GaWx

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!