GaWx

No worries. Indeed, that's how it is looking. But my point was about any assumption that the Arctic blocking, itself, would play out as was projected yesterday considering how the current blocking didn't even start to be recognized by the daily GEFS forecasts until within 10 days. The models have an extra challenge when the SPV is very weak. Look at today's GEFS mean vs yesterday's. Yesterday's had the AO on day 10 (3/10) near zero. Today's for 3/10 has it still down at -0.9.

The chances of the upcoming March NAO ending up sub -0.5 is pretty good considering how displaced/weak is the strat and how negative it is progged to be for the first 10 days. Since 1950, there have been 20 of these out of 73 (just over 1 in 4 chance). I did some calculations based on these 20 for RDU: 1. Temperature: 7 MB, 5 B, 7 N, 1 A (60% MB to B, 35% N, 5% A) AVG -2.8 2. Snow/IP (I didn't do ZR): - Measurable in 8 of 20 (40% of these vs 33% of all) - 4"+ in 3 of 20 (15% of these vs 10% of all)(all 3 cold) - Max 9.3" (1969) - Average: 1.2" vs longterm average for all of 1.1" (so not bad but not much difference from average considering the high percentage that were cold)

Today's NAO of -0.9 was the most negative day in February since February 28th of 2018, which was 16 days after the 2/12/2018 major SSW. As recently as just 11 days ago, the GEFS mean had today's NAO only down to zero with runs a couple of days earlier than that still positive for the last days of Feb. Also, it wasn't but 4 days ago that the GEFS had the AO stay positive through the entire run. The point is that the models were slow to see this blocking, which illustrates well the difficulty the models have with the troposphere starting by week 2 after an SSW vs the much easier to forecast strat out several weeks. Looking ahead: with today's renewed plunge of the 60N winds at 10 mb (to -18 or -19 m/s, which is significantly lower than the -13 m/s of the mid Feb major SSW) and thus a weak and extremely displaced SPV, folks shouldn't assume that the NAO, AO or anything else is anywhere near set in stone once looking ahead to week two, especially after day 10. Currently, the GEFS has on day 10 the NAO rise back to -0.4 and the AO rise back to 0. Will these actually verify?

A map that averages 51 members with 8 BN way out at hour 300 is a very strong BN signal and means a lot more than merely taking a day's climo average and subtracting 8 degrees. Thus, I think Michael Muccilli is looking at this the wrong way.

When an ensemble run's mean of dozens of members shows 8 BN for a period of a week or so, that implies that individual members for their respective coldest individual days will be much colder than 8 BN. There'd likely to be many cases of 20 or more BN on certain days for certain members.

The 12Z EPS is by a good margin the coldest run yet for much of the E US!

The 12Z EPS is by a good margin the coldest run yet for much of the E US!

The 12Z EPS is by a good margin the coldest run yet for much of the E US!

The correlation of a -NAO with BN SE temps is higher during March vs all other months: https://psl.noaa.gov/cgi-bin/data/correlation/corr.test1.pl?iregr=1&var=Air+Temperature&level=Surface&mon1=3&mon2=3&iy[1]=&iy[2]=&ilead=0&ilag=0&type=3&timefile=&customtitle=&labelc=Color&labels=Shaded&cint=&lowr=&highr=&scale=&switch=0&proj=USA&xlat1=&xlat2=&xlon1=&xlon2=&custproj=Cylindrical+Equidistant&level1=1000mb&level2=10mb&Submit=Create+Plot Edit: Also, the correlation to BN in the SE during March is higher for -AO and -NAO vs any other indices such as +PNA.

Looking at the monthly NAO table back to 1950, the above maps are actually for when the March NAO averages lower than -0.5. The NAO looks to start that way but it remains to be seen whether or not it will stay predominantly negative enough through the month for it to end up sub -0.5. However, with the strong start being helped by the very weak SPV, I think the odds are pretty high. NAO monthly table: https://www.cpc.ncep.noaa.gov/products/precip/CWlink/pna/norm.nao.monthly.b5001.current.ascii.table

And now we have an even bigger plunge of the 10 mb strat winds at 60N to -19 m/s occurring now! The major SSW plunge to -13 m/s in mid Feb was impressive enough, but even it pales somewhat in comparison to what's happening now. So, this tells me that the SPV is very likely the weakest it has been during winter by a good margin since the great Feb of 2018 SSW.

The 0Z GEFS in week 2 just about completely caved to the colder EPS!

Lol, I think he lives in the NYC region and accidentally posted in the wrong forum. Meanwhile, the 0Z GEFS in week 2 just about completely caved to the colder EPS!

Have you seen the 0Z GEFS in week 2? It just about completely caved to the colder EPS!

Today's Euro weeklies, which are an extension of today's 0Z EPS, vs the prior run are as was already known colder for the week March 6-13. They are about the same as the prior run for March 13-20. However, the week March 20-27 is actually warmer vs the prior run. So, whereas the prior run's coldest period was March 13-27, the new run's coldest period is March 6-20 (more specifically more like March 10-20). This is all fwiw and very much subject to change on the next run, of course.

Indeed, I had just looked at it and agree that it is the coldest EPS run to date at 2m late in the run though it was slightly warmer than the prior run through about 288. It became slightly colder than the 0Z 312-348, making it the coldest run yet for 3/12-3. It is also colder at hours 288+ at 850 and at hours 276+ at H5. Needless to say, we have significant differences between the EPS and the GEFS/GEPS at 12Z as the EPS is colder earlier by 1-2 days per my eyeballs and has quite a bit lower H5. At H5 at RDU, the EPS gets down to 548 dm as of hour 282 (on 3/11 at 6Z) which is a notable 14 dm BN, and is the lowest H5 to date for then on any EPS. Here's the H5 trend for 6Z on 3/11: 2/25 12Z run: 565 2/26 0Z run: 560 2/26 12Z run: 560 2/27 0Z run: 552 2/27 12Z run: 548 vs 558 GEPS vs 564 GEFS Also, this EPS has the most wintry precip in the SE of any EPS yet March 10-12 vs no wintry precip of note on the GEFS/GEPS. Model war! The problem for those who prefer cold and thus prefer the EPS to be on the right track is that all of the models have been too cold on most days of this winter outside of late Dec. Is it going to finally be different this time?? One thing to keep in mind is that for the first time this winter there's the after effects of a combo of the mid Feb major SSW (which is only now starting to cause big changes in the troposphere, making it extra difficult for the models to handle) that dropped strat winds at 10 mb at 60N to -13 m/s and tomorrow's drop to a very impressive and rare -19 m/s. That is the lowest since Feb of 2018, which means an extremely weak SPV (makes it much easier than normal for cold to move down into the mid latitudes): Edit: Also, La Niña is about dead finally with last week's Nino SST anomaly up to -0.3 C.

There's a big difference in the SE at H5 between the 12Z GEFS (weak ridge and NN) and the 0Z EPS (weak trough and 10 dm BN) as of March 11th. Will the 12Z EPS backtrack again to warmer? The odds favor it imo.

And now today's 0Z EPS mean not only went back to a strong/large high in SW Canada on 3/7-8 like on the run from 24 hours ago, it has SE ridging unlike on any earlier EPS disappear on March 8th (the last AN SE day). There is none the rest of the run as BN temperatures take over, making it easily the coldest EPS yet for March 9th+ in the E US. This run will be the one used by the Weeklies later today. What will be notable is that the week Mar 6-13 will be significantly colder in the E US than what the prior Weeklies had. Will the 12Z run again backtrack? It certainly wouldn't surprise me if it does for the 2nd week in March since this run was so much different from prior runs.

Although I'm not giving up yet due to inherent uncertainties that far out, I don't blame anyone who does based on how amazingly relentless the warmth has been overall this winter along with the related cold bias of the models. Other than a few days here and there, about the only time the model consensus wasn't too cold this winter was for the period 12/17-26, which was nailed well. From what I understand from several pro mets, the record warmth in the Maritime Continent of the W Pacific has a good bit to do with the unrelenting warmth/SE ridge of the last few years. This leads to a dominant Pacific flow similar to what it would be in the MC MJO phases regardless of the actual MJO phase, which also favors a SE ridge. Of course, the La Niña of the last 3 years is an important warmth favoring factor overall, too. Why the models can't ever seem to get a clue and handle this as opposed to so often being too cold even out just a few days in many cases is a mystery. Isn't the added ocean warmth an input in the model initializations?

The 12Z EPS mean backed off a good bit from the prior EPS trend of a higher SLP peak in SW Canada for ~3/8. The 0Z had as mentioned a very impressive and rarely seen on day 10 of the EPS 1046 mb along with 20% of the members with a record high SW Canada SLP for March. The 12Z has only 1041 with increased troughing just off the west coast. This lead to lower SLP and thus not as cold in the Midwest.

The trend of the EPS mean has been for higher SLPs in SW Canada ~March 8th from Arctic highs dropping down toward Montana/ND. The mean in the latest run has risen to well up into the 1040s, which is uncommonly high for 10 days out on a 51 member ensemble in March, especially when one realizes that the March record for SW Canada isn't that much higher than that (1053) as this image shows: About 20% of the 0Z EPS members are above that 1053 March record in SW Canada with a couple even way up at 1060+. As we get closer to March 8th, it will be interesting to see whether or not this trend of the mean toward a higher SLP continues. If so, that would increase the chance for a major cold plunge getting into the US ~March 9th-10th. Keep in mind that Arctic plunges are often under forecasted that far out in time by ensemble means. The trend on the EPS has also been toward a weakening of the SE ridge late in the runs. If this were to keep up, it would open the door for what potentially could be the coldest air for the SE since the late Dec historic plunge near or just after March 10th.

The record highest daily minimum temperature for all of Feb was broken yesterday by 4 F at KATL (69 vs old Feb record of 65 set in 2018)! RECORD EVENT REPORT NATIONAL WEATHER SERVICE PEACHTREE CITY GA 0417 AM EST FRI FEB 24 2023 ...RECORD DAILY AND MONTHLY HIGH MINIMUM TEMPERATURE SET AT ATLANTA... A RECORD HIGH MINIMUM TEMPERATURE OF 69 WAS SET AT ATLANTA YESTERDAY. THIS BREAKS THE OLD RECORD OF 63 SET IN 2022. THIS ALSO BREAKS THE ALL TIME RECORD HIGHEST FEBRUARY MINIMUM TEMPERATURE, WHICH WAS PREVIOUSLY 65 SET ON FEB 21 IN 2018.

The idea is that with a stronger cold signal that there would be a decent chance for at least one Arctic airmass to bring, say, a few days of highs in the 40s and lows in the 20s in much of NC along with sub 0C 850s on the coldest days. If RDU were to have a week averaging 5-7 BN as the WB Euro weekly map shows for midmonth, that would imply the coldest couple of days could average, say, ~15 BN (45 high/25 low kind of thing if there were full sunshine). That would be a cold enough airmass to allow for wintry precip at RDU if there were to be a storm with a favorable track.

You never know with March though. In mid March of 2017, NYC actually had a colder week than any so far this winter (along with 9.7" of snow from two storms) and that month as a whole was only 4 BN! So, don't count out that kind of thing even though it is unlikely. Did you know that the day with the coldest normal for the Arctic north of 80N isn't til Feb 25th? Also, the coldest day there so far this winter was today! This doesn't mean that it is capable of getting anywhere near the coldest ever recorded in DJF. But it does mean that it is still capable of getting quite cold if the atmospheric mechanisms and nearby snowcover are in place: https://ocean.dmi.dk/arctic/meant80n.uk.php

Yes, strongest cold signal vs normals for the respective weeks.