bluewave

The Western cluster from the EPS last Thursday did a great job. LONG TERM /FRIDAY THROUGH TUESDAY/... ...Once in a Generation Winter Storm to Slam the Region Heading into and THROUGH the Christmas Weekend... Old Man Winter will unleash the full fury of winter upon our region during this period...as an extremely amplified longwave pattern will spawn one of the most intense storm systems in decades to impact the Mid West and Great Lakes region. This system will likely end up setting low pressure records once it passes north of the border and will have the potential to generate at LEAST storm force winds over the Lower Great lakes. As if the very real threat for damaging winds of 60-70 mph were not enough...there will also be the risk for a prolonged...paralyzing heavy lake effect snow event. The very strong to damaging winds, blowing and drifting snow with localized blizzard conditions preceded by a rapid flash freeze all coming right before the Christmas holiday weekend resulted in a *long duration* winter storm watch being issued for western NY. A Winter Storm Watch has also now been issued for Jefferson and Lewis county from midday Friday through Monday. While heavy lake effect snows have already occurred this winter season...this will be the first event with multiple impacts from such intense winds. Winter storm watches are already in effect for parts of western New York with the high component wrapped into the same product. An extremely amplified longwave pattern during this period will spawn one of the most intense storm systems in decades to impact the Mid West and Great Lakes region. This system will likely end up setting low pressure records once it passes north of the border and will have the potential to generate storm force winds over the Lower Great lakes. Explosive cyclogenesis will take place over the mid western states into southern Ontario on Friday...as an anomalously strong 150kt H25 jet will pass through the base of a very deep longwave trough. This will support rapid deepening of a corresponding sfc low that will track southern Ontario by late Friday. The `bombing` low will deepen from roughly 990mb in the vcnty of Lake Erie/Lower Michigan late Thursday night...to 982mb over southernmost Ontario Friday morning to about 968mb near the Ontario-Quebec border by Friday evening... easily meeting the definition of bombogenesis (24mb/24hrs). Such deepening is relatively rare in the LOWER Great lakes...but more common across the UPPER Great Lakes and certainly with Nor`easters along the coast. Some of the parameters of this intense storm are climatologically `off the charts`...such as MSLP and strength of both the low level and upper level jets. One could certainly describe this storm system as a once in a generation type of event. Subtle differences remain...but there remains general model agreement in the overall large scale scenario...which adds confidence.

Yeah, NYC now has a 10 year average around 40° in December. It only took 30 years for us to get what used to be normal for DC in the 1990s. So we are becoming more like the Midatlantic. Monthly Mean Avg Temperature for Washington Area, DC (ThreadEx) Click column heading to sort ascending, click again to sort descending. Year Dec Season Mean 40.2 40.2 2000 31.8 31.8 1999 42.0 42.0 1998 44.4 44.4 1997 41.0 41.0 1996 43.0 43.0 1995 35.6 35.6 1994 44.2 44.2 1993 38.1 38.1 1992 39.6 39.6 1991 42.3 42.3 Monthly Mean Avg Temperature for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Year Dec Season Mean 40.6 40.6 2021 43.8 43.8 2020 39.2 39.2 2019 38.3 38.3 2018 40.1 40.1 2017 35.0 35.0 2016 38.3 38.3 2015 50.8 50.8 2014 40.5 40.5 2013 38.5 38.5 2012 41.5 41.5

The December temperatures have risen about 5 degrees since 1981.

Models have our greatest December 12 hr temperature drop on Friday. Mid 50s around 8am dropping to mid 10s by 8 pm. So a possible 40° drop. The previous record drop was 35°. https://mesonet.agron.iastate.edu/plotting/auto/?_wait=no&q=169&network=NJ_ASOS&zstation=EWR&hours=12&month=dec&dir=cool&how=exact&_r=t&dpi=100&_fmt=png

NYC will need at least 3.0” in December to have a shot at normal or better seasonal snowfall during a La Niña year. This has been the La Niña pattern going back to the 1990s. So it will be interesting to see how we do with snowfall when the month ends in around 10 days. You would think that we a least have a shot before the blocking relaxes near the end of the month. La Ninas since 1991 Monthly Total Snowfall for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Year Oct Nov Dec Jan Feb Mar Apr Season 2021-2022 0.0 T 0.2 15.3 2.0 0.4 0.0 17.9 Monthly Total Snowfall for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Year Oct Nov Dec Jan Feb Mar Apr Season 2020-2021 0.0 0.0 10.5 2.1 26.0 T 0.0 38.6 Monthly Total Snowfall for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Year Oct Nov Dec Jan Feb Mar Apr Season 2017-2018 0.0 T 7.7 11.2 4.9 11.6 5.5 40.9 Monthly Total Snowfall for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Year Oct Nov Dec Jan Feb Mar Apr Season 2016-2017 0.0 T 3.2 7.9 9.4 9.7 0.0 30.2 Monthly Total Snowfall for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Year Oct Nov Dec Jan Feb Mar Apr Season 2011-2012 2.9 0.0 0.0 4.3 0.2 0.0 0.0 7.4 Monthly Total Snowfall for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Year Oct Nov Dec Jan Feb Mar Apr Season 2010-2011 0.0 T 20.1 36.0 4.8 1.0 T 61.9 Monthly Total Snowfall for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Year Oct Nov Dec Jan Feb Mar Apr Season 2008-2009 0.0 T 6.0 9.0 4.3 8.3 T 27.6 Monthly Total Snowfall for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Year Oct Nov Dec Jan Feb Mar Apr Season 2007-2008 0.0 T 2.9 T 9.0 T 0.0 11.9 Monthly Total Snowfall for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Year Oct Nov Dec Jan Feb Mar Apr Season 2005-2006 0.0 T 9.7 2.0 26.9 1.3 0.1 40.0 Monthly Total Snowfall for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Year Oct Nov Dec Jan Feb Mar Apr Season 2000-2001 T 0.0 13.4 8.3 9.5 3.8 0.0 35.0 Monthly Total Snowfall for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Year Oct Nov Dec Jan Feb Mar Apr Season 1999-2000 0.0 0.0 T 9.5 5.2 0.4 1.2 16.3 Monthly Total Snowfall for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Year Oct Nov Dec Jan Feb Mar Apr Season 1998-1999 0.0 0.0 2.0 4.5 1.7 4.5 0.0 12.7 Monthly Total Snowfall for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Year Oct Nov Dec Jan Feb Mar Apr Season 1995-1996 0.0 2.9 11.5 26.1 21.2 13.2 0.7 75.6

It may be our best chance of putting some snow points on the board before the warm up at the end of the month. These strong -AO patterns in a December usually do better than this one has so far. It would be like leaving the bases loaded if we can’t get a least some snow before the month ends.

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.