bluewave

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.

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.

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.

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.

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.

These differences in handling the short term storm details really magnifies the ensemble spread by day 10. That’s why I want to see how each individual storm verifies before looking past day 8-10. The EPS, GEFS, and GEPS all have varying solutions day 8-10.

The 12z Euro finally ejects enough energy from the SW for a more phased coastal rain and wind event on the 5th. 12z today 12z yesterday

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

I was pointing out back in the October and early November threads how the atmosphere wasn’t showing the canonical La Niña patterns. We have been experiencing these more Niño-like +AAM spikes since the fall. So I mentioned that we may not follow a typical La Niña November. This is much like the last few years with mismatched Niño and Niño-like influences at the same time. This is due to all the competing record equatorial and off equatorial SST warmth from the Indian Ocean into the Pacific.

Those long range strat forecasts for change are very uncertain given how strong the PV has been.

The OP GFS longer range has had less of a cold bias than the ensembles over SE Canada. Sometimes, the lower resolution ensembles smooth out the ridge near the near the Northeast too much. Where the OP runs don’t.

The Euro is really struggling with the split flow. Notice how much different the GFS and CMC are at day 10. Remember, the errors at day 7-10 often build into the day 11-15.

Longer range, we need to watch for the ridge east of New England verifying stronger than forecast. This has been the pattern for a while now. Today is just the most recent case. 7 day Forecast Verification

The 7-8th will depend on the evolution of the storm threat for the 5th. If the storm on the 5th is more amped, then the 7-8th could get suppressed like the CMC shows. Have to see which model gets the evolution on the 5th correct. The Euro may be struggling with hanging too much energy back to the SW again on the 4-5th.

Plenty of spread between the model guidance at 12z. UKMET and CMC are west while GFS and Euro east. Euro may be struggling with holding back too much energy to the SW again.

It has been an ongoing issue for the GEFS. I can’t wait until machine learning brings us bias corrected model guidance maps. Maybe someday we can look at day 11-15 bias corrected maps which will take long range forecasting to the next level. But that will probably require quite a bit more computer power.

The first week of December will start out milder in the Northeast than some of the guidance was indicating a week ago. New run Old run

2016 to 2018 featured great snowstorms that melted a few days later in many cases. 2014 to 2015 had long lasting snow cover but the storms weren’t as impressive in my area as 2016 to 2018. 2010-2011 was the rarest of them all with great snowstorms and long lasting snow cover. I can still remember the snow mountains from the road crews piled high near the LB Boardwalk into the spring.