bluewave

This was the strongest WWB event in the EPAC during the month of November following such a strong El Niño winter. Reminds me a bit of the unusually strong EPAC WWB activity we saw that kicked off the El Niño in the winter and spring of 2023. This isn’t something we see during El Niño to La Niña transitions.

My guess is that the more Nino-like look to the 500 mb pattern this week is a result of the unusual EPAC WWB we just experienced. The million dollar question is how long this pattern lasts? We need it to continue for more than just a few weeks. Ridge axis shift from 30N to 60N

We need the UL to dig further south like the Euro and other guidance to have a chance at a wetter scenario than the GFS which doesn’t dig as much.

There have been other factors than the MJO driving the pattern this month. The first half of November was roughly similar to the MJO 1 but much more amplified. The Southeast just experienced their warmest first half of November on record which is much warmer than we would typically see with MJO 1 this time of year. My guess is that the forecast pattern for the 2nd half of November is related to the wave break producing the record warmth and 500mb ridge near Iceland. This pattern is lingering in the means to some extent for the next few weeks on the ensembles with blocking near the Aleutians and Greenland with a trough north of Hawaii mimicking a classic +PDO. I use the term mismatch to refer to when the pattern at 500mb deviates from the SST -PDO background. It’s too early to speculate on whether this is a transition pattern next few weeks before changing again in early December. But we haven’t had a December with a trough north of Hawaii and in the Northeast since 2017. That was the last time we had a La Niña mismatch following a very amplified MJO 5 in October somewhat like what we saw this October. That is the early indicator I have been discussing since October. It allows the MJO to go more into the background with other factors becoming more dominant and driving the pattern. We can go back to the 15-16 super El Niño and only find a small amount of times the hostile MJO 4-7 pattern hasn’t been driving our winter patterns. If we focus on December, then only 2 Decembers out of the last 9 haven’t had the hostile MJO 4-7 run the table. So 7 out of the last 9 Decembers have had a hostile MJO or Pacific. The only two memorable Decembers around NYC since then were 2020 and 2017. Those happened to be the exceptions when the amplified MJO 5 in October was followed by more muted MJO 4-7 activity in December. But as I said back in October, we had the amplitude in October but this La Niña has been much weaker than 2017 and 2020. So the next few weeks into early December will be an interesting test to see if other factors continue to drive the pattern or the MJO becomes more of an active pattern driver and we switch back to a more hostile MJO 5-6 pattern in later model runs.

As strong as this emerging MJO wave is in the IO, it’s not really having much of an impact on the current pattern. The current 500 mb pattern with record blocking near Aleutians and Greenland is completely different from what we would expect of the MJO were driving the pattern. So at least over the next week to 10 days we’re are getting a mismatch pattern. Need to see that trough stay anchored north of Hawaii which is an atmospheric +PDO pattern going against the -PDO SST. We want this to continue into early December which would mean the October early MJO indicator is working like in 2020 and 2017. But if the pattern begins to shift warmer in later runs as we get to early December, then we’ll know the MJO is starting to to have an influence. This will be a very high stakes game over the next few weeks which will determine December and potentially the rest of the winter. Trough north of Hawaii is an effective atmospheric +PDO going against -PDO SST

The Pacific Jet is finally going to come SE this week from the Aleutians.

This is probably one of the most amplified patterns in terms of blocking near Alaska and Greenland that we have seen in mid-November. So it would be a really big disappointment if this didn’t produce our best event of the fall so far. Granted the bar is set very low to be the best of this fall.

While we have been in a record dry pattern, at least the strong block and cutoff low this week will represent the best potential we have seen this fall for over .50 of rainfall.

RONI didn’t work last winter since the warmth greatly exceeded all previous super El Niños globally and nationally which had significantly higher ONI and RONI values.

This is the same old story we have seen in recent years. Models try to develop a -EPO after day 10. Then the closer we get in time there is a trough near Alaska and we get a Southeast Ridge. New run Old run

You have to examine the magnitudes to understand the rarity. There were no El Niños this soon after a +2.0 or greater ONI event like we had last winter. Think 15-16, 97-98, 82-83, 72-73 and 65-66. None of those events had a follow up El Niño only 2 years later. That’s why it would be extremely rare for us to go back to El Niño so soon unless the unprecedented global temperature rise last 17 months is signaling some type of new climate shift. But it’s way to early to know the state of the ENSO next winter since in the past another La Niña has been favored.

At least the 0z models didn’t loose the idea of a weak secondary or triple point low to help boost the rainfall potential over .5.

Yeah, the Gulf low looks to get suppressed like we have been seeing since late August. So our best bet is for a triple point low to form near DC as the GL low wraps up. If the secondary or triple point low gets going too late, then most of the moisture will stay to N and W.

This will be a rare occasion when the forum wants to see a stronger and wetter cutter.

Models finally starting to agree on a strong cutter next week which could bring the best rains this fall. Want to see this continue in the runs next few days. But it may be the best chance we have of a decent rainstorm this fall. Hopefully, the retrogression works out for us like it has in the past.

One of the issues the EPS has is the barrier effect. So it underestimates the longer range convection over the Maritime Continent. This is why the more amped GEFS MJO forecasts often do better when the MJO is phase 1-4 and its forecast to go into 5-6. So unless we get some type of mismatch pattern in December like 2020, then EPS will probably be playing catch up with a milder pattern since it often underestimates the long range MJO 4-6 amplitude.

The Euro weeklies changed a few days ago following the record block near Europe. My guess is this wave breaking event helped to shift the mean ridge position across the Northern Hemisphere from around 40N to 60N. So this lifting of the ridge axis changed the whole forecast for the 2nd half of November. I don’t have much confidence in the weeklies beyond 15 days so we’ll need to see what the first week of December forecast looks like in a few weeks once it get within the more reliable EPS week 1 to week 2 range. What we want to see happen is for early October MJO indicator to work out where the strong MJO in October is followed by a weaker MJO influence in December like we got back in 2020. This allowed other factors to win out leading to the +PNA mismatch for the -PDO and La Niña. But if the MJO comes out of the gate into the warm phases during December and the pattern begins reverting back to the stronger mid-latitude ridges we have seen all fall, then we’ll know the early indicator didn’t work out due to the La Niña being much weaker than the 2020 and earlier La Niña mismatch Decembers. We should have a good idea which one of these ideas wins out by the first week of December.

Any December which can’t make it to 3” in NYC during a La Niña finishes the season below average. 22-23….Dec snow…..T……season….2.3 21-22…..Dec snow….0.2…season…..17.9 20-21…..Dec snow….10.5…season…38.6 17-18……Dec snow….7.7…..season…40.9 16-17…….Dec snow…3.2…..season…30.2 11-12…….Dec snow….0…….season….7.4 10-11…….Dec snow….20.1….season….61.9 08-09…..Dec snow….6.0……season….27.6 07-08…..Dec snow…..2.9…..season….11.9 05-06…..Dec snow…..9.7…….season…40.0 00-01……Dec snow….13.4……season….35.0 99-00…..Dec snow…..T……….season….16.3 98-99…..Dec snow…..2.0……..season….12.7 95-96…..Dec snow…..11.5……..season….75.6

Dry pattern continuing on both models next week to 10 days.

Thanks. The issue this year is that while the October MJO indicator was closer to the mismatch La Niña years like 20-21, the La Niña strength is similar to the weaker years like 16-17 which were very warm. We haven’t had this divergence before going back to 2010. So I am not sure whether it will continue to work. On top of that the warmth this fall across the CONUS is the highest on record even exceeding the 2015 super El Niño. So I would like to see what the pattern and forecasts look like into the first week of December. If the MJO comes of the gate into the warm phases like we have seen so often during recent Decembers and drives the pattern,then we’ll know the MJO indicator didn’t work out probably due to the strength of the La Niña not matching the better La Niña winters which were stronger. Warmest SEP-OCT on record ahead of 2015 for the CONUS

I will have my outlook by the first week of December and this is what I posted in the main forum. The next 3 weeks are going to be very telling. On one hand we had the split between the MJO and strength of the ENSO back in October that I went into detail about in an earlier post. So we’ll know one way or another by December 7th if there is to be some type of mismatch where the Niña and -PDO background gets nullified like we saw in 20-21 with the much better December which carried through the winter. That was our only winter since 15-16 without at least one month with a +10 for a spot in the CONUS. But if the warmer pattern the seasonal models have been advertising becomes evident during the first week of December, then the MJO will probably slow down in the warmer phases and the mid to late part of December will be the warmest part of the month. Then we wait and see what happens near the start of January. My post from late October The MJO activity in MJO 5 is unusually strong for weaker La Niña this month. The latest RMM index is closer to 2020, 2017, and 2010 than 2022, 2021, 2016, and 2011. Whether we use the ONI or RONI this fall so far is closer to the weaker La Niña years like 2016. But for some reason we are still getting the stronger October MJO response which preceded the better La Niña winters. These Decembers like 2020, 2017, and 2010, had more of a mismatch pattern where the December patterns were snowier and in some cases colder like 2017 and 2010. Since we are getting this divergence between the strength of the La Niña and early MJO response not really sure what to make of it yet. Since our best La Niña winters were actually the stronger ones of the groupings and not the weaker ones. Plus there is no guarantee that this indicator will continue to work as it did in the past. As always, we may just have to wait until December actually gets underway in order to know for sure. Especially since there are other indicators signaling the potential for above to potentially well above normal temperatures and below average snowfall in NYC. It’s based on the MJO RMM amplitude and VP anomalies in phase 5-6 during La Niña Octobers since 2010. The stronger October MJO responses had better winters in NYC relative to the other La Ninas in the multiyear event group. Those stronger MJO 5-6 Octobers also had the more robust peak La Niña ONIs from fall into winter of the multiyear groups. All the La Niña winters around NYC since 11-12 have averaged warmer than normal. But even the warmer than average 17-18 and 20-21 winters had better snowfall than the other years in the multiyear group. In addition, we haven’t had any cold neutral ENSOs in the -0.1 to -0.5 peak range with a strong -PDO since 2010. So not sure how the relationship would work for any year with the official CPC ONI not getting colder than -0.5. The other thing to consider is that we don’t know how long this relationship will continue to work it. http://www.bom.gov.au/clim_data/IDCKGEM000/rmm.74toRealtime.txt https://origin.cpc.ncep.noaa.gov/products/analysis_monitoring/ensostuff/ONI_v5.php Multiyear La Niña groupings below with peak MJO 5-6 strength and the peak ONI from the fall into winter…….Strongest October MJO 5-6 and La Niña ONI leading to best NYC winters of the multiyear group bolded http://www.bom.gov.au/clim_data/IDCKGEM000/rmm.74toRealtime.txt October 2024….Phase 5 peak +2.762…ONI….latest weekly only -0.3 October 2022…Phase 6 peak +2.177…..ONI….-1.0 October 2021….Phase 5 peak +2.087….ONI….-1.0 October 2020…Phase 5 peak +2.818….ONI…..-1.3 October 2017….Phase 6 peak +3.353….ONI….-1.0 October 2016….Phase 5 peak +1.800….ONI….-0.7 October 2011….Phase 6 peak +1.674….ONI….-1.1 October 2010….Phase 5 peak +2.880…ONI…..-1.6

I mentioned this the other day. The warmer MJO phases since October have been responding much warmer than past events. The cooler phases this month have been much warmer than past occasions.

The tropical system ends up getting suppressed again like all of them since late August and the northern stream doesn’t have much moisture for us this run.

This may be why October was the 2nd warmest on record for the CONUS well beyond what would have been suggested by just looking at the MJO.

The next 3 weeks are going to be very telling. On one hand we had the split between the MJO and strength of the ENSO back in October that I went into detail about in an earlier post. So we’ll know one way or another by December 7th if there is to be some type of mismatch where the Niña and -PDO background gets nullified like we saw in 20-21 with the much better December which carried through the winter. That was our only winter since 15-16 without at least one month with a +10. But if the warmer pattern the seasonal models have been advertising becomes evident during the first week of December, then the MJO will probably slow down in the warmer phases and the mid to late part of December will be the warmest part of the month. Then we wait and see what happens near the start of January. My post from late October The MJO activity in MJO 5 is unusually strong for weaker La Niña this month. The latest RMM index is closer to 2020, 2017, and 2010 than 2022, 2021, 2016, and 2011. Whether we use the ONI or RONI this fall so far is closer to the weaker La Niña years like 2016. But for some reason we are still getting the stronger October MJO response which preceded the better La Niña winters. These Decembers like 2020, 2017, and 2010, had more of a mismatch pattern where the December patterns were snowier and in some cases colder like 2017 and 2010. Since we are getting this divergence between the strength of the La Niña and early MJO response not really sure what to make of it yet. Since our best La Niña winters were actually the stronger ones of the groupings and not the weaker ones. Plus there is no guarantee that this indicator will continue to work as it did in the past. As always, we may just have to wait until December actually gets underway in order to know for sure. Especially since there are other indicators signaling the potential for above to potentially well above normal temperatures and below average snowfall in NYC. It’s based on the MJO RMM amplitude and VP anomalies in phase 5-6 during La Niña Octobers since 2010. The stronger October MJO responses had better winters in NYC relative to the other La Ninas in the multiyear event group. Those stronger MJO 5-6 Octobers also had the more robust peak La Niña ONIs from fall into winter of the multiyear groups. All the La Niña winters around NYC since 11-12 have averaged warmer than normal. But even the warmer than average 17-18 and 20-21 winters had better snowfall than the other years in the multiyear group. In addition, we haven’t had any cold neutral ENSOs in the -0.1 to -0.5 peak range with a strong -PDO since 2010. So not sure how the relationship would work for any year with the official CPC ONI not getting colder than -0.5. The other thing to consider is that we don’t know how long this relationship will continue to work it. http://www.bom.gov.au/clim_data/IDCKGEM000/rmm.74toRealtime.txt https://origin.cpc.ncep.noaa.gov/products/analysis_monitoring/ensostuff/ONI_v5.php Multiyear La Niña groupings below with peak MJO 5-6 strength and the peak ONI from the fall into winter…….Strongest October MJO 5-6 and La Niña ONI leading to best NYC winters of the multiyear group bolded http://www.bom.gov.au/clim_data/IDCKGEM000/rmm.74toRealtime.txt October 2024….Phase 5 peak +2.762…ONI….latest weekly only -0.3 October 2022…Phase 6 peak +2.177…..ONI….-1.0 October 2021….Phase 5 peak +2.087….ONI….-1.0 October 2020…Phase 5 peak +2.818….ONI…..-1.3 October 2017….Phase 6 peak +3.353….ONI….-1.0 October 2016….Phase 5 peak +1.800….ONI….-0.7 October 2011….Phase 6 peak +1.674….ONI….-1.1 October 2010….Phase 5 peak +2.880…ONI…..-1.6