bluewave

I mentioned that I didn’t look like Hartford would get near another 2nd snowiest snowiest first week of December. The heaviest snows will be to their northeast time time around. But shows how an unfavorable pattern like last December in NYC can produce for New England. Time Series Summary for Hartford Area, CT (ThreadEx) Click column heading to sort ascending, click again to sort descending. Rank Ending Date Total Snowfall Dec 1 to Dec 7 Missing Count 1 2003-12-07 18.5 0 2 2019-12-07 16.5 0 3 1949-12-07 12.6 0

The +PNA ridge was too flat and merged with the ridge east of New England. Plus we are coming off a record warm November. Great storm track for a change, but very limited amounts of cold air this far south. Just goes to show how New England can get by with what are negative factors for us. Forecast NYC biggest early December snowstorm composite since 2000.

Those vendors that show EPS teleconnections have their own custom indices. So they are not using the same methodology as the CPC. It’s an apples to oranges comparison. Plus they don’t have an archive of indices back to 1950 to compare against. https://ftp.cpc.ncep.noaa.gov/cwlinks/ https://www.cpc.ncep.noaa.gov/products/precip/CWlink/daily_ao_index/teleconnections.shtml

This was one of the highest daily December +PNA readings on record. It looks like it reached a +1.9. The only other years with a +1.9 that I could find were 2002 and 1989. December 2002 was a moderate El Niño and 1989 was a neutral ENSO. This would be the first for a moderate La Niña. November 2020 reached a -1.32 monthly Niño 3.4 anomaly. Both those Decembers started much colder for NYC than this year with lows under 20 during the first week. So this year is an unusually warm +PNA. This is related to the record warm November lead up to this major amplification of the ridge over Canada. There was no cold to trap underneath for us and the ridge was flatter and extended further east to the Canadian Maritimes.

We would probably need an ENSO time machine for that. https://www.news.gatech.edu/2019/11/25/el-nino-swings-more-violently-industrial-age-hard-evidence-says Blowing models away The physical proof taken from three islands that dot the heart of the ENSO zone has also thrown down scientific gauntlets, starkly challenging computer models of ENSO patterns and causes. A prime example: Previously unknown to science, the study showed that in a period from 3,000 to 5,000 years ago, the El Nino-La Nina oscillations were extremely mild. “Maybe there’s no good explanation for a cause. Maybe it just happened,” Cobb said. “Maybe El Nino can just enter a mode and get stuck in it for a millennium.”

Yeah, it looks like more of a MJO 4 pattern as the AAM and PNA falls. So we get a Niño-like to Niña-like progression this month. Something for all the different ENSO fans.

Yeah, you can see the more poleward +PNA on the NYC biggest early December snowstorm composite since 2000.

The last few years have been oddball combos of Niño and Niña-like features. This year we get the record warmth in November like the November 2015 super El Niño. Then a Niño-like +PNA to start December with a strong STJ. We finally get something resembling a BM track but with a lack of cold. I think the +PNA ridge was just too flat with Pacific air underneath instead of Arctic. This would have been a year when a cold November ahead of the storm could have worked out for us.

6z Euro if it wasn’t posted yet.

I think the main problem was all the antecedent warmth this November. So the big +PNA spike trapped the Pacific air in place. Had this November been cold like last year, the snowfall totals we are seeing to the NW on the models would be closer to the coast. But maybe we can get some flakes down to the coast at the very end of the storm.

We could get another big track jump by 0z or 12z. The ICON just came pretty far west at 18z. Maybe it will take another run or two for the models to converge.

This will be the first storm for the upgraded HRRR once we get within its effective range,

The ridge verifying stronger to our south and east than longer range model guidance has been our new normal in recent years. There have been so many week 2 forecasts that suddenly correct stronger within the day 7-10 range. It would be nice if we had bias corrected model maps to deal with this. Maybe this will be the next step in long range model forecasting. The exception to the rule is strong -AO and -NAO blocking. https://www.ecmwf.int/en/about/media-centre/science-blog/2019/will-machine-learning-replace-conventional-weather How could machine learning be used in numerical weather prediction? There are a large number of possible application areas for machine learning throughout the workflow of numerical weather prediction. Here, the “system” could be a tool to pick and bias-correct observations that are used within data assimilation; a tool to project real-world observations into a representation of variables as they are used within models; or a part of the numerical forecast model – such as the radiation scheme which predicts the heating of the atmosphere given surface temperature, cloud patterns and incoming radiation from the sun. It could also be a tool that is used in post-processing of the output of a weather forecast model, for example to detect extreme weather events in forecasts or to bias-correct forecasts for a specific location.

A different day and another set of solutions.

It did very well from Hurricane Sandy in 2012 to Nemo in February 2013. But really stumbled with the January 2015 event. It managed to do very well with Joaquin in 2015. Too suppressed with the January 2016 blizzard. Also too close to Houston with Laura. So maybe the amazing job it did with Sandy just set expectations too high. That will stand as the forecast of the century in my book.

I guess model mayhem is the end result when the pattern tries to shift from more Niño-like to more Niña-like in the same month.

I can’t remember the last time the Euro jumped around this much from run to run. Maybe one of the recent upgrades threw the model off?

The minimum temperature record was more impressive than the maximum. The max beat the DJF record by 1°. But the min beat the previous record by 5°. Time Series Summary for Caribou Area, ME (ThreadEx) - Month of Dec Click column heading to sort ascending, click again to sort descending. Rank Year Highest Min Temperature Missing Count 1 2020 50 30 2 1964 45 0 3 2003 43 0 - 1939 43 6 5 2011 40 0 - 1951 40 0 Time Series Summary for Caribou Area, ME (ThreadEx) - Month of Jan Click column heading to sort ascending, click again to sort descending. Rank Year Highest Min Temperature Missing Count 1 1950 41 0 2 1986 40 0 3 1979 38 0 - 1956 38 0 4 2008 37 0 - 2007 37 0 5 2017 36 0 Time Series Summary for Caribou Area, ME (ThreadEx) - Month of Feb Click column heading to sort ascending, click again to sort descending. Rank Year Highest Min Temperature Missing Count 1 1994 42 0 2 1970 41 0 3 1981 39 0 4 1988 38 0 5 1996 37 0 Time Series Summary for Caribou Area, ME (ThreadEx) - Month of Dec Click column heading to sort ascending, click again to sort descending. Rank Year Highest Max Temperature Missing Count 1 2020 60 30 2 1950 58 0 3 2010 57 0 4 2001 56 0 - 1969 56 0 5 2000 54 0 - 1982 54 0 - 1973 54 0 - 1966 54 0 Time Series Summary for Caribou Area, ME (ThreadEx) - Month of Jan Click column heading to sort ascending, click again to sort descending. Rank Year Highest Max Temperature Missing Count 1 2013 53 0 - 1995 53 0 2 1986 52 0 3 2018 51 0 - 2005 51 0 - 1996 51 0 - 1983 51 0 - 1950 51 0 4 2006 50 0 5 2008 48 0 - 1999 48 0 - 1945 48 0 Time Series Summary for Caribou Area, ME (ThreadEx) - Month of Feb Click column heading to sort ascending, click again to sort descending. Rank Year Highest Max Temperature Missing Count 1 1994 59 0 2 1990 52 0 - 1981 52 0 3 2018 51 0 4 2017 50 0 - 2016 50 0 5 2000 49 0 - 1988 49 0 - 1976 49 0

The persistent ridge east of New England continues to beat expectations.

All models have their individual biases. That why I pointed out the other day that the Euro was leaving too much energy back to the SW. So it’s now more phased for the 5th instead of squashing the low off the SE Coast. New run Old run

The parallel GFS is actually closer to the Euro. But it’s not quite as amped yet.

It’s a variation on the same theme. Last December 2nd had the low track just south of Long Island also. But there was more cold available to start last December than this year near the coast. It’s interesting that we are seeing a similar track almost a year to the day.

Thanks. Updated for November 2020. 11....2020...EWR....4...NYC...1....LGA....1...JFK...4...BDR...5....ISP....4

Even the EPS drops the cold into Montana in about 8-10 days. But the GEPS and GEFS dig a little more into the Rockies. Montana and surrounding areas have really been the focus of what little cold departures there have been in recent years.

First 60° temperature on record today in Caribou during meteorological winter.