bluewave

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.

These seasonal forecasts can give the temperature tendency fairly well. But the smaller details they really don’t see very well. Most seasonal model forecasts have been biased too cool with the exception of a mismatch like 20-21 and Jan 22. But the clues about those winters became slightly better known only after October in 2020 but not until nearly the start of January in 22. My guess is that the models can’t handle the MJO amplitudes and changes much before the 6-10 and 11-15 day forecasts. My work has been to identify these model deficiencies and add corrections to them.

The CFS monthly forecast only becomes somewhat reliable as we approach the first of the given forecast month. My guess is this is because it’s mostly a repeater model. And does better when the early month pattern continues through the rest of the month.

If the new Euro seasonal that just came out a few minutes ago is correct, then we’ll be looking at our 10th warmer winter in a row for the Northeast. Not really surprising given the very strong -PDO La Niña background state. The ridge axis near the Aleutians and near the East have become very persistent since the 15-16 super El Niño.

Most Novembers since the 15-16 super El Niño have been cooler in the East. So there isn’t much we can draw from that specific forecast about the winter. Plus we don’t know yet whether we just revert to the recent November decadal mean or this year does something different. We’ll have better clues after October. It’s been the only month of the year which has gone against the much warmer pattern.

Looks like our typical September endless summer pattern of recent years from mid to late month after an anomalous cool start.

Those greenings were the result of the more gradual temperature change associated with the orbital precession. They are working on newer modeling to handle the faster warming climate of today. So the pattern may vary from what slower changes in the orbit caused. https://theconversation.com/the-sahara-desert-used-to-be-a-green-savannah-new-research-explains-why-216555#:~:text=These images depict a period,%2C Niger%2C Chad and Mali.

Some of the model projections have wetter Sahara along the south and the drier edge encroaching north into Southern Europe. https://www.realclimate.org/index.php/archives/2022/02/future-rainfall-over-sahel-and-sahara/