bluewave

You are fortunate to be in an area where the record warm lakes staying open longer works to your advantage with all those cutter storm tracks we have seen.

We’ll see if the later runs can cool enough so RDU doesn’t break their latest first freeze record.

One of the long range model biases has been to underestimate the strength and influence of the Pacific Jet. This is why long range modeled colder patterns usually modify the closer in we get. None of the long range models from a few weeks ago were this strong with the Pacific Jet for the record breaking event next few days. Remember the previous 11-15 day forecast was much colder than the present 6-10 day forecast. New run Old run

The forecast issue going forward may be that the La Niña is so weak that we get a mix of Nino-like and Nina-like intervals. Kind of like a windshield wiper effect. So would be a challenge getting any sustained cold with since a strong Pacific Jet.

The 12z GFS took a step toward the more amplified and wetter models. New run UL and vort digging more into GA Old run

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