bluewave

Happy New Year everyone. After a mild start to the year, the Euro is bringing a very intense polar vortex to SE Canada. This is due to the very strong -EPO and +PNA around day 10. So it will be interesting to track the progress of this Arctic outbreak as we get closer.

A perfect Nov to Apr -NAO /-EPO pattern with a ridge near California. Maybe Walt can comment on what the long range forecasts looked like. I really got interested in longer range forecasting after reading Walt’s great AFD’s out of the Boston NWS office in the late 90s. Probably the greatest long range AFDs in NWS history.

I would consider 95-96 a wall to wall winter. Snowstorms from late November into April and 90.75” at BNL. Even though we got that big flood cutter in late January, the monthly average temperature was below freezing.. So consistent cold and snow from the fall into the spring. BNL https://www.bnl.gov/weather/4cast/MonthlySnowfall.htm 4.5…15.5…23.5…20.0…11.25…16.0…90.75 Monthly Mean Avg Temperature for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Year Nov Dec Jan Feb Mar Apr Season 1995-1996 43.6 32.4 30.5 33.8 38.9 52.2 38.6

Hopefully, the EPS holds that 12z look going forward. It has been pretty volatile from run to run in recent days. Just goes to show important the forcing shifting east closer to phase 7-8 will be for our January snowfall potential.

Yeah, nice to see it finally roll east after being stuck for so long around those record SSTs near Australia and New Zealand. That’s why the EPS +PNA is so much better than just a few days ago. Even the CPC commented on the non canonical behavior of the recent forcing. The RMM indices indicate MJO-related convection in Phase 8, but this convection has not followed the canonical eastward propagating evolution of typical MJO events over recent weeks and may be more reflective of other tropical signals besides the MJO. Ensemble mean forecasts of the RMM indices suggest a westward retreat of the signal before weakening into the Week-2 period.

That EPS forecast is starting to look like something from late January 2015. When I made my comment about losing a favorable Atlantic the other day, it was based on the ridge being much further west in the old EPS forecast. That kind of blocking over Western North America could produce a 6”+ snowstorm in NYC even with a very +AO vortex. Old run I commented on ridge further west

The STJ may be getting a Nino-like boost with the current WWB near the dateline.

40° and warmer Decembers have become much more common in recent years.

Several stations will finish 2021 in top 5 warmest years. You can see how many top 10 warmest there have been in recent years. The minimum temperature for the year was also among the warmest on record. Time Series Summary for NEWARK LIBERTY INTL AP, NJ Click column heading to sort ascending, click again to sort descending. Rank Year Mean Avg Temperature Missing Count 1 2021 57.9 1 2 2012 57.8 0 3 1990 57.5 0 4 2020 57.3 0 - 2011 57.3 0 5 2016 57.2 0 - 1998 57.2 0 6 2010 57.0 0 - 2006 57.0 0 - 1973 57.0 0 7 1991 56.9 0 8 2002 56.5 0 - 1993 56.5 0 9 2017 56.4 0 10 1999 56.3 0 Time Series Summary for ISLIP-LI MACARTHUR AP, NY Click column heading to sort ascending, click again to sort descending. Rank Year Mean Avg Temperature Missing Count 1 2012 55.2 0 2 1998 55.0 0 3 2020 54.9 0 4 2021 54.7 1 - 2016 54.7 0 5 1999 54.3 0 6 2017 54.2 0 - 2011 54.2 0 - 1991 54.2 0 - 1990 54.2 0 7 2010 54.0 0 8 2006 53.9 0 9 2018 53.7 0 10 2002 53.6 0 Time Series Summary for NEWARK LIBERTY INTL AP, NJ - Jan through Dec Click column heading to sort ascending, click again to sort descending. Rank Year Lowest Min Temperature Missing Count 1 2002 18 0 2 2021 16 1 3 1949 15 0 - 1937 15 0 Time Series Summary for ISLIP-LI MACARTHUR AP, NY - Jan through Dec Click column heading to sort ascending, click again to sort descending. Rank Year Lowest Min Temperature Missing Count 1 2021 13 1 - 2020 13 0 - 2006 13 0

The EPS VP anomalies as of the 0z showed more motion to the east. Starts out in phase 6 next week and progresses over to phase 7 during the 2nd week of January. So it’s no surprise there is so much volatility from run to run with the NEPAC pattern.

You can see the models continuing to struggle with the forcing. The GEPS was more in phase 6 and a flatter +PNA. While the GEFS has phase 7 and stronger +PNA ridge. Just goes to show how a few degrees difference of forcing location can have such a big effect on the pattern.

Yeah, that’s exactly what a recent study found. https://www.pnas.org/content/116/11/ However, human evaluation of weather as either normal or abnormal will also be influenced by a range of factors including expectations, memory limitations, and cognitive biases. Here we show that experience of weather in recent years—rather than longer historical periods—determines the climatic baseline against which current weather is evaluated, potentially obscuring public recognition of anthropogenic climate change.

DFW just had their version of 2015 in our area beating the next warmest December by more than 7°. Time Series Summary for Dallas-Fort Worth Area, TX (ThreadEx) - Month of Dec Click column heading to sort ascending, click again to sort descending. Rank Year Mean Avg Temperature Missing Count 1 2021 61.3 2 2 1933 54.0 0 3 2015 53.6 0 4 1970 53.5 0 5 1965 52.8 0

This is the 2nd warmest December so far at Newark and Islip. NYC is sitting in 5th place with a few days to go. You can see how the majority of the top 10 warmest Decembers have occurred since the late 90s. Time Series Summary for NEWARK LIBERTY INTL AP, NJ - Month of Dec Click column heading to sort ascending, click again to sort descending. Rank Year Mean Avg Temperature Missing Count 1 2015 49.8 0 2 2021 44.2 2 3 2001 43.5 0 4 2006 43.0 0 5 1982 42.8 0 6 2011 42.5 0 7 1990 42.2 0 8 1998 41.8 0 9 1994 41.4 0 10 1971 41.3 0 Time Series Summary for ISLIP-LI MACARTHUR AP, NY - Month of Dec Click column heading to sort ascending, click again to sort descending. Rank Year Mean Avg Temperature Missing Count 1 2015 48.4 0 2 2021 41.3 2 3 2001 41.2 0 - 1984 41.2 0 4 2006 41.1 0 5 2012 40.5 0 - 2011 40.5 0 6 1982 40.1 0 - 1971 40.1 0 7 1998 40.0 0 8 1990 39.9 0 9 1994 39.7 0 10 2014 39.6 0 Time Series Summary for NY CITY CENTRAL PARK, NY - Month of Dec Click column heading to sort ascending, click again to sort descending. Rank Year Mean Avg Temperature Missing Count 1 2015 50.8 0 2 2001 44.1 0 3 1984 43.7 0 4 2006 43.6 0 5 2021 43.4 2 6 2011 43.3 0 7 1998 43.1 0 8 1982 42.7 0 9 1990 42.6 0 10 1891 42.5 0

I agree. These marine heatwaves have been interfering with the typical ENSO responses during recent winters. A marine heatwave in the WPAC didn’t allow the El Niño to couple in 18-19. The next year we had the record warm SSTs associated with the record fall IOD. Studies found that this may have contributed to the supercharged polar vortex in the 19-20 winter. Last winter the record off equator SST warmth for a La Niña prevented the expected La Niña response. So using past analogs for winter forecasts hasn’t been working out in this new marine heatwave regime.

This is more than the typical La Niña standing wave. The cat 4 marine heatwave in the area is enhancing the convection near Australia and New Zealand. So it’s no surprise that the models have been trying to decrease the convection in those areas too quickly.

Yeah, the 12z GEPS was the same as the 12 EPS at 360 hrs. Looks like a blend of phase 6 and phase 7 forcing. That’s where the standing wave has been stuck for a while now.

The convection on the 12 EPS 360 forecast is strung out across the phase 6 and 7 regions. 12z 360 hr EPS forecast

I think that you put your finger on it. The 360 hr EPS below is a La Niña phase 6 for January on the Pacific side. So it may be really struggling in where to place the convection from run to run. We probably need to see what it does in the next few runs. Image below courtesy of the New England forum

I completely understand the motivation. I don’t think most posters that leave weenies are being malicious. But it’s important to weigh the potential strengths and weaknesses of any long range projected patterns. I post some of those tweets and maps in the interest of sharing weather information. The tweets that I post contain model charts that some people don’t have access to. There are some +AAM and hi res VP anomalies charts only available with commercial subscription packages.

I wouldn’t call it that. But their have been a number of posts getting weenied over the last month for just posting model data. Now I can understand if the charts were long range GFS OP snowfall maps. But most of the posts were just 500 mb height anomaly maps discussing teleconnections. We need to take emotions out of long range model discussions.

That’s not what we were talking about.

The tweet from Matt that you weenied is still there.

The posts that you were referencing are still there. So I am not sure what you are talking about. You even posted yesterday that we may only have a short window to make something work. So if this is the case, wouldn’t you want to maximize our potential like I mentioned?

Why do you keep arguing against points that were never made? You were called out in the December thread for the same issues. Nobody has mentioned specific snowfall amounts in a forecast period beyond one week. We have been discussing which pattern combinations maximize our snowfall potential. So it’s great if we finally get some cooperation from the Pacific side. But it would be nice if it occurred while we still have some Atlantic blocking for a bigger potential. So nobody has said that all the stars need to align to get snow in NYC.