donsutherland1

Tomorrow will be partly cloudy and unseasonably warm. Temperatures will top out in the lower 80s. The warmer spots could see some middle and perhaps upper 80s. 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 +4.40 today. The preliminary Arctic Oscillation (AO) was -0.972 today. Based on sensitivity analysis applied to the latest guidance, there is an implied near 54% probability that New York City will have a warmer than normal September (1991-2020 normal). September will likely finish with a mean temperature near 69.3° (0.1° above normal). Supplemental Information: The projected mean would be 1.3° above the 1981-2010 normal monthly value.

I meant for this to be in the banter thread, but the point is that one has to use established definitions consistently for clear communication. Otherwise, confusion can erode preparedness and public safety.

Perhaps because his tropical forecast is in bad shape due to a quiet hurricane season so far, Joe Bastardi is now insisting that meteorologists embrace his private fiction of what constitutes a tropical cyclone. As noted previously, the system had fronts. It was a nor'easter. It was not a tropical cyclone. It should not have been classified as a tropical cyclone any more than a winter nor'easter should be classified as a tropical storm or hurricane.

The overall dry September is consistent with the exceptionally dry end to August that had occurred. Indeed, the monthly CFSv2 initially called for a wet September before finally reverting to a dry September. Despite early rainfall during the month, highlighted by an unusually wet week following such a dry end to August, monthly rainfall is now below normal in New York City. Central Park: September 1-18: 2.30" 1991-2020 Average: 2.52" The guidance shows little or no rainfall for at least the next seven days. Statistically, the odds would somewhat favor a rebound in rainfall during October. Since 2000, 64% of drier than normal Septembers were followed by somewhat wetter to wetter than normal Octobers. However, with quasi-resonant amplification driven by changes in the Arctic producing "stuck patterns" that lead to longer-duration patterns, a dry October is possible. Indeed, during the last 10 years, dry Septembers were somewhat more likely (56%) to be followed by a drier than normal October. The most recent such case was October 2024. At present, the CFSv2 is showing drier than normal conditions in the Northeast. The ECMWF weeklies also begin October with near normal to possibly drier than normal conditions. October 2005 saw greatly elevated rainfall due to tropical moisture. Moisture from Subtropical Depression 22 dumped 4.49" of rain during October 7-8. Another system moving along a stalled frontal boundary brought 8.64" of rain during October 11-14. Nassau and Suffolk County saw the heaviest amounts with Lynbrook picking up 14.82", Riverhead receiving 14.26", and Wading River seeing 14.52". Moisture from Extratropical Wilma enhanced rainfall from a developing system along a frontal boundary that saw 2.36" rain fall during October 24-26. The emerging 500 mb pattern could provide insight as one draws closer to October. Very dry Octobers (<1.00" monthly rainfall) 1990-2024: Very wet Octobers (7.00" or more) 1990-2024: The September 18, 2025 0z EPS at 240 hours and 360 hours leans toward a dry start: 240 Hours: 360 Hours:

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