bluewave

It looks like the consolidation of the TPV between the Alaska and Greenland has moved up closer to Christmas from earlier runs which kept the ULs separate. New run Old run

Record marine heatwave this summer into fall on Hudson Bay and delayed freeze up contributing to a new Arctic sea ice low extent for December 12th. https://sites.google.com/view/arctic-sea-ice/home/nsidc-arctic https://nsidc.org/sea-ice-today/analyses/sluggish-freeze-warming-north This past summer saw an unusually early ice retreat in eastern and southern Hudson Bay. When the ice retreats early, there is more time for the ocean to absorb solar energy that otherwise would be reflected by the brighter, white sea ice. Since the sea ice had already broken up in southeastern Hudson Bay by May, ocean temperatures started to rise early, with much of southeastern Hudson Bay experiencing marine heat waves, especially in June, July, and October. A marine heat wave occurs when the sea surface temperature exceeds the ninetieth percentile for that time of year for at least five consecutive days. Between June and October, this part of Hudson Bay had experienced more than 60 percent of days with a marine heat wave—a new record. Marine heat waves can have major ecological implications, contributing to declines in species like eelgrass (Zostera marina), which play important roles in the region’s coastal and estuarine ecosystems. Since the ocean heat gained during summer must be released to the atmosphere ice before sea ice can form, the excess ocean heat is likely to delay the freeze up. This lengthens the ice-free period, with adverse consequences to the local polar bear populations as they will have to fast for a longer period. Polar bears prefer to feed by waiting on sea ice for seals to appear at breathing holes. They eat very little—basically fasting—while remaining on land in the ice-free season. A longer ice-free season means they must fast for longer. This is a concern for the southern Hudson Bay polar bear populations. Using the date of ice retreat together with the current ocean heat content, it is estimated that new ice formation may not occur until mid-December this year, which would extend the ice-free period, and hence the fasting period, to more than 190 days.

Yeah, the Niña-like forcing west of the Dateline is probably enhancing the Pacific Jet along with the strong SST gradient east of Japan. But the Nino-like forcing over the EPAC with the +AAM keeps building the +PNA ridge. So we get the ridge building out west only to pushed further east from time to time by the faster Pacific flow. Unusual split Pacific forcing pattern with both La Niña and El Niño elements at the same time

If you look at the monthly forecasts issued back on December 1st, then you will see the Aleutian Low pressing closer to Alaska with a stronger Pacific Jet than forecast. This will be evident when the next 2 weeks get averaged in with the first half of December. The models originally missed the big warm up this week with 60s. Plus they also were too cold with the warm up forecast for next week. The reason they missed the cool down before Christmas is that a piece of Pacific energy was able to make it through near Alaska and drop south. But after that the Aleutian low will move back east again for another warm up near or after Christmas. So the much faster Pacific Jet has been the one common denominator.

The main difference back then is NYC didn’t have 3 consecutive Decembers with under 1” of snow like they did in 2021,2022, and 2023. Time Series Summary for NY CITY CENTRAL PARK, NY - Month of Dec Click column heading to sort ascending, click again to sort descending. 2023 T 0 2022 T 0 2021 0.2 0 2020 10.5 0 2019 2.5 0 2018 T 0 2017 7.7 0 2016 3.2 0 2015 T 0 2014 1.0 0 2013 8.6 0 2012 0.4 0 2011 0.0 0 2010 20.1 0 2009 12.4 0 2008 6.0 0 2007 2.9 0 2006 0.0 0 2005 9.7 0 2004 3.0 0 2003 19.8 0 2002 11.0 0 2001 T 0 2000 13.4 0 1999 T 0 1998 2.0 0 1997 T 0 1996 T 0 1995 11.5 0 1994 T 0 1993 6.9 0 1992 0.4 0 1991 0.7 0 1990 7.2 0 1989 1.4 0 1988 0.3 0 1987 2.6 0 1986 0.6 0 1985 0.9 0 1984 5.5 0 1983 1.6 0 1982 3.0 0 1981 2.1 0 1980 2.8 0

Nice to see some areas with more than 5.00” since November 20th. Data for November 20, 2024 through December 13, 2024 Click column heading to sort ascending, click again to sort descending. NY SEAFORD 0.4 SE CoCoRaHS 8.36 NY MOUNT SINAI COOP 6.83 NY ST. JAMES COOP 6.54 NY BAITING HOLLOW COOP 6.48 CT GUILFORD COOP 6.27 NY RIVERHEAD RESEARCH FARM COOP 6.20 NY CENTERPORT COOP 6.16 NY UPTON COOP - NWSFO NEW YORK COOP 6.06 NY BRIDGEHAMPTON COOP 5.89 CT DANBURY COOP 5.81 NY NESCONSET 1.4 SSW CoCoRaHS 5.78 CT GROTON NEW LONDON AP WBAN 5.70 CT NEW CANAAN 1.9 ENE CoCoRaHS 5.67 NY ORIENT POINT STATE PARK COOP 5.60 NY CENTERPORT 1.1 SE CoCoRaHS 5.56 CT NORWICH PUBLIC UTILITY PLANT COOP 5.56 NY ISLIP-LI MACARTHUR AP WBAN 5.54 NJ HARRISON COOP 5.43 NY NEW WINDSOR 3.3 W CoCoRaHS 5.41 NY SHIRLEY BROOKHAVEN AIRPORT WBAN 5.31 NY PORT JEFFERSON STATION 0.3 SSW CoCoRaHS 5.25 CT NORWALK 2.9 NNW CoCoRaHS 5.14 CT FAIRFIELD 1.5 NE CoCoRaHS 5.13 CT STAMFORD 1.0 S CoCoRaHS 5.08 CT DARIEN 3.6 N CoCoRaHS 5.05 CT STRATFORD 0.9 W CoCoRaHS 5.05 NY ALBERTSON 0.2 SSE CoCoRaHS 5.02 NY THORNWOOD 0.7 NW CoCoRaHS 5.01

The Aleutian Low keeps verifying further east than the long range forecasts have been indicating with the faster Pacific Jet.

Very fast Pacific flow continues. Warm up next week followed by a cool down before Christmas. Then another warm up near to after Christmas. Looks like the TPV may be trying to consolidate at that time with a +EPO +AO.

All the guidance is starting to show a warmer +EPO +AO pattern in later December as it looks like the TPV is trying to consolidate.

Such a strong near record high would have been much colder in the old days. But it should still be a good radiational cooling event for the usual spots around the Northeast. Feb 34 was a 1050 mb high just north of Cleveland.

While these storms moving across the Great Lakes aren’t a great pattern for snow near the coast, we really do need the rain.

All we are seeing on the guidance is the ridge axis shifting east and pulling back west every 3-4 days or so. So we warm up ahead of the storm systems and then we cool down after they go past. It’s tough for the models to see the individual shortwaves in the longer range moving through the fast flow. So the timing of the ridges and troughs will probably be off the further out in time you go.

While we have been able to sustain the +PNA as the ridge axis pushes east and pulls back at times, the ridge can’t retrograde enough to keep the EPO negative with such a fast Pacific Jet.

We would all be much better off it they just made the OP runs available to 168 hours and everything beyond that time ensemble means.

But a storm signal doesn’t equal big snowstorm along the coast.

Great example of a long range OP GFS outlier run among its ensemble mean.

Between 09-10 and 17-18 the Pacific Jet was much weaker. So we didn’t get the constant parade of storms cutting through the Great Lakes and hugging the coast that has been dominant since 18-19. When the Pacific Jet was weaker, we could get even get cold storm tracks in warm patterns. Meaning the Pacific was able to relax enough to allow a clean benchmark track with no weak lows over the Lakes. These days even benchmark tracks can have a weak low over the Lakes which warms the airmass too much ahead of the low pressure formation to our Southeast. Now we get warm storm tracks even during shorter cold intervals like we had in early December. Warm up ahead of the storm and cool down behind. The reason the snowfall has been so low in the 2020s is that we are getting both warm winters and warm storm tracks. Much stronger Pacific Jet since 18-19

I just said it that way since the wave break which is initiating the NAO shift is originating near the East Coast.

It could just be something as simple as the much warmer Gulf Stream east of the Carolinas leading to a stronger Western Atlantic Ridge. The big Western Atlantic Ridge amplification last few days with 60s into the Northeast is preceding the NAO rise going forward. Higher heights near the East Coast usually leads to a trough formation several days later near Icekand.When we had the trough near the East Coast in early December heights were higher near Western Europe and Iceland.

Those were the days with extended December cold when we could get the whole month averaging around 32°. Now all our Decembers are in the upper 30s or the 40s. While we did get some real cold before Christmas 2022 with the NYC single digit lows, there was near 60° warmth before and after so the month on average was still 38.5°. Data for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. 2022-12-23 58 8 -4.1 2022-12-24 15 7 -25.9 2022-12-25 28 14 -15.7 2022-12-26 29 18 -12.9 2022-12-27 35 29 -4.2 2022-12-28 47 33 4.0 2022-12-29 51 40 9.7 2022-12-30 62 46 18.4 2022-12-31 55 50 17.1

Overall a nice event to start weakening the drought with 1-2 west of NYC and 2-4 east.

It will be interesting to see what happens. My one concern is that the MJO is currently contributing to the pattern rather than running it. We continue to get more of an El Niño influence blending in with the EPAC forcing. While the CFS and EPS have more of a MJO 7 look in early January, the GEFS looks different. So the GEFS doesn’t have a clean MJO signal like the EPS and CFS. Not sure which way it will go at this point since competing influences make the very long range more uncertain. Plus you can see some La Niña influences in the GEFS.

It’s only seasonable since the new 30 year climate normals around NYC are close to 40° in December. Back in the old days seasonable was closer to the mid 30s. We used to get a really cold December around or below freezing once every 5 to 10 years . Now we will make it 14 years without a really cold December.

Looks like the fast Pacific flow continues until further notice. Warm ups ahead of the Great Lakes lows and cool downs behind the storms. This could be a -1 to +1 month that doesn’t get decided + or - until New Year’s Eve.

The WAR was much stronger than forecast back around the start of December. But the Pacific Jet has been very fast also. So the trough couldn’t go negative tilt fast enough for areas west of NYC to get the heavier rains that Long Island is getting. Very northern stream dominant pattern.