bluewave

One of the few areas of North America that does really well with +EPO 500 mb pattern.

You would have loved the 1960s with snowy winters and drought conditions the rest of the year. Monthly Total Snowfall for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Mean T 0.4 8.3 7.1 10.1 6.1 0.1 32.0 1959-1960 0.0 0.5 15.8 2.5 1.9 18.5 0.0 39.2 1960-1961 T 0.0 18.6 16.7 18.2 1.2 T 54.7 1961-1962 0.0 T 7.7 0.6 9.6 0.2 T 18.1 1962-1963 T T 4.5 5.3 3.7 2.8 T 16.3 1963-1964 0.0 T 11.3 13.3 14.1 6.0 T 44.7 1964-1965 0.0 0.0 3.1 14.8 2.5 2.8 1.2 24.4 1965-1966 T 0.0 T 11.6 9.8 T 0.0 21.4 1966-1967 0.0 0.0 9.1 1.4 23.6 17.4 T 51.5 1967-1968 0.0 3.2 5.5 3.6 1.1 6.1 0.0 19.5 1968-1969 0.0 T 7.0 1.0 16.6 5.6 0.0 30.2

Subsurface warmth continuing to increase. Getting close to +12 now in spots. The +30C warm pool shifting further east is also a first.

JMA has a great site with many different ENSO composites. https://ds.data.jma.go.jp/tcc/tcc/products/clisys/enso_statistics/index.html

Looks like a drier interval relative to JAS coming up this week. The next heavy rainfall potential may come around Columbus Day. Tropical moisture with the super El Niño STJ is forecast to stream north from the Gulf around a strong Southeast ridge.

October is showing overlapping influences compared to past El Nino climatology. The typical -EPO blocking ridge is displaced further south than usual into the Western US. This is a continuing theme from last spring with enhanced mid-latitude ridges. It’s developing a little more south of 2015 which would be the closest match. The North Pacific low looks displaced or stretched into a +WPO position.

Unfortunately, the arrival of spring warmth is coming earlier while the date of the last freeze has held more steady over time.

The Euro was fairly close this month. It had forecast a global mean average temperature of 1.67 C in September. The September average came in a +1.63 C.

The original paper that RONI is based on discusses it mostly being developed to prevent weak La Nina’s from getting lost in the mix rather than some deficiency in measuring super El Niño events. Plus the weaker El Niños not being able to fully couple. Both instances were also a function of the record WPAC warm pool. So the ONI and the absolute SSTs are a good measure of how intense this event is becoming. My original ONI post was correct as the original ONIs we relied on for many years into the 2010s had the ONI with the 1972-1973 event peaking at the +2.0 to +2.1 range. So a lower end super El Niño event.

The planet doesn’t care about squabbles based on how humans define things. It just responds to the actual temperatures. So the headline story for the planet right now is that we are exceeding past super El Niño events by a wide margin and it’s still only early October. All-time SST records are increasing from Nino 3.4 to 1.2.

The old ONI that we used before the recent updates was also +2.1. It’s perfectly fine to use the ONI as a measurement of the actual intensity of the event. With an event as extreme as this RONI can make the event seem weaker than it actually is. https://x.com/BenNollWeather/status/2105084471750037987 From a scientific perspective, part of the challenge is that weather patterns in different parts of the world are not equally sensitive to the same El Niño index. In South America, for example, Niño 1+2 is particularly important, while patterns across the U.S., Australia, Singapore and many other regions are more closely associated with conditions in Niño 3.4. Some rely on a blend of ocean-atmosphere indicators (e.g., ONI, RONI, SOI, EQSOI, OLR, MEI, etc.) to capture coupling. For the public, the minutiae of those indices matter much less. What's record-breaking in one index may not be record-breaking in another, and I think it's incumbent on the communicator to make that clear. At the very least, if a record is being claimed, then a reference to the index/data set being used is essential (see attached). Not everyone will read the fine print, but it's duty of care. I think there's an opportunity for a larger body to step in (e.g., WMO) to classify a record El Niño event, if there's sufficient evidence, like they would a global temperature record. Lastly, I think the RONI-ONI debate will go on for years. RONI is more closely tied to atmospheric responses. ONI informs absolute extremes. In the ONI space, every tenth of a degree matters to global water vapor levels and temperatures, and therefore, the weather. The best approach is up for debate, but I think showing both is a fair balance. One El Niño, many ways to measure it! https://x.com/WeatherProf/status/2105064342441939064 On the other hand, if you are trying to communicate the absolute strength of this El Niño vs other historic El Nino’s, how global warming has impacted it, or how it may impact global temperatures in the coming months - then use the traditional ONI or raw sea surface temperature anomalies. Certainly it can be confusing to the public, but I’d argue the relative index inadvertently obscures the larger climate signal - it can be misleading because it basically subtracts the warming that has occurred in recent decades. So it’s unintentionally deceptive.

Warm spots from Philly to Newark could be closer to the AI in the mid to upper 80s with enough sun today. It’s possible some of the locally cooler spots across the region could dip under 40° next week with some frost. But looks like a quick warm up a few days later. Not much cold to work with so much warmth across the CONUS.

It was a+2.1 event up until a few years ago before the CPC dropped it to +1.8. So until very recently it was rated as a lower end super.

There has been a deep upper low across the Arctic since the spring with record 500 mb ridging across the mid-latitudes. So this looks like a continuation of the same theme. Both the AO and NAO have been mostly positive over this period. Almost looks like some type of rebound following the strong winter blocking with the early SSW back in November. The last time we had a +AO October with a super El Niño was 1972. But even October 1972 managed to get the more common -EPO.

Yeah, they could reach 80° today with enough sun ahead of the main warm push tomorrow. So a warmer start to the month before we cool down next week. The interior areas have a shot at their first frost next Tuesday into Wednesday.