bluewave

Record low Arctic sea ice extent for the Chukchi Sea in 2019.

We had the timing down for a while now with the window around the 5-6th. Long Island typically does better than NYC in rain to snow situations. This gets reversed with snow to rain when NYC usually beats parts of Long Island.

The storm probably tracks near or maybe just south of Long Island with a change to snow at the end. Temps will be marginal for accumulations. But we could see something on the colder surfaces if it snows hard enough. Even a C-3 event would be nice before the eventual warm up around the 10th.

Even the EPS is split on track. A number of members take the low right across Long Island and others to the south.

Be careful with those Euro snowfall accumulation maps. While the NAM and other models are warmer than the Euro, the Euro is counting mixed precipitation in the mid 30’s as accumulations.

This goes to show how extreme the heatwave driving those SST’s north of Australia has been.

That rapid SST increase north of Australia near MJO 4-5 may be why some models want to linger the forcing there.

The Euro and GFS agree that the MJO could reach a 2 or greater amplitude in both phases 4 and 5. The last rime this occurred during January was 2013 and 2007. It would be nice if the February pattern improves like it did in those winters.

I am just talking about the dominant storm track. The warmth coming up was addressed in my earlier MJO posts. The mild start to January next few days is a continuation of the late December pattern. But you can see how even a less amplified MJO 4-6 warmed the recent pattern. A much more amplified and warmer MJO 4-5 pattern will begin to be felt around the 10th.

We are starting 2020 with same Pacific dominated pattern as 2019. All models have a continuation of the wet cutter and hugger storm track. This gives new meaning to a persistence forecast.

The 2010’s finish with 8 out of 10 warmer than average Decembers. 2010’s December temperature departures .............EWR....NYC....LGA 2019....+1.1....+0.8....+0.7 2018....+2.9....+2.6....+2.3 2017....-1.9......-2.5.....-2.0 2016....+1.2....+0.8....+2.1 2015...+13.3..+13.3...+12.6 2014....+3.6....+3.0....+2.4 2013...+0.4....+1.0......0.0 2012...+4.6....+4.0....+4.5 2011...+6.0....+5.8.....+5.1 2010...-3.6......-4.7......-3.2

This was the first time that we experienced 9 consecutive +NAO Decembers. Something flipped in the atmosphere following the record snows in December 2010.That was the last time NYC finished the month with 10+ inches of snow and strong -NAO. The Boxing Day Blizzard was the most recent high end KU event for the month. December NAO and NYC snowfall 2019.....+.............2.5 2018.....+0.61......T 2017.....+0.88.....7.7 2016.....+0.48.....3.2 2015.....+2.24......T 2014.....+1.86....1.0 2013.....+0.95.....8.6 2012....+0.17....+0.4 2011....+2.52.....0.0 2010.....-1.85....20.1

That’s the January MJO phase 4-5 composite. Looks like this one has a chance to go above +2 in 4 and 5. Not a surprise given the rapid warming of the WPAC. Phases 5-7 are becoming stronger and more frequent.

This was the wettest December on record at JFK. First time reaching 8.00” or more during the month. The top 3 wettest Decembers were all since 2014. Time Series Summary for JFK INTL AP, NY - Month of Dec Click column heading to sort ascending, click again to sort descending. Rank Year Total Precipitation Missing Count 1 2019 8.03 1 2 2014 7.04 0 3 2018 6.76 0

A poorly installed wind turbine blew down in the Bronx. Larchmont Harb N/A 39 N/A N/A NE38G51

Impressive looking cell for late December. Continuation of the steep midlevel lapse rates that have become more common in recent years.

With two milder days to go, all our stations will finish another warmer than average December. Not much in the way of cold across the US as the Pacific continues to dominate. Through 12-28 EWR....+0.6 NYC....+0.4 LGA....+0.2 JFK.....-0.1 BDR....+0.3 ISP.....+0.7

I would like to wait until the models get within 5 days of any potential event. Just too much volatility in these day 6-10 OP runs. Any snowfall before January 20th is a bonus. But it’s the back half of the winter that typically has our most snowfall. The only exception to the rule this decade was 10-11. NYC snowfall ............By January 19th......After January 19th 18-19....7.1......13.4 17-18....17.9....23.0 16-17....10.1....20.1 15-16....0.4......32.4 14-15....3.7......46.6 13-14....15.0....42.4 12-13....5.1.....21.0 11-12....2.9.....4.5 10-11...31.9....30.0 09-10....13.2...38.2

It’s fitting that we should get one more rain event to close out December. JFK already had its wettest December on record. You can see how wet our climate has become with the top 3 wettest Decembers since 2014. Time Series Summary for JFK INTL AP, NY - Month of Dec Click column heading to sort ascending, click again to sort descending. Rank Year Total Precipitation Missing Count 1 2019 7.17 3 2 2014 7.04 0 3 2018 6.76 0 4 1986 6.73 0 5 2009 6.25 0 6 1969 6.16 0 7 1983 6.14 0 8 1974 6.07 0 9 1948 6.05 0 10 1996 6.00 0

I try to go more by the actual VP anomalies especially with the GFS. The GFS can really struggle with those RMM diagrams. The Euro, CMC, and GFS all get the forcing over to phase 4-5 in early January. So with the lag, the MJO 4-5 influence about a week later. The ultimate amplitude of the MJO 4-5 is still uncertain. But we could be looking at mild to cold and back to mild temperature swings January 1-15. The exact change dates to be determined later. Forcing shifting to Maritime Continent in early January on the GFS

It looks like pretty good agreement between the Euro, GFS, and CMC on the MJO. Lingering mild phase 5-6 influence to start out January. Then a shift to colder a few days later after we go through phase 7-8. Followed by a shift back to mild with phase 4-5. So The January 1-15 progression should be mild...cold...mild. Exact dates of the quick transitions to be determined later. The GFS VP anomalies eventually get out of the the COD and over to 4-5 like the other models. The GFS can struggle with those RMM charts. That why I like to look at the VP anomalies.

Excellent post. That’s why the events this month were right in line in with recent experience You can see the emergence of this new pattern after 1981. But it became more pronounced in recent times.

There can be a lag between the MJO and its effects. But depending on the overall pattern, the results can be more in real time. So the mild start to January can be the continuation of this 5-6 influence. A cool down a few days later would be in line with 7 or even 8. Beyond that, a move back to 4-6 would cause another temperature rebound should the models be correct. But there is plenty of time to watch that. Don has an excellent discussion in the January thread.

The warm up was timed pretty well with the warm MJO 5-6 phases.

The clouds and higher dewpoints allowed the minimum temperature departures to exceed the maximums across the Northeast. Matches the recent theme of it being so wet. We needed that brief dry pattern in September for those record mid 90’s on October 2nd.