September 2025 OBS-Discussion centered NYC subforum

[wdrag]

Am not using GEFS predictors etc beyond 2 weeks and messing up the anticipation mid month onward, like the August 2025 post. 

Instead I've added the 6-10 day issued yesterday, as well as the page you can go to look at CPC's daily updates of 6-10, 8-14 day, the weekly Friday updates of the 2-3 week and twice monthly updates of the monthly outlook, as well as other occasionally helpful predictors, based on the still nascent developing long ranging science beyond 2 weeks.  

https://www.cpc.ncep.noaa.gov

[wdrag]

fwiw...5H pattern is looking interesting for me here as of the 06z/27 ensembles. my interest is west of I95 where it's been pretty darn dry since the 22nd.  Am I seeing opportunity for for 1/2-2" of rain in nw NJ next week beginning periodically Monday night Sept 1?  

[Stormlover74]

Euro still has a storm next week but not until Wednesday now. Given its track record of late and no other model support I'd say its a long shot

[donsutherland1]

Miscellaneous: New York City's two highest hourly rainfall amounts occurred in September. 3.15" fell from 8 pm-9 pm on September 1, 2021 and 3.05" fell from 11 pm - 12 am on September 4, 1913. Times are standardized (standard time).

Note: The highest average maximum temperature at Newark for a September that is missing no daily records is 83.3°, which was set in 2005. The erroneous 1891 value was left in the table.

[Stormlover74]

3 hours ago, Stormlover74 said:

Euro still has a storm next week but not until Wednesday now. Given its track record of late and no other model support I'd say its a long shot

Aaaand its gone.

[wdrag]

21 hours ago, wdrag said:

fwiw...5H pattern is looking interesting for me here as of the 06z/27 ensembles. my interest is west of I95 where it's been pretty darn dry since the 22nd.  Am I seeing opportunity for for 1/2-2" of rain in nw NJ next week beginning periodically Monday night Sept 1?  

Updated 654A/28: I am seeing a probable approximate 1/2-2" rain event or periodic rains between Tue and Sat of next week. 00z/28  Ensembles coming into agreement with fairly substantial high amplitude troughing near and west of 80W longitude the middle of next week.    Who gets 2 and who gets relatively meager 1/2" far too early but finally in my viewer assembling, a more widespread event appears on the distant ensemble horizon.  The 2" reference is not necessarily the high end.

[MANDA]

2 hours ago, wdrag said:

Updated 654A/28: I am seeing a probable approximate 1/2-2" rain event or periodic rains between Tue and Sat of next week. 00z/28  Ensembles coming into agreement with fairly substantial high amplitude troughing near and west of 80W longitude the middle of next week.    Who gets 2 and who gets relatively meager 1/2" far too early but finally in my viewer assembling, a more widespread event appears on the distant ensemble horizon.  The 2" reference is not necessarily the high end.

High amplitude troughing near and west of 80W.....I'll take it!  Please!  Would be nice to have something in the tropics to take advantage of that position but nothing in the pipeline.

Hoping for something meaningful.  In the meantime August looks to finish with nothing and be a very dry month overall.

[wdrag]

2 hours ago, MANDA said:

High amplitude troughing near and west of 80W.....I'll take it!  Please!  Would be nice to have something in the tropics to take advantage of that position but nothing in the pipeline.

Hoping for something meaningful.  In the meantime August looks to finish with nothing and be a very dry month overall.

at least you got your surprise .20 two nights ago... we've traced the past couple of afternoon-evenings.  I didnt check CoCoRaHs and the Mesonet climate sites but am sure there were some meager amounts.  Grandsitting another day or two.

 

 

[RU848789]

On 8/27/2025 at 9:37 AM, wdrag said:

fwiw...5H pattern is looking interesting for me here as of the 06z/27 ensembles. my interest is west of I95 where it's been pretty darn dry since the 22nd.  Am I seeing opportunity for for 1/2-2" of rain in nw NJ next week beginning periodically Monday night Sept 1?  

Walt (or others) - would be interested in your take on 9/6 in the SNJ area adjacent to Philly, as our son is getting married there that day and hoping to do an outdoor ceremony (it's at a working farm) followed by an "upscale barn" reception.  Not too worried about rain, as there is an enclosed space next to the barn if it rains, but would love it to not be hot and humid.  Right now the 6-10 day and 8-14 day CPC forecasts look like normal to maybe a bit below normal in temps, but normal to above normal in precip.  Obviously, those aren't predictions for a specific day, but I am happy to see no major heatwaves on the horizon and the last few deterministic model runs (GFS/Euor/CMC at least) show some significant rainfall on 9/4-5 clearing out for 9/6 with seasonable or below temps, but 9 days out we all know that that timing can change, but all things being equal, I'll take it for now.  TIA.  

[wdrag]

10 minutes ago, RU848789 said:

Walt (or others) - would be interested in your take on 9/6 in the SNJ area adjacent to Philly, as our son is getting married there that day and hoping to do an outdoor ceremony (it's at a working farm) followed by an "upscale barn" reception.  Not too worried about rain, as there is an enclosed space next to the barn if it rains, but would love it to not be hot and humid.  Right now the 6-10 day and 8-14 day CPC forecasts look like normal to maybe a bit below normal in temps, but normal to above normal in precip.  Obviously, those aren't predictions for a specific day, but I am happy to see no major heatwaves on the horizon and the last few deterministic model runs (GFS/Euor/CMC at least) show some significant rainfall on 9/4-5 clearing out for 9/6 with seasonable or below temps, but 9 days out we all know that that timing can change, but all things being equal, I'll take it for now.  TIA.  

Well reviewed. I can’t quibble. Main thing for favorable decent event  is a southern short wave separation from northern Jet, eventually shoving northeast.   That option is still there   

if it’s weak then not so good for rain.  WPC starting to show rainfall D7 and CPC with new 6-10 D outlooks etc around 3-4p

[MANDA]

It's the GFS and it's a little over a week away but it will be interesting to see how this trends on the GFS and other modeling / ensembles.  You have to admit it looks impressive.

I'd take this look any day from December through March much less early September.

[donsutherland1]

As September increasingly becomes an extension of summer, New York City has been experiencing a long-term decline in cases where September's coldest temperatures have fallen into the 40s. During 1961-1990, 83.3% of Septembers saw one or more lows in the 40s. September averaged 2.1 such days. During the current 1991-2020 baseline, just 33.3% of Septembers have seen lows in the 40s and the annual September average has plunged to 0.8 days per year. The last time the temperature fell below 50° in September was September 24, 2022 when the mercury dipped to 49°.

A strong argument can be made that September 2025 could buck that trend and experience one or more lows in the 40s.

Based on the 8/29 12z NBM, August 20-31 will finish with five days with low temperatures falling below 60° at New York City's Central Park. The forecast lows for August 30 and 31 are 57° and 59° respectively. That would be the most such days since there were five days in 1987. The last time there were more was in 1946 when there were six. The record of eight days was set during August 20-31, 1940.

Since record-keeping began in 1869, there were 16 cases when August 20-31 had five or more lows in the 50s and 81.3% of those cases saw one or more lows in the 40s during September. The figure for all other years was 65.7% of cases. Both cases with five or more days since 1980 (1986 and 1987) saw the lowest September temperatures fall into the 40s. The most recent year when August 20–31 had five or more lows in the 50s, but no September lows in the 40s, was 1934 when the monthly minimum temperature was 51°.

In a city where concrete holds the heat and the climate grows steadily warmer, the return of a truly crisp September morning has become an increasingly uncommon and fleeting gift. Yet all signs suggest that September 2025 may break from recent tradition and deliver a breath from a vanishing earlier New York climate.

[rclab]

5 hours ago, donsutherland1 said:

As September increasingly becomes an extension of summer, New York City has been experiencing a long-term decline in cases where September's coldest temperatures have fallen into the 40s. During 1961-1990, 83.3% of Septembers saw one or more lows in the 40s. September averaged 2.1 such days. During the current 1991-2020 baseline, just 33.3% of Septembers have seen lows in the 40s and the annual September average has plunged to 0.8 days per year. The last time the temperature fell below 50° in September was September 24, 2022 when the mercury dipped to 49°.

A strong argument can be made that September 2025 could buck that trend and experience one or more lows in the 40s.

Based on the 8/29 12z NBM, August 20-31 will finish with five days with low temperatures falling below 60° at New York City's Central Park. The forecast lows for August 30 and 31 are 57° and 59° respectively. That would be the most such days since there were five days in 1987. The last time there were more was in 1946 when there were six. The record of eight days was set during August 20-31, 1940.

Since record-keeping began in 1869, there were 16 cases when August 20-31 had five or more lows in the 50s and 81.3% of those cases saw one or more lows in the 40s during September. The figure for all other years was 65.7% of cases. Both cases with five or more days since 1980 (1986 and 1987) saw the lowest September temperatures fall into the 40s. The most recent year when August 20–31 had five or more lows in the 50s, but no September lows in the 40s, was 1934 when the monthly minimum temperature was 51°.

In a city where concrete holds the heat and the climate grows steadily warmer, the return of a truly crisp September morning has become an increasingly uncommon and fleeting gift. Yet all signs suggest that September 2025 may break from recent tradition and deliver a breath from a vanishing earlier New York climate.

Accu weather long range is more pessimistic, the lowest September temperature is 55 degrees., it holds off the first low in the 40’s until October 12th and the first low in the upper 30’s until November 11th. That’s as of today’s long range. Stay well, as always …. 
 

[donsutherland1]

5 minutes ago, rclab said:

Accu weather long range is more pessimistic, the lowest September temperature is 55 degrees., it holds off the first low in the 40’s until October 12th and the first low in the upper 30’s until November 11th. That’s as of today’s long range. Stay well, as always …. 
 

At this lead time, August looked warmer than normal and the number of lows in the 50s that we've seen was almost inconceivable. There's no guarantee that the temperature will fall into the 40s next month, but even a short but sharp push of cold air that wouldn't necessarily show up in the weeklies, can't be ruled out during the second half of the month. Weekly forecasts lose skill beyond two weeks. Daily forecasts are unreliable beyond even 7-10 days. It would be interesting to examine how the daily numbers for September fare vs. climatology.