GaWx

Morning lows at KSAV 2/19-21: 33, 34, 36 One last sub 40 in the string likely tonight and then Sun (2/25). Another beautiful, very low dewpoint day with another high in the middle 60s expected today. A great time to be outside with pollen still moderate, no bugs, and near perfect wx!

My bad. I was in DJF mode. In reality, phases 4 and 5 average near normal in the SE for FMA with 6 and 7 the warmest ones averaged out. Coldest averaged out are 1, 2 and 3. But regardless, MJO phase correlations are only moderate:

Today’s MJO forecasts suggest an increased chance for moderate or stronger phases 4 and 5 starting ~March 5. The folks wanting it mild to warm then should be happy about this though the correlation of those phases to warmth isn’t that strong as MJO correlations tend to be moderate. Also although very much a fwiw being how poorly they’ve done, yesterday’s Euro Weeklies are mainly mild Mar 1-10.

It wasn’t just the extended models that failed badly. Failing that far out isn’t at all unusual due to low skill. But look at how badly the GEFS (other models were similar) busted with the very strong -AO predictions made 2/6-8 for 2/13-20: 2/6 predicted -3.5 2/7 predicted -3.0 2/8 predicted -3.2 2/6 AO prediction: -3.5 for 2/13-20 (all days sub -3.0!) Actual AO: -0.6 for 2/13-20 (2/16-20 all ended up above all 30 2/6 prediction’s members!)(2/20 ended up +2 vs -3 progs!) https://ftp.cpc.ncep.noaa.gov/cwlinks/norm.daily.ao.gefs.z1000.120days.csv

I was curious because I had never analyzed this. The following analysis of the top 10 ACE seasons suggests to me that a weak to moderate correlation of ACE to BOS/NYC snowfall the next cold season quite possibly exists, especially BOS, though ACE definitely shouldn’t be weighted heavily: Top 10 ACE years/snowfall following cold season 1933 NYC: 52.0”; BOS: 62.7”; mod La Nina 2005 NYC: 40.0”; BOS: 39.9”; wk La Nina 1893 NYC: 39.2”; BOS: 64.0”; mod La Nina 1926 NYC: 22.3”; BOS: 41.1”; neutral 1995 NYC: 75.6”; BOS: 107.6”; mod La Nina 2004 NYC: 41.0”; BOS: 86.6”; wk El Niño 2017 NYC: 40.9”; BOS: 59.9”; mod La Niña 1950 NYC: 9.3”; BOS: 29.7”; neutral 1961 NYC: 18.1”; BOS: 44.7”; neutral 1998 NYC: 12.7”; BOS: 36.4”; strng La Nina AVG NYC for top 10 ACE: 35.1” vs 28.5” mean of all years since 1868-9 or 23% above mean snowfall 2 MAN (including record heaviest), 4 AN, 0 NN, 2 BN, 2 MBN; 60% of top 10 ACE seasons had above snowfall median to follow —————————————- AVG BOS for top 10 ACE: 57.3” vs 43.1” mean all years since 1890-1 or 33% above mean snowfall 2 MAN (both in top 5), 3 AN, 4 NN, 1 BN, 0 MBN; 70% of top 10 ACE seasons had above snowfall median to follow ———————————— ACE: https://en.m.wikipedia.org/wiki/Accumulated_cyclone_energy#:~:text=Accumulated cyclone energy (ACE) is,into a single index value. NYC: https://www.weather.gov/wrh/Climate?wfo=okx BOS: https://www.weather.gov/wrh/Climate?wfo=box *Edit: This is a small sample but is it possible that a moderate La Niña has a notable correlation to heavier snow in BOS and/or NYC? Anyone know?

The historical data (each year's ACE and each winter's snowfall by EC city) is out there in case someone wanted to see if there's any significant correlation.

This EPO dipped only down to -218 vs the models showing -300: 2024 02 12 -47.15 2024 02 13 -167.32 2024 02 14 -186.38 2024 02 15 -187.46 2024 02 16 -216.35 2024 02 17 -218.04 2024 02 18 -150.94

As bad as all of the models have been, we shouldn’t trust ANY tropospheric model output for over a few days into the future. The strat progs are less unreliable because the strat is normally a bit easier for the models to forecast than the troposphere. But even so, the actual effect of the strat on the troposphere would still be more uncertain. Even if this next SSW along with followup weak SPV were to verify, who’s to say that that would lead to a new round of -NAO and/or -AO? After the major bust of the -AO and -NAO for the current period, I wouldn’t trust them, regardless. And then even if that were to occur, who’s to say that that would definitely lead to a colder E US?

From today’s Euro Weeklies, here’s the 10 mb winds: next major SSW ~March 4-5 followed by a dip of the mean way down to -10 m/s during ~3/8-10, lowest this season for any of the progged SSWs beating yesterday’s -8. Many members dip to sub -15. Then the mean stays weak the rest of March. Will the NAO/AO respond by also dipping?

The last few runs of the GFS hts at 10 mb have suggested the winds getting well down into the second most negative territory for March back to 1959. Although that means it is very likely overdone, it does show how strong a signal there is for yet another major SSW ~March 5th. The 12Z at 384 has a strat HIGH over the N pole (~3,175 dm), where more typically there’s a low there or nearby (the SPV). The SPV on this is very weak (~3010 dm) and is way south in the Atlantic near 53N! It doesn’t get much weaker/displaced than that. So, take the level of weakness shown with a grain.

Lows of 33 yesterday and 34 today here. Those are ~10 BN. A couple more lows in the 30s are quite possible. Yesterday’s high was 63 with plenty of sun. The next two days look pretty similar with dewpoints in the upper 20s to 30s and sunny skies. Absolutely gorgeous and great for the outdoors! I wish it were like this all year round.

As per the post I’m quoting, look at how badly the GEFS (other models were similar) busted with the very strong -AO predictions made 2/6-8 for 2/13-20: 2/6 predicted -3.5 2/7 predicted -3.0 2/8 predicted -3.2 2/6 prediction: -3.5 for 2/13-20 (all days sub -3.0!) Actual: -0.6 for 2/13-20 (2/16-20 all ended up above all 30 2/6 prediction’s members!) https://ftp.cpc.ncep.noaa.gov/cwlinks/norm.daily.ao.gefs.z1000.120days.csv

1. RONI max through NDJ: 2023-4 doesn’t fit in as it is only borderline moderate/strong 2023-4: +1.49 2015-6: +2.39 1997-8: +2.35 1982-3: +2.53 1972-3: +2.26 2. MEI max through DJ: 2023-4 doesn’t fit in as it is only low end moderate 2023-4: +1.1 2015-6: +2.2 1997-8: +2.2 1982-3: +2.6 1972-3: +1.9 RONI data: https://www.cpc.ncep.noaa.gov/data/indices/RONI.ascii.txt MEI data: https://psl.noaa.gov/enso/mei/ https://www.webberweather.com/multivariate-enso-index.html

Enjoy the current chilly nights/pleasantly cool days for the first half of this week because there’s no reason at this time to expect a dominant cool pattern anytime soon. The main indices, which suddenly made a very strong reversal (model consensus forecasts from Feb 5-9 were horrible busts) to suggest warmer than normal to dominate, haven’t backed off that reversal. What about March as a whole? Extended range models, other than for the stratosphere, are currently dead to me for obvious reasons. So, I’m left with mainly the always available climo. Looking at El Niño March climo for ATL since 1879: - 47 Nino Marches or 32% of the 145 years - Temperatures: 22 (47%) BN, 16 (34%) NN, and only 9 (19%) AN - 7 of the top 10 (70%) coldest Marches were during El Niño vs Nino occurring only 32% of the time. So, El Niño has had a far higher frequency of top 10 cold in March than other ENSO. The other 3 coldest were during neutral ENSO meaning no top 10 cold March during La Niña. - Even after adjusting for warmer normals, the last 4 Marches have been AN. The last BN was 2018, which only barely qualified as BN. Before that, one has to go back to 2014. The last MBN (again based on warmer climo) was 2013. The last really cold ones were way back in 1971, 1969, 1962, and the legendary 1960. - Measurable March wintry precip during El Niño: 9 of the 47 (19%). That compares to only 15% for non-Nino March. So, a moderate increase for El Niño March. - For 1”+ March snow since 1890, 7 of the 42 (17% or 1 in 6) El Niños had it vs a mere 3 of the 92 (1960, 1993, and 2009) (3% or 1 in 33) non-Nino Marches. That’s a stark contrast! - No measurable wintry precip in March in 14 years. That compares to the longest period on record between measurable wintry events of 15 years (1899-1914). So, if ATL doesn’t get measurable this March, that will insure at least a tie for the longest period between them. - So, in summary, despite the misery of a lack of wintry precip and persistent cold this winter and absolutely nothing showing on the foreseeable horizon, history says that just having El Niño ups the chances for a cold and snowy March at Atlanta (and much of the SE by proxy)vs not having El Niño. When combined with the current major SSW along with all models forecasting a very weak SPV in March, we at least have reason for some hope for a turnaround next month.

Tropical systems bring excessive heat from the tropics and move it to higher latitudes. With the Arctic warming much more strongly than lower latitudes due to AGW, there's less heat imbalance. Shouldn't that factor alone lead to reductions rather than increases in overall tropical activity?

As the globe warms further, I wonder how much increased warmth in the tropics will increase tropical activity. Arctic has warmed much more than other regions overall over the last few decades. So, even as the tropics get warmer, what if they overall continue to not warm as quickly as waters at much higher latitudes? Related to this, I’m familiar with the idea that ~79F is often the temp needed to allow for TC genesis. Assuming GW continues, will that temp increase? I’m sort of thinking in a RONI kind of way. Any thoughts?

It was in the low 50s here all day with breezy N winds and overcast skies. The high of the day was near midnight at 53, 13 BN. A 53 would be MBN even in mid-Jan. The daytime high was only 51. The pleasant chill made it a near perfect day for walking with dewpoints only in the 30-34 range. The next three nights’ lows could all be in the upper 30s with highs in the low to mid 60s along with mainly sunshine and 30s dews, near ideal for outdoors and much better than recent days through yesterday.

Thank you. It’s been fun! Here’s an interesting tweet stating that the DC area’s Dulles airport (IAD) this evening (0Z of 2/18/24) had its 2nd strongest recorded upper level wind going back to mid 20th century (230 knots from WSW at ~34-35K ft associated with the split flow squeeze). It missed the strongest (12/6/2002, another Nino) by only 2 knots!

Chuck, good job with your MidAtlantic/NE forecasts. I have this winter as basinwide/cross between EP and CP as 1+2 fell sharply before winter and 3 has been about same as 3.4. In addition, 4 has been quite warm vs its own climo. Also, an argument can be made that this was a moderate if one were basing this on either the RONI peak of only +1.49: https://www.cpc.ncep.noaa.gov/data/indices/RONI.ascii.txt or on the MEI peak of only +1.1: https://psl.noaa.gov/enso/mei/

Although one can see a similar but more subtle NW trend on the Euro, it still is showing no SE snow from this Gulf low. And the EPS still has nada like all runs before. All 50 members are still too far south to show snow. The GEPS also still has no members with snow. This vs 60% of GEFS members with back edge snow falling (most probably have none sticking), mainly light. The main reason GEFS has so many with snow is that its mean sfc low is further N and slightly stronger. Whether or not it’s also too cold I can’t say. But a more wound up low with heavier precip will bring down colder air. Summary: Euro/UK/ICON all remain too far SE though with subtle NW trends that we’ll see weather will continue. GFS/CMC are further NW and are at least close to producing some snow falling on the NW edge of the precip. Same camps as two days ago. Key is whether or not the NW trend will continue.

I know I “Kevined” out on the 2/18-9 threat the night before last. But for the record the GFS (12Z) won’t stop its teasing and it has been trending back this way (the semi-reliable NW trend) the last few runs with sharper H5 near Miss. River along with a more organized sfc low. In addition, the GEFS, which had been having ~1/3 of its members with similar, has increased to 60% of its members (the most yet) with similar on the 12Z. Like it or not, going to have to watch this being that it’s back to showing snow falling on the back end and now this is at only hour 48 (actually hour 42 is showing snow falling over S AL). Textbook split flow: And then the 12Z CMC is doing its own kind of teasing.

Most were nothing special in the SE, too, and thus I’m not optimistic at this point, especially in this day and age. Also, El Niño is what gets me excited more than anything by a good margin and especially those following La Niña. If it is going to be La Niña, I’ll pull for a weak to low end moderate one as they have a better chance of being cold than stronger ones in the SE. For example, though not immediately following El Niño, 1917-8 (cold and wintry precip in Dec/Jan)and 2017-8 (cold Jan, snow in Dec/Jan) were great. But, are you familiar with 1903-4? In addition to 1995-6 and 2010-1, 1903-4 was quite a cold winter in much of the E US to Midwest. In addition, Boston got 72.9” of snow, the heaviest between 1890-1 and 1914-5. For the SE, I’ve got 1903-4 and 2010-1 standing out as cold La Niña winters following El Niño. 1902-3 was a strong Nino and 1903-4 was a WEAK Niña. I’ll give 1964-5 an honorable mention for snow though temps were near normal: https://www.webberweather.com/ensemble-oceanic-nino-index.html

Without further ado folks after following this particular period with lots of enjoyment for several weeks, an important milestone has arrived for me for 2/18-9. Also, I currently see no threats down the road at least as of this point. There are no longer any encouraging signs and also it is getting late. This may be it for this winter.

Just over one year ago George started the El Niño thread and it’s already up to 266 pages! Will this thread be that long one year from now? We’ll see!

The 12Z Euro, UKMET, and ICON are all strongly suppressed and thus don’t have precip get anywhere far enough north for a close call to snow. OTOH as already noted, the not as suppressed GFS and CMC are at least close on the back edge of the precip. to some snow falling 2/18-19. Some snow falling would be a big deal for this winter to date. What camp are you in? The I don’t care camp doesn’t count as this thread is for forecast discussion for serious folks.