September 2025 OBS-Discussion centered NYC subforum

[bluewave]

Record 500 mb ridge to our north will keep the heaviest rains to our south this week.

 

 

[SnowDemon]

11 hours ago, SnoSki14 said:

Endless summer. GFS OP showing 90s late September lol

And the 6z this morning says what 90s? lol. 

[jm1220]

Yawn. But Sept is usually a yawn month here unless a hurricane is coming up. Amazing how this season is dead as a doorknob though. 

[bluewave]

Friday looks like the warmest day of this week with Euro and GFS showing 85-90° potential on a dry W to NW downslope flow.

 

 

[donsutherland1]

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.

[SACRUS]

Records:

Highs:

EWR: 94 (1983)
NYC: 92 (1927)
LGA: 91 (1993) 
JFK: 85 (2008)


Lows:

EWR: 47 (1975)
NYC: 44 (1873)
LGA: 49 (1975)
JFK: 45 (1975)

Historical:

 

 

1747: Some historical accounts of a hurricane caused flooding on the Rappahannock River in Virginia. A slave ship was overturned, and several fatalities were reported.

 

1752 - A great hurricane produced a tide along the South Carolina coast which nearly inundated downtown Charleston. However, just before the tide reached the city, a shift in the wind caused the water level to drop five feet in ten minutes. (David Ludlum)

1910 - Rains of .27 inch on the 14th and .73 inch on the 15th were the earliest and heaviest of record for Fresno CA, which, along with much of California, experiences a ""rainy season"" in the winter. (The Weather Channel)

1916: St. Paul's earliest snow ever. (Ref. AccWeather Weather History)

1922: The noon wet bulb temperature of 79.3°F was the highest ever-recorded in Washington, DC until this date. (Ref. Washington Weather Records - KDCA)

1939 - The temperature at Detroit MI soared to 100 degrees to establish a record for September. (The Weather Channel)

1939" The temperature at Detroit MI soared to 100 °F to establish a record for September. (The Weather Channel)
(Ref. WxDoctor) (Ref. Many Additional Temperatures Listed On This Link)

1944: Boston, Massachusetts recorded its lowest September pressure of 28.62 inches of mercury from the "Great Atlantic Hurricane". (Ref. NOAA Boston Weather Events)

1945: A hurricane entered the south Florida coast at Homestead, curving northward right up through the center of Florida, remaining over land, and exited near Jacksonville Beach with winds gusting to 170 mph. The following is from the Homestead Air Reserve Base. “On Sept. 15, 1945, three years to the day after the founding of the Homestead Army Air Field, a massive hurricane roared ashore, sending winds of up to 145 miles per hour tearing through the Air Field's buildings. Enlisted housing facilities, the nurses' dormitory, and the Base Exchange were all destroyed. The roof was ripped from what would later become building 741, the Big Hangar. The base laundry and fire station were both declared total losses. The few remaining aircraft were tossed about like leaves.”

1965: Heavy snow across parts of Wyoming from the 13th through the 15th was by far the heaviest for so early in the season, resulting in 23 inches in Rawlins and 20.7 inches in Lander. (Ref. AccWeather Weather History)


1975: Marilyn struck the Virgin Islands as a Category 3 Hurricane with maximum sustained winds of 115 mph and an estimated minimum central pressure of 952 millibars or 28.11 inches of mercury. The strongest, most damaging part of the storm passed directly over the island of St. Thomas. The island of Culebra reported an unofficial wind gust of 125 mph. Storm surge was generally 6 to 7 feet with an isolated 11.7 storm surge in St. Croix. 80% of the homes and business on St. Thomas were destroyed and 10,000 people were left homeless. 30% of the homes on St. John were destroyed and 60% were left roofless. Marilyn caused 8 deaths and $1.5 billion dollars in damage. (Ref. Wilson Wx. History)

1977: Sioux Falls, SD residents received a rude awakening during the morning hours as thunderstorms rolled through the city. Over 2.5 inches of rain fell in the city in an hour and 15 minutes. The large amount of rain in a short period of time led to street flooding in some areas. Lightning strikes from the storms also started several fires. (Ref. Wilson Wx. History)
 

1982 - A snowstorm over Wyoming produced 16.9 inches at Lander to esablish a 24 hour record for September for that location. (13th-15th) (The Weather Channel)

1987 - The first snow of the season was observed at the Winter Park ski resort in Colorado early in the day. Eight inches of snow was reported at the Summit of Mount Evans, along with wind gusts to 61 mph. Early morning thunderstorms in Texas produced up to six inches of rain in Real County. Two occupants of a car drowned, and the other six occupants were injured as it was swept into Camp Wood Creek, near the town of Leakey. Late afternoon and evening thunderstorms produced severe weather in central and northeastern Oklahoma. Wind gusts to 70 mph and golf ball size hail were reported around Oklahoma City OK. (National Weather Summary) (Storm Data)

1988 - Thunderstorms brought much needed rains to parts of the central U.S. Rainfall totals of 2.87 inches at Sioux City IA and 4.59 inches at Kansas City MO were records for the date. Up to eight inches of rain deluged the Kansas City area, nearly as much rain as was received the previous eight months. Hurricane Gilbert, meanwhile, slowly churned toward the U.S./Mexican border. (The National Weather Summary)

1989 - Showers and thunderstorms produced locally heavy rain in the Central Appalachians. Virgie VA received 2.60 inches of rain during the evening hours, and Bartlett TN was deluged with 2.75 inches in just ninety minutes. Heavy rain left five cars partially submerged in high water in a parking lot at Bulls Gap TN. Thunderstorms over central North Carolina drenched the Fayetteville area with four to eight inches of rain between 8 PM and midnight. Flash flooding, and a couple of dam breaks, claimed the lives of two persons, and caused ten million dollars damage. Hugo, churning over the waters of the Carribean, strengthened to the category of a very dangerous hurricane, packing winds of 150 mph. (Storm Data) (The National Weather Summary)

1995: Hurricane Marilyn strikes Virgin Islands. It hit the U.S. Virgin Islands as a strong category 2 storm with top winds of 115 mph. The strongest, most damaging part of the storm passed directly over St. Thomas Island. It caused 8 deaths and $1.5 billion in damages. (Ref. AccWeather Weather History)



2004: (Sep. 13th-16th) Hurricane Ivan affected coastal AL/W FL Panhandle; landfall occurred near Gulf Shores, AL, early on 16th. A buoy just S of the AL coastal waters reported an incredible peak wave height of 52 feet today before breaking loose of its mooring.
(Ref. Weather Guide Calendar with Pheno

 

2010: The largest hailstone in Kansas was found in southwest Wichita. It measured 7.75 inches in diameter.

 

2011: An EF0 Waterspout moved ashore in Ocean City, Maryland.

[jm1220]

1 hour ago, bluewave said:

Friday looks like the warmest day of this week with Euro and GFS showing 85-90° potential on a dry W to NW downslope flow.

 

 

Yep, will probably hit 90 IMBY and maybe on the south shore if we keep the WNW flow going into the afternoon. Soil moisture is low which will help. 

[anthonymm]

2 hours ago, Dark Star said:

And on September first, PhiEaglesFan712 said fall had set in...

Cold start to a month usually means blowtorch finish. It's very difficult to pull off BN months these days. I can see a huge -PNA ridge over the east to finish off the month. Probably upper 80s for everyone south of SNE.

[Brian5671]

3 minutes ago, anthonymm said:

Cold start to a month usually means blowtorch finish. It's very difficult to pull off BN months these days. I can see a huge -PNA ridge over the east to finish off the month. Probably upper 80s for everyone south of SNE.

Dry soil will only help the cause-imagine if we did not get that 1-3 inches of rain last weekend

[bluewave]

55 minutes ago, jm1220 said:

Yep, will probably hit 90 IMBY and maybe on the south shore if we keep the WNW flow going into the afternoon. Soil moisture is low which will help. 

The source region to our west has been record dry since August 1st.

 

 

[anthonymm]

7 minutes ago, bluewave said:

The source region to our west has been record dry since August 1st.

 

 

Are you seeing September finish above normal for the park? I'm seeing a lot of muggy nights (almost 70 degree overnight lows!) in the upcoming week, which should erode the cooler start totally.

[SACRUS]

 

Latest SST anomaly

 

 

 

[Brian5671]

wonder what's causing that cold patch off our coast?

[Dark Star]

11 minutes ago, Brian5671 said:

wonder what's causing that cold patch off our coast?

I guessing upwelling from the Hurricane that scooted off to our east about 2 weeks ago?

[anthonymm]

40 minutes ago, SACRUS said:

 

Latest SST anomaly

 

 

 

That pacific look is awful actually for the eastern US. The strongest warm anomalies are in the western pac. I think this is gonna reinforce western Aleutian ridging and troughing over the rockies. Should be a very familiar feeling winter for the I95, similar to the last few years with western storm tracks/great lakes cutters.

[psv88]

82. Summer hanging on?

[Big Jims Videos]

Ocean temp is still in the low 70s at the beaches. Had quite a few rescues yesterday in this area 

[Sundog]

This is the wettest Euro run yet for the coastal low. This is 6z:

 

[Brian5671]

some of the 12z runs have a bit of an inverted trough feature over the region...

[FPizz]

2 minutes ago, Sundog said:

This is the wettest Euro run yet for the coastal low. This is 6z:

 

12z Ukie pretty wet

[MANDA]

1 hour ago, Brian5671 said:

wonder what's causing that cold patch off our coast?

Also have to believe that is keeping the humidity in check when the wind is off the water as opposed to having a warm pool there as we've had over the last several years.  Also have to believe that maybe the cool pool is keeping heavy rainfall events in check when conditions favor such events.

[MANDA]

1 hour ago, Dark Star said:

I guessing upwelling from the Hurricane that scooted off to our east about 2 weeks ago?

I think the cool pool has been in place / developing since Spring?  Somebody I'm sure can confirm that.

[Big Jims Videos]

26 minutes ago, MANDA said:

I think the cool pool has been in place / developing since Spring?  Somebody I'm sure can confirm that.

What was nice this summer was unlike in 2024, when upwelling kept water temps in the 50s most of the summer, this year it was 70s from June through now yet. 

[SACRUS]

33 minutes ago, MANDA said:

I think the cool pool has been in place / developing since Spring?  Somebody I'm sure can confirm that.

We had a period of warmer SST vs normal in the late Jun - late July period then Erin caused tremendous upwelling and the recent easterly barrage has created the current cool pool anomaly.

[SACRUS]

 

79 / 57 here

 

[bluewave]

3 hours ago, anthonymm said:

Are you seeing September finish above normal for the park? I'm seeing a lot of muggy nights (almost 70 degree overnight lows!) in the upcoming week, which should erode the cooler start totally.

Quite a big departure spread this month. The cooler spots have a shot at finishing the month with a small cold departure. But the warmer stations like EWR, HPN, and ISP could finish with a small warm departure. 

ISP….-1.2

HPN….-1.4

EWR…..-1.4

NYC…..-2.3

BDR……-2.5

LGA……-2.9
 

[Picard]

17 hours ago, donsutherland1 said:

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"

Look how much lower Sussex is compared to Mt. Pocono for YTD and 2024, which is probably only about 40-50 miles as the crow flies.  Impressive difference.

[bluewave]

3 minutes ago, Picard said:

Look how much lower Sussex is compared to Mt. Pocono for YTD and 2024, which is probably only about 40-50 miles as the crow flies.  Impressive difference.

This year has been defined by the sharp cutoffs to the heavy rainfall. The aerial coverage from most events hasn’t been very good. So this allowed MPO to go up 13.00” this year on the precipitation over FWN.
 

Time Series Summary for SUSSEX AIRPORT, NJ
Click column heading to sort ascending, click again to sort descending.

2025-09-15

20.02

17

 

Time Series Summary for Mount Pocono Area, PA (ThreadEx)
Click column heading to sort ascending, click again to sort descending.

1

2025-09-15

33.40

1

[psv88]

2 hours ago, Big Jims Videos said:

Ocean temp is still in the low 70s at the beaches. Had quite a few rescues yesterday in this area 

 My kids were swimming off the boat on the north shore yesterday. Some of the protected harbors still in the mid 70s by late afternoon on the warmer days 

[donsutherland1]

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.