bluewave

Maybe we are moving in the direction of making some small improvements on that front if the claims about this new AI corrected version of the EPS weeklies turn out to be correct.

Near record upper low off of Southern California matches with the extreme east based forcing leading to the ridge shifting into the East later in October.

MPO had some of the warmest departures in the area due to the much higher minimums. CLIMATE REPORT NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 152 AM EDT WED OCT 21 2026 ................................... ...THE MOUNT POCONO PA CLIMATE SUMMARY FOR OCTOBER 20 2026... CLIMATE NORMAL PERIOD: 1991 TO 2020 CLIMATE RECORD PERIOD: 1901 TO 2026 WEATHER ITEM OBSERVED TIME RECORD YEAR NORMAL DEPARTURE LAST VALUE (LST) VALUE VALUE FROM YEAR NORMAL ................................................................... TEMPERATURE (F) YESTERDAY MAXIMUM 65 3:31 PM 75 1963 56 9 59 MINIMUM 44 11:59 PM 18 1972 37 7 44 AVERAGE 55 46 9 52 CLIMATE REPORT NATIONAL WEATHER SERVICE NEW YORK, NY 227 AM EDT WED OCT 21 2026 ................................... ...THE KENNEDY NY CLIMATE SUMMARY FOR OCTOBER 20 2026... CLIMATE NORMAL PERIOD 1991 TO 2020 CLIMATE RECORD PERIOD 1948 TO 2026 WEATHER ITEM OBSERVED TIME RECORD YEAR NORMAL DEPARTURE LAST VALUE (LST) VALUE VALUE FROM YEAR NORMAL ................................................................... TEMPERATURE (F) YESTERDAY MAXIMUM 71 254 PM 81 1969 63 8 68 MINIMUM 48 449 AM 32 1952 48 0 55 AVERAGE 60 56 4 62

The BOM RONI values in the East getting close to +6 are more in line with the ONI numbers.

The modoki-style forcing out near the Dateline following the shutdown of the MJO 5 forcing which drove the record warmth in December. The hand-off of the forcing from the MC to the DL caused the whole pattern to invert from December to January. This allowed the NP low to back off in the Pacific from late January into early February.

The latest first freeze for LGA which is the UHI capital was 1-4-16. NYC snuck one in on 11-24-15. The average first freeze for LGA since then has been 11-30 and NYC 11-20. Frost/Freeze Summary for LAGUARDIA AIRPORT, NY Each section contains date and year of occurrence, value on that date. Click column heading to sort ascending, click again to sort descending. 2015 03-29 (2015) 27 01-04 (2016) 15 280 2001 03-28 (2001) 31 12-23 (2001) 32 269 1998 03-22 (1998) 31 12-22 (1998) 24 274 2021 04-02 (2021) 29 12-19 (2021) 31 260 Data for November 24, 2015 through November 24, 2015 Click column heading to sort ascending, click again to sort descending. NY MONTAUK AIRPORT WBAN 37 NY SETAUKET STRONG COOP 35 NY LAGUARDIA AIRPORT WBAN 33 NY NY CITY CENTRAL PARK WBAN 32 NY JFK INTERNATIONAL AIRPORT WBAN 31 Frost/Freeze Summary for LAGUARDIA AIRPORT, NY Each section contains date and year of occurrence, value on that date. Click column heading to sort ascending, click again to sort descending. Minimum 03-01 (2020) 11-08 (2019) 226 Mean 03-25 11-30 249 Maximum 04-06 (2016) 01-04 (2016) 281 2025 03-23 (2025) 32 12-04 (2025) 25 255 2024 03-24 (2024) 32 11-30 (2024) 32 250 2023 03-30 (2023) 32 11-25 (2023) 32 239 2022 03-30 (2022) 30 11-19 (2022) 32 233 2021 04-02 (2021) 29 12-19 (2021) 31 260 2020 03-01 (2020) 26 12-08 (2020) 32 281 2019 03-13 (2019) 32 11-08 (2019) 31 239 2018 04-02 (2018) 32 11-15 (2018) 30 226 2017 03-23 (2017) 26 11-10 (2017) 27 231 2016 04-06 (2016) 32 12-09 (2016) 32 246 2015 03-29 (2015) 27 01-04 (2016) 15 280 Frost/Freeze Summary for NY CITY CENTRAL PARK, NY Each section contains date and year of occurrence, value on that date. Click column heading to sort ascending, click again to sort descending. Minimum 03-01 (2020) 10-31 (2020) 218 Mean 03-28 11-20 236 Maximum 04-10 (2016) 12-09 (2016) 250 2025 04-09 (2025) 31 11-29 (2025) 32 233 2024 03-24 (2024) 31 11-30 (2024) 30 250 2023 03-30 (2023) 31 11-25 (2023) 30 239 2022 03-30 (2022) 29 11-19 (2022) 31 233 2021 04-03 (2021) 32 11-23 (2021) 32 233 2020 03-01 (2020) 25 10-31 (2020) 32 243 2019 03-18 (2019) 32 11-08 (2019) 29 234 2018 04-09 (2018) 32 11-14 (2018) 32 218 2017 03-23 (2017) 23 11-10 (2017) 25 231 2016 04-10 (2016) 31 12-09 (2016) 29 242 2015 04-01 (2015) 32 11-24 (2015) 32 236

Centered right under Nino 3 at +4.47 now. Starting to see a +30C warm pool bridge develop from Nino 3.4 over to the coast of Central America. Matches up with the record east based forcing for so early in an event.

Looks like as we head into late October the expression of ENSO becomes more of split North Pacific low between the Bering Sea and Southern California. It will be interesting to see if these centers can eventually merge into one giant low as we head into November and December. If some semblance of a split remains, then it would be indicative of the background 500mb pattern which has been keeping the PDO negative instead of leading to a +2.00 PDO.

Which has been the case this year so far leading to much warmer than expected conditions across the CONUS 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.

January 1998 had dual forcing with one cell in Nino 3.4 and another near 1+2. The dominant forcing wound up shifting more eastward back to 1+2 in February. Both months were equally as warm. So we are just going to have to wait and see how the finer details within this much stronger historic event work out.

This developing historic El Niño has had a much stronger ridge sitting to our west in the means since last spring than we have seen before for the early development time period. Toward the end of the month the ridge begins shift eastward closer to the Northeast. The further east ridge axis is typically what we see from super El Niño events in the past heading into later fall and the winter.