donsutherland1

The EPS and GEFS are indicating that the WPO will spend much of the December 10-20 period at or below -2.000. Regardless of whether the EPO is positive, AO is positive, and PNA is negative, severely negative WPO patterns tend to overwhelm the impact of the other teleconnections. Such patterns typically feature colder than normal conditions in the eastern half of North America and warmer conditions in the western half. December 15-18, 2013 offers a representative case with the distribution of warm and cold anomalies:

JFK Airport has now reached 20°. That ties the daily record that was set in 1966.

Some 6 am temperatures: Albany: 2° (tied record set in 1886 and tied in 1926 and 1989) Binghamton: 5° (tied record set in 1971 and tied in 1989) New York City-LaGuardia Airport: 20° (old record: 21°, 1942) White Plains: 14° (tied record set in 1966) Albany has its coldest temperature so early in the season since 1989.

The coldest air mass so far this season is now overspreading the region. The temperature will tumble into the lower 20s by tomorrow morning in New York City. Many areas outside the City will see lows in the teens. Daily record low marks for December 5th could be challenged or broken in Bridgeport, New York City-JFK Airport, New York City-LaGuardia Airport, and White Plains. The weekend will be cool but dry. A fresh surge of cold air could arrive Sunday night. The ongoing stretch of below normal temperatures will likely continue into or through the second week of December. December 1-10 will be a solidly colder than normal period. The potential exists for the coldest first 10 days of December since at least 2007 (33.4°, 5th coldest December 1-10 since 2000). The five coldest December 1-10 periods since 2000 were: 1. 30.6°, 2002 2. 32.2°, 2003 3. 32.4°, 2000 4. 33.1°, 2005 5. 33.4°, 2007 All 5 of these cases had measurable snowfall in Central Park. The ENSO Region 1+2 anomaly was -0.1°C and the Region 3.4 anomaly was -0.6°C for the week centered around November 26. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.18°C and the ENSO Region 3.4 anomaly has averaged -0.67°C. La Niña conditions will likely continue through at least mid-winter. The SOI was -43.70 today. That is the lowest SOI figure since February 9, 2024 when the SOI was -46.54. The preliminary Arctic Oscillation (AO) was -0.366 today.

Congratulations.

And perhaps that figure has increased a little more today with the snow squall that blew through.

Retired After Last Use December had begun on a strangely toasty note. The temperature had climbed to a balmy 57° (the third time in the last five years the mercury reached at least 57° on the first day of December), and the New York Public Library, perhaps out of nostalgia, perhaps out of quiet defiance, filled the marble halls of its iconic Beaux-Arts Fifth Avenue building with sepia-toned photographs of children tunneling through drifts taller than themselves. The exhibit captured an era that residents increasingly believed had slipped out of reach. A public weather notice board calling itself "American Weather" had given the display a name that struck Marisol, a student at Columbia University, as both melodramatic and heartbreaking: “The Final Snowfall.” Walking home after a full day of classes, Marisol passed one of Midtown’s newest absurdities: a synthetic snow dome where wealthy Manhattan parents paid $95 an hour to show their children what “winter” once felt like. She never stepped inside. Those plastic flakes felt like an insult. Her father had always said that snow gave New Yorkers a common language of spontaneous generosity. Cheap plastic could never measure up. Almost four years had passed since the last daily snowfall of four inches or more. Even two consecutive snow-starved years had never occurred before. Four such years were unimaginable. As Marisol passed one of American Weather’s public boards, a small sculpture beside it stopped her cold. There stood a dented aluminum snow shovel mounted upright like a relic. At its base, an engraved bronze plaque read, “Retired after last use: February 21, 1929.” She felt her throat tighten. "Snow is something you can only remember now," she thought. Then came the second thought. It was a much darker one, perhaps from having spent too much time reading "American Weather" on her way home from classes. "Soon there will be no one left who remembers at all," she worried. Her grief was premature. Just over two weeks later, a storm swept across the City, dropping 6.7" of snow on December 17 and another half-inch the following day. Less than two months after that, an even larger snowstorm buried Central Park beneath 10.0" of luminous white. Today marks the 1,405th consecutive day without a daily snowfall of four inches or more. Pessimism mixes with fatalism. Yet New York City has lived through snow droughts before, even as this one is the longest on record. As happened in December 1932, the streak will break. Eventually. Even with supercomputers, AI-driven forecasts, and models capable of simulating the atmosphere down to microphysical detail, the exact date of the next significant snowfall remains unknowable at this time. Patience is required. But so is confidence. December is now on course to register its coldest start in more than fifteen years. That's a hopeful start. The arrival of the cold reveals that Winter has not yet forgotten New York City.

Here's the data for New York City: Below are the composite 500 mb anomalies for WPO<0 December cases for 4" or more daily snowfall. To date, the guidance does not suggest the kind of pattern shown below. It should also be noted that snowfalls tend to be light during the first half of December when the AO/NAO/PNA are all negative.

It also looks likely to persist through at least mid-December, if not longer.

Yes, there's a different methodology. I use the BOM values when assessing patterns and impacts.

The coldest air mass so far this season will overspread the region tomorrow night. The cold front could touch off a few scattered snow flurries or snow showers. The temperature will tumble into the lower 20s by Friday morning in New York City. Many areas outside the City will see lows in the teens. It now appears that the weekend will be cool but dry. A colder than normal pattern is in place. A prolonged stretch of below normal temperatures will likely continue into or through the second week of December. December 1-10 will be a solidly colder than normal period. The potential exists for the coldest first 10 days of December since at least 2007 (33.4°, 5th coldest December 1-10 since 2000). The five coldest December 1-10 periods since 2000 were: 1. 30.6°, 2002 2. 32.2°, 2003 3. 32.4°, 2000 4. 33.1°, 2005 5. 33.4°, 2007 All 5 of these cases had measurable snowfall in Central Park. The ENSO Region 1+2 anomaly was -0.1°C and the Region 3.4 anomaly was -0.6°C for the week centered around November 26. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.18°C and the ENSO Region 3.4 anomaly has averaged -0.67°C. La Niña conditions will likely continue through at least mid-winter. The SOI was -28.49 today. The preliminary Arctic Oscillation (AO) was -0.144 today.

We agree that he’s brilliant. His MJO work is groundbreaking. On this point, I think he’s extrapolated where the coefficient of determination is fairly low. His overall linkage isn’t wrong, but other factors can easily overwhelm ENSO, the AAM, etc. It will be interesting to see the final outcome.

There's an ERA-5 dataset that goes back to 1940. https://www.psl.noaa.gov/mjo/mjoindex/omi.era5.1x.webpage.4023.txt

Thank you. It seems that the formula dropped "T" rather than counting it as 0 on the spreadsheet. Mean: 3.5"; median: 2.0"

For reference, New York City area locations where daily records could be challenged or broken on December 5th: