GaWx
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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.
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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
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Yes, strongest cold signal vs normals for the respective weeks.
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No, I meant strongest cold signal of any March of 2023 week on the Euro Weeklies forecast to date. There have been 10 earlier runs since Jan 19th, which was the first run going into March. None of those 10 runs had even a single March week with this strong of a cold signal in the E US. I'll go even further. No single week in any of Jan, Feb, or March of 2023 on any Weeklies run back to Jan 5th (14 runs excluding today's) has had as strong a cold signal (vs normal of course) for the E US as today's for March 13-20 with today's run for March 20-27 and last week's for March 13-20 about tied for second coldest signal.
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Tony/all, The prior Euro Weeklies run's March 13-20 had had the strongest cold signal for the E US for any week in March of 2023 yet. And now the brand new one for that week (see image below) has a significantly stronger cold signal than even that one. In addition, the subsequent week (March 20-27) on this new run has a much stronger cold signal than the prior run had for that week and about as strong a signal as the prior run's March 13-20. So, this is an impressively strong cold signal for the E US overall on today's Euro weeklies for 3/13-27! The major SSW and the upcoming new very notable strat weakening are looking to do their thing apparently! This new strat weakening is projected to bring 60N 10 mb winds all the way down to near -17 m/s on Feb 28th! The major SSW, though quite impressive in its own right, brought those winds down "only" down to -13 m/s (on Feb 18th). The latest extended GEFS largely agrees. So, the Feb that we've missed out on may actually finally arrive here in March! Tony, sleet could still be in your near future for all anyone knows! I'll go even further. No single week in any of Jan, Feb, or March of 2023 on any Weeklies run back to Jan 5th (14 runs excluding today's) has had as strong a cold signal (vs normal of course) for the E US as today's for March 13-20 with today's run for March 20-27 and last week's for March 13-20 about tied for second coldest signal.
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Don/Folks, The prior run's March 13-20 had had the strongest cold signal for the E US for any week in March of 2023 yet. And now this one that you just posted has a significantly stronger cold signal than that one. In addition, the subsequent week (March 20-27) on this new run has a much stronger cold signal than the prior run had for that week and about as strong a signal as the prior run's March 13-20. So, this is an impressively strong cold signal for the E US overall on the latest Euro weeklies for 3/13-27! The major SSW and the upcoming new very notable weakening are doing their thing apparently! This new strat weakening is projected to bring 60N 10 mb winds all the way to near -17 m/s on Feb 28th! The major SSW, though quite impressive in its own right, brought those winds down only to -13 m/s (on Feb 18th). *Edited to clarify that I'm talking about strongest cold signal for any week in March of 2023
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Piggybacking off of my reply to Don's question that I focused on Athens, GA, for my answer: This Weathermodels map has Athens at ~1/2 C BN or ~1 F BN as of 7 PM on March 9th. The TT EPS mean map had Athens at ~55 F then. It says on your map that Weathermodels uses 20 years for climate. Now consider this for Athens using this great site: https://www.wunderground.com/history/daily/us/ga/athens/KAHN/date/1981-3-9 2001-2020 avg for 7PM: 59 F 2003-2022 avg for 7PM: 59 F So, 55 F - 59 F = -4 F. Thus, for Athens as a representative for the SE, the anomaly on their map of ~-1 F should have been more like -4 F if we assume they're using either 2001-2020 or 2003-2022 for climo.
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Don, I earlier ITT said I was concerned about WxBell anomalies often having too large extremes and thus not trusting their anomaly maps. However, I decided to try to answer your question based on an objective analysis: 1. I decided to focus on Athens, GA, because you're focusing on the SE, the 360 hour forecast map I posted below shows them at ~55 F at 7 PM EST on 3/9/23, there's a large discrepancy there in the anomalies between WxBell and TT, and there's easy to find history for Athens. 2. WxBell (using 1991-2020 as a base) has them 4 F BN, implying a 59 F norm for 7 PM on March 9th for the period 1991-2020. 3. Tidbits (using 1981-2010 as a base) has them ~1.75 C AN or ~3 F AN, implying a 52 F norm for 7 PM on March 9th for the period 1981-2010. 4. So, I next needed to find Athens' average 7 PM March 9th temperature for both 1991-2020 and 1981-2010. 5. I found a great site with hourlies for any date going back to 1981. This link is for 3/9/1981. Just click on 7 PM on the top chart and then change the year to get the same for 1982-2020: https://www.wunderground.com/history/daily/us/ga/athens/KAHN/date/1981-3-9 6. Based on the data from this site, the 1991-2020 avg for 7PM on March 9th at Athens is 57 F. WxBell implied it was up at 59. Thus, WxBell's Athens normal for 7PM that day is 2 F too warm, which means that WxBell's 4 F BN should have instead been 2 F BN. 7. Based on the data from this site, the 1981-2010 avg for 7PM on March 9th at Athens is 56 F. TT implied it was only 52. Thus, TT's Athens normal for 7 PM that day is 4 F too cold, which means that TT's 3 F AN should have instead been 1 F BN or ~0.5 C BN. 8. Conclusion: The 7 F discrepancy between the WxBell and TT maps regarding the 7 PM March 9th normal at Athens (as representation for the SE) was due to a combination of them using different base periods (1 F), WxBell using a normal that is 2 F too warm, and TT using a normal that is 4 F too cold. So, although all three are factors, TT (4 F) was surprisingly the biggest factor rather than WxBell (2 F) or the different base periods (1 F). Without doing this, I would have guessed that WxBell was the biggest factor based on my prior impression about them. ---------------------------- This 0Z 2/23/23 run's 360 hour EPS mean map has Athens at ~55 F:
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That's not a problem for RDU. They had 83 F on 2/3/1989 followed by 11.1" from two storms later that month along with light accumulations in both March and April.
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Maybe I know my posts related to the stratosphere seem endless. I empathize. But keep in mind that we won't be two weeks past the only major SSW of this winter to date until about 240 hours from now. Only around then will we finally be at the "put up or shut up" time. I always thought it would be mild at least until either the last few days of Feb or first week of March (with regard to the major SSW). And we do have a real live strong -NAO on the model consensus starting within a week. So, I'm anxious to see what happens.
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Fwiw since it is an operational run at 240, the end of the 12Z Euro has an NAO that is probably bordering on a -2 (March 4th). They don't get that much stronger than that. This would be consistent with the typical timing of blocking setting up after a major SSW as that is at the 2 week point. Thus, this solution isn't as far fetched as it may seem.
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Don, Part of the discrepancy may be due to the first map being based just on today's 6Z run, alone. Although I don't trust the WxBell algorithms used to produce that first map (I believe their extremes are often overdone), I'm guessing it was a cold run. In contrast, it looks like the maps at the bottom are based on an average of runs from 6Z 2/19 through 0Z 2/22. Note the "initial conditions". Am I looking at this correctly? Regardless, I'm no JB fan due to his mainly cold biases, which I think are partially due to having energy clients. Reading between the lines, he often seems to want natural gas prices to rise.
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Keep in mind that just 5 days ago, the GEFS mean based NAO forecast had it drop only to zero Feb 26th-Mar 2nd. Today's has it drop way down to a strong -NAO (-1) on Mar 2nd. What will the ensemble mean maps have on them five days from now for the E US and other areas for early March? The point is that this is an extra difficult situation (recent major SSW and another major 60N 10 mb wind drop way down into negative territory projected Feb 26-28) for models that have already been performing poorly this winter even without these big strat changes. We shouldn't assume that they have much of a clue about what's going to happen ten days from now, much less two weeks out.
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2022-2023 Fall/Winter Mountains Thread
GaWx replied to BlueRidgeFolklore's topic in Southeastern States
I know it is way out there in fantasyland (11-14 days) on an operational model and thus is for entertainment only and will understandably make some laugh. But for the record: if the 18Z were to somehow happen to have the right idea, the mountains would be hammered by upslope snow on and off during March 4th-7th. Regardless of the atrocious nature of the models this winter as well as the mildness of this winter to date overall, we still are the better part of a week away from when the recent major SSW can possibly first affect the tropospheric pattern. That SSW combined with an additional strong 60N 10 mb wind reversal progged for a week from now make things much more unpredictable than normal on Feb 21st when looking ahead to March. This is especially the case when considering the insistence of the models on a strong -NAO, which is very likely being caused by the SSW. Keep in mind that just five days ago, the GEFS mean had had the +NAO fall only to neutral in very late Feb/early March vs solidly negative on today's run. A lot has changed and still can change from what current runs, including ens means, are showing. Edit: It is the Happy Hour run. So, the GFS could just be drunk. -
This really should be in the March thread, but since that thread doesn't exist yet: Check this out about the major SSW and how the Euro Weeklies and extended GEFS are now clearly suggesting that the E US will be significantly affected especially on and after March 10th: https://www.severe-weather.eu/global-weather/polar-vortex-sudden-stratospheric-warming-main-weather-impacts-united-states-canada-europe-forecast-fa/
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Check this out about the major SSW and how the Euro Weeklies and extended GEFS are now clearly forecasting that the E US will be strongly affected especially on and after March 10th: https://www.severe-weather.eu/global-weather/polar-vortex-sudden-stratospheric-warming-main-weather-impacts-united-states-canada-europe-forecast-fa/
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After a mild period through 3/5 (warmer than the prior run), today's Euro weeklies *fwiw* are significantly colder than the prior run thanks to a stronger and persistent -NAO throughout March. The highlight is in mid-March, when nearly the entire US is BN (3/13-19)(see image below). That is the coldest map for any March week of any Weeklies run to date. I understand if folks doubt this based on this winter so far. Some may laugh at this, which would be understandable. But the major SSW we just had along with, believe it or not, another reversal of the 60N winds at the 10 mb level now being forecasted for about one week from now along with the progged solid -NAO throughout March tell me that a legit cold period is believable. Would that be cold enough for wintry precip in parts of the SE if it were to occur? Who knows but mid March is often still early enough for a state like NC at the least:
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The models are doubting the freezing part other than near the VA border, but regardless, much of NC has a good chance to be 40-45 colder Saturday afternoon vs Thu afternoon! They're projecting dewpoint drops from 60s to 20s during Friday.
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- The closest I could find for GSP to something big is a 79 two days before the 5.1" of 2/26/1982. - But RDU had 6" on 2/18/1989, which was 15 days after an 83 - RDU came very close with 79s three times before other biggies: 7" on 3/24/1983 nine days after, 11.1" on 3/1-2/1980 7-8 days after, and 8" on 3/10/1934 three days after. - ATL: couldn't find 80 prior to a big one but they had 80 nine days before a small one (0.7" of 2/23/1989). - ATL: came very close with 79 seven days prior to 2.7" of 3/2/1980.
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Related to 2018, there have been 15 sub -0.90 March NAOs since 1950. All 15 respective AOs were sub -0.5, which is the threshold I use for -AO. Even more telling is that 12 of the 15 (80%) had a sub -1.0 AO. So, assuming the -NAO will actually persist through all of March, it will be interesting to see whether or not we end up with a -AO despite what current modeling shows.
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Keep in mind that the historically cold and winter storm filled March of 1960 had a PNA of -0.4! But it obviously would be best to have a higher PNA, which could still occur, plus March of 1960 was an extreme anomaly.
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March of 1960, a very cold and wintry March throughout the E US, had a strong -AO and a moderate -NAO. But what may surprise folks is that it had a -PNA (-0.40).
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The GEFS (used in CPC daily updated charts for indices) based NAO forecasts have gone markedly in the -NAO direction over the last 4 day period: - The 2/13 forecast had only 2 members (~6%) with a sub -0.25 NAO (what I consider -NAO) on 2/27. The mean for 2/27 on the 2/13 run was up at +0.5 vs 0 on the 2/16 run and -0.3 on the 2/17 run. - The # of members with a -NAO on 2/27 rose sharply on the 2/14 run from 2 to 8 members (~25%). - The 2/15 and 2/16 forecasts each had ~10 members (~33%) with a -NAO on 2/27. - The 2/17 forecast has ~15 members (~50%) with a -NAO on 2/27. - So, the progression from the 2/13 run to the 2/17 run has been 2 to 8 to 10 to 10 to 15 members with a -NAO on 2/27. - The 2/16 forecast had ~10 members (~33%) with a -NAO on 3/1 vs ~23 (~75%) on the new one - The 2/16 forecast had only 3 members (~10%) with a sub -1 NAO (what I consider a strong -NAO) on 3/1. The 2/17 forecast has 10 (~33%). - The 2/16 forecast had 12 members (~40%) with a +0.25+ NAO (what I consider +NAO) on 3/1 vs only 3 (~10%) on the 2/17. With this trend toward -NAO for 2/27-3/1+ remaining strong even on today's run as per the above, I wonder if the trend will continue to an even stronger -NAO over the next few days of runs as the models get an even better grasp of the downwelling of the major SSW that won't peak til tomorrow (as per the 10 mb 60N winds). Keep in mind that the main period in question (2/26+) is still 9+ days out, which for this uncommon situation (a major SSW with a dip to ~-15 m/s 10 mb winds at 60N) is probably not the easiest for the models to handle well. Also, are the models correct in keeping a +AO with this increasingly strong progged -NAO? Or is the modeled AO going to start dropping if the progged -NAO keeps strengthening? I especially wonder about this since a strong -AO is often the hallmark of a successfully downwelled SSW. What do others think? It remains to be seen whether or not the SE will cool down significantly by early March. Unlike the NE even if the AO ends up also falling, the SE is likely going to also need the PNA to rise (better Pacific than currently). So far, modeling is hardly budging there.
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The GEFS (used in CPC daily updated charts for indices) based NAO forecasts have gone markedly in the -NAO direction over the last 4 day period: - The 2/13 forecast had only 2 members (~6%) with a sub -0.25 NAO (what I consider -NAO) on 2/27. The mean for 2/27 on the 2/13 run was up at +0.5 vs 0 on the 2/16 run and -0.3 on the 2/17 run. - The # of members with a -NAO on 2/27 rose sharply on the 2/14 run from 2 to 8 members (~25%). - The 2/15 and 2/16 forecasts each had ~10 members (~33%) with a -NAO on 2/27. - The 2/17 forecast has ~15 members (~50%) with a -NAO on 2/27. - So, the progression from the 2/13 run to the 2/17 run has been 2 to 8 to 10 to 10 to 15 members with a -NAO on 2/27. - The 2/16 forecast had ~10 members (~33%) with a -NAO on 3/1 vs ~23 (~75%) on the new one - The 2/16 forecast had only 3 members (~10%) with a sub -1 NAO (what I consider a strong -NAO) on 3/1. The 2/17 forecast has 10 (~33%). - The 2/16 forecast had 12 members (~40%) with a +0.25+ NAO (what I consider +NAO) on 3/1 vs only 3 (~10%) on the 2/17. With this trend toward -NAO for 2/27-3/1+ remaining strong even on today's run as per the above, I wonder if the trend will continue to an even stronger -NAO over the next few days of runs as the models get an even better grasp of the downwelling of the major SSW that won't peak til tomorrow (as per the 10 mb 60N winds). Keep in mind that the main period in question (2/26+) is still 9+ days out, which for this uncommon situation (a major SSW with a dip to ~-15 m/s 10 mb winds at 60N) is probably not the easiest for the models to handle well. Also, are the models correct in keeping a +AO with this increasingly strong progged -NAO? Or is the modeled AO going to start dropping if the progged -NAO keeps strengthening? I especially wonder about this since a strong -AO is often the hallmark of a successfully downwelled SSW. What do others think? -------------------------------- 2/13/23 GEFS based NAO prog (see middle graph): look at how + it was at end (for 2/27) with only two members having a -NAO! 2/17/23 GEFS based NAO prog: look at the huge drop in it as of 2/27 vs just 4 days ago with half the members now having a -NAO that day (vs only 2 members 4 days ago) and almost all having a -NAO by 3/1:
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Are you saying that you don't think that the upcoming -NAO is largely due to the current major SSW? The timing is about right with it starting ~10 days after the SSW although I realize that a -AO usually accompanies the -NAO.
