JBG

Central Park is getting more forested as we go. KEWR is surrounded by I-78, the New Jersey Turnpike and highly urban Newark. Those areas aren't going to forest. The disparity will be huge in summers where the area fringes 90 often, with say KNYC getting 87 or 88 pretty often. Other such summers were 2004, 2008, 2009 and I think last summer. In summers such as 2005, 2010 and 2011 where the whole area is often in the mid-90's there won't be much of a difference.

I am quite sure, if we had good records going back to the beginning of the "Common Era" (or for Christians the time of Christ) there'd be thousands of fluctuations during moving 30-year periods. That is why I have long suggested using 50 year base periods, now that we have good records at most stations. I think there is a lot of statistically insignificant "noise." Add to that the effect of "smoothing." One note in the other direction. The 30 year averages, for the longest time, gave KNYC a mean of 78 for a week or so in mid-to-last July. That has now been "smoothed" to make the 77 figure hold as the mean from about July 10 to August 10. And the mean high temperature has been "reduced" from 85 to 84. Do these changes mean anything?

Further to this analysis, KNYC has been plagued by a reverse of the UHI effect. New York City's Central Park is actually man-made. Previously it was a mixture of slums, farms and slaughterhouses. It has been progressively getting more densely forested. New York City's weather station is also located there. Back in the 1970's the thirty-year moving average for summer temperatures included about a week where the mean was 78, implying a high of about 86 and a low of about 70. It could have been an 85/70 split since the practice is to round upwards. By the early 2000's the "78 degree" bulge was cut to two days and in the most recent thirty-year period eliminated. Now the average maximum high-low is rated as 84/69, for the period, roughly, July 10 through August 10. This works out to a 76.5 mean, or a full degree lower than the mean for most of the corresponding period historically. The number of 90+ days has also dropped at Central Park (KNYC), so that in the recent summer we have only touched 90 for 7 or 8 days (today may be the 8th day). This summer was considered a cool one. Summers with similar weather patterns, i.e. relatively cool ones, such as 1969, 1972 and 1979 had more 90+ days. 1969 did have a few 96 or 97 days that clearly would have topped 90 even now but nowadays the same situations that created 90-92 degree Central Park readings now create 87-89 degree readings. All you have to do is look at statistics for LaGuardia Airport (KLGA) to see the difference. I am thinking about originating this as a separate thread.

At least at KNYC we exactly matched 1972 for first 90 degree day. I will point out that in those days KNYC had less vegetation and the high that day was 91. So in real world this first 90 day was probably a hotter day than 1972.

Any chance we don't go over 90 this summer? I know that in Niño summers August tends to run cool.

How do things change if this El Niño fails, similar to 1977 (started later) and 1980? Joseph D'Aleo once had a piece on failed Niños turning into fairly robust summers.

Why only one cold-phase analog, 1957?

It wasn't done yet.

Did all that and more today, long after 8/20.

We went as far as early October, 1927 (a year where all 90's were early and late) for 90+ weather. And we came close in 2007 and again last October, on, I think, October 9.

1969, 1972 and 2009 sure broke that pattern.

I was going to ask about 1952-55.

Not sure if the post in question (about 90 after midnight) but I think it may have happened 7/14-15/1995. I recall the temperature dipping to 84 around 9 a.m. in a brief shore before going over 100. That heat wave ended in the famous derecho in upstate NY. Edit. I was right, at least at LGA (link). It was around 90 at midnight. I remember seeing that also on my home thermometer when I came back from my 20 year High School reunion that night. We didn't pick up a 90 degree day though since that day, July 15, it made it to 102, and July 14 had a high of 98. It was under 90 by the wee hours of July 16.KNYC's reading was not available.

it's on the list... I'm surprised 1999 isn't there.

1955 had no 100+ days in KNYC. It had a record or close to record number of 95+ days.

I'm surprised that 1953 following 1952 isn't in there. Or 1971 following 1970. Or 1974 following 1973 (not that the latter would have helped). Edited to say I went back and checked links. The summers I mentioned were just barely under the 25 threshold. Still, for example, 1970 and 1973 summers were memorable, albeit concentrated in August/September.