jconsor

True, but we just had a snowstorm produce widespread 6-8"+ from I-95 south and east (other than lighter amounts in the urban heat island near NYC) with -PNA, though in that case the NAO was slightly positive and AO highly positive. *If* we are going to see a 6"+ snowstorm in a -PNA pattern during a La Nina, it almost definitely will come from northern stream system e.g. a highly amplified clipper/Miller B.

The NWS map looks underdone to me for eastern/central LI and eastern Connecticut. I would expect widespread gusts of 55+ mph and scattered 65-70 mph gusts. HREF *mean* has 70 mph hugging the South Shore of Suffolk County and the Twin Forks, and HRRR is similar. We often overperform in southerly windstorms in the winter ahead of cold fronts.

I agree with you in general. However, there is a timeframe that I think has more potential for a negative tilt, digging trough late next week into next weekend (Dec 11-14). This is the timeframe that both operational models and ensembles show the blocking retrograding from western Greenland to near Baffin Island and then into central Canada, and possibly linking up with western US ridging. The period when blocks retrograde and decay into Central Canada and then link up with western US ridging is the one when significant snowstorms are most likely in the coastal parts of the NE US. Now to clarify, I don't see the potential for a significant (6"+ snowstorm) for the I-95 corridor from NYC to BOS. But my point is that the pattern does match periods which are more favorable for significant coastal storms along with sufficient cold air for snow. Given the northern stream/clipper dominated pattern and the troughs turning negative tilt relatively late, snowfall would be most favored across far northern NY and northern New England, but eastern Long Island to SE New England also climatologically can do well in these types of events if they dig far enough south. The ECMWF and (to a degree) the GEM both show the above-mentioned blocking and negative tilt/digging trough trends late next week into next weekend.

I agree that the -WPO will remain the most dominant influence on the cold through mid-Dec. However, there are increasing indications that in the 10-15 day period (Dec 13 and beyond), the center of the most anomalous ridging will shift significantly NE from the Kamchatka Peninsula/western Bering Sea to the Bering Strait, with the eastern extent of positive anomalous also shifting notably eastward into AK and even parts of the Northwest Territories. Combined with the increased negative anomalies north/NE of Hawaii and below normal heights over the NE US, that suggests a -EPO. This more eastward position of the ridging could theoretically allow the most anomalous cold air to be directed toward the NE US beyond Dec 15, though the lack of ridging over Greenland and the relatively northward position of the polar vortex indicated by the guidance e.g. north of Hudson Bay (I am mainly speaking about EPS and GEPS) would counteract this.

I hear your point about the dangers of oversimplying ENSO-PNA relationships, Don, and wholeheartedly agree. However, from my perspective there is increasing evidence the PNA will average neutral overall (with some periods of slightly positive PNA, especially Dec 7-9 and Dec 14-20) the second and third weeks of Dec. True, the EPS pattern days 3-7 and 11-15 is not fully in line with a canonical +PNA (the positive anomalies are shifted south and west vs. the typical position over western Canada and the NW US, the negative anomalies are concentrated over SE Canada and the NE US vs. the mid-Atlantic and SE US, and the upstream negative anomalies are in the e. Gulf of Alaska vs. the typical position further SW in the north-central Pacific). However, both the EPS and GEPS have been trending toward a more neutral PNA in most of the next two weeks (e.g. Dec 7-10 and Dec 14 and beyond). The charts you showed were from the GEFS, which has the most -PNA (and SE US ridge) biased of all the models recently. Also, looking at the EPS individual members it is evident that a few members with a highly negative PNA are skewing the mean downward Dec 14 onward. A slightly majority of members (about 55-60%) actually show a +PNA during that timeframe! The GEPS is not as aggressive, but still has about 40-50% of members showing a +PNA in the same timeframe. Regarding the last third of Dec, there is too much uncertainty to comment much on that period. While I favor the SE US ridge returning to a degree, I am skeptical of the strength of the NW/N-central US trough and SE US/W Atlantic ridge shown in the past two EPS long-range runs.

Some thoughs on ENSO heading into next hurricane season: https://x.com/yconsor/status/1986046871349936133

Very impressively backloaded hurricane season this year. Here are some stats: https://x.com/yconsor/status/1983980828268097557

Severe damage in Montego Bay: https://x.com/rj_smith_3/status/1983506193994666304

The part of SE Cuba expected to be hit hardest (Santiago de Cuba) has very little precedent for Cat 3s, and none for Cat 4s: https://x.com/yconsor/status/1983236668933988715

Unlikely it gets closer than Andros Island in the Bahamas. Only way I could see Melissa getting really close to FL is if the day 7 trough/cutoff low misses it and it lingers somewhere from Cuba south into the NW Caribbean, *or* if it dives WSW and gets so far south (e.g. near Nicaragua/Honduras border) that by the time that trough picks it up it ends up near FL while turning NE. Both are highly unlikely in my view, but the past few KMA runs (not a reliable model) have shown something like one of these two scenarios.

The westward trend continues. Very few members going east of Cuba now, with a substantial increase in the number of members west of 80W by next Wed.

There are quite few analogs for the time of year and Melissa's expected path and intensity. https://x.com/yconsor/status/1980991500482994204

Notable left trend on FNV3 (Google DeepMind ensemble) from 12z run yesterday to today's 6z run - both in terms of the the members that show a sharp NE curve into Hispaniola being further west (Haiti vs. DR) and a lot more members turning west into the NW Caribbean

With 98L's increased organization in the past 12 hours, the hurricane models finally seem to be getting a better handle on its track and intensification. https://x.com/yconsor/status/1980253973345923256

AIFS seems off showing too much of a hole in the W Atl ridging N/NW of 98L. The other ML models don't support its scenario of 98L curving sharply NE toward Hispaniola. https://x.com/yconsor/status/1979887548240650357

Erin left a heck of a cold wake across the nw Atlantic, while the ENSO regions have cooled dramatically past two weeks. How will this influence Atlantic hurricane activity this month, and what are the two areas I am watching besides the E. Atl system? I go into depth on the large-scale factors for the next few weeks including Sep analogs, while looking at the "elephant in the room" that is being largely ignored IMHO because most tropical enthusiasts are focusing on the East Atlantic system. https://hurricanehacker.substack.com/p/the-times-they-are-changin

Please post the link for the vertical instability graphic. Thanks

ECMWF and Australian BOM models (amongst other seasonal models) suggesting a Central Atlantic NIno developing. This, along with portion of the very warm anomalies west of Europe gradually bleeding SW the Canary Islands and eastern tropical Atlantic, could help ramp up activity in the deep tropics, particularly west of 40W. https://x.com/yconsor/status/1930624747382964591

Hi Chuck, Interesting comparisons! I personally think using named storms to characterize active vs. inactive years is not particularly meaningful, given the human subjectivity and changes in NHC criteria over the years in terms of what is named. If we take the years with the most and least ACE since 1995, removing years that were El Ninos in the Apr-May timeframe (since they tend to be strongly correlated with -NAO), here are the most active years: 2020, 2005, 2004, 2003, 1999, 1996, 1995 The least active years: 2014, 2013, 2009, 2007, 2006 This year has some characteristics in common with the least active years (-MSLP anomaly from NW Territories of Canada to Greenland and +MSLP anomaly from the NW US to Hudson Bay and off the coast of the NE US). However, what is different from the inactive year composite, and closer to the active year composite, is the -MSLP from near Newfoundland to the central Atlantic near the Azores and then southward into the far east Atlantic and w. Africa. Additionally, the strong +NSLP from near the UK to Iceland is more similar to the active year composite. In short, a mixed bag, probably closer to inactive years but not a clear signal!

I was referring to highly unlikely possibility that so many of the hurricanes in both basins will become majors.

7 hurricanes and 5 majors in the Atlantic (and 6 and 5 in the East Pacific) is a rather comical outlook

In my view, it's mportant not to lump all La Ninas together. Modoki (central Pacific-based) La Ninas are notably different from traditional (East Pacific-based) Ninas. This has big implications for the level of Atlantic TC activity and where in the basin it tends to be focused. This year is more likely to end up a Modoki La Nina, with cooler water relative to normal focused in the central Pacific: https://x.com/yconsor/status/1927306239920283821

Thread explaining why I think chances for tropical development in the NW Caribbean and Gulf of Mexico ramp up significantly around Jun 4-10. https://x.com/yconsor/status/1926690131181731976

After not being much of a factor from 2019-24, looks like the N. Atlantic warm hole, a pool of relatively cooler water south of Greenland, is returning and should remain through peak hurricane season. This tends to ramp up the risk for E. Coast hurricanes, particularly slow-moving ones: https://x.com/yconsor/status/1925494559032668254

268Weather, an eastern Caribbean-based forecast service, has updated its hurricane season outlook: They are going for 21 TS, 9 hurricanes and 5 MH, with ACE expectation of 185. They indicate a 48% chance of ACE above 223 and a 52% chance of at least 11 hurricanes, each of which would place 2025 amongst the most active hurricane seasons on record. Seems odd that their baseline forecast for H is 9 and ACE is 185, yet there is around a 50% chance of ACE and hurricanes well above these numbers. If you look back at their track record, their May forecasts were considerably too high (bullish) in 2021 (ACE forecast 179), 2022 (175) and 2024 (218). On the other hand, their May 2017 forecast (ACE of 110) strongly underestimated activity. They were on the few seasonal forecasting agencies to catch onto slightly above normal activity (based on 1950-2020 normals) in 2018 and 2019. https://268weather.wordpress.com/2025/05/16/268weather-may-2025-update-atlantic-hurricane-season-still-projected-to-be-above-normal/