Rain Feed

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

 

 



 

 

 


December 2019 Repeats December 2018's Wet Conditions

Dec 13 grand central wreath

 

December 2019 was the wettest month of the year and fifth wettest December on record (7.09" was measured).  Much of its precipitation fell in the first two weeks of the month.  In fact, the 5.05" that was measured during this period was the third greatest amount to fall in the first two weeks of any December.   Looking at temperature, the month was slightly above average (+0.8°).  Although Dec. 1-22 was 2.5 degrees colder than average, the rest of the month was mild enough (+9 degrees), to push the entire month into the above average column.  The mildest reading of the month was 58° (on 12/10), making this the first December since 2005 not to have any readings of 60° or warmer.  The coldest reading, 16° on 12/19, was three degrees colder than the typical coldest reading of December.  The 19th was also the only day that had a high of 32° or colder (25°).

 

Despite the month's surplus precipitation there were ten consecutive days with no measurable precipitation (Dec. 19-28).  This matched a 10-day stretch in September - the longest dry spells of the year.  (September 2019 had just 0.95" of rain, making it the eighth driest September on record).  Coincidentally, last year's wet December (ninth wettest) also had a ten-day stretch with no precipitation.

 

Being the wettest month of a year is rare for December.  Before 2019 only two other years had December as their wettest month - in 1957 (when 5.26" was reported) and in 1973 (9.98" was measured).  Another distinction for Dec. 2019 is that it was just the 13th month to have more than seven inches of rain as well as a streak of 10 or more days without any measurable precipitation.  (The longest streak during one of these months was thirteen days in June 2006).

 

Chart - 7 inches monthly rain

In addition to the soggy first two weeks, other December highlights included the season's first measurable snowfall on 12/2 (1.3" fell) and an out of the ordinary snow squall of 10-15 minutes during the afternoon of 12/18 that ushered in the coldest weather of December (0.4" accumulated, and an additional 0.3" fell from a snow shower a few hours later).  Additionally, the first four days of the month had highs/lows stuck in the 30s, just the sixth time there's been a streak of this length or longer.

 

Snow squall dec 19 2019

 

Finally, December 2018 and 2019 joined December 2008 and 2009 as the second pair of consecutive years to be among the ten wettest Decembers (2009 is #4; 2019 is #5; 2008 is #9; and 2018 is in tenth place). 

Previous December recaps:

2018

2017

2016

2015

 

 


In a Rut: Temperatures Stuck in the 30s

30s

 

This post was inspired by the first four days of December 2019, all which reported highs and lows in the 30s.  The last time there was a streak of this length was in January 1998, when there was one of five days.  Although days "stuck in the 30s" aren't rare, as a typical year sees a half dozen of them, strings of three days or longer happen infrequently, about once very five years.  Not surprisingly, nine out of ten of these days have occurred from December thru March, with December having the most. (They've occurred as early as Oct. 26 and as late as April 11).

 

Chart - days in 30s by month

 

More than half of these days have reported measurable precipitation (57% to be exact); one in four have reported measurable snow.  Since many of these days have temperatures around freezing (two-thirds have a reading of 32° or colder for at least part of the day) the type of precipitation that falls is a mixed bag (i.e., rain, freezing rain, sleet and wet snow).  Often the type of snow that falls doesn't readily accumulate on paved surfaces if the temperature is above freezing.  And although temperatures in the 30s are far from frigid, the fact that they're often accompanied by overcast skies or precipitation makes these days feel raw and colder than the air temperature. 

 

Snow and rain

 

The most precipitation to fall on one of these "stuck" days was 2.03" on March 29, 1984 (high/low of 36°/34°); 1.8" of the precipitation was snow.  Additionally, there have been four other storms that produced two+ inches of liquid precipitation that crossed over to other days - in Jan. 1987, March 1967, Dec. 1930 and Dec. 1914 (all days were in the 30s).  The biggest of them all produced 3.49" of precipitation and lasted three days during the first week of March 1967; two inches of snow fell on the first day of the storm. 

 

Speaking of snow, the most to fall on a day with temperatures in the 30s for its entirety was ten inches on Feb. 10, 2010 (high/low was 34°/30°).  And 11.8" fell from a storm that crossed over into a second day on March 21-22, 1956.  In addition to these snowfalls there have been nine others that dropped six to ten inches (most recently on March 21, 2018 when 8.2" fell on a day in which the high/low was 39°/31°). 

 

Shoveling slust

 

In the years since 1900, the longest streak of days stuck in the 30s is five, which has happened three times: in Jan. 1998, Dec. 1970 and in Dec. 1914.  The most days in one winter was 20, which occurred in the winter of 1997-98.  Every winter except one, 1924, has had two or more days stuck in the 30s. (The winter of 1924 had one day.)  Finally, the most in one month is eight, which has happened twice - in January 1987 and January 1998.  (December 2019 had seven.)

 

Chart - stuck in the 30s

Chart - stuck in 30s by winter

 

If this analysis leaves you cold, I also posted one last year about days stuck in the 70s.

 

Stuck in a rut

 

 

 


May 2019 Continued April's Wet Trend, But With More Rain

Cold-rain-and-wind-bear-down-on-new-york-city-commuters-20190513081420-84079800

 

Like the month preceding it, May 2019 was characterized by a surfeit of rainy days.  There were 19 with measurable rain, which tied December 1972 and May 1973 for the second greatest number for any month.  (The most days, 20, occurred in July 1871 and May 1888).  However, May 2019 distinguished itself by having more rain than those other months (see chart below).  The amount that fell, 6.82", made this May the 12th rainiest on record.  Although it had one more day of rain than April (its 18 days was a record for April), nearly two-and-a-half inches more rain fell.  But despite the high frequency of rain, much of it occurred on just five days: 1.31" on 5/5; 1.32" on 5/12; 0.70" on 5/13; 0.80" on 5/29; and 0.95" on 5/30.

 

Chart - 5 months with most days of precip
 

In addition to the well above average number of rainy days, this May will also be remembered for the damp and unusually cool conditions on Mother's Day and the two days after.  2.32" of rain fell on these three days (1.32" of it on Mother's Day) and the average high/low of 53°/43° was 14 degrees cooler than average.  By contrast, the Memorial Day weekend was mostly nice,  the exception being later in the afternoon on Sunday when clouds moved in and there was an hour of heavy showers.  The three-day weekend's average high/low was 79°/60°, four degrees above average, and featured the warmest reading of the month, 86° on Sunday.  (The warmest mean temperature, however, occurred on 5/20, one week before Memorial Day, with a high/low of 85°/66°).

 

Temperature-wise, the month was average (officially, 0.2 degree below average), with the first half of May three degrees below average while the second half was two degrees above average.  (If the chilly three-day period from May 12-14 were taken out, the month would have been 1.3 degrees milder than average.)  Seven days were five or more degrees above average while six were five or more below average.  Four days with highs in the 80s were balanced by four days with lows in the 40s, both fewer than the month's average (of seven and six days, respectively). 

 

Finally, there was an eight-day streak of rainy days (May 10-17) that had 2.56" of rain.  This was just the thirteenth eight-day steak since 1900.  Coincidentally, last May had rain on seven of eight days around the same time of the month (May 12-19), which amounted to 2.14".  And Mother's Day both years was cool (59°/43° this year, 54°/52° in 2018).

Here are recaps of the previous four Mays:

2018

2017

2016

2015

 

 


Reviewing 2018's Top Weather Stories: Raindrops Kept Falling On Our Heads

2018 recap

 

It was a wet year, indeed, ranking as the fourth wettest on record (behind 1983*, 2011 and 1972).  However, it began on the dry side, with January receiving just 2.18" of precipitation (it was the third drier than average month in a row, with just 5.97" measured in total; and five of the six years preceding 2018 had below average rainfall).  And while the amount of precipitation that fell during the first half of the year was close to average, the rain gauge worked overtime in the second half as 40 inches was measured, 56% greater than what fell in the first half (five of the six months had six inches or more of precipitation).  And although the year wasn't the wettest on record, it did claim the crown for most days of measurable precipitation.  As 2018 came to a close it seemed fitting that it ended with a soaking rain on New Year's Eve, making it the wettest 12/31 since 1948, and the first time since 1994 that rain fell as the ball dropped in Times Square.

* An argument can be made for 2018 being ranked third because 1983's claim as New York's wettest year has been called into question after it was revealed that the rain gauge in Central Park was broken for a large part of the year, allowing rain to enter from multiple.

 

Raindropskeepfalling

 

Now let's shine some light on the year's other major weather stories:

  • The year began with the continuation of a two-week cold wave that started the day after Christmas 2017 and lasted thru 1/8, making it the second longest on record (average high/low for its entirety was 23/13).  During this cold wave the biggest snowstorm of the winter snarled the City with nearly ten inches of wind-blown snow on 1/4.
  • February was the mildest on record (pushing Feb. 2017 to second place) and featured a temperature of 78° on 2/21 (35 degrees above average); this was the warmest reading ever posted in the first two months of the year.
  • March was cold (at 2.4 degrees below average it was colder than our mild February) and stormy, with four nor'easters wreaking havoc.  The last one, which occurred the day after the spring equinox, dropped 8.4" of snow, the biggest March snowfall since 1993 (and 0.1" more than the snowfall of March 1-2, 2009).
  • Cold spring weather continued into April (3.6 degrees below average), which saw the biggest April snowfall since 1982.  5.5" fell the morning of Easter Monday (4/2), forcing the Yankees to postpone their home opener.  2018 suffered through the coldest March/April since 1984.  (However, among all years it ranks 56th as springtimes before 1950 were significantly chillier.)
  • May was a reversal of March-April and was the sixth mildest on record.  The month began on the hot side, with highs in the 90s on the 2nd and 3rd; later in the month there were three days with highs in the upper 80s.
  • A severe, quick-moving thunderstorm during evening rush hour on 5/15 caused extensive disruptions (including my flight to JFK which was cancelled).  Then six months later a surprise snowfall during the afternoon and evening was even more debilitating, snarling the evening commute for hours.
  • Despite May's warm conditions, Mother's Day was chilly and overcast, with a high/low of 54/52.  By contrast Father's Day was sunny and hot, with a high/low of 91/66. 
  • The year's rainiest period was a six-week stretch in July and August (7/12-8/22) when 15.77" fell (nearly ten inches above average for the period).  This included a deluge of 2.24" in little more than an hour on 7/17.  However, the year's biggest rainstorm occurred in April when 3.29" fell on 4/15-16. 
  • The latest dates for a 80-degree and 70-degree low were reported on 8/29 and 10/10, respectively.  The year had 55 days with lows of 70° or warmer, the fourth most on record (following 1906, 2005 and 2015, and tied with 2010).
  • A surprise snowstorm on 11/15 (6.4") was followed a week later by a frigid Thanksgiving Day (high/low of 28/17).  This resulted in the coldest temperatures ever encountered during the the Macy's Thanksgiving Day parade - and the following morning was even colder, with a low of 15°.  After this early taste of winter there wouldn't be another measurable snowfall or colder temperatures for the rest of the year.
  • Like the majority of years this century 2018 ranked among the 25 warmest years on record, ranking 18th.  However, it wasn't as warm as the previous three years (2017 ranked 14th, 2016 ranked sixth and 2015 placed ninth).
  • Finally, 2018's diurnal variation between its average high and low was the smallest in more than 100 years (2003's and 1996's were close behind, 0.1 degree wider).  Interestingly, there are 15 years with smaller variations, all which occurred between 1878 and 1910.    (Many thanks to Eugene Demarco for sharing his analysis with me.)

 

Chart - 2018 summary

If you'd like more in-depth findings about 2018, click here.  And to read recaps of previous years click on 2017, 2016 or 2015.

 

 

 


Very Wet 2018 Ends With Wet December

Rainy times square

 

2018 was New York's fourth wettest year on record (third if the disputed 1983 is excluded) and the final month of the year followed that theme.  December was the year's fifth month with six inches or more of precipitation (all of them occurring in the second half of the year).  The month ended with the wettest New Year's Eve since 1948, and for the first time since 1994 rain fell during the ball drop in Times Square (pictured).  Most of the month's 6.51" of rain (the ninth wettest December on record) fell after 12/13.  This followed a ten-day dry spell, which was the longest in more than a year.  Four days had an inch or more of rain, all in the second half of the month. 

 

December was 2.6 degrees milder than average.  The month started out colder than average, with Dec. 1-13 averaging three degrees below average, then a shift occurred and the rest of the month was nearly six degrees above average.  The final twelve days of the month all had above average temperatures (as did sixteen of the last eighteen).  The range in temperatures was rather narrow, from 24° to 61° (the coldest reading in December is typically in the upper teens while the mildest reading is in the low 60s).

 

November 2018 was snowier and had colder readings than December (two days had lows in the teens).  Typically December is ten degrees colder than November but this year it was only four degrees colder.  Just ten other Decembers have been closer to November's average temperature.

 

Chart - nov vs dec

 

After 6.4" of snow fell in November (all on 11/15) there was just a trace of snow in December.  This was the twentieth December on record with a trace of snow or less (nine of them have been in the past 25 years).  And it joined a handful of Decembers with much less snow than November. 

 

Chart - Dec vs Nov Snow

 

Finally, December had the same average temperature as March (40.1°).  December is typically about five degrees colder.  However, while the overall temperature was the same as March's, December's average high was about a degree colder than March while its average low was about one degree milder.  And while both month's had above average precipitation, March was much snowier, with 11.6" measured.

 

Chart - nov vs dec

Other December recaps:

2017

2016

2015

 


Weather Considerations When Planning an Outdoor Wedding

Rainy wedding at Brooklyn-Botanic Garden

 

Readers contact me occasionally to ask what the best time of year is to plan a rain-free outdoor wedding.  But since this advice is asked months ahead of the event, any guidance is more or less a crap shoot.  (Of course, if one had the luxury of planning just a week ahead of the ceremony, the risk would be much less.)  However, even after choosing optimal dates based on historical averages, no outdoor wedding is risk-free as every calendar date has had precipitation fall in some years.  And there's not just rain to consider - heat, humidity, wind, fog, gray skies, threatening skies, even vermin, can present challenges.  The best advice is to have a back-up plan, i.e., an indoor space, a large tent at the ready, or umbrellas to hand out to guests. 

 

Another thing to keep in mind is that weather conditions can be very different just a few apart, especially with thunderstorms (the bane of summertime plans of all kinds).  For instance, a couple at the Brooklyn Botanic Garden might be blessed with sunny skies while at the very same time another couple is waiting out a downpour soaking the New York Botanical Garden in the Bronx.

 

And while having a dry day is considered the ultimate gift of Mother Nature, a sunny day with hot temperatures may prove as challenging as a rain shower, with the wedding party contending with sweat-soaked outfits (not to mention the increased chance of someone fainting).  With this in mind, the best week to avoid to reduce chances of experiencing temperatures in the 90s, or hotter, is the week of July 16 (what I refer to as "Hell Week").  But discomfort isn't restricted to temperatures in the 90s (or hotter) as sauna-like conditions can occur in lower temperatures if the humidity is high. 

 

Outdoor wedding_Tanler_Davis_Danya_Jimenez_Photography

     

Here is how I answered the most recent request for weather guidance, from a couple considering a fall wedding between mid-September and mid-October:

I get this type of question every now and then and, as you yourself acknowledged, it's not one with an easy answer (but not quite as challenging as a question from a colleague at work who was planning an outdoor wedding that incorporated flags and balloons and wanted to know the likelihood of high winds).  No matter the date, even during traditionally drier times of the year, every calendar date has experienced significant rainfall.  However, on average, a calendar date sees measurable precipitation in NYC in one out of three years; however, this considers precipitation that's fallen anytime during the day, so this means the chance of precipitation during a particular time of day would be less than that. 
 
To point out the limitation of depending on historical averages, if, based on the fact that no rain had fallen on Sept. 12 for 20 years in a row from 1988-2007, you had planned a wedding in 2008 on that date, imagine how crestfallen you'd have been when the streak was broken and light rain fell throughout the afternoon.  There are no guarantees when planning so far in advance.  
With this said, you'll be happy to know that the period you're considering for the wedding is the time of year in New York that tends to have the most dates least likely to see rain.  In fact, half of the 25 driest calendar dates have occurred between Sept. 8 and Oct. 17, including eight of the ten driest dates. 
 
Finally, and not to end on a negative note, there have been years in which major rainstorms occurred between mid-September and mid-October.  For instance, in  1985 hurricane Gloria struck in late September; tropical storm Floyd flooded the City with five inches of rain on 9/16; in the second half of Sept. 2004 tropical storms Frances and Ivan produced close to seven inches of rain; in October 2005 more than 13" of rain fell from 10/7 thru 10/14; and a tornado tore through Brooklyn and Queens during the evening of Sept. 16, 2010.  Finally, in 1987 I attended a friend's outdoor wedding in Westchester County on 9/13 that had to be moved under a tent because of an all-day rain (the first time in 13 years that rain fell on that date).
 
And I shared with them the calendar dates least likely to have had measurable precipitation in New York (those shaded in blue are those that fall, approximately, in the date range they were considering):
 
 Chart - least rainy dates
 
 Wedding planner2

 
 
 

 

 

 

 


Can 'Trace' Amounts of Precipitation Add Up to Measurable Amounts?

Thinkng man

 

When a day's precipitation is reported as 'T', which signifies a "trace" amount, this indicates that less than 0.01" fell (ranging from just a few raindrops or snowflakes up to 0.0044").  From 2000 thru 2017 there have been, on average, two days each month with a trace of precipitation.  In the years I've been writing this blog I've become more and more curious whether trace amounts falling on multiple days can add up and become a measurable amount - something that weather records don't recognize.  (Additionally, on days when a trace falls there are often multiple hours with a trace.  Furthermore, there are days with measurable precipitation that report an hour or more of trace amounts.)

 

ILLUSTRATING MY POINT

Let's say we have a month in which five days had just a trace of precipitation:

 

Traces of precip

Although the amounts are considered traces, precise measurement might report very small amounts of liquid:

 

Traces of precip converted

Therefore, the five-day total of these trace amounts would indicate that 0.0102" fell during these five day (or 0.01").  The example above would also apply to a day with multiple hours of traces of precipitation. 

 

SOME ADDITIONAL FACTS ABOUT TRACE AMOUNTS

December 1989 had the most days on record, fifteen.  Four of the five years with the most days with a trace of precipitation occurred from 1938 to1943.  The four years with the least were all in the 2000s.  Curiously, the average number per year since 1999 has been half the number in the prior years (46 days vs. 23).  However, it appears 2018 is on its way to having the most in 20 years.

 

IN CONCLUSION

With the today's measurement technology able to measure more granular amounts of liquid, weight, speed, etc., surely a device must exist that can show that trace amounts added together may result in a measurable amount.  Granted, these additional measured amounts won't be large (and which date would be given credit for a measurable amount over the course of multiple days?) but they would make weather records more precise, which is something "Big Data" types could appreciate.  (Perhaps precipitation can be reported to three decimal places?  In a previous post I made a case for reporting temperatures to one or two decimal places). 

 

Trace


August 2018 Weather Recap: Unusually Wet, With Unusually Warm Nights

Summer downpour

 

July's rainy and warm conditions carried over into August, which was even warmer and wetter, ending up as the ninth warmest August on record and the twelfth wettest.  It was 2.9 degrees above average and warmer than July (something that's happened in 22% of the years since records began in 1869).  Despite August being warmer than July (by 0.5 degrees), July's average high was slightly higher (84.9 vs 84.3); it was August's average low that made it warmer overall (72.0 vs. 70.4).  In terms of rainfall, August's 8.59" was about an inch more than what was measured in July (7.45"), with much of it falling during heavy downpours during thunderstorms.  Here are additional observations worth noting:

 

  • There were seven days in the 90s, which occurred during two heat waves - one was four days in length (8/5-8) and one lasted three days (8/28-30).  The four-day heat wave was one of the least impressive among those of this length. The hottest reading of the month was 94° on 8/28.  The coolest reading of the month, which was reported twice, was 65°, which tied August 2005 and 1906 for the mildest minimum temperature in the month of August.  The typical coolest low temperature in August is 59° (in the years since 1980).
  • This was the thirty-second warmest August in terms of average high, but it had the fourth warmest average low.  (The low was 4.2 degrees above average, the high was 1.7 degrees above.)  This produced the ninth warmest August overall (tied with Aug. 1955, which was even rainier than this August, with nearly eleven inches measured).  Three of the past four Augusts have now placed among the ten warmest.

 

Chart - warmest average lows in august

  • Twenty-three days had lows in the 70s, tying August 1980 and 2005 for the most in the month of August (the typical number of such days is 13).  The month's first 18 days all had lows in the 70s, only the second time it's occurred, joining August 1988.  It appeared the City was going to set an August record for most lows of 70 or warmer, but it was not to be as the mercury fell to 69° the evening of 8/31.  On 8/29 the low of 81° established a new record for the latest date for a low in the 80s, smashing the previous record by two weeks (which occurred in 1985 and 1988).  This summer was just the eighth in which both July and August had average lows above 70° (two of the other summers were in 2015 and 2016).
  • The month's diurnal variation (i.e., the difference between the high and low) was just 12.3 degrees, which was the smallest in August since 2000 (also 12.3 degrees).  The only variations smaller than this occurred more than 100 years ago, when eight Augusts in the years before 1911 had variances between 10.4 and 11.7 degrees (at the other end of the spectrum, the greatest diurnal variation in August is 20.4 degrees, which occurred in both 1964 and 1944.)
  • This year has had the twelfth wettest August, the fourth wettest July-August, and the twelfth wettest summer.  Almost all of July and August's rain fell in a soggy six-week period (July 12 - Aug. 22).  Ironically, while August is the year's wettest month (so far), it also had the longest streak with no measurable rainfall - eight days, from the 23rd to the 30th.

 

Chart - 10 wettest july-aug

  Storm approaches in august

 

Chart - 10 hottest augusts

Here are previous August recaps:

2017

2016

2015

 

 

 


July 2018 Weather Recap: Hot Temperatures, Followed by Torrents of Rain

Rain slicker

 

If July 2018 were a cocktail its ingredients would be one part heat, three parts rain.  After a hot start, with temperatures nine degrees above average during the month's first five days (average high/low was 92°/78°), the rest of July was seasonably warm, which moderated the month's average temperature to 1.1 degree above average.  As for the rain, after a dry start, with just 0.24" measured through July 11, the skies opened up and the rest of the month was very rainy, with 7.21" measured.  With 7.45" in total this was the rainiest month in more than four years, since April 2014, and the rainiest July in fourteen (and the fourteenth wettest July on record).

 

In late July there were seven days in a row (July 21-27) in which measurable rain fell.  This was the fourth streak of six days or more this year, joining 1989 as the only two years since 1900 with four streaks of six days or longer.  (Besides the persistent rain, dew points throughout this week-long period were in the uncomfortable 72°-74° range.)

 

Chart - 6+ Days of Rain in 2018

 

The seven-day streak with rain was the first since 2012, but this year's had considerably more rain (2.89" vs. 0.86").  The last streak of seven days or more with more rain was in May 2009, when 3.81" fell.

 

Downpours on 7/12 and 7/30 were confined to upper Manhattan; Central Park had 0.71" and 0.37", respectively, but my neighborhood, Greenwich Village, four miles south of the park, was dry.  And during the afternoon of 7/17 Manhattan was the bulls-eye for torrential rain from a severe thunderstorm, with 2.24" pouring down in little more than an hour.  Conversely, on 7/27 thunderstorms during late afternoon thru evening produced more than an inch of rain in most parts of the metro area (and 3-5" in parts of east-central NJ) but Central Park had only 0.25". 

 

July's rainfall in Central Park was considerably more than the three other reporting sites in the metro area:

 Chart - July 2018 Rainfall

Other July observations: 

  • Four of the first five days in July had highs in the 90s; the only one that didn't was the 4th of July, but its high of 86° was the warmest reading on this holiday in five years.  However, due to its very warm low of 77°, the mean temperature was the warmest since 2010.

 

Chart - 4th of July

 

  • Thirteen days in a row (July 8-20) had highs of 80° or warmer, the longest such streak since one of 19 days in August 2016.  (The record is 62 days in a row, set three years ago.)
  • What was most impressive about the hot beginning to July were the low temperatures, all  which were 76° or warmer.  This happens almost as infrequently as five-day streaks with highs of 95°+.
  • This was the ninth July in a row with no lows in the 50s, the longest such streak in the years since 1900.  Before 1980 more than half of Julys had at least one low in the 50s, but since 1980 that portion has fallen to 25%.
  • By July 25 the month had picked up more rain than the combined amount in May and June (6.80" vs 6.64").

 

Here are links to previous July recaps:

2017

2016

2015

2014