bluewave

December version of the Dust Bowl.

Parts of Florida are near their peak right now.

Some NYC trees still holding onto their leaves as of a few days ago. Even here in SW Suffolk, there were a few fully leafed out trees until this past weekend. But the recent strong winds finally blew them down.

Thursday and Friday will be our annual warm up within about 5 days of the solstice. KEWR GFSX MOS GUIDANCE 12/15/2021 1200 UTC FHR 24 36| 48 60| 72 84| 96 108|120 132|144 156|168 180|192 THU 16| FRI 17| SAT 18| SUN 19| MON 20| TUE 21| WED 22|THU CLIMO N/X 46 62| 46 64| 40 44| 36 46| 25 39| 27 49| 32 45| 34 28 43

New December all-time high temperatures in Iowa.

The extremes just keep coming.

Out of season warmth, severe, and 500 mb ridges have become more common in recent years. We had our extreme winter ridge record in February 2018 with the record 80° February warmth. Now the areas to our west are setting new 500 mb height and temperature records for December. Unfortunately, the clash with the December jet stream leads to dangerous severe outbreaks.

Yeah, it’s all related. The MJO slowing in phase 6-7 this month is right over those record SSTs causing the extreme marine heatwave. In recent years during La Ninas, the most amplified MJO phase 6-7 phases were later in the winter. So this much amplitude in December is something new for us.

The very amplified and slow moving MJO is related to the extreme marine heatwave near Australia and New Zealand.

That’s for sure. More out of season severe and warmth across the country today. One of the warmest starts to December for the US averaged out.

The GEFS and GEPS pattern near the end of December is what we want to see. This is the first long range run with rising heights out West and and an improving PNA. Hopefully, we can start putting some snow points on the board near the end of December and start of January. We just need the raising heights out West and let the storm track details work themselves out in later runs.

Thanks. Our most famous version of a Pacific improvement was in 10-11. We can all remember the numerous long range snowstorms that the models were showing during the first 3 weeks of December in 2010. But the hostile Pacific resulted in only a T of snow at Newark from Dec 1 to Dec 25. The improved Pacific gave Newark a record breaking 61.5” from 12-26 to 1-27. That pattern was on track to surpass what it took 95-96 to do from November to April. But the February La Niña climo caught up with the pattern and the snows shut off. T of snow at Newark with hostile Pacific 61.5” with the big Pacific improvement

A small shift in the Pacific can make a big difference in our snowfall outcomes with -NAO and -AO patterns. Jan and Feb 2010 are probably the most extreme example of this. The NEPAC vortex in Jan was too far east so NYC only got 2.1” of snow for the month. In Feb it backed off and NYC got 36.9”. Just looking at the Greenland block both months, you would have thought that Jan would have been much better for NYC snowfall. So while the models correcting stronger on the NAO and AO block is great to see, they still have a ways to go for the Pacific to get where we want it. We need the -PNA to weaken in future runs. Since models are always a work in progress, it would be nice to see later runs come around to a more favorable Pacific. While I am always open to models getting better than they look right now, we still have the record NEPAC vortex since the fall. Hopefully, this can change in later runs. Jan 10 only 2.1” in NYC…trough near West Coast a little too strong Feb 2010 36.9” in NYC…the trough backs off slightly and allows the -NAO snd -AO block to do its thing

Thats only true for OP run storm tracks and precipitation forecasts beyond 3-5 days. The ensemble mean 500 mb and temperature patterns forecasts have been doing pretty well through 6-10 days. But the longer range 11-15 day ran too cool for our area in early December which verified warmer. The effective range for OP runs for storm tracks is only about 3-5 days. But the general ensemble means for 500 mb patterns and temperatures skill extends to 6-10 and sometimes 11-15 if we get lucky. People on these forums are well aware that extended runs beyond 15 days don’t have that much skill. But we still like to talk about them. We never use those longer range products to try to pin down individual storm tracks. I would consider a model forecast beyond 2 weeks a success if it can identify at least one teleconnection pattern that has a significant influence.

The only constant in this pattern has been disappointment when getting invested in individual model solutions for storms beyond 5 days with such a fast Pacific flow. Sometimes I wish that they stopped making operational models available beyond 120 hrs and just had ensemble means. I have no idea why they run the GFS OP beyond 10 days. This really creates more public relations issues for the NWS than it’s worth. Way too much posting of long range snowfall charts on these forums and social media. It has the effect of eroding the public confidence in the weather forecasting profession. While ensembles do well with general 500 mb and temperature patterns, operational models have almost no skill with snowfall forecasts beyond a few days.

Just returning the favor for him giving the weenie to my earlier post.

I left off last winter since the La Niña never coupled. But you can use it if you want. NYC had a snowy December and it was reflected in the seasonal totals coming in above normal. The La Niña relationship holds for JFK also. Under the 25.9” seasonal normal if they get under 3.0” in December during a La Niña. 2017….6.7….35.5 2016….3.3…30.9 2011…..0.0….3.7 2010….15.8….42.0 2008….4.9…..22.3 2007….2.4……11.7 2005….5.0…..25.4 2000….11.9…..33.8 1999….0.1……14.1 1998….2.3…..12.3 1995….10.5…69.0 1988…..0.7….8.2 1984….5.5….27.3 1983…..1.2…..22.0

If the -NAO blocks have been strong enough over the last 10 years, they have usually been able to retrograde back to the PNA region. So what the models are showing now is something different with a strong -PNA and -NAO. It’s probably related to the record NEPAC vortex since the fall. Plus the ensemble effective range is only about 2 weeks. So we are just seeing a brief model snapshot. The actual pattern will likely vary away from what may or may not look like a match from the past. Most analog matches usually occur after the fact. That’’s why using specific analogs well before the new month starts rarely works out.

We are on track for a top 10 warmest first half of December across the area. Between 6 out of the 8 top 10 warmest years occurred since the late 90s. So with the new warmer December climate normals, the stations did this with a +4 to +5 departure. EWR….+5.4 ISP…….+3.8 LGA……+4.2 Time Series Summary for NEWARK LIBERTY INTL AP, NJ Click column heading to sort ascending, click again to sort descending. Rank Ending Date Mean Avg Temperature Dec 1 to Dec 13 Missing Count 1 1998-12-13 50.6 0 2 2001-12-13 50.0 0 3 2015-12-13 49.2 0 4 1951-12-13 45.9 0 5 2021-12-13 45.7 0 - 1953-12-13 45.7 0 6 2012-12-13 44.8 0 7 1982-12-13 44.3 0 8 1999-12-13 44.2 0 - 1991-12-13 44.2 0 9 1973-12-13 43.7 0 10 1993-12-13 43.5 0 Time Series Summary for ISLIP-LI MACARTHUR AP, NY Click column heading to sort ascending, click again to sort descending. Rank Ending Date Mean Avg Temperature Dec 1 to Dec 13 Missing Count 1 1998-12-13 48.1 0 2 2015-12-13 47.7 0 3 2001-12-13 46.5 0 4 2012-12-13 43.8 0 5 1972-12-13 43.6 0 6 1991-12-13 43.5 0 7 2021-12-13 43.1 0 8 2004-12-13 42.0 0 9 1999-12-13 41.9 0 10 2011-12-13 41.6 0 Time Series Summary for LAGUARDIA AIRPORT, NY Click column heading to sort ascending, click again to sort descending. Rank Ending Date Mean Avg Temperature Dec 1 to Dec 13 Missing Count 1 1998-12-13 52.9 0 2 2001-12-13 51.7 0 3 2015-12-13 50.9 0 4 1953-12-13 48.2 0 5 1951-12-13 47.5 0 6 2021-12-13 46.7 0 7 2012-12-13 46.3 0 8 1991-12-13 45.9 0 9 1999-12-13 45.8 0 10 1948-12-13 45.5 0

No recent years going into January had anything close to that 500 mb pattern. The only January with such a prominent -EPO/-PNA/-NAO was 1969. FWIW, NYC finished at 31.8°, 1.10” of precipitation, and only 1.0” of snow. It was a very dry month. The caveats are that the extended EPS is only just a snapshot of what it’s showing from the end of December into early January. Skill falls off beyond the 2nd week.

The extended EPS is -NAO/-EPO/-PNA from late December into January. Dec 20-27 Dec 27 to Jan 3 Jan 3 to Jan 10

No doubt. We will need to weaken the -PNA enough in late December into early January for the -EPO and -NAO to work for us.

It’s easier to get pattern improvements after January 20th in El Niño years since they are back-loaded like 15-16. But we want to start putting snow points on the board by the end of December in La Ninas to reach normal snowfall. That’s why the December the 3” rule for NYC has worked out every La Niña since the 1990s. La Niña years that we have to wait until after January 20th for a decent snow like 99-00 usually underperform in the snowfall department.

There really is not set time limit on how long a pattern can last. While some patterns only last weeks, other can extend to a year or even longer. Plus you can have sub patterns existing within even larger patterns. The larger over the top warm pattern ran from last December until this November with only short breaks. This month is something new with the warmest departures to our south. So any cool down to the pattern will begin to press from the north rather than the Southeast cooling off first.

In very warm winter patterns like we have now, it usually takes a series of steps to shift the pattern to something more favorable. Some models try to rush things. So it’s often better to look at the more conservative outcomes before the pattern flips. New England usually cashes in before our area does. So that is the place to look at first if you want to start seeing more wintery outcomes. The good news is that the longer range guidance continues to indicate that the pattern right after Christmas is showing improvements.