GaWx

The GEFS NAO prog continues to correct to more positive. Check out how much it has risen over the last 8 forecast days: Oct. 13th fcast mean had it never getting >+1 and that on Oct. 15th with it later down to sub -0.8 for 6 days with it continuing through end of forecast period; It had Oct. 27th down at -0.9: Today’s forecast is so much more positive: it actually peaked way up at +1.73 on Oct 19th and with forecast now dipping only to -0.7 on Oct 22nd followed by a sharp rise to +0.8 on Oct 27th (vs the Oct 13th run having it down at -0.9): Per @Stormchaserchuck1this solidly +NAO in Oct. is actually a good sign if one wants the chance for a -NAO domination in winter to increase. I’m just passing that along as it isn’t my own idea. Forecast models are suggesting a good chance of a -NAO in Feb, regardless. Before that will be tough imho due to at least solar but we’ll see.

Absolutely that can happen with how E based it is progged to be! This is especially the case for Feb as the CFS has been showing. I’m expecting a very mild Dec and a mild to NN first half of Jan. Then the fun times could really get going starting late in Jan and especially in Feb and possibly continuing through early March.

The CFSv2 for the last 2 months worth of daily 10 day mean runs has been persistent in showing Feb ‘27 to have an extreme couplet of a much warmer than normal E Canada and a cold dominant CONUS. No other mid-Oct. 10 day CFSv2 mean (back to 2012, its first one) has shown anything anywhere close to this, which has not only 80% of Conus BN but also a very mild E Canada acting as a very strong block: In this post in the main forum, I compared this mid-Oct CFSv2 forecast to all other CFSv2 mid-Oct forecasts for Feb (back to first one for Feb ‘12) and its implications regarding what may actually happen in Feb ‘27: Aside: @buckeyefan1would you mind pinning this winter outlook thread? It is getting relatively little viewing and thus few posts (only 50 in 6 months) due to being so far down on the topics list even after a recent post since 5 other threads have already been pinned.

Anthony, Maybe this person saw this latest 10 day CFSv2 mean for Feb ‘27 (Nino): 80% of CONUS BN; much AN E Canada: No other mid Oct 10 day mean for Feb back to 2012 has had anything even closely resembling this extreme couplet, and a cold dominant Feb US/much warmer than normal E Can have been on EVERY 10 day mean since they started going out that far in mid August! Check out how much Feb of ‘27 differs from all other 10 day mean forecasts made in mid-Oct for other Febs back to the start of the CFSv2: 2026: 1% of CONUS BN; BN E Can: 2025: 0% of CONUS BN; BN E Can 2024 (Nino): 0% of CONUS BN; AN E Can 2023: 33% of CONUS BN; BN E Can 2022: 6% of CONUS BN; BN E Can 2021: 20% of CONUS BN; BN E Can 2020: 1% of CONUS BN; BN E Can 2019 (Nino): 5% of CONUS BN; BN E Can 2018: 20% of CONUS BN; BN E Can 2017: 3% of CONUS BN; BN E Can 2016 (Nino): 4% of CONUS BN; AN E Can 2015 (Nino): 0% of CONUS BN; BN E Can 2014: 4% of CONUS BN; BN E Can 2013: 1% of CONUS BN; BN E Can 2012: 15% of CONUS BN; BN E Can Feb: % BN Conus; E Can anom ‘27 (Nino): 80% BN US; much AN E Can ’26: 1% BN US; BN E Can ’25: 0% BN US; BN E Can ’24 (Nino): 0% BN US; AN E Can ’23: 33% BN US; BN E Can ’22: 6% BN US; BN E Can ’21: 20% BN US; BN E Can ’20: 1% BN US; BN E Can ’19 (Nino) 5% BN US; BN E Can ’18: 20% BN US; BN E Can ’17: 3% BN US; BN E Can ’16 (Nino): 4% BN US; AN E Can ’15 (Nino): 0% BN US; BN E Can ’14: 4% BN US; BN E Can ’13: 1% BN US; BN E Can ’12: 15% BN US; BN E Can ————————————— Analysis of above: -Feb of ‘27 80% BN US vs only 33% (‘23) for next closest! Avg of only 7.5% BN US for 2012-26 and a mere 2% BN for the four El Niño cases! -The other 4 Nino Febs had no more than 5% BN US! The two strongest Nino Febs had US BN of 0% (‘24) and 4% (‘16)! So, there’s virtually no resemblance to ‘27. -BN in the SE US virtually nonexistent on any of 2012-2026 with most of them mild. But in stark contrast, 2027 has a very cold SE! -Feb of ‘27 has by far the warmest E Can. Only 2 others had any degree of AN (much less intense than ‘27) and they were the 2 strongest El Niños (‘24 and ‘16). —————— In closing, Feb of ‘27 has been very persistently (for 2 months!) showing on the CFSv2 a highly unique (among all Febs on record) extreme couplet of a cold dominant CONUS and extreme blocking/very warm E Canada. The CFSv2 has been trying to tell us something it never has and though I’m not at all saying to trust it, I am suggesting that it not be dismissed.

The latest CFSv2 10 day mean prog for RONI for Oct is +2.5 and for Nov is +2.75. The current record high for any month since 1950 is the +2.5 of Jan of 1983. Judging by the blue lines all being at or below +2.75, this graph’s +2.75 mean for Nov is likely heading down in future 10 day runs. @40/70 Benchmark’s prediction for RONI is looking pretty good: https://www.cpc.ncep.noaa.gov/data/indices/Rnino34.ascii.txt

Today’s Euro Weeklies 10 mb zonal mean wind prog is even weaker than yesterdays, which had its lowest at 14 m/s, with it down to 12 m/s:

Today’s GEFS NAO forecast is even more positive than yesterdays, which itself was much more + than last week’s GEFS: Today: gets down to only -0.6 and then quickly rises to +0.5 followed by drop back to 0: Yesterday: Last week:

Agreed

The most similar that I found to what the Euro Weeklies are forecasting late Oct-late Nov were 2016-7, 2009-10, and 1979-80 with the last two being El Niños: 2016 La Niña: similar late Oct/early Nov though late Nov weaker 2009 El Niño: not as weak late Oct/early Nov and weaker mid Nov vs 2026 (dip ~2 weeks later than 2026) 1979 El Niño: not as weak late Oct but early to mid Nov similar to 2026 although late Nov much weaker vs 2026

Are you asking for the record relative trimonthly 3.4? Or the record relative weekly 3.4? Weekly record of relative 3.4 is +2.9 (12/29/1982) Trimonthly RONI record is +2.40 in DJF 1982-3.

Yesterday’s NOAA official relative weekly SSTa update for last week had this: note the 0.3 cooling in Nino 4 to -0.1 and that 3.4 stayed at +2.4: 07OCT2026 4.4 3.4 2.4 0.2 14OCT2026 4.4 3.5 2.4 -0.1 https://www.cpc.ncep.noaa.gov/data/indices/rel_wksst9120.txt

This is now Invest 93L. 0Z UKMET almost gets to H strength: TROPICAL STORM 93L ANALYSED POSITION : 35.0N 70.7W ATCF IDENTIFIER : AL932026 LEAD CENTRAL MAXIMUM WIND VERIFYING TIME TIME POSITION PRESSURE (MB) SPEED (KNOTS) -------------- ---- -------- ------------- ------------- 0000UTC 20.10.2026 0 35.0N 70.7W 1004 37 1200UTC 20.10.2026 12 35.2N 70.5W 998 40 0000UTC 21.10.2026 24 35.5N 69.8W 998 45 1200UTC 21.10.2026 36 36.2N 69.5W 995 40 0000UTC 22.10.2026 48 36.9N 69.7W 989 51 1200UTC 22.10.2026 60 38.1N 68.1W 982 52 0000UTC 23.10.2026 72 39.4N 63.9W 975 63 1200UTC 23.10.2026 84 42.8N 56.7W 975 57 0000UTC 24.10.2026 96 45.9N 51.6W 986 54 1200UTC 24.10.2026 108 46.7N 48.5W 992 45 0000UTC 25.10.2026 120 48.0N 42.4W 991 45 1200UTC 25.10.2026 132 54.1N 32.9W 980 40 0000UTC 26.10.2026 144 CEASED TRACKING

Indeed as it on today’s Euro Weeklies gets down to +14 in early Nov, weakest run yet. Nothing earth shatteringly weak but interesting, regardless:

Look how much the forecasted mean GEFS NAO has risen from its Oct 13th forecast to today’s forecast! Oct 13th: peaking at only +1.0 on Oct 15th and then plunging to -1/remaining down at -0.9 on Oct 27th: Today’s prog (Oct 19th): peaked not til today way up at +1.73 and already after a dip to -0.8 back up to ~0 on Oct 27th: I’m assuming this drastic change is related to the actual strong storm offshore the E US that wasn’t even forecasted back on Oct 13th thus leading to lower actual SLP in Iceland today than progged 6 days ago. Daily NAO: https://ftp.cpc.ncep.noaa.gov/cwlinks/norm.daily.nao.gefs.z500.120days.csv

After a decent rise in last week’s release from +0.59 to +0.88, the latest weekly IOD update had no change. But that could easily just be a short-lived pause in the general upward trend since June 1st. Based on the history of IOD usually maxing out by Nov, I’m giving it another month to see if we get a very strong IOD peak this late autumn/early winter. One can see on this chart how much stronger was the +IOD in autumn 2023! At this time then, the IOD was already peaking way up at +1.91! Even in 2019 on this date it was way up at +1.94! https://www.bom.gov.au/clim_data/IDCK000072/iod_1.txt?1791781094025 @snowman19

@LibertyBellasked me this: “Are these similar to the naturally occurring doldrums at the horse latitudes that Columbus experienced?” ———— My answer: Good question. Quite possibly.

I closely followed the DMI site’s 80+N Arctic temps showing 2026 being THE coldest on record (back to 1958) by a good margin late May-early August and posted many times about that here and in the Arctic Ice thread. There’s little doubt it was notably colder there than recent summers, especially N of Alaska, and it helped the Arctic ice. However, as@bluewave@OSUmetstudemphasized in discussions with me, they convinced me to think that comparing to DMI charts prior to 2002 per Chris (see his quote below) and possibly even to all years through 2025 per @OSUmetstud (due possibly to a cooler ECMWF bias introduced in May of 2026) MAY make the appearance of the summer of 2026 being significantly colder than all years 1958-2025 per the DMI graphs deceptive because of the DMI ECMWF data. Per Chris in Arctic Ice thread: “Even the less reliable ECWMF only starts in 2002, so an apples to apples comparison to any year earlier than 2002 can’t be made.” —————— However, I’m still very open-minded about just how cold it really was in 80N+ late May-early Aug relative to 1958-2025, especially 2002+, pending continued research of other knowledgeable people’s opinions. Look how cold June 2026 was N of 80N per actual ERA5 reanalysis: 1. only ~1/7 is in warmest 1/2 of years vs ~6/7 in coldest 1/2 2. a little >50% is in 4 coldest colors meaning coldest 11 of 87 while only ~6% is in warmest 11, which is <1/8 the size of coldest 11 3. ~25% is in coldest 3 of 8 while only ~1% is in warmest 3 of 87, which is a mere 1/25 of the size of coldest 3 This 80N+ close-up came from this image below: only the relatively small area (~1/7 of 80N+) of light green, beige, yellow, orange, and reds is warmer than the median while >50% (4 coldest colors or coldest 11 of 87) is 87%+ percentile cold! So, does this cold of an ERA5 reanalysis (in image above) actually support this cold of a DMI 80N+ June ‘26 (in image below)? Food for thought at least. Keep in mind that it says this at the DMI site, itself: “The 'plus 80 North mean temperature' graphs can be used for comparing one year to an other.”

Thanks. So, since this pattern of this offshore low and associated cooler air in the E US is likely indirectly related to the very strong Nino, is this possibly a sign of things to come this winter?

Is the offshore E US strong low bringing down the cool air into the E US this entire week likely related to the very strong Nino? 0Z 10/12 GEFS forecast for 6Z 10/21: no offshore storm and thus no cool air pinned in E US: 0Z 10/18 GEFS forecast for 6Z 10/21: much cooler E US in reality associated with offshore strong storm working in tandem with 3 Canadian highs keeping cool dry Canadian air pinned in E US: Cool air this week E US thanks to the above pattern consistent with Euro Weeklies’ significantly cooler change: (had been warm on runs from Oct 12-13 when no offshore storm)

^Further to the above: illustrates the E US cooling power of the offshore storm this week!

1. Temps: Euro Weeklies 10/12 run for 10/19-25: warm E US because there was no offshore storm on model yet 10/18 run for 10/19-25 is much cooler E due to strong offshore storm: thank you storm! ——————- 2. Precip for 10/19-25: 10/12 run: no offshore storm 10/18 run: strong offshore storm keeping it cool in E US!

The non-tropical low now forming gas gone orange: Tropical Weather Outlook NWS National Hurricane Center Miami FL 800 PM EDT Sun Oct 18 2026 1. Off the East Coast of the United States: A storm-force non-tropical low pressure area is developing along a frontal boundary tonight off the southeast coast of the United States. This low is likely to move slowly and erratically over the next couple of days while it initially remains non-tropical. Later this week, if the system stays over the Gulf Stream, environmental conditions could become more conducive for the low to develop some subtropical characteristics. A subtropical cyclone could form over the second half of this week as the system begins moving generally northeastward, offshore of the eastern United States. Regardless of development, this system will cause high winds, coastal flooding, and dangerous surf along portions of the U.S. East Coast. Please consult statements and warnings from local National Weather Service offices and the Weather Prediction Center for more information, along with High Seas Forecasts and Storm Warnings issued by the National Weather Service. * Formation chance through 48 hours...low...near 0 percent. * Formation chance through 7 days...medium...40 percent.

Thanks. Do you know whether or not it’s normal for +AAM to be prevalent within 30-50N at any point during a strong El Niño? Or does it tend to stick closer to the equator? Have you seen any actual data? The only other El Niño for which I can see latitude based relative AAM from this site’s data is 23-4 because it only goes back to 2022. Reviewing 23-4, the 30S to 30N region had the main +AAM only during Dec 1st-Jan 15th and it never exceeded +3 SD for any latitude. That paled in comparison to Sept 14th-Oct 3rd of ‘26, when it exceeded +4 SD in portions of 15S to 15N!

POSSIBLE LOW LEVEL INVEST NEAR 36.0N 71.0W FOR 20/1800Z.

Ray et al, A similar theme to what Ray emphasized last month remains even nearly a month later where the really impressive +AAM emphasis is mainly 30S to 30N: Is it normal during El Nino for the +AAM (atmosphere rotating faster than the solid earth as I understand it), which we know is characterized as El Niñoish, to usually be strongest mainly in the 30S to 30N latitudes (with the highest near the equator) since that is nearer to the Nino regions than latitudes outside of that region? If so, do the regions outside of 30S to 30N normally get consistently positive during strong El Niños? Do they ever consistently average +AAM for long periods or is that typically relegated to 30S to 30N even during the subsequent N hem. winter? ———————— By the way, the relative AAM by lat. above is not surprisingly still supporting a very strong global relative mean +AAM with it back >+3 since Oct 12th: