bluewave

The big question is whether we can get a strong enough WWB this winter in order to initiate a large enough oceanic kelvin wave so we go back into El Niño by the summer? If not then we would probably see next winters La Niña stronger than this winter as the SSTs with this one are really struggling against the record warm global background state. Still too early to know which way it will go.

The December pattern this year is a first for any El Nino to La Niña transition regardless of strength.

I was discussing the mismatch potential back in October when the early MJO indicator came in similar to December 2020, 2017, and 2010. But I also mentioned at the time that the La Niña was much weaker than those past instances so there could be issues with the comparison past December La Niña mismatch events. While we got the +PNA this month, the Pacific Jet was much stronger than the previous mismatch Decembers. So the ridge axis keeps shifting into the East instead of staying anchored near the West Coast. The faster Pacific Jet is probably related to the WPAC record warmth and forcing competing with the +AAM influence and EPAC forcing. So it’s as if we have an El Niño pattern interfering or running concurrently with La Niña conditions.

It’s more about the northern stream being too dominant than timing. We were better off last February with the borderline super El Niño. At least some spots were able to go over 10” on the season due to the STJ being able to dominate over the northern stream for about a week.

The coastal could be too suppressed. But even a northward correction in later runs would be an issue along the coast with the low in the Great Lakes instead of a cold high.Very difficult to pull off a good thread the needle along the coast with such a fast northern stream Pacific flow.

The 12Z Euro is even more northern stream dominant with stronger low in the Great Lakes.

It’s been challenging to get these type of thread the needle events to work out near the coast when we have low pressure in the Great Lakes instead of a cold high.

Need to lose that low over the Great Lakes which is eroding the cold high on the GEFS mean as it would probably lead to P-Type issues near the coast should it trend stronger in later runs like the CMC and 0z Euro.

Yeah, it’s a good question. 2010 to 2018 featured continuous benchmark tracks with blizzards even in warm patterns like in 16-17. But something changed in 18-19 when NYC started getting warm storm tracks even in cold patterns.

December 2022 was the last below normal average December temperatures with the single digit lows before Christmas.

Not surprising given how dominant the Pacific Jet is with the very fast zonal flow. Most of the storm tracks in this regime are cutters or huggers. In the old days we used to get more clippers diving south of NYC. These days we hardly ever see this track.

Back and forth pattern until further notice. Day 1-5 warm up followed by 6-10 cool down. Then a 11-15 warm up.

If the EPS and GEFS are correct, then we could see another round of strong EPAC WWBs like we had back in November last week of December. So there could be more EPAC warming around 1+2 into January. Maybe more of a west based La Niña pattern in terms of SSTs since the trades should be stronger initially near the Dateline.

The pattern leading up to the record high was one of the coldest we have seen. It was the last time that NYC averaged under 30° from 12-01 to 2-13. So these record highs in the past have usually come near the peak or end of very cold patterns. This time North America had one of its warmest falls without time to build any record breaking cold around our area. I guess this one was more like December 1949 when NYC got the monthly record high pressure for December. That was a very mild December by those standards. February 1934 had a 1050 mb high to our north with historic cold. January 1994 also had a 1050 mb high to our north and was one of our coldest January patterns since the 1980s. Time Series Summary for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. 1 1918-02-13 23.9 0 2 1881-02-13 25.7 0 3 1977-02-13 26.8 0 4 1920-02-13 27.4 0 5 1873-02-13 27.5 0 6 1904-02-13 27.6 0 - 1875-02-13 27.6 4 7 1883-02-13 27.8 0 8 1936-02-13 28.0 0 9 1888-02-13 28.1 0 10 1877-02-13 28.3 0 11 1893-02-13 28.4 0 12 1948-02-13 28.6 0 - 1905-02-13 28.6 0 13 1961-02-13 29.1 0 14 1945-02-13 29.2 0 - 1887-02-13 29.2 0 15 1884-02-13 29.4 0 16 1872-02-13 29.5 0 17 1981-02-13 29.6 0

NYC will approach its all-time record high pressure tomorrow but probably come up just short. Models have near a 1048 mb pressure or 30.95 inches of mercury. The all-time record was 1052 mb or 31.08 inches of mercury set on 2-13-81. https://www.weather.gov/media/okx/Climate/CentralPark/extremes.pdf https://www.weather.gov/epz/wxcalc_pressureconvert

Along with the record warm water temperatures in the Great Lakes, it has had a moderating influence on the cold in the Northeast.

More a recognition of what the Pacific has been doing since the 18-19 winter than being jaded.

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.