donsutherland1

The system responsible for today's showers and periods of rain will slowly move away from the region tonight and tomorrow. As a result, clouds will break tomorrow morning and a partly to mostly sunny afternoon will follow. Temperatures will return to the upper 70s tomorrow and then rise further into the lower 80s on Friday. The warmer spots could see some middle 80s on Friday. Cooler air will return for the weekend with another warmup possible starting early next week. The ENSO Region 1+2 anomaly was -0.2°C and the Region 3.4 anomaly was -0.5°C for the week centered around September 10. For the past six weeks, the ENSO Region 1+2 anomaly has averaged +0.10°C and the ENSO Region 3.4 anomaly has averaged -0.37°C. La Niña conditions will likely develop during mid- or late-autumn. The SOI was +4.93 today. The preliminary Arctic Oscillation (AO) was -1.179 today. Based on sensitivity analysis applied to the latest guidance, there is an implied near 51% probability that New York City will have a cooler than normal September (1991-2020 normal). September will likely finish with a mean temperature near 69.1° (0.1° below normal). Supplemental Information: The projected mean would be 1.1° above the 1981-2010 normal monthly value.

For New York City, the connection isn't as strong. Since 2000, a wet fall is more likely to be followed by a wet winter. Dry falls were only slightly more likely to be followed by wet winters (using the 1991-2020 baselines) for New York City (Central Park). Drier than Normal Falls: 54.5% were followed by above-normal winter precipitation (Last: Fall 2024/Winter 2024-2025) 45.5% were followed by below-normal winter precipitation (Last: Fall 2017/Winter 2017-2018) Wetter than Normal Falls: 61.5% were followed by above-normal winter precipitation (Last: Fall 2023/Winter 2023-2024) 38.5% were followed by below-normal winter precipitation (Last: Fall 2022/Winter 2022-2023)

Picard, My data comes mainly from: https://xmacis.rcc-acis.org/ I periodically use teleconnections data: https://ftp.cpc.ncep.noaa.gov/cwlinks/ and Climate Data: https://www.ncei.noaa.gov/access/monitoring/climate-at-a-glance/ Most of this data can readily be downloaded or converted into .CSV and .XLSX files

He's done invaluable work. I share your sentiments.

If one is looking for an idea of the warmest potential for any winter (month, season, or year) in the current climate regime (defined as the most recent 30 periods e.g. winters), one can come up with confidence intervals from a linear regression equation. A 1-in-1,000 year probability for the current regime would be the 99.9% confidence interval. For NYC, that value for a winter mean temperature is currently 44.8° (record is 41.6°, in 2001-02). The coefficient of determination for NYC is 0.545. Recently, though, some cities have seen months or even seasons breach this threshold e.g., July 2023 in Phoenix.

It seems quite bizarre, especially with the embedded simulated radar image from a snowstorm that almost certainly won't be equaled during any of our lifetimes in the Deep South.

Latest HREF:

Joe Bastardi is arguing that the current nor'easter that has dumped more than 3" of rain at Norfolk over the past two days with gusts of 50 mph should be counted as a tropical cyclone: The flaw in his reasoning is that the system has fronts. Thus, it is not a tropical cyclone.

A strong nor'easter was bringing gusty winds and heavy rain to parts of the Middle Atlantic region late this afternoon. Through 4 pm, Norfolk had picked up 2.14" of rain. The wind has gusted to 44 mph there. This storm will bring some showers and periods of rain tomorrow into Thursday. The Delmarva and Jersey Shore will see the heaviest amounts. There, 1.00" or above amounts are likely. The temperature will top out in the upper 60s to lower 70s tomorrow. Readings will likely return to the upper 70s on Thursday and the lower 80s on Friday. Cooler air will return for the weekend. The ENSO Region 1+2 anomaly was -0.2°C and the Region 3.4 anomaly was -0.5°C for the week centered around September 10. For the past six weeks, the ENSO Region 1+2 anomaly has averaged +0.10°C and the ENSO Region 3.4 anomaly has averaged -0.37°C. La Niña conditions will likely develop during mid- or late-autumn. The SOI was -2.20 yesterday. The preliminary Arctic Oscillation (AO) was -1.002 today. Based on sensitivity analysis applied to the latest guidance, there is an implied near 56% probability that New York City will have a cooler than normal September (1991-2020 normal). September will likely finish with a mean temperature near 68.9° (0.3° below normal). Supplemental Information: The projected mean would be 0.9° above the 1981-2010 normal monthly value.

So far, rainfall is running above the guidance in a number of locations through 18z.

The 9/16 12z HREF:

I agree. I don't think it's non-viable. I just don't think it's the slam dunk some are making it out to be.

Belmar and perhaps Staten Island could see an inch. I think amounts will be less on Long Island, though.

I haven't looked closely at all the details at this time given how much can change. It is a better North Pacific match than 2013-14, at least right now. It wasn't a bad winter, either.

Coastal low is a broad term for the system. Nor'easters are coastal lows.

I'm not expecting perfection. But I think boundary conditions, particularly SSTAs are probably the most important variables. The area of warmest Winter 2013-14 North Pacific SSTAs are not a great match with what currently exists. At present, Winter 2020-21 is a better North Pacific Match (again not perfect, but better).

It seems that 2013-14 is a popular analog on social media right now. That the North Pacific SSTs are not similar to those of 2013-14 doesn't phase those speculating. Right now, if the anomalies stay as is, one would be dealing with a weaker Aleutian Low, which teleconnects to milder conditions in the East. Should dual areas of excessive warmth persist, there could be some variability, but again not the kind of consistent cold seen during winter 2013-14. We'll see how things evolve in coming months.

I believe Wdrag's analysis is on the mark with rainfall potential for parts of the area. The system responsible is an impressive and strengthening coastal low (non-tropical). The guidance can sometimes be too sharp with the cutoff of precipitation. It wouldn't surprise me to see Atlantic City wind up with 0.50"-1.00" to perhaps 1.50" of rain and NYC wind up with around 0.25". I do think we'll see amounts fall off sharply north and west of New York City. In terms of outcomes, Atlantic City and Georgetown have already received more rainfall than had been expected on the guidance for the 6-hour period that will end at 18z.

Happy birthday.

After a cooler than normal first half of September in New York City, the second half looks to be warmer than normal based on the latest weekly guidance and ensembles. This development is consistent with the temperature trends since 1980. The second half of September is warming notably faster than the first half. Finally, there have been 10 cases where September 16-30 had a higher mean temperature than September 1-15. The most recent such case was 2017. Records go back to 1869.

No. There's a different dynamic involved. Because the Arctic warms faster near the surface but the tropics warm more in the upper atmosphere, wind shear is increasing at cruising altitudes, leading to more clear-air turbulence

With rising temperatures, cloud formation is occurring at higher altitudes. Thinner, high clouds are becoming relatively more common. Those clouds are idea for allowing in solar radiation and then slowing its escape. The thick stratocumulus clouds are become less frequent, yet it is those clouds that block out a lot of incoming solar radiation. This data is consistent with paleoclimate records and more recent climate modeling.

Temperatures will reach the lower to middle 70s tomorrow and mainly the lower 70s on Wednesday. Readings will likely return to the upper 70s on Thursday and the lower 80s on Friday. Cooler air should return for the weekend. In terms of near-term precipitation, a cutoff system near the Delmarva could bring some showers or a period of rain on Wednesday into Thursday. Parts of the Delmarva and Jersey Shore will likely see the heaviest amounts. The ENSO Region 1+2 anomaly was -0.2°C and the Region 3.4 anomaly was -0.5°C for the week centered around September 10. For the past six weeks, the ENSO Region 1+2 anomaly has averaged +0.10°C and the ENSO Region 3.4 anomaly has averaged -0.37°C. La Niña conditions will likely develop during mid- or late-autumn. The SOI was -0.18 yesterday. The preliminary Arctic Oscillation (AO) was -0.603 today. Based on sensitivity analysis applied to the latest guidance, there is an implied near 56% probability that New York City will have a cooler than normal September (1991-2020 normal). September will likely finish with a mean temperature near 68.9° (0.3° below normal). Supplemental Information: The projected mean would be 0.9° above the 1981-2010 normal monthly value.

Some model guidance has periodically shown a 90° or above temperature for the New York City area after September 15th. The forecast AO-/PNA- combination has seen a disproportionate share of such events. However, these are infrequent events, so a lot more would need to be seen before it is evident that such an event is likely. 90° or Above Highs after September 15th (1980-2024): New York City-Central Park: 7 days New York City-JFK Airport: 6 days New York City-LaGuardia Airport: 12 days Newark: 18 days One would need to see consistent guidance on multiple models with good run-to-run consistency. A big caveat this September is the fact that the ECMWF/EPS has been running a strong warm bias in the 2-5-day range. Moreover, in the cases of New York City and Newark, 80% of the years that saw such late-season 90s had warmer first halves of September than will be the case in 2025. At LaGuardia, 78% of such years had warmer first halves of September. At JFK, that percentage was 83% of years. The most prominent notable exception that followed a cooler first half of September was 2017, which occurred to a highly amplified pattern. Currently, a 2017-type pattern is not showing up on the ensembles. In sum, unless there are some fairly dramatic changes, a 90° or above high in the New York City area during the second half of September appears unlikely. Newark has the best shot on Friday, but could fall several degrees short.

Areas for which I have data: September 1-14: Mount Pocono: 2024: 1.49"; 2025: 0.15" Scranton: 2024: 0.42"; 2025: 0.96" Sussex: 2024: 1.13"; 2025: 1.61" Year-to-Date: Mount Pocono: 2024: 66.61"; 2025: 43.47" Scranton: 2024: 48.65"; 2025: 35.70" Sussex: 2024: 46.60"; 2025: 27.93"