bluewave

December has been one of the most challenging months for sustaining deep -NAO patterns since 2011. Pretty much the opposite of May. This is one of the reasons why we haven’t seen a repeat of record December snows from 2000 to 2010 around NYC.

Mount Mansfield off to a great start.

This is why I would much rather roll the dice with a very strong El Niño even if the winter is very warm like 23-24. We got a one week relaxation from the overpowering Northern Stream which has been dominating last 7 years. The El Niño driven Southern Stream was 2nd strongest on record for DC.

This is also a function of the weaker PNA than last December which we were both expecting. More cold available in Canada than last December. But the same stubborn storm track.

Which is better for the Great Lakes into New England. Gradients usually end up farther north than originally forecast once we get into the short term compared to the longer range forecasts. Models not varying the storm track pattern with a dominant Northern Stream.

The ensembles always show variations with week 2 forecasts. There really hasn’t been that much of a change. Still looking at a Southeast ridge or Western Atlantic ridge and a trough digging into the Baja to start December. New day 6-10 Old day 11-15

The significant trend the models have been showing for early December is more of a Southeast ridge. Of course every run is going to show the departures on any given day being a little different when we are talking week 2 modeling. Some days the ridge will pulse up and others pulse down. But the continuing very fast Pacific flow will continue to limit or storm track options at least into early December.

It’s less important what the long range models are showing since that can vary from run to run. But the long range forecast biases for each type of regime remain more constant over time. Plus the inability of the models to see seasonal repeating patterns until the actual pattern is getting close to occurring.

Same storm track pattern heading into December. Great Lakes cutter, I-78 to I-84 hugger, and suppressed Southern Stream. Plus we haven’t had a gradient pattern work for us in over a decade.

Looks a little above average but noting too extreme like I pointed out in my original post.

We haven’t had any real cold around Thanksgiving since 2018. Data for November 22, 2018 through November 23, 2018 Click column heading to sort ascending, click again to sort descending. NY PORT JERVIS COOP 4 CT DANBURY MUNICIPAL AP WBAN 6 CT OXFORD WATERBURY WBAN 6 NY WESTHAMPTON GABRESKI AP WBAN 6 NJ CHARLOTTEBURG RESERVOIR COOP 7 NY SHRUB OAK COOP 7 NY MONTGOMERY ORANGE COUNTY AP WBAN 7 NY CARMEL 4N COOP 7 CT DANBURY COOP 9 CT MOUNT CARMEL COOP 9 CT MERIDEN MARKHAM MUNICIPAL AP WBAN 10 NY WEST POINT COOP 11 NJ CALDWELL ESSEX COUNTY AP WBAN 11 NY WESTCHESTER CO AP WBAN 11 CT STAMFORD 5 N COOP 12 NY SHIRLEY BROOKHAVEN AIRPORT WBAN 12 CT GROTON NEW LONDON AP WBAN 12 NJ NEWARK LIBERTY INTL AP WBAN 13 NJ CANOE BROOK COOP 13 NJ HARRISON COOP 13 CT IGOR I SIKORSKY MEMORIAL AIRPORT WBAN 13 CT NEW HAVEN TWEED AP WBAN 13 NY UPTON COOP - NWSFO NEW YORK COOP 13 CT GROTON COOP 13 CT NORWICH PUBLIC UTILITY PLANT COOP 13 NY FARMINGDALE REPUBLIC AP WBAN 14 NJ TETERBORO AIRPORT WBAN 14 NY MATTITUCK COOP 14 NY JFK INTERNATIONAL AIRPORT WBAN 15 NY NY CITY CENTRAL PARK WBAN 15 NY CENTERPORT COOP 15 NY ISLIP-LI MACARTHUR AP WBAN 15 NY BRIDGEHAMPTON COOP 15 NY ORIENT POINT STATE PARK COOP 15 Data for November 22, 2018 through November 23, 2018 Click column heading to sort ascending, click again to sort descending. PA POCONO MOUNTAINS MUNICIPAL AIRPORT WBAN -2 NJ SUSSEX 1 NW COOP 5 NJ SUSSEX AIRPORT WBAN 6 PA SPRINGTOWN 1 NNE COOP 7 PA EAST STROUDSBURG COOP 7 PA BELTZVILLE DAM COOP 8 PA LEHIGHTON 1SSW COOP 8 NJ BELVIDERE BRIDGE COOP 8 NJ AEROFLEX-ANDOVER AIRPORT WBAN 8 NJ HIGHTSTOWN 2 W COOP 9 NJ WERTSVILLE 4 NE COOP 9 NJ SOMERSET AIRPORT WBAN 9 NJ NEW BRUNSWICK 3 SE COOP 9 PA BLUE MARSH LAKE COOP 10 PA GRATERFORD 1 E COOP 10 PA SELLERSVILLE COOP 10 PA BUCKSVILLE COOP 10 NJ FLEMINGTON 5 NNW COOP 10 NJ FREEHOLD-MARLBORO COOP 10 NJ BOONTON 1 SE COOP 10

86-87 was one of those years when the 45-“50” amounts went just to our south with the El Niño that year. Data for October 1, 1986 through April 30, 1987 Click column heading to sort ascending, click again to sort descending. SUSSEX 1 NW COOP 70.0 HIGH POINT PARK COOP 53.9 LAKEHURST NAS WBAN 53.3 ESTELL MANOR COOP 48.1 NEW BRUNSWICK 3 SE COOP 47.3 New Brunswick Area ThreadEx 47.3 POTTERSVILLE 2 NNW COOP 46.1 OAK RIDGE RESERVOIR COOP 45.5 INDIAN MILLS 2 W COOP 45.4 HIGHTSTOWN 2 W COOP 44.8

Yeah, missing data interrupts the streaks even though they continue. The only time we had some relaxation of the Northern Stream of the Pacific Jet in recent years was in mid-February 2024. That was when that really narrow snowband in association with the record El Nino STJ streak occurred. But since it was only a one week pattern in such a warm winter, there wasn’t sufficient time for follow up events to occur and end the NYC and LGA streaks. So it upped the odds of the streak continuing at spots like NYC and LGA.

It’s a function of the snow drought that we have been in over the last 7 years that the entire area hasn’t had a daily 4” snowfall. Load the dice for lower seasonal snowfall totals over time and it makes streaks like this more likely. If we had long term continuous snowfall observations at smaller sites than NYC and LGA, then I am sure other spots beyond NYC and LGA would be continuing their under 4” streak also.

It looks like the LGA daily record streak under 4” is continuing also. There may be a glitch in the program they use to calculate. Since it shows it ending last January 10th and there were no daily 4” snowfall totals after that date. But there were several daily 3.5” totals last winter. Number of Consecutive Days Snowfall < 4 for LAGUARDIA AIRPORT, NY Click column heading to sort ascending, click again to sort descending. Period of record: 1940-01-01 to 2025-11-22 1 1077 2022-01-30 through 2025-01-10 2 1051 1961-02-05 through 1963-12-22 3 761 2018-11-16 through 2020-12-15 4 746 1950-02-14 through 1952-02-29 5 744 1979-02-20 through 1981-03-04 6 743 1996-03-09 through 1998-03-21 7 742 2011-01-28 through 2013-02-07 8 715 1972-02-24 through 1974-02-07 9 701 1975-02-13 through 1977-01-13 10 690 1941-03-09 through 1943-01-27 Climatological Data for LAGUARDIA AIRPORT, NY - January 2025 Click column heading to sort ascending, click again to sort descending. Sum 1165 845 - - 1003 0 0.51 4.1 2025-01-01 52 40 46.0 9.9 19 0 T 0.0 0 2025-01-02 44 35 39.5 3.6 25 0 T 0.0 0 2025-01-03 40 32 36.0 0.3 29 0 0.00 0.0 0 2025-01-04 34 29 31.5 -4.0 33 0 0.00 0.0 0 2025-01-05 34 28 31.0 -4.4 34 0 0.00 0.0 0 2025-01-06 32 23 27.5 -7.7 37 0 0.04 0.5 0 2025-01-07 34 20 27.0 -8.0 38 0 0.00 0.0 T 2025-01-08 31 24 27.5 -7.4 37 0 0.00 0.0 T 2025-01-09 34 24 29.0 -5.7 36 0 0.00 0.0 0 2025-01-10 41 28 34.5 -0.1 30 0 0.00 0.0 0 2025-01-11 36 29 32.5 -2.0 32 0 0.02 M T 2025-01-12 43 31 37.0 2.6 28 0 0.00 0.0 0 2025-01-13 44 34 39.0 4.8 26 0 0.00 0.0 0 2025-01-14 36 26 31.0 -3.2 34 0 0.00 0.0 0 2025-01-15 33 24 28.5 -5.6 36 0 0.00 0.0 0 2025-01-16 31 25 28.0 -6.0 37 0 T T 0 2025-01-17 44 27 35.5 1.6 29 0 0.00 0.0 0 2025-01-18 46 36 41.0 7.1 24 0 0.11 0.0 0 2025-01-19 41 26 33.5 -0.3 31 0 0.18 3.6 M 2025-01-20 28 18 23.0 -10.8 42 0 T T 2 2025-01-21 20 13 16.5 -17.3 48 0 0.00 0.0 2 2025-01-22 21 13 17.0 -16.8 48 0 0.00 0.0 1 2025-01-23 30 18 24.0 -9.8 41 0 0.00 0.0 1 2025-01-24 34 25 29.5 -4.3 35 0 0.00 0.0 1 2025-01-25 33 23 28.0 -5.8 37 0 0.00 0.0 1 2025-01-26 44 32 38.0 4.2 27 0 0.00 0.0 T 2025-01-27 42 33 37.5 3.6 27 0 0.00 0.0 0 2025-01-28 42 33 37.5 3.6 27 0 0.00 0.0 0 2025-01-29 53 32 42.5 8.5 22 0 0.00 0.0 0 2025-01-30 38 26 32.0 -2.1 33 0 0.00 0.0 0 2025-01-31 50 38 44.0 9.9 21 0 0.16 0.0 0 Climatological Data for LAGUARDIA AIRPORT, NY - February 2025 Click column heading to sort ascending, click again to sort descending. Sum 1174 827 - - 810 0 2.61 7.7 - Average 41.9 29.5 35.7 -0.6 - - - - 0.3 Normal 42.7 29.9 36.3 - 804 0 2.93 9.8 2025-02-01 50 22 36.0 1.8 29 0 T 0.0 0 2025-02-02 32 18 25.0 -9.3 40 0 0.10 1.2 0 2025-02-03 49 31 40.0 5.6 25 0 T T T 2025-02-04 50 31 40.5 5.9 24 0 0.00 0.0 0 2025-02-05 37 27 32.0 -2.7 33 0 0.00 0.0 0 2025-02-06 40 29 34.5 -0.3 30 0 0.32 0.4 T 2025-02-07 45 30 37.5 2.6 27 0 0.00 0.0 0 2025-02-08 36 27 31.5 -3.6 33 0 0.58 3.5 0 2025-02-09 36 31 33.5 -1.7 31 0 0.05 0.1 2 2025-02-10 38 31 34.5 -0.9 30 0 0.00 0.0 2 2025-02-11 36 27 31.5 -4.1 33 0 0.12 1.0 1 2025-02-12 36 31 33.5 -2.2 31 0 0.10 0.5 2 2025-02-13 47 34 40.5 4.6 24 0 0.18 T T 2025-02-14 37 30 33.5 -2.6 31 0 0.00 0.0 T 2025-02-15 36 28 32.0 -4.3 33 0 0.37 0.6 0 2025-02-16 49 34 41.5 5.1 23 0 0.79 0.0 0 2025-02-17 38 27 32.5 -4.1 32 0 0.00 0.0 0 2025-02-18 28 20 24.0 -12.8 41 0 0.00 0.0 0 2025-02-19 31 18 24.5 -12.5 40 0 0.00 0.0 0 2025-02-20 30 19 24.5 -12.7 40 0 T 0.4 0 2025-02-21 35 22 28.5 -8.9 36 0 0.00 0.0 T 2025-02-22 41 22 31.5 -6.1 33 0 0.00 0.0 0 2025-02-23 47 35 41.0 3.2 24 0 0.00 0.0 0 2025-02-24 49 34 41.5 3.5 23 0 0.00 0.0 0 2025-02-25 57 43 50.0 11.8 15 0 0.00 0.0 0 2025-02-26 57 43 50.0 11.6 15 0 T 0.0 0 2025-02-27 55 40 47.5 8.8 17 0 T 0.0 0 2025-02-28 52 43 47.5 8.6 17 0 T 0.0 0

Several of us came to the conclusion that the PNA would be weaker than last December by using different methods which converged on the same solution.

Thanks for the kind words. I really enjoy our discussions over the years. My guess is that the reason for both the CCKW and MJO activity following the pattern we have been describing is the extensive +28 to +30C warm pool near the 6-7 zones on the chart that you posted. So this has been causing the looping activity on the RMM charts that we have been frequently observing over recent years. The CCKW and MJO interaction could also be why we are seeing these stronger Southeast ridge patterns than just using a straight MJO 7 composite. I was hinting at this in our recent conversation on the MJO 7 composites. Perhaps these composites lose some effectiveness since the sample size of events is smaller and merged with the CCKW interactions which has been more recent as the WPAC warm pool has been expanding. So when the forcing stalls closer to the 6-7 regions, it delays the passage into Phase 8 like we have seen so often since February 2022. Plus the continuing 6-7 area convection interferes with the typical MJO 8 composites like last January when the Pacific Jet remained rather strong due to the lingering forcing there in concert with the very strong SST gradient over the midlatitude Pacific to the east of Japan and south of the Aleutians.

Thank you for the kind words. It’s good to see that we can each use different methods and converge on similar solutions. You do a fantastic job putting together your seasonal outlooks. It’s why this extended format discussion forum is such a valuable resource bringing us all together in the same spot.

Yeah, this is what I have been discussing. The rapid warming of the WPAC tropical SSTs near the near the Maritime Continent has been stalling the MJO in the warmer storm track and background temperature phases. So the MJO progression tends to linger longer in the 4-7 phases and spend less time in phase 8. This is why January 2022 was the last time that the RMM and VP anomaly charts were both solidly in Phase 8. From March 2022 through the winter of 2024-2025 the few MJO 8s per the RMM charts had lingering forcing in phase 5-7 regions. So we didn’t fully realize the MJO 8 pattern which we last had in January 2022. Many times the models try to rush the progression through phase 8 and it gets delayed and or weakened the closer in time we get to the forecast period. This is what is shown when we subtract the last 16 years from the previous 16 years. You can see the stronger forcing closer to phases 6-7 where the warmest SSTs on earth near +30C are found during the winter. This +28C +30C warm pool has been steadily expanding across that region.

During more +PNA intervals like this fall the, the Southeast ridge was focused to the east building into Eastern New England and Canada on our 10 wettest storm days. So these frequent WAR and Southeast ridge patterns are interchangeable. They both have been leading to dominant Great Lakes cutter and hugger storm tracks whether we have had +PNA or -PNA patterns over the last 7 years since 2018-2019. 10 wettest days storm track 500 mb composite this fall around the area with dominant Great Lakes cutter and hugger storm tracks and strong +PNA WAR pattern

The long range EPS keeps underestimating that forcing in the 120E to 150E Maritime Continent regions. New run Old run

Record WPAC warm pool in conjunction with the cold over Siberia continue to create the very strong thermal gradient leading to the faster Pacific Jet and dominant Northern Stream Storm track. The tropical warm pool near the equator and the record subtropical warm pool to the east of Japan and south of the Aleutians both enhance the Southeast ridge. Plus the record Gulf Stream SSTs also contribute. Models tend to underestimate this long range influence as we are seeing with the new forecasts in early December with stronger Southeast ridge than originally forecast. Once this pattern becomes established, it can linger longer than expected as we have often seen heading into December over the last decade. New EPS forecast for December 1-8 Old EPS forecast December 1-8

It’s good that all of us using different methods had a weaker PNA for this December than the record +PNA La Niña mismatch last December following the stronger amplitude MJO 5 over +2.70 in October 2024.

I guess it will be fitting that Thanksgiving is set to follow the same windy pattern we have seen all year. Mild Great Lakes cutter storm track on Wednesday. Then strong W to NW flow on Thursday. The one hope is that the strongest winds of around 40 mph peak after parade time. But you can see this year already has double the number of 40 mph gust days as any previous year at over 60. Most of the gusts since January have occurred behind Great Lakes or hugger storm tracks on W to NW flow. The one lone coastal storm back in October was one of the few days with a NE gust over 40 mph.

The long range EPS generally underestimates the Pacific Jet and the forcing near the Maritime Continent. So both those factors lead to a stronger Southeast ridge. Plus it makes it challenging to get a clean MJO 8 pattern with forcing lingering there.