mjr

Having a hard time finding historical lists of annual 90+ days for various stations, for example LGA, EWR, BOS, DCA, with LGA being a proxy for the NY metropolitan area. While there is no question that BOS<LGA<DCA, I'm wondering if there have been any years in which either part of the inequality didn't apply (Central Park is a different story). While it seems to apply so far in 2022, it would be interesting if artificial local anomalies (tree canopy or Newark hot spot as opposed to proximity to ocean) are able to overwhelm climatological norms this year so that EWR would have more 90+ days than DCA while NYC would have fewer than BOS in the same year. After a slow start BOS has been gaining on NYC. Of course, number of 90+days is one dimensional and totally misleading but that is the benchmark that everyone uses.

Great idea...problem solved.

Backdoor cold fronts suck. They can happen at any time of the year. I believe that the geography of LI Sound helps funnel NE winds into NYC and propels some of these fronts through when one might expect them to remain to the east of us. Also, I feel that this makes it more difficult for them to return through NYC as a warm front. I have been frustrated at forecasts predicting sunny 80 degree temps only to spend the day in the 50s while central NJ gets up to 80. I have no evidence to back this up but it seems to me that these fronts frequently occur in situations that feature an upper level eastern ridge. Upper level eastern ridges can translate to surface highs over Eastern Canada which send down backdoor fronts. I am also pretty pessimistic about EWR reaching 70 Tuesday unless we experience unexpected afternoon breaks of sun.

September will end up with a mean temperature above 70, probably around 70.3. The Central Park thermometer tried its best to make sure that it would not happen but the month ended one day too early. A few weeks ago someone was going to write a letter concerning the foliage issue to the powers that be. I wonder if anything ever came of that. w

Very interesting research. I have always considered the C-D boundary to extend from St. Louis to NYC, roughly following the Ohio river. Amazing how changes of a fraction of a degree can put you in a completely different climate zone. I guess the line has to be drawn somewhere, though. When I looked at the Britannica article, though, it struck me that on the map, the Eastern seaboard of the US could not be based on a 26.6F demarcation. I dug a little deeper and it turns out that the map is based on a 2007 revision which does, in fact, use 32.0F. Thanks for sharing this.

A south wind at JFK comes directly off the cool ocean (about 1500 miles of it). At Newark, even a south wind with no westerly component, travels over about 50 miles of land. Places like LGA and NYC are far enough away from the ocean so that they can experience significant daytime heating even if an afternoon sea breeze eventually cuts it off. During the spring there can be times when the temperature difference between Newark and JFK can be 20 degrees or more. La Guardia underperforms if the wind direction is from the NE or ENE coming off Long Island Sound. Central Park underperforms if the trees have leaves on them. Interestingly, the Boston airport station is also directly on the ocean but there the ocean is to the east. Thus, a south or southwest wind at Boston will allow for hot temperatures and a west wind even hotter because of a downslope effect. However, a wind from the north through the east (or, alternatively, a light pressure gradient allowing for an afternoon sea breeze) will result in unpleasantly chilly temperatures. Geography is destiny.

At this time of year, under the right conditions, the high sun angle and dry ground can cause a hot air mass to be created in the Northern Plains without the need for the heat to be advected from the south. More southern areas may possibly be less extreme because of clouds, precipitation or whatever. This hot northern airmass can eventually be transported eastward to northern New England and Quebec. In this scenario, the heat goes from west to east and not from south to north.

Excellent.

Hope so. This midafternoon flatline effect occurs too often to just be a coincidence.

NYC was doing ok up to 2pm, generally keeping up with most other stations. No appreciable effect of the rain yesterday. Then, all of a sudden, it basically flatlines while other locations add 2-4 degrees more. This happens very frequently even with no sea breeze. It cannot take advantage of mid or late afternoon temperature increases. It seems likely that it because of deprivation of sun after about 2pm.

Nantucket is more likely to see such temperatures than Central Park. Seriously, would not be surprised if many stations in New England end the season with more 90s than NYC. They have a good head start.

Good forecast except NYC flat lined at 81 from 2pm on. Sunny skies, no sea breeze, only station to do so. Have seen this frequently in past years.

It is precisely because of its significance that the historical record should not be corrupted by unrepresentative (of the larger surrounding area) data. They did "mess" with the site when the moved it to its current location back in the 1990s. To be fair, they probably could not foresee that this would lead to any significant change from the previous location but the "mess" soon became apparent. As is true in the stock market, they should have just "cut their losses" and rectified the situation. Even if, in an ideal world, the local population and the local media would be aware of the situation and analyze/report accordingly, this would not address the misconceptions that are created when national/world media as well as professional weather news and forecasting outlets summarize a summer season by using 90 degree days and give an inaccurate portrayal of New York City (no mention of any park).

Here is a fall version of 90+ days. Listed are the number of 70+ days at certain locations for the month of October. It is likely that these will be the final figures. Lakehurst, NJ (WRI) 15 EWR 12 LGA 11 Hartford (BDL) 9 Providence 9 Boston 8 JFK 8 Bridgeport 7 NYC 6

I am surprised that the misleading and distorted description "subtropical" is still in use for the Cfa climate category. Something like humid warm temperate would make more sense. Anyway, as you said, it served the Times' purpose and probably elicited a lot of "You must be kidding" responses from people for whom "subtropical" evokes images of Orlando, New Orleans or Houston. Actually those three locations are in the same Cfa climate zone as NYC. However, if one uses 32F as a northern boundary, Yonkers is not. I realize that the line has to be drawn somewhere and in my opinion the problem is that there are not enough "lines". Given the steep temperature gradient along the east coast during the colder months one can easily make the argument that there should be a different zone every few hundred miles, not one huge zone from central FL to NYC. There are other alternative classifications and climate maps that try to do this. The crepe myrtle and sweet magnolia may be happy here, and I wish them all the best, but IMHO putting NYC and Orlando into the same zone is just absurd. As an aside, when I was 7 or 8 years old my parents bought me Encyclopedia Brittanica. Like every normal kid, the first sections that I turned to were Weather and Climate. There, staring me in the face was a Koppen climate classification map that had NYC solidly in the colder Dfa climate zone. I remember getting a pencil, erasing the offending boundary line and redrawing it north of NYC.

Thanks for your detailed analysis. The numbers appear to be consistent with anecdotal evidence and intuitive assumptions. The number of 90 degree days has become one of the primary metrics for describing summer heat at any given location and this is the exact measurement that is most affected by the Central Park issue.

I am curious as to why someone of your stature, knowledge and experience continues to use KNYC as a reflection of afternoon heat (no. of 90 degree days, heat wave occurrence) actually experienced in NY City. The legitimacy of the thermometer reading seems to have been severely corrupted by its placement in an area of dense foliage. When one thinks of NY City, midtown Manhattan comes to mind. The best proxies would seem to be LGA, EWR or TEB (or Central Park before 1996). Hypothetically, if those three sites were to record temperatures in the low to mid 90s while NYC only reached 89 because it might have rained two days earlier, and to thus conclude that New York City did not experience a heat wave, does not reflect reality. On this site, observers from Staten Island, Brooklyn and the Bronx all report significantly more 90+ days. In addition, to look at 2019 and conclude that NY City had only15 90 degree days, the same number as Boston, would be very misleading to an outside observer who did not know that LGA, EWR and TEB had 26-37 such days. A casual observer would certainly find it hard to believe and might form an inaccurate picture of actual NY summer conditions. KNYC is a proxy for its own small few hundred square foot area. It does not accurately represent any place else. To pretend otherwise risks legitimizing a false narrative of NYC summers

Another example of Central Park erroneously being used as a legitimate proxy for New York City.

Unfortunately, even top level meteorologists on the Accuweather Professional website, when doing comparisons of 90+ days in the east, BOS, NYC, PHL, DCA among others, use Central Park as the benchmark for New York City. They then attempt to do analyses based on this flawed data. For example, trying to explain why as of June 28 NY City still had not reached 90 (it had, just not in Central Park) or why New York had fewer 90+ days in 2018 than Boston did (in reality LGA had substantially more).

NYC hit 90 a little after 1pm. Soon after, temperatures fell off a cliff.

What I have noticed on many occasions is that the NYC temperature seems to hit a wall at about 1pm or so capping any further rise. This occurs during various synoptic scenarios and has nothing to do with the onset of a sea breeze. Here, for example, at noon, NYC is right in the thick of things. By 4 pm, however, NYC is only 92 (daily high) while almost every other station, except ISP and JFK with their sea breeze, are 3 or 4 degrees higher. Just look at the hourly readings and you will find that this happens on a majority of days.

I like your NYC number to make a point of how ridiculous NYC has become. In reality, though, a day in the upper 90s is too much for even the NYC foliage to resist and LGA minus 4 is probably more accurate. I love your 88 though.

2015 was interesting in that during Aug. and Sept., NYC actually equaled or exceeded LGA and EWR in terms of heat and 90+ temps. Possibly a result of a relatively dry summer or else a massive defoliation.

I don't disagree with you on LGA. I've been following Central Park ever since I was a small child and the "official" NYC obs were moved from the Battery to Central Park in 1960. I remember being very happy at the time since the summer of 1960 had just concluded as the first summer in recorded history without a 90 degree reading. Tops at the Battery was 89. However, the Park did reach 91 that year so NY was saved the ignominious fate of going through a year without officially reaching 90. During the years there were ups...May 19, 1962 (99), April 1976 (96) and of course July 1966. I recall being somewhat surprised on July 3 when the highs I believe were NYC 103, EWR 103, JFK 104 (strong NW wind all day) and LGA 107. It was unusual at the time for LGA to be so far out in front of the rest. Possibly the NW wind. There were also downs. I remember staying up all night in late Aug. 1986, listening to the hourly reports on the radio, to see if the temperature would fall below 50 for the first time ever during July or August. It did not. During most of this time, though, there was never an issue of NYC not being a valid proxy for Manhattan. I did not pay much attention to the ASOS thing in 1996 and first really noticed it during the early 2000s. On July 31, 2009 there was an article in the NY Times lamenting the cool summer thus far and that it had not exceeded 86 during all of July. Well, the summer was certainly well below normal but LGA recorded days of 87,87,88 and 89 (on the day of the article). No big deal really except to illustrate how what is being viewed as reality is actually based on a false premise. This year, when it comes time to review the summer, the media will probably report the fifteen (maybe a few more) 90+ days at NYC and draw conclusions from that. I will be pleasantly surprised if they mention the 30+ (maybe close to 40 when all is said and done) 90+ days at LGA and discuss the foliage issue. I would be even more pleasantly surprised if this finally motivates Upton to correct this situation.

Hard to find a good proxy for NY City as LGA seems to be running a bit warm and NYC is a joke. Average high temperatures for Aug. through 8/20 LGA 88.1, TEB 88.1, EWR 87.3, New Brunswick 86.8, BDR 85.2, ISP 84.5, NYC 84.4, JFK 84.1, HPN 83.6.