GaWx

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.

The 12Z GFS has a short period of snow 2/18 on the radar depiction fwiw for the 4th of the last 5 runs in a portion of coastal NC due to very dry air aloft. But with temps in the low 40s, there's no accumulation. A good number (8) of the 30 GEFS ensemble members show similar. So, though not at all likely, it is also far from impossible.

The cold biased CMC (12Z run) gives a 39 F cold rain to a portion of the FL/GA border early on Feb 19th. In addition, 850s get as low as +1C and 925s as low as 0C with light rain in Brunswick but temps get down only to the low 40s there on the run. If only the low were stronger/precip heavier bringing the colder air aloft to the surface. OTOH, this model is cold biased, regardless. So, it is likely overdone with how cold the rain is.

In just 6 days, the GEFS AO forecast went from this on Feb 8th: To this today: the forecast for Feb 21st has risen from -3 to +1, one of the biggest forecast turnarounds I can recall within just 6 days! So, it isn’t just the Weeklies that failed. The Weeklies failing isn’t unusual. The within two week ensemble timeframe (for all ensembles) has also badly failed, which is the biggest disappointment: The NAO and PNA have similarly badly failed.

Some of the Rocky Mountain states as well as CA and WA are amazing to me as regards the stark contrast between nearby districts! Is this due to varying elevations? Examples: -S CA coast 88 vs desert's 17 -The neighboring districts in WA that are 17 and 69 -The neighboring districts in NM that are 19 and 80

0Z GFS, due possibly to less new snow over the MW/N Plains, isn’t as cold as recent runs. Let’s see whether this leads to a less cold rain in the SE. Edit: It seems to have done that showing the importance in the model of new snow-cover.

The 18Z Euro suite is less suppressed than recent runs. If that were a sign of what’s to come in future Euro runs, that would be good because it like the ICON has been too suppressed to do any good for anyone since the 0Z 2/12 run, regardless of the temps. But even so, the 18Z EPS, which is slightly less suppressed and thus has more qpf along the Gulf coast, still has little snow anywhere in the SE.

Further to the above post, the GFS/GEFS seem to be on an island suggesting much of a chance for SE wintry precip mainly on the back edge 2/17-18. The 18Z GEFS has 13 of 30 members with some of that, mainly light/not necessarily sticking. The reason these last two runs have had more seems to be somewhat of a delay in the low moving out in the means vs runs just before these.

18Z GFS is still teasing us with the back edge of the rain changing to snow for brief periods of 2/17-18 though with temps comfortably above 32. 0Z and 12Z runs also had this. So, 3 of last 4 runs with what could be somewhat interesting. But other models are showing pretty much nothing.

Regarding any potential GOM/offshore SE low, there are still 13 of 30 12Z GEFS with mainly light snow mostly in E Carolinas. But the 12Z EPS and GEPS suggest very little chance.

Compared to yesterday’s outlier cold 12Z CMC with its hard to believe single digits over NW 2/3 of MO for 12Z on 2/17 (cold airmass preceding potential GOM storm) with max SLP NW MO 1041 mb, today’s 0Z and 12Z are much warmer there with the 12Z 10-15 warmer with mainly 13-22 and max SLP only 1033 mb. Related to this later over the E portion of the SE to the coast, the rain isn’t nearly as cold with mainly 40-47 on today’s 12Z run instead of 33-37 of yesterday’s 12Z and the little bit of wintry precip it actually had. Still, the 2/18-19 period is not a done deal for SE wintry from any potential Gulf to offshore SE low although chances are dropping as we get closer. I didn’t see much to get excited about on the 12Z model consensus. We need a colder airmass from the N stream to interact just right with any low.

0Z Euro: no SE wintry precip

0Z GEFS: 12Z 2/17 Midwest/Plains and 12Z 2/18 SE 2m temps are both the coldest in at least a week’s worth of runs (per TT site…easy to compare).

0Z CMC: no SE winter storm. Run not as cold as prior run as of 12Z on 2/17. That carries over later to not as cold NW of the offshore SE low and thus not as cold a rain/not as close a call. (actually 12Z had a little bit of wintry precip).

0Z GFS has more IA and vicinity snow and a possibly related stronger push of cold. Let’s see whether this pushes moisture/storminess away from the SE or else it teams up with moisture and gets more interesting. Edit: the former though it gets close. We need the low/moisture to lag more/come in later to mix with the cold instead of riding along the cold front, which usually doesn’t work out (cold chasing moisture). Edit: This GFS is coldest in SE for 12Z on 2/18 in at least a week per TT old runs. *Corrected