47

The big ridges off of both coasts since the super El Niño in 15-16 have been forcing what little cold there has been down the Plains.

Low 60s to upper 10s would challenge the all-time December 24 hr temperature drop at Newark set in 1998. https://mesonet.agron.iastate.edu/plotting/auto/?_wait=no&q=169&network=NJ_ASOS&zstation=EWR&hours=24&month=dec&dir=cool&how=exact&_r=t&dpi=100&_fmt=png

Sure there is luck sometimes. But this storm is classic long range model bias recognition case. All the guidance has been underestimating the ridge east of New England for years day 8-15. Below is just the most recent 90 day model error which is more of the same.

2-3C of warming by later this century will be tough to avoid. But maybe nuclear fusion can become viable and cheap enough within the next 50 years to prevent 4-5C of warming. Fossil fuels will still be our primary energy source for decades to come. https://www.bbc.com/news/science-environment-61802802 Their 17th annual status report draws on over 600 experts to produce a snapshot of what is really happening in terms of renewable energy. The study says that the transition to renewables, in essence, has stalled. The use of coal, oil and gas continues to dominate total energy consumption. The share of renewable energy has moved in the last decade from 10.6% to 11.7%, but fossil fuels, all coal and gas have moved from 80.1% to 79.6%. So, it's stagnating," said Rana Adib, the executive director of REN21. "And since the energy demand is rising, this actually means that we are consuming more fossil fuels than ever."

Yeah, that was the big announcement during the week.

Yeah, that’s outsourcing of emissions as our emissions have been in decline. But at least we have much cleaner air here with more natural gas instead of dirty coal. Automobile emissions have really improved with much less smog than we had years ago. Emissions and global temperatures didn’t rise that much from 1880 to 1980, so we were still able to get the historic cold in the 1970s. But with the rapid increase in emissions in Asia due to all the manufacturing and population growth, the temperatures have really taken off since the 1980s. https://www.climate.gov/news-features/climate-qa/if-carbon-dioxide-hits-new-high-every-year-why-isn’t-every-year-hotter-last

It’s tough to bet against the perma ridge to our east which has been setting record after record since 15-16.

The EPS is a little better at detecting the ridge axis out near 60-65W than the GEFS close to day 10. At least the EPS didn’t have the 50/50 low there like the GEFS which used to be common under these set ups in the past. I would apply machine learning bias correction to those maps from 192-360. Maybe that will be the next step at ECMWF now that that they have their new super computer facilities. New run Old runs

The models have been underestimating the ridge along 65W beyond the 7 day range for the last 7 years. It’s a persistent model bias. So the model developers need to fix their models to make longer range forecasting more reliable in our region. Integration of AI or machine learning would be a good start.

That new ridge to our east was the topic of the paper and presentation I posted in the other thread.

There is no luck involved with this persistent ridge along 65W which is causing an unlikely cutter. It’s part of a persistent pattern since the super El Niño in 15-16. There are several theories including a slowing AMOC due to the melting Arctic. But some feature of the warming climate is behind the historic ongoing marine heatwave to our east. Nobody has said that -4 -AOs and +1 PNA won’t produce snowstorms again in the future. But the chance that we’ll see cutters instead is beginning creep up when they never occurred in situations like this in the past.

These indices used to be more reliable before the big ridge and warm pool developed to our east following the super El Niño in 14-15. So we need to be more cautious using older analogs in our new climate. That ridge probably needs it’s own separate index.

Looks like our regular warm up a few days before Christmas ahead of the cutter. Then a cool down behind it for several days. Followed by our next warm up near the end of the month as the EPO goes positive.

We are on track for one of the least snowiest Decembers with such a -AO. What makes this one really unusual is that we are getting a +1 PNA this week with the storm. In 2012 we didn’t get the +PNA spike like this year with the -4 AO. So that one was more understandable. December -3 or lower daily values since 2000 and NYC snowfall 12-11-22….-4.2378……? 12-28-20….-3.197……..10.5” 12-8-12…….-3.902……0.4” 12-18-10……-5.265…..20.1” 12-21-09……-5.2821….12.4” 12-05-05……-3.569….9.7” 12-28-01…….-3.293….T 12-29-00……-4.688….13.4”

Just goes to show how much better the EPS is than the GEFS near the end of it’s effective day 10 range. At least the EPS had the hint of the ridge building east of New England. But the GEFS had the classic 50/50 low in the same spot. The day 8-15 forecasts almost always miss the ridge axis along 60W. This has been the model bias since the super El Niño in 15-16. New forecast Old forecasts

The 5 days leading up to Christmas have become the least snowy of the whole month since 2011. Time Series Summary for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Ending Date Total Snowfall Dec 1 to Dec 5 Missing Count 2021-12-05 0.0 0 2020-12-05 T 0 2019-12-05 1.6 0 2018-12-05 0.0 0 2017-12-05 0.0 0 2016-12-05 0.0 0 2015-12-05 0.0 0 2014-12-05 0.0 0 2013-12-05 0.0 0 2012-12-05 0.0 0 2011-12-05 0.0 0 Time Series Summary for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Ending Date Total Snowfall Dec 6 to Dec 10 Missing Count 2021-12-10 T 0 2020-12-10 T 0 2019-12-10 0.0 0 2018-12-10 0.0 0 2017-12-10 4.6 0 2016-12-10 0.0 0 2015-12-10 0.0 0 2014-12-10 1.0 0 2013-12-10 2.1 0 2012-12-10 0.0 0 2011-12-10 0.0 0 Time Series Summary for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Ending Date Total Snowfall Dec 11 to Dec 15 Missing Count 2021-12-15 0.0 0 2020-12-15 T 0 2019-12-15 0.2 0 2018-12-15 T 0 2017-12-15 2.4 0 2016-12-15 0.4 0 2015-12-15 0.0 0 2014-12-15 T 0 2013-12-15 5.0 0 2012-12-15 0.0 0 2011-12-15 0.0 0 Time Series Summary for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Rank Ending Date Total Snowfall Dec 16 to Dec 20 Missing Count 1 2021-12-20 0.0 0 2 2020-12-20 10.5 0 3 2019-12-20 0.7 0 4 2018-12-20 T 0 5 2017-12-20 0.0 0 6 2016-12-20 2.8 0 7 2015-12-20 0.0 0 - 2014-12-20 0.0 0 9 2013-12-20 1.5 0 10 2012-12-20 0.0 0 - 2011-12-20 0.0 0 Time Series Summary for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Ending Date Total Snowfall Dec 21 to Dec 25 Missing Count 2021-12-25 0.2 0 2020-12-25 0.0 0 2019-12-25 0.0 0 2018-12-25 T 0 2017-12-25 T 0 2016-12-25 0.0 0 2015-12-25 0.0 0 2014-12-25 T 0 2013-12-25 T 0 2012-12-25 T 0 2011-12-25 0.0 0 Time Series Summary for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Ending Date Total Snowfall Dec 26 to Dec 31 Missing Count 2021-12-31 T 0 2020-12-31 0.0 0 2019-12-31 T 0 2018-12-31 T 0 2017-12-31 0.7 0 2016-12-31 T 0 2015-12-31 T 0 2014-12-31 0.0 0 2013-12-31 T 0 2012-12-31 0.4 0 2011-12-31 0.0 0