July 2025 Discussion-OBS - seasonable summer variability

[donsutherland1]

1 minute ago, LibertyBell said:

also much rainier summers and shorter heatwaves, something which I outlined in an earlier post.

Wetter summers but not more frequent rainfall. But the decoupling between Central Park, JFK, LaGuardia, and Newark, which are experiencing similar rainfall trends suggests its Central Park's local environment that is playing the larger role in somewhat reduced high temperatures.

[LibertyBell]

Just now, donsutherland1 said:

The average number of days with 0.01" or more rainfall per week during the summer hasn't really changed too much. The amount of rainfall has increased and was at its highest 30-year average for the 30-year period ending in 2020. If one goes beyond 2020, the most recent 30-year period (1995-2024) averaged 2.42 days per week with 0.01" or more rain during the summer and average total summer rainfall of 13.99".

But what about these fronts stalling near the coast, something we really did not see at least in the month of July in summers like 1991, 1993, 1999, 2002, etc (basically the summers with the longest heatwaves since 1953.)

From what I remember of 1993 and 1999 and 2002 especially, the fronts always died out before they made it into our region (at least in July.) This enabled us to have extra long heatwaves without being interrupted with days of rain.

 

[LibertyBell]

Just now, donsutherland1 said:

Wetter summers but not more frequent rainfall. But the decoupling between Central Park, JFK, LaGuardia, and Newark, which are experiencing similar rainfall trends suggests its Central Park's local environment that is playing the larger role in somewhat reduced high temperatures.

Yes, it's completely out of range compared to the other reporting stations.  But the wetter climate might be shortening the length of heatwaves and also limiting the frequency of 100 degree temperatures (compared to how frequent 7 day heatwaves and 100 degree temperatures were during the 1990s for example.)

[donsutherland1]

Just now, LibertyBell said:

But what about these fronts stalling near the coast, something we really did not see at least in the month of July in summers like 1991, 1993, 1999, 2002, etc (basically the summers with the longest heatwaves since 1953.)

From what I remember of 1993 and 1999 and 2002 especially, the fronts always died out before they made it into our region (at least in July.) This enabled us to have extra long heatwaves without being interrupted with days of rain.

 

That's something the data can't really illustrate. But one would expect similar trends in the nearby locations as one is seeing at Central Park if synoptic developments were largely responsible. Instead, Central Park has been decoupling from the nearby locations when it comes to high temperatures. Indeed, absent the trees, Central Park would likely have had two 100° days so far, including a June record 102° high (pre-2000 regression equation). 

[donsutherland1]

1 minute ago, LibertyBell said:

Yes, it's completely out of range compared to the other reporting stations.  But the wetter climate might be shortening the length of heatwaves and also limiting the frequency of 100 degree temperatures (compared to how frequent 7 day heatwaves and 100 degree temperatures were during the 1990s for example.)

Yes, all things being equal, a wetter climate can temper heatwave intensity and duration.

[LibertyBell]

13 minutes ago, donsutherland1 said:

The average number of days with 0.01" or more rainfall per week during the summer hasn't really changed too much. The amount of rainfall has increased and was at its highest 30-year average for the 30-year period ending in 2020. If one goes beyond 2020, the most recent 30-year period (1995-2024) averaged 2.42 days per week with 0.01" or more rain during the summer and average total summer rainfall of 13.99".

Thanks Don, so the rainfall amounts are still rising even compared to the 1990-2020 period.  From 2.41 days per week and average total summer rainfall of 13.69 inches to 2.42 days per week and 13.99 inches of average total summer rainfall for 1995-2024.  At this rate the 2001-2030 period should be the first one that averages 14.00 inches of average total summer rainfall.

Something else I noted from your graphs, is that although the 1911-1940 period peaked with 2.45 rain days per week, it only averaged 12.42 inches of rain per summer.  The driest period was 1941-1970 which was also during our big heatwave/100+ degree bonanza period of the 1940s, 1950s and 1960s (not a coincidence) when we averaged 2.17 rain days per week and only 10.64 inches of rain per summer.  The dryness probably led to the extreme heat and longer heatwaves of that era.

There is no other 30 year period that comes close to matching 1941-1970 for dryness and the second driest period came right after it, 1951-1980 with 2.21 rain days per week and 11.03 inches average total summer rainfall. All the other periods are near 12 inches of total summer rainfall or above.

 

[LibertyBell]

7 minutes ago, donsutherland1 said:

Yes, all things being equal, a wetter climate can temper heatwave intensity and duration.

it's amazing how dry 1941-1970 and secondly 1951-1980 were compared to the 30 year periods that came before and after those two periods. No wonder they had so many 100 degree days and 7+ day heatwaves.

[LibertyBell]

10 minutes ago, donsutherland1 said:

That's something the data can't really illustrate. But one would expect similar trends in the nearby locations as one is seeing at Central Park if synoptic developments were largely responsible. Instead, Central Park has been decoupling from the nearby locations when it comes to high temperatures. Indeed, absent the trees, Central Park would likely have had two 100° days so far, including a June record 102° high (pre-2000 regression equation). 

And several more 90 degree days, JFK is out to a similar lead that they had in 2010.  Do you think Central Park should have broken its all time 90 degree day record in 2010 just like JFK, LGA, and EWR did and perhaps even have had more 100 degree days, Don? It would be interesting to do a reanalysis of Central Park's data from 2010 to see if they should have broken the records they set in 1991 and 1993 of 39 90 degree days.

 

[LibertyBell]

3 hours ago, Dark Star said:

That's because our night time lows are higher...

Yes, that's the way we are getting higher average temperatures.  High temperatures are going up too, but at a slower rate than low temperatures.  I think at some point the high temperatures will flatten out depending on how close you are to the ocean.  For example, JFK's average high temperatures will probably flatten out at under 90 but higher than 85 (based on the temperature increase data I've looked at.) While EWR's average high temperatures will probably flatten out at under 95 but higher than 90.  

[donsutherland1]

11 minutes ago, LibertyBell said:

And several more 90 degree days, JFK is out to a similar lead that they had in 2010.  Do you think Central Park should have broken its all time 90 degree day record in 2010 just like JFK, LGA, and EWR did and perhaps even have had more 100 degree days, Don? It would be interesting to do a reanalysis of Central Park's data from 2010 to see if they should have broken the records they set in 1991 and 1993 of 39 90 degree days.

 

Yes. It should have easily beaten the record (46 +/- 5 days using the pre-2000 summer regression equation).

[LibertyBell]

9 minutes ago, donsutherland1 said:

Yes. It should have easily beaten the record (46 +/- 5 days using the pre-2000 summer regression equation).

That was the hottest summer I've ever experienced here and hot from beginning to end (we even had upper 90s in early September.)

[steve392]

So gross out I don't even wanna mow.  

 

What kind of rainfall totals we see?  South Jersey just seems to be under water at this point. 

[mgerb]

19 minutes ago, steve392 said:

So gross out I don't even wanna mow.  

 

What kind of rainfall totals we see?  South Jersey just seems to be under water at this point. 

Click link to zoom in: https://maps.cocorahs.org/?maptype=precip&units=us&base=std&cp=BluYlwRed&datetype=custom&displayna=0&from=2025-07-01&to=2025-07-02&dc=0.9&key=dynamic&overlays=state,county&bbox=-76.93176269531251,38.63189092902837,-72.31750488281251,40.44276659332215

 

 

[steve392]

Sun is clearing out the clouds. Some rain falling while sitting outside.  The sun is scorching hot once it breaks through though... 

[SACRUS]

Clearing out quick as steve3 mentioned

 

[donsutherland1]

July Mean Temperatures and Precipitation at Central Park: 

In general, drier outcomes are correlated with hotter outcomes. However, 1991-2020 has become both warmer and wetter than the 1961-1990 base period.

 

[Roger Smith]

Also for history buffs the severe 1901 and 1911 heat waves were nearing peak intensity. They were both comparable to 1966 in regional impacts. 1901 set records in the brief NYC data to that time for four days including June 30 to July 2, and still holds the last two (sharing today with 1966). A record 95F on June 30 was tied in 1931, broken in 1945 (97F) and that was again broken in 1964 (99F). The 1911 heat wave was well into the 100s in a lot of places, NYC must have been somewhat reduced by sea breezes because its highest values were near 100F.  Toronto had 103F on July 3, 1911. The NYC data show records set on July 3, 4, 5, 6, 10 and 11, but none survived, broken by 1966, 1919, 1919, 1999, 1936 and 1988. 

Despite the smaller urban heat island, these heat waves had some stifling warm nights. For July 1, 1901 the record set was 78F not surpassed until 79F in 2018. For July 2, 1901 the record set (82F) still stands for the date. In 1911 the minima were all near 77F and were not daily records even then but there was little relief for ten days of heat. 

The 1966 heat wave(s) broke or tied five daily maxima, and did not set any high minima although four readings were 1F lower than existing records, some of which have since been broken. These were all in the high 70s. Even the 1936 heat wave did not set any daily records for high minima but when it only drops to high 70s after mid-100s, that isn't enough time to ventilate scorching interiors without A/C. Further inland the 1936 heat wave was more prolonged and had even worse overnight conditions, Toronto had lows close to 80F during it and had three consecutive 105F readings (July 8 to 10). Even in southern Manitoba and northwestern Ontario the 1936 heat wave had readings near 110F and overnight lows above 80F. Of course in North Dakota it was close to 120F in that unprecedented event. Western Canada returned to the same level of heat the next summer but that 1937 heat was somewhat modified when it spread east (even so it hit 100F in NYC). 

[SACRUS]

 

83 / 70 now partly cloudy

[JonClaw]

SPC has NYC square in the center of slight risk tomorrow. 12z NAM has a line coming through around 7pm.

[bluewave]

5 hours ago, LibertyBell said:

There is no other 30 year period that comes close to matching 1941-1970 for dryness and the second driest period came right after it, 1951-1980 with 2.21 rain days per week and 11.03 inches average total summer rainfall. All the other periods are near 12 inches of total summer rainfall or above.

Tree ring studies suggest that the 1960s were rated as a 500 year drought. Something that hasn’t been able to repeat in this much warmer climate with increased moisture. So we have been spared peak highs in the 110° to 115° range which would occur here with the much warmer climate of today and 1960s drought and westerly flow. 

https://ocp.ldeo.columbia.edu/res/div/ocp/glodech/PDFs/Pederson_etal_NYCdrought_revised.pdf

[donsutherland1]

Generally warm weather will prevail through Saturday. New York City will see highs in the middle to perhaps upper 80s during this stretch. 

Parts of the region could experience some thunderstorms tomorrow afternoon or evening. After that, the next rainfall will likely occur during a frontal passage early next week.

Excessive heat does not appear likely to return through at least the first week of July. There remains some potential for a shot of more significant heat during the July 6-8 period. The worst of the heat, should it develop, will likely occur away from the coastal plain. 

The ENSO Region 1+2 anomaly was +1.0°C and the Region 3.4 anomaly was 0.2°C for the week centered around June 18. For the past six weeks, the ENSO Region 1+2 anomaly has averaged +0.47°C and the ENSO Region 3.4 anomaly has averaged -0.03°C. Neutral ENSO conditions will likely continue through at least late summer.

The SOI was +7.32 today. 

The preliminary Arctic Oscillation (AO) was +1.176 today. 

 

[Dark Star]

5 hours ago, LibertyBell said:

Yes, that's the way we are getting higher average temperatures.  High temperatures are going up too, but at a slower rate than low temperatures.  I think at some point the high temperatures will flatten out depending on how close you are to the ocean.  For example, JFK's average high temperatures will probably flatten out at under 90 but higher than 85 (based on the temperature increase data I've looked at.) While EWR's average high temperatures will probably flatten out at under 95 but higher than 90.  

I don't know, I think 103 degrees is pretty high...

[winterwarlock]

reached a muggy high of 88 today

[SACRUS]

3 minutes ago, Dark Star said:

I don't know, I think 103 degrees is pretty high...

Yeah outside of JFK/NYC  which is the area he's referring to (i think) . 2010 - 2024(5) summer years  have featured heat / strong heat as much as 48, 49, 53, 63, 66, 80,83,88, 91,93, 99 etc.

[SACRUS]

 

trough/cold front moving through thu evenig focuses storms, rain showers north.   The next 5 - 6 days look very dry /warm-hot (outside the 4th) .  Next rain chances 7/8.

 

[Roger Smith]

Alligators falling from the sky in thunderstorms ... I wonder how that would look in a METAR?

KCHS __ 29/27 3125G38 TRW+ Alligators all quads

[forkyfork]

1 hour ago, JonClaw said:

SPC has NYC square in the center of slight risk tomorrow. 12z NAM has a line coming through around 7pm.

shear could be better but this is a good wind sounding 

[LongBeachSurfFreak]

1 hour ago, forkyfork said:

shear could be better but this is a good wind sounding 

That’s a pretty good sounding for around here. Someone is going to pull off damaging winds. I like the setups where storms come down from CT for the island. Some of the best wind events historically have been in that setup. 

[LibertyBell]

1 hour ago, Dark Star said:

I don't know, I think 103 degrees is pretty high...

That's just this summer, I'm talking about the entire period after 2013 has been pretty mediocre, this is the first great summer since that historic period ended.

[LibertyBell]

1 hour ago, SACRUS said:

Yeah outside of JFK/NYC  which is the area he's referring to (i think) . 2010 - 2024(5) summer years  have featured heat / strong heat as much as 48, 49, 53, 63, 66, 80,83,88, 91,93, 99 etc.

The extreme heat has been isolated to the Newark area (and only in a few select summers like 2021.)  Basically what I'm looking for (as far as Newark is concerned) is at least 40 90 degree days and at least 3 100 degree days.  For this area, at least 20 90 degree days and at least 1 100 degree day.  NYC somewhere in between, 30 90 degree days and 1 100 degree day.