bluewave

The GFS has been doing much better than the Euro recently. The Euro had the core of the heat focused over our area last week. Now the new Euro takes the core of the heat to our north into upstate New York and New England. Plus the 850 mb to surface temperatures have been running too high. This matches our pattern of recent years with a further north subtropical ridge into New England allowing more SSE flow at times. We will probably see our warmest temperatures later in the week and possibly into the weekend as the flow turns more SW. New run 0z JUN 20 Old run ridge axis and core of heat too far south

Yeah, the HRRR has the strongest Ambrose Jet of the season today with 30-40 mph gusts at the South Shore beaches.

I think portions of New England have a shot at their all-time June warmest temperatures as this starts out in true over the top fashion with the subtropical ridge pushed much further north than usual. All-time max 500mb height records could also be challenged.

NYC hasn’t been able to get over 98° since late July 2013 since the vegetation got so thick. This is the longest streak on record. During the strongest heatwaves in recent years we had to subtract 2° to 5° off of wherever the max was at Newark. Number of Consecutive Days Max Temperature < 99 for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. 1 4350 2024-06-15 2 4022 1977-07-17 3 3260 1894-06-24 4 2844 1911-07-02 5 2212 1917-07-30

Sunday morning may be the coolest we see for a while with 40s and some pockets of 30s over the interior Northeast.

Yeah, that’s why JFM 15 was so special for you guys. Historic -EPO and +PNA block. The El Niño was weak enough so the northern stream was able to dominate. It’s interesting how JFM 15 was one of the most favorable Pacific patterns on record. Just several months later in December 15 we began to shift toward some of the most hostile Pacific patterns on record into recent years.

https://wcd.copernicus.org/articles/5/753/2024/ An alternative possibility is that the changes seen in the reanalyses are a combination of natural variability and a forced response that is not represented in CMIP6 models. This might explain why the models are systematically biased towards underestimating the variability in the explained variance of the NAO, as seen in Fig. 3. If part of these changes in the relative strength of the NAO are indeed due to a forced response that is lacking in climate models, then there is a risk of a systematic underestimation of the changing risks of climate extremes over Europe in a warming world. A second alternative is that the change is the results of a long-term, multi-decadal variability (perhaps with a variability of 60–80 years such as that found in studies on Bjerknes compensation). If the models reproduced such oscillations and were initialized in different phases of the multi-decadal signal, this could possibly produce the observed differences in the long-term changes in variance explained by the NAO. However, it would be very difficult to reliably confirm a 60–80-year oscillation in a 150-year simulation since you would barely have two full cycles. Both of these alternatives are speculation and would need significant further investigation to confirm. While the large-scale patterns derived using an EOF analysis are a good indicator of the changes in weather systems over the North Atlantic, recent works have found that jet regimes are better at capturing spatial structure compared to patterns like the NAO and have the advantage of a greater physical connection to the underlying weather systems (Madonna et al., 2021). Future work is planned to investigate how these jet regimes have varied over time in the reanalyses and how well the CMIP6 models capture these variations.

Yeah, this could be one of the strongest June heatwaves on record for areas to our north away from the onshore flow near the coast.

The GFS shows the SSE flow as the heatwave moves in next Tuesday and Wednesday. It has 100s NW of Boston. There could even be near 100° readings just west of the sea breeze influence in portions of Central NJ near Philly. But you can see the core of the +20C 850mb temperature axis starting out just to our north.

Florida is experiencing increasing flooding from higher sea levels and record rainfall as a warmer atmosphere holds more moisture.

The 0z GFS is also initially bringing the 100° heat to our north next Tuesday and Wednesday. The ridge is so strong that the surface high is east of New England instead of down near Bermuda like it used to be with these heatwaves in the past. So a large expansion of the subtropical ridge from the days past like we have frequently seen in recent years. We get just enough SSE flow from around NYC and east for a sea breeze influence instead of deep westerly flow at least Tuesday and Wednesday. I think the ensemble means are smoothing the ridge out too much. So these OP runs which show near record 600 dm heights could be correct. It’s possible that the 100° heat could sag south toward our area before the heatwave ends. But those details are still outside the best range of the guidance.

The 12z Euro is beginning to shift to another over the top warm up for next week like we have often seen in recent years. So like the GFS is showing, the warmest temperatures may initially go to our north. But we’ll have to see if the warmest day ends up being when the warmth begins to shift south before another cold front arrives. That may be the best chance of the locally onshore SSE flow shifting to the SW before the heatwave ends. New run 0z Thu 20 Jun Old run

Allentown also saw a steep decline from the 2010s into the 2020s. So it’s another station which had a fantastic snowfall outcome during the 2010s. State College had its peak during the 1990s. But the first 5 seasons of the 2020s so far are way down like all the other stations. Allentown 80s….31.0” 90s….29.8” 00s….32.1” 10s….39.7” 20s…22.9” State College 80s….38.8” 90s….55.1” 00s….39.9” 10s…..38.1” 20s….27.4”

My guess is that our snowfall peaked along the 1-95 corridor from BWI to BOS during the 2010s. The first 5 seasons of the 2020s so far have seen a steep decline. So we are going to need to see some big snowfall improvements next 5 years in order to avoid the 2020s becoming the lowest snowfall decade following the highest decade in the 2010s. Baltimore 80s….18.5” 90s….17.7” 00s….18.0” 10s….24.1” 20s….7.7” Philadelphia 80s….20.6” 90s….18.5” 00s…20.8” 10s….31.9” 20s….9.7” New York City 80s….19.7” 90s…24.4” 00s…28.0” 10s….37.9” 20s…14.2” Boston 80s…32.8” 90s…49.9” 00s…45.6” 10s….53.0” 20s…26.1”

The surface ridge axis on the CMC is further north. So we get SSE winds off the ocean. The Euro is further south allowing more westerly flow. Once within 120 hrs the models should start to agree on one solution or the other. But it’s been tough in recent years to get a strong westerly flow with our heatwaves. So the Euro would be a departure from recent experience. That’s why I would like to see some agreement in future runs.

Still plenty of spread with the models for the heatwave next week. It s the Euro vs the cooler GFS and CMC. The Euro has our first 600dm ridge for the month of June. The location of the maximum heights and specific wind direction varies across all the models also. So the details will have to wait until the models can come into better agreement.

I think the concept of what qualifies as a good or great La Niña winter has been diminishing over time as the winters have been steadily warming. For the posters around NYC Metro 95-96 was the gold standard in terms of wall to wall cold and snow from November into early April. This was followed by our first global temperature spike in 98. So while 10-11 was still an amazing winter, the snow cut off about a month too early to challenge 95-96 around NYC. Not as cold as 95-96 was from November into April but no complaints due to the epic snowfall from late December to late January. Then the next big global temperature spike in 15 and our next multiyear La Niña in 16-17 and 17-18. The 17-18 winter was very snowy but not up to the levels we saw back in 10-11 around NYC. March was really special though especially out east on Long Island. This was the first time we had an 80° reading in February around NYC and the record warmth allowed the decent cold anomaly from after Christmas into early January to essentially get erased. Our better La Niña winter in 20-21 featured the best snowfall outcome of the 2020s so far. But it was also our warmest winter around NYC with so many -AO days along with a -5 or daily AO reading. So even with such great blocking which could be likened to a weaker reflection of 10-11, we still finished a little above normal against an already warmest new 91-20 climate normals period. Plus we had the very warm Christmas flood cutter and flash melt which damaged the ski resorts. The warmer La Niña winter pattern began to emerge in 05-06. Great snowfall outcome around NYC but the January warmth was so strong the winter finished above normal. This was followed by the milder 07-08 La Niña and less snow but not so bad by modern day poor La Niña standards. Then the 11-12 La Niña winter with a combination of lack of snow and warmth. But still not bad as 22-23 for warmth and lack of snow. 16-17 had great blizzards but was still near a 40° winter around NYC. 21-22 was split with a good January for snow and cold in an otherwise sea of warm. So the better La Niña winters have been warming since 95-96 with a decline in snowfall. The poorest outcome La Ninas have also been warming and loosing snowfall. So 22-23 was about as bad as we have seen for both warmth and lack of snow. We have never seen any winter with a December -AO averaging under -2.000 put up such poor metrics for snow and cold. Now that we have seen another big global temperature spike and the 3rd since the late 90s, I am not sure what a good La Niña winter will look like after the most recent temperature spike. But I am also concerned what a poor outcome winter La Niña outcome will look like in the against this new higher global temperature baseline with the record global 23-24 global temperature rise. I would be happy if any of the potential La Niña winters in this new grouping put up better snowfall numbers than 22-23 did. But don’t have much expectation that the record 9 consecutive warmer winter streak in the Northeast will end based off of anything I am seeing now in regard to the La Niña and -PDO early development. Will check in after October to see if we get some early snowfall MJO clues based on past La Niña Octobers.

I am not sure why this relationship has worked for every La Niña year since 10-11. But the La Niña Octobers with a more amplified MJO 4-6 went on to have better snowfall than the years with weaker October MJO 4-7 activity. But all the La Niña years since 11-12 were warmer than normal regardless of what the MJO did in October. So it only seems to work for snowfall. The first grouping of years was 10-11 and 11-12. The October 2010 MJO 4-6 was much stronger in 2010 than 2011. This was followed by October 2017 having a more amplified 4-6 than 2016. More recently October 2020 had the strongest MJO 4-6 activity out of the 2020-2021 to 2022-2023 La Niña. It works for RMM and velocity potential anomalies. That being said, who knows if this pattern will continue again since it only began in 2010 and the oceans have seen such a big increase in heat last few years.

Yeah, the early indications based on the strength of this -PDO and forecast La Niña background state would argue for our 10th consecutive warmer than normal winter here in the Northeast. But not sure yet whether we can see some improvement in the snowfall department over the last two seasons. We may get some clues with the October potential early MJO indicator which has worked with all La Ninas back to 2010.

We are probably going to need some version of a weaker La Niña pattern correlation like we got in 20-21 in order to see any level of improvement over the last 2 winters. Our only successes with recent La Ninas were the +PNA intervals. -PNA periods haven’t worked out for us in recent years like they were able to back in the 1950s and 1960s. I have been researching the reason for the 20-21 deviation from the norm for such a robust La Niña. The only difference I could see was that the MJO 4-6 amplitude peaked in October rather than the winter through the beginning of February. Beyond that point it really didn’t matter much since we had such a good snowfall outcome already in the bank. Remember the seasonal models missed this pattern. So I will look at the MJO amplitude after we get through October in order to see if there is any positive indication there. I would be happy with just a small amount of what we got in 20-21 and even Jan 22. But absent that kind of influence, we would probably be looking at another very warm and relatively snowless -PNA Southeast ridge winter. Plus the new wild card is that will be our first winter following the record global temperature spike over the last year. https://www.climate.gov/news-features/blogs/enso/did-northern-hemisphere-get-memo-years-la-niña The pattern correlations are usually substantially positive for moderate-to-strong La Niñas, which indicates that most events share some basic similarity with the average La Niña pattern. This confirms that La Niña is a reliable source of predictability outside of the tropics (and a big reason that we have an ENSO Blog!). However, the pattern correlation for the December 2020 – January of 2021 is the lowest of the 13 events and is actually slightly negative. That means you can argue that the Northern Hemisphere atmosphere looked a little more like El Niño than La Niña!

All 3 models have the first 95° or higher temperatures of the season next week for the usual warm spots. But only the Euro goes over 100° and has a much stronger ridge. I like to wait and see if the other models come on board before knowing if the Euro is correct or overdone like it sometimes is beyond 120 hrs. Need to get the flow more SW and have the weak front further north for the Euro to be closer. The GFS has more convection and the CMC somewhere in middle.

I was using the 500 mb maps and not any CPC definition. The AMO index doesn’t really do justice to the extreme North Atlantic warming in recent years. The index doesn’t look nearly as impressive at the raw SSTs. This is probably why there were warm AMO periods in the 1950s to early 1960s without a Southeast ridge with a deep -PNA trough in the West and -AO -NAO Greenland block. I have actually been mentioning the rapidly warming Atlantic in relation to the record Southeast ridge since the 15-16 super El Niño.

So we agree then since my comment about the pattern was for the mid-Atlantic to CT/RI and not the MA pike and up.

The seasonal pattern leading up to the storm has a really big influence. The storm tracks were really poor for SNE from December on. So there was just too much of a Southeast ridge influence in March for the coast. The whole storm track was just to far north. It was the worst snowfall performance on record from NYC to Boston with a winter with such a low -AO in December. The only above normal snowfall season for NYC during the 2020s so far was 2020-2021. That December -AO pattern which produced the nice snowstorm along the coastal plain occurred during a +PNA. But since the block was so south based, the low tucked in close to ACY that BGM got the 40” jackpot instead of NYC to Boston. The late January into February period was the only productive productive -PNA pattern for the 2020s so far. My guess is the main reason that it worked out in places like NYC was that the PNA was positive for the first half of the season. After it flipped in late January the storm track still remained far enough south with Southeast ridge suppression continuing. So the favorable seasonal storm track established during the early part of the winter with the +PNA lingered after the the PNA turned negative.

March 2023 didn’t have much to do with luck. The -NAO was linked up with the Southeast ridge leading up to the storm. So the low tracked too far north and the interior Northeast jackpot instead of closer to the immediate coast. It was the same reason the near record -AO in December didn’t produce.