bluewave

The Pacific Jet was the strongest on record for the summer near the SW portions of the Bering Sea.

It’s possible the next few days will be the last solid cool departure days we see until at least October.

It’s tough to tell if the observed SST cooling near Iceland and Greenland is a result of the slowing AMOC, stronger winds, or a blend of the two. https://pure.psu.edu/en/publications/century-long-cooling-trend-in-subpolar-north-atlantic-forced-by-a Abstract A well-known exception to rising sea surface temperatures (SST) across the globe is the subpolar North Atlantic, where SST has been declining at a rate of 0.39 (± 0.23) K century−1 during the 1900–2017 period. This cold blob has been hypothesized to result from a slowdown of the Atlantic Meridional Overturning Circulation (AMOC). Here, observation-based evidence is used to suggest that local atmospheric forcing can also contribute to the century-long cooling trend. Specifically, a 100-year SST trend simulated by an idealized ocean model forced by historical atmospheric forcing over the cold blob region matches 92% (± 77%) of the observed cooling trend. The data-driven simulations suggest that 54% (± 77%) of the observed cooling trend is the direct result of increased heat loss from the ocean induced by the overlying atmosphere, while the remaining 38% is due to strengthened local convection. An analysis of surface wind eddy kinetic energy suggests that the atmosphere-induced cooling may be linked to a northward migration of the jet stream, which exposes the subpolar North Atlantic to intensified storminess.

Yeah, 16-17 was the 7th warmest winter for NYC. We were fortunate to have the lingering +PDO pattern from 13-14 to 15-16 and BM storm track back to 09-10. So we had a great blizzard in February even though there record mid-60s the day before. Time Series Summary for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. 1 2001-2002 41.5 0 2 2022-2023 41.0 0 - 2015-2016 41.0 0 3 2023-2024 40.6 0 4 2011-2012 40.5 0 5 1931-1932 40.1 0 6 1997-1998 39.6 0 7 2016-2017 39.3 0 8 2019-2020 39.2 0 9 1990-1991 39.1 0 10 1998-1999 38.6 0

At least some good news with this most recent study.

The upper ridge at 500 mb actually expanded a bit further north from earlier runs as has been the model forecast pattern for a long time now. But we also got more Bermuda high development at the same time to our south. So the areas away from the sea breeze will be the warmest like we have seen all summer. Could be some tropical development in the Western Gulf next week. But the strong high and ridge to the north may really slow it down and maybe cause it to stall out for a time to our SW. So we’ll probably have to be patient a while longer for another big tropical soaking like we got out of Debby. New run more high pressure to our south with Canadian high pushed further north Old run had too much onshore flow with less high pressure south

Strongest WPAC warm pool on record during the summer.

One more cool down before we get the next 590 dm heat ridge and 90° potential this week.

There has been plenty going on the last few years with record global temperature spike. This jump in temperatures was above and beyond what any model was forecasting. The hurricane season last year greatly exceeded any seasonal forecasts. It was the first 20+ named storm season with such a strong El Niño. Then we started noticing much more SAL than usual earlier this summer even as Beryl was able to go Cat 5. Even though the Euro successfully forecast all the dry air this summer over the MDR, it wasn’t able to forecast the record lull since mid-August. At least the U.S. forecast worked out very well for the Euro with the warmer along the coasts and cooler in the middle. So the issues with the hurricane forecast didn’t hurt its skill for the summer temperature forecast. It has been the case with these seasonal forecasts that they have been able to forecast some things very well and miss others. All these competing marine heatwaves are probably making the model forecasts more difficult since the interactions can lead to changes like the ITCZ shift reducing the hurricane count from the earlier forecasts.

I haven’t made any official forecasts specifically for December yet. But I will note that the 2 great December La Niña snowfall outcomes for NYC during La Ninas since 15-16 were +PNAs in 2020 and 2017. Before those Decembers we had the more amplified October MJO 4-7 phases with weaker MJO 4-7 December activity. In the multiyear groupings those were the strongest of the La Ninas. So far this La Niña isn’t looking as strong as those like we saw in 2016 coming out of that super El Niño event. But I still want to see how the MJO responds in October before making any early guesses. When using the term mismatch I am referring to positive +PNA reversing the Aleutian Ridge pattern. I took it from the CPC discussion back during the stronger 20-21 La Niña when the +PNA was strongest on record for such a robust December La Niña. The much less snowy December outcomes were the weaker December La Niñas in 2016, 2021, and 2022 relative to the multiyear groupings. But my focus is only on NYC and not further north in New England or the Great Lakes which have much more leeway when it comes to snowfall. December +PNA above average NYC snow December -PNA below average NYC snow

Big disparity between the 500mb heights over Iceland which were the lowest on record for record for the month of August.

The 597 dm ridge forecast next few days is near the all-time record for this time of year. It actually shifts the pattern to much warmer in the East next week. This has been the repeating pattern of recent years with the record Aleutian Ridge followed by a big ridge several days later from the Great Lakes to Northeast.

New Mediterranean SST record for August. The Euro actually forecast the higher stability this summer over the MDR. So they will have to look at why that didn’t translate into a lower seasonal hurricane forecast matching the current record lull since mid-August. This reminds me of other seasonal forecasts from the Euro where it does very well with some seasonal forecast parameters and not well with others.

Even though the El Nino development peaked around Labor Day in 2012, we still got the classic El Niño progression. Very warm December into mid-January before the pattern got colder in February. Then one of the greatest blizzards of all-time for Central LI north into Southern New England with Nemo in February.

The latest forecasts are signaling that this will be a record breaking 11th warmer than average September in a row for spots like Newark. Sep 2023…+2.0 Sep 2022….+0.5 Sep 2021….+3.3 Sep 2020….+0.9 Sep 2019…..+2.6 Sep 2018…..+3.2 Sep 2017….+2.7 Sep 2016….+3.6 Sep 2015….+5.2 Sep 2014….+1.6 Sep 2013…..-1.0

I don’t think that you could call it major since nothing like the upper and lower atmosphere temperature difference occurred at any solar max going back to 1950. Plus none of those seasons had the lull in development like this one did since mid-August near peak solar with such a strong +AMO. So it’s most likely other factors. Plus we never experienced a global temperature spike like we have since last year.

Warmer SSTs from Japan across to south of the Aleutians. Also stronger warm pool east of New England. More defined colder ENSO signal in Nino 3.4 and 4.

He wrote a great article about this extreme event. https://www.daanvandenbroek.com/svalbards-3rd-consecutive-warmest-summer-on-record-august-shattering-multiple-records/ Southerly winds Besides global warming and its impacts (diminishing sea ice, warming oceans and atmosphere, etc.), the extremely warm Augst was caused by anomalously persistent southerly winds, advecting extremely mild air from lower latitudes to the region. This flow pattern was due to persistent high pressure systems towards Svalbard’s east, with low pressure systems coming up from the southwest, pushing mild (and often humid) air towards the Archipelago. Fastest warming place on earth Svalbard is one of the fastest warming places on Earth. The reason for the faster-than-average warming is due to several feedbacks, such as the ice-albedo feedback. Even more, Svalbard is strongly affected by changes in ocean currents and shifts in wind patterns. Specifically, Svalbard ends up on the ‘warmer side’ of cyclones more frequently, and relatively warm Atlantic water penetrates further into the Svalbard region and its fjords, a process known as Atlantification. read more about Longyearbyen’s climate here Most of Svalbard’s warming has been concentrated in the winter months. Nevertheless, the last few summers have been astounding, with the summer of 2024 defying every statistical norm.

Solar influence isn’t strong enough to cause the disparity we saw this season since this is the greatest difference between the upper levels and surface since 1950.

We don’t have the luxury of really large sample sizes that we used to enjoy in a much more stable climate of the past. So we just have to do the best with what we have. Non linear or threshold behavior doesn’t really become known until it’s already in the rear view mirror.

I said alteration or reinterpretation filtered through competing marine heatwaves but not necessarily a discontinuation in a traditional sense.

Our next warm up from mid to late September could get some enhancement when the flow eventually turns more SW and travels across the flash drought to our SW.

Not in the manner which has manifested since around 2010.

We have seen some counterpoints to the traditional AMO and PDO cycle discussions in recent years. The first one was when the AMO began shifting negative around 10 years ago especially more so on the Klotzbach index he developed. We noticed a strong warming of the NW Atlantic east of New England around this time which didn’t let the developing -AMO really take shape. Instead we shifted to all-time Atlantic warmth in the last few years which exceeded any historic precedent during +AMOs. Then we got the sharp and rapid shift to one of the strongest +PDO patterns in terms of SST and +NPM overlap in 13-14 into 15-16. Then this pattern suddenly reversed and transitioned to one of the strongest -PDOs off all time. But just as the warming of the NW Atlantic was different for past -AMOs, this is the first -PDO defined by the 2nd eof and record SST warmth to the east of Japan and south of the Aleutians. So in effect competing marine heatwaves have altered past -PDO, +PDO, -AMO, and +AMO expectations. My guess is that we continue to see competing marine heat waves alter past expectations of ENSO, AMO, and -PDO. While these indices can sway from negative to positive, it may not look like what we used to get in the past.