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.

[wdrag]

In the meantime,  I like how this coming week is shaping up for rainfall.  Won't uprise if sct light showers develop Tue or Wed, and think WPC is too conservative by 1/2" on its total week 1 forecast (00z/30 cycle) for our NYC subforum.   Am in the 1/2-2" bracket for starters between Thu-Sat.  Have a day.  Thanks Don for the Sep stats earlier this thread and Bluewave for the continuing updates on temp stats.  

The new monthly outlook by CPC.

[MJO812]

Happy meteorological Autumn

[Volcanic Winter]

I honestly can’t believe how the end of summer has played out, and seemingly the beginning of fall. For me, it doesn’t get better this time of year. It’s been absolutely beautiful.

I haven’t been around much but I’m coming back, I just have to catch up in a few threads for a while. I’m growing excited to see where the rest of this year takes us, into next year. 

[nycwinter]

On 8/30/2025 at 6:30 AM, wdrag said:

In the meantime,  I like how this coming week is shaping up for rainfall.  Won't uprise if sct light showers develop Tue or Wed, and think WPC is too conservative by 1/2" on its total week 1 forecast (00z/30 cycle) for our NYC subforum.   Am in the 1/2-2" bracket for starters between Thu-Sat.  Have a day.  Thanks Don for the Sep stats earlier this thread and Bluewave for the continuing updates on temp stats.  

The new monthly outlook by CPC.

so above normal for the month in the west and northeast that  i find hard to believe..

[winterwarlock]

So a window of rain Thursday night and small chance later Friday...doesn't sound impressive 

[Dark Star]

On 8/28/2025 at 8:30 PM, MANDA said:

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.

540 line still in Canada...

[Dark Star]

7 hours ago, Volcanic Winter said:

I honestly can’t believe how the end of summer has played out, and seemingly the beginning of fall. For me, it doesn’t get better this time of year. It’s been absolutely beautiful.

I haven’t been around much but I’m coming back, I just have to catch up in a few threads for a while. I’m growing excited to see where the rest of this year takes us, into next year. 

Good to see you back.  Any volcanic activity worth noting?

[donsutherland1]

Recent guidance has been trimming rainfall prospects for the New York City area during the first week of September. The 9/1 12z NBM now shows just 0.24" for the first week of September with maximum 1-day rainfall of 0.21". These numbers may yet change, but statistically odds favor less than 0.50" following the kind of dry end to August that occurred. Sample size is limited to just 10 cases, so sample size issues might somewhat affect the outcomes. Below is the data:

The final CFSv2 forecast from August 31 favored a drier to much drier than normal September in the Northeast.

[bluewave]

28 minutes ago, donsutherland1 said:

Recent guidance has been trimming rainfall prospects for the New York City area during the first week of September. The 9/1 12z NBM now shows just 0.24" for the first week of September with maximum 1-day rainfall of 0.21". These numbers may yet change, but statistically odds favor less than 0.50" following the kind of dry end to August that occurred. Sample size is limited to just 10 cases, so sample size issues might somewhat affect the outcomes. Below is the data:

The final CFSv2 forecast from August 31 favored a drier to much drier than normal September in the Northeast.

Something seems to have shifted with the drought pattern which emerged last fall. It used to be that rain events could be relied upon to beat model expectations. Now we seem to generally underperform longer range model expectations.

When the wet patterns do materialize, then the heaviest is often localized with other areas not getting as much. So widespread soaking events have been more the outlier than the norm.  

Not sure yet if this is just a one year blip and we reverse again back to much wetter again down the road. But things have been getting very dry in Canada which we haven’t typically seen before. It’s probably too early to know if the wet pattern which began in 2003 is starting to get some pushback from recent drier tendencies. We also got some drier periods over this stretch but they didn’t last very long.

[Stormlover74]

1 hour ago, winterwarlock said:

So a window of rain Thursday night and small chance later Friday...doesn't sound impressive 

Its not. Looks like scattered showers 

[anthonymm]

NYC is already in drought conditions. I can see a repeat of last fall, maybe not as bad. 

[donsutherland1]

12 minutes ago, bluewave said:

Something seems to have shifted with the drought pattern which emerged last fall. It used to be that rain events could be relied upon to beat model expectations. Now we seem to generally underperform longer range model expectations.

When the wet patterns do materialize, then the heaviest is often localized with other areas not getting as much. So widespread soaking events have been more the outlier than the norm.  

Not sure yet if this is just a one year blip and we reverse again back to much wetter again down the road. But things have been getting very dry in Canada which we haven’t typically seen before. It’s probably too early to know if the wet pattern which began in 2003 is starting to get some pushback from recent drier tendencies. We also got some drier periods over this stretch but they didn’t last very long.

It's possible that the local climate is moving into a cyclical drier period, even as the overall climate has grown wetter. If so, one might see an increase in underperformance cases. 

Canada's dryness is more widespread than what is expected, in general, for summer. The climate models don't provide interannual variability, though. Some climate projections from Canada's most recent national assessment in 2019.

According to more recent research, summers are expected to see warmer and somewhat wetter conditions in western Canada and warmer drier conditions in both central and eastern Canada according to more recent information. The paper also notes that the climate models have shown a wet bias, so far. Finally, with regard to drought risk, it notes:

The highest number of consecutive dry days are clustered in the northern regions of Canada (Fig. S7). Aside from the north, high elevation areas along the Rockies, north-western regions and the Canadian prairies have a higher number of CDD than the rest of the country. Sushama et al. (2010) reported similar results with the highest number of dry days concentrated in northern Canada followed by the Canadian Prairies. Given that Canadian Prairies is already a drought-prone area, future increase in dry spells over the region is concerning as shown by several other studies (Singh et al., 2020; Bonsal and Regier 2006).

[donsutherland1]

5 minutes ago, anthonymm said:

NYC is already in drought conditions. I can see a repeat of last fall, maybe not as bad. 

Here's where things currently stand. I expect the drought coverage to increase on Thursday's update:

[Dark Star]

Happy Meteorological Fall...

[winterwarlock]

my forecasted highs for  this week have all been boosted 3-5 degrees from a few days ago and are now in the 80-83 range

[mgerb]

7 minutes ago, donsutherland1 said:

Here's where things currently stand. I expect the drought coverage to increase on Thursday's update:

Can confirm that this is likely, at least on the NJ side (subject to the final call by the author).