bluewave

Which has been the case this year so far leading to much warmer than expected conditions than we typically see from such strong El Niños.

February 2025 was the exception when the Southeast Ridge verified much stronger right around storm time leading to the record snows ending up near Toronto.

It will be interesting to see if the new PBC EPS weeklies actually can do better than just defaulting to climatology after 15 days.

We are just going to have to wait until we get through December and January to see what happens in February. The issue with the seasonal models is that they default to an El Niño climatology package in February which incudes many weaker events. 2023-2024 and 1997-1998 didn’t necessarily follow the typical February climatology. This event is much stronger than both of those so we should probably keep expectations low and if we do better than those two years in February it’s a nice surprise.

These October Ural to Scandinavian blocks have become the new normal especially in October in the low Arctic sea ice era since 2007.

These strong Scandinavian-Ural blocks have become fairly common post 2007 with the record low Arctic sea ice state. We also saw this late October into early November SPV weakening and bounce back pattern in 2021 and 2022. But as always it’s the Pacific which has the final say.

Beyond 15 days the weeklies have been defaulting to El Niño climatology. The forecast from the start of October illustrates this point. Hopefully, they start releasing the new bias corrected versions of the weeklies to the public so we can see how much skill they have compared to uncorrected version. Notice how more of a spilt low pattern between the Aleutians and California developed than the default to October El Niño climatology. New October 19 to 26 forecast Old forecast defaulted to October El Niño climatology

Just remember that a weaker SPV was also a feature with the 1997-1998 event. There was also an impressive area of stratospheric warmth above the Urals to Barents region. It’s the overpowering Pacific which is the main feature when east based El Niños get this strong. So it’s not uncommon to see this during super El Niño events as we also had something similar with the weaker 2023-2024 super El Niño.

You can see on days like today when the cooling influence of the offshore flow wanes we are right back to upper 60s to near 70° in spots.

The model did a good job with the general 500mb pattern forecast. Notice the ridge axis is actually now expected to be more amplified over the Great Lakes. But we got the low off the East Coast keeping our flow more onshore. So more of an Omega pattern than originally forecast. Also another El Niño feature. Once the low to our east moves out in late October, it will allow the ridging to shift closer to our area. But with the high east of New England, we could still see some onshore flow. With the trough getting stronger out West in response to the El Niño, it should mean a warmer pattern for us heading into late October and early November. The average split for late October and early November is around 60/43 at EWR. So any day with highs into the mid-60s and lows near 50° is considered warmer. New run Old run

Yeah, I only posted the guidance for the next 15 days along with actual pattern for the month so far. The AIFS-ENS has been doing very well with both the 500mb and storm tracks including hurricanes. The EPS weeklies beyond 15 days and other guidance is lower skill. But they have developed an AI bias corrected version (PBC) of the EPS weeklies that they claim has better scores than the weeklies do. I will post some forecast images from this new AI bias corrected EPS weeks 2-6 when and if they become available to the general public. https://www.nature.com/articles/s41586-026-11126-x?utm_source=x&utm_medium=social&utm_campaign=nature&linkId=64119704 Decision-makers rely on weather forecasts to plant crops, manage wildfires, allocate water and energy and prepare for weather extremes1,2,3. Today, such forecasts enjoy unprecedented accuracy as far as 2 weeks thanks to steady advances in physics-based dynamical models and data-driven artificial intelligence models4,5,6,7,8,9,10. However, model skill drops precipitously at subseasonal timescales (2–6 weeks ahead) due to compounding errors, systemic model biases and the chaotic nature of the atmosphere11,12,13,14,15. To counter this degradation, we introduce probabilistic bias correction, a machine learning framework that substantially reduces systematic error by learning to correct historical probabilistic forecasts. When applied to the leading dynamical and artificial intelligence models from the European Centre for Medium-Range Weather Forecasts (ECMWF), probabilistic bias correction doubles the modest subseasonal skill of the AI Forecasting System16 and improves the skill of the operationally debiased dynamical model17 for 91% of pressure, 92% of temperature and 98% of precipitation targets.

Looks like a fairly average temperature pattern over the next 5-10 days. As the historic El Niño continues to intensify, the ridge axis is forecast to shift closer to our area. So the core of the warmth which has been to our west in early fall is forecast to shift east from late October into early November.

Same general theme with more amplitude and warmth potential.

The models are developing two upper low pressure centers in the North Pacific as we head into late October. One area of lower pressures has already been developing over the Bering Sea through the first 16 days of October. The next center is forming over California and the Baja. My guess is that the stronger mid-latitude pattern which has been keeping the big ridge east of Japan is currently overlapping with the super El Niño forcing. Almost like a filter if you like. So this leads to the persistent -PDO that we have been experiencing instead of a +2.00 PDO which we would normally be getting with such a strong El Niño and +PMM. With such an historic east based event, the trough getting pushed into the West Coast will cause the Nino ridge to persist from the Upper Plains across the Great Lakes and into the East. October 500 mb pattern through the 16th Forecast into late November

The forcing has had more of an eastward lean than 1997 did so far. Notice especially how much stronger the forcing was during the Southern Hemisphere winter closer to the West Coast of South America. Also the extension of the forcing into the Southwest CONUS has been stronger early on than 1997. This make sense it’s the most east based event on record so far.