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August 2020

Spring Awakening - The Year's First High Temperature in the 70s

70+

 

So far this century, the average date for the first reading of 70° or warmer in Central Park has been March 19 (and in the past five years it's been March 5).  This is four weeks earlier than what the average date was during 1869-1899; and during the 20th century this first occurrence was at the end of March.  The earliest date for a 70+ reading has been Jan. 6, which happened in 2007 (joining two other "first 70s" in January, in 1932 and 1950); the latest date is May 9, which happened in 1875 (and it's happened in May in five other years, the last time being in 1940).

 

Chart - earliest first 70s

Chart - latest first 70

 

The average high temperature on the day of the first 70+ has been 74°; the average low on that day, 48° (this diurnal variation of 24 degrees is much wider than the typical daily variation of 15 degrees).  The average high of the day before the first 70+ is 60°; the average high on the day following the first 70+ day  is 66°. 

 

11 years' first 70+ reading also served as those years' first 80°+ reading, with the most recent occurrence being in 2003.  And in 1927 the year's first 70+ served not only as the first 80+, but as the year's first reading in the 90s.  Meanwhile, 15 other years had their first 80+ come the day after the first 70+ (the last time this happened was in 2013).

 Chart - warmest first 70s

 

Back-to-back years with very early dates for the first 70+ are 1949 (Feb. 15) and 1950 (Jan. 26), and 2017 (Feb. 21) and 2018 (Feb. 24).  And there have been two periods of three consecutive years with very late dates: 1883 (May 3), 1884 (May 2) and 1885 (April 21); and 1875 (May 9), 1876 (May 6) and 1877 (April 23).

 

The greatest difference in high temperature between the day before and the day of the first 70+ is +34 degrees, in March 1935 (from 43° to 77°), and +33 degrees in April 2001 (from 45° to 78°).  And the biggest decline on the day after occurred in March 1934, -35 degrees (from 71° to 36°), and -34 degrees in Feb. 1874 (from 72° to 38°).  Lastly, the biggest increase on the day after is +14 degrees in 1902 (from 70° to 84°).

 

Chart - biggest temp diff day before first 70

 Chart - biggest temp drop after first 70

The greatest diurnal variation on the day of the first 70+ is 42 degrees, with a high/low on March 13, 1990 of 85°/43°.  The coldest reading to occur on the day of the first reading of 70+ is 30° on March 18, 1934.  It came after the high of 71° was reached and a cold front moved thru mid-afternoon.  (This is the also the only time a reading of 32° or colder occurred on the same day as the first 70°+.)

 

After a reading of 70°+, the average number of days before the next reading of 70°+ has been 11, with the greatest hiatus being 80 days in 1932 (when the first 70+ was on 1/14).  Not surprisingly, the most days to elapse before the next 70+ high have occurred in Jan/Feb -  with the average hiatus being 43 days.  In about one-third of the years, the first 70°+ was followed the very next day by another high of 70+, with the longest streak being eight days, in April 1896 (including highs of 87°, 88° and 90°).  The longest streak in the years since 1900 has been six, set in April 1952.  

 

Spring awakening
 

 

An early first 70+ isn't predictive of a hot summer as some very hot summers had their first 70+ at a late date.  This includes the year with the second hottest summer, 1966, which didn't see its first 70+ until April 25.  And the fifth and sixth hottest summers, in 1983 and 1993, didn't have their first 70+ until April 25 and April 19, respectively.

 

About 20% of the dates of the first 70+ reported measurable rain; two-thirds of these years had amounts less than 0.10".  (By contrast, 40% of the days with the first 60+ reading had rain.)  Just one date had more than an inch, on April 6, 1937.  On that day, 1.02" of rain fell before dawn and ushered in mild air (the high reached 72°).

 

And, finally, some more interesting occurrences:

> In 2018, after a high of 78° on Feb. 21 (the warmest reading ever in Jan/Feb), more than seven weeks passed before the mercury rose above the low 60s.

> In 1998 the first 70+ reading was 83°, and it was the first of five days in a row in the 80s - at the end of March (March 27-31), when the average high is in the mid-50s. 

> The first high of 70+ in 1988, 76° on 3/24, came just two days after a low of 17°

> The day of 1980's first 70+ followed a big rainstorm of 3.42" the day before.

> In 1967, a week after the first 70+, on March 11, there was a week of harsh winter conditions, with an average high/low of only 31°/20°, including a reading of 8° on 3/19; and three snowfalls produced 15.4" of snow. 

> 1947's first 70+ on 4/6 was the day after nearly two inches of rain fell. 

> In 1929 the first 70+ came three days after a low of 12°.  (In 2009 a low of 12° in March came four days before the year's first 70+.)

> In 1874, two days after a high of 72° on Feb. 23, 7.5" of snow fell. 

 

Springtime in central park

 

To read an analysis about the first readings of 60+ each year, double click here.

 

 

 


Central Park's Puzzling, Flawed Weather Station

Wtf 3This post has been a long time coming.  New York City, arguably the world's preeminent city, ironically, has a weather station in Central Park (serving as the official measurement site for NYC) that brings to mind that of a third world country.  There are regularly occurring instances of reporting glitches.  Last week, for instance, hourly sky conditions went missing.  (Looking out the window wasn't an option?).  This joined a host of other "irregularities": missing hourly precipitation/temperature reports (often during rainstorms); a five-month period in 2018-19 in which the anemometer was out of commission; a broken rain gauge that resulted in exaggerated amounts of rain for months in 1983; and flawed snowfall measurements in the winters of 2015 and 2016.

 

 

Central park weather site
Central Park's weather station at Belvedere Castle

 

The rain gauge fiasco occurred during a year that may have been the wettest on record as 80.56" was reported (16 inches more than the previous wettest year, 1972).  But it turns out that besides rain entering the gauge's calibrated opening, a faulty weld was allowing extra water to seep in.  Because of this malfunction, designating 1983 as the wettest year is questionable.  Although some cities in the mid-Atlantic did report their wettest year in 1983, confidence about 1983's amount in Central Park is lacking.  Like Barry Bonds' home runs, 1983 should have an asterisk placed next to it.  Meanwhile, 2011, which had 72.81", may actually be the legitimate wettest year.   

 

The revision of winter 2016's snowfall came nearly three months after the blizzard of Jan. 23, 2016.  At the time, the National Weather Service reported that 26.8" of snow had accumulated, which made it the City's second biggest snowstorm, 0.1" behind the blizzard of February 2006.  Then, curiously, the amount was revised upward by 0.7" in late April.  The previous winter the NWS revised New York's winter snowfall upward by 3.3" for three snowfalls.  Specifically, snowfall was adjusted on three dates: Jan. 6 (from 0.5" to 1.0"); Jan. 24 (from 2.5" to 3.6"); and Feb. 2 (from 3.3" to 5.0").

 

Frustrated_clip art
 

What makes this situation more frustrating is the fact that the metro area's three airports (LaGuardia, Kennedy and Newark Liberty) experienced none of these issues.  So what does this say about the Central Park operation?  A lack of trained employees?  A lack of enthusiasm by those manning the site (perhaps they're hired from the same pool of applicants as the DMV)?  Or, is it due to a lack of funding?  Whatever the reason, a city with the cachet of New York deserves better.

 

The greatest city in the world

 

 



 

 

 


July 2020 Is Seventh Hottest; Drought Eases Up

Seventh place

 

Following a June that was 2.3 degrees warmer than average, July 2020 was even more above average, +3.5 degrees, with an average high/low of 87.4°/72.6°.  The month's average temperature of 80.0° made it the seventh hottest July on record.  July records were set for mildest reading for coolest low temperature (67°) and the most lows in the 70s/80s (26).  Additionally, it joined eight other Julys with 14 or more highs of 90° or hotter.  Low temperatures were instrumental in placing the month so high in the rankings as it was third warmest in that category while the average high was ranked sixteenth.  Precipitation was also a significant story as the 6.58" that fell made this the wettest month of the year, so far, and the wettest of the 15 hottest Julys (July 2019 previously held that distinction).  Tropical storm Fay contributed a significant portion of the month's rainfall.

 

As mentioned above, July had 14 days with highs in the 90s, the most since 2010.  This included two five-day heat waves.  Despite the large number of hot days the heat wasn't overbearing as only one day had a high of 95° or hotter (96° on 7/6).  This was the fewest of any July among the 10 hottest.  However, there were nine days with lows of 75°+ (tied for fifth most of any July), including two in the 80s (the counterpart to high temperatures in the triple digits).  And of the six days with below average mean temperatures, just one of them had a low temperature that was cooler than average.

 

Highline during covid-19
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After an exceedingly dry May and June, with both months reporting less than two inches of rain, July had 6.58", making it the wettest month so far this year (nearly double the combined rainfall of the preceding two months).  More than half of the rain was from tropical storm Fay on 7/10 (2.54") and a severe thunderstorm the evening of 7/22 that dumped 1.23" in an hour.  (Newark Airport, just 20 miles to the west, was much rainier, with 11.17" measured - its wettest July on record).

 

Chart - july 2020 top 10 julys

 

Finally, June and July 2020 were the seventh warmest June-July combination.  And the number of lows of 70°+ in June and July (37) tied June-July 2010 for the greatest number.  (37 is the  average number for an entire year.)

 

Chart - hottest june_july combos

 

Here are previous recaps of July from 2014 thru 2019:

July 2019

July 2018

July 2017

July 2016

July 2015

July 2014

  Tropical