RodneyS

Yes, thanks very much for all the time that you spend on this each year, Roger.

DCA _ NYC _ BOS __ ORD _ ATL _ IAH ___ DEN _ PHX _ SEA 1.4 1.5 2.7 2.7 1.0 -0.3 1.4 0.5 2.0

2020 precipitation at DCA finished at 57.34 inches, 7th highest in DC history. That pushed the record-breaking 3-year total to 165.96 inches and the 2011-2020 decade yearly average to 44.51 inches. The most notable aspect of 2020 DCA precipitation was the second half total of 36.73 inches, which exceeded every past second half except 2018, which was 41.10 inches.

And DCA tied for the 4th hottest November (along with 1985) at 54.3 degrees. 2001 is # 1, at 54.8, and 1975 and 1979 are tied for 2nd at 54.4.

I just posted this to the Capital Weather Gang webpage: I think the bigger news about today's precipitation at DCA is that it pushed the 3-year total, 2018-2020, to 161 inches, with one month remaining to add to that record amount in official DC precipitation history, which began in January 1871. That total eclipsed the previous DC 3-year record of 160.64 inches, set 142 years ago, 1876-1878. Moreover, the current decade, 2011-2020, has averaged 44.0 inches per year, which is DC's second wettest of 15, behind only 1881-1890, which averaged 47.1 inches. The previous second wettest decade was 1931-40, which averaged 43.8 inches. In contrast, 1961-1970 was the driest DC decade, averaging 36.5 inches. See https://www.washingtonpost.com/weather/2020/11/30/dc-area-forecast-stormy-warm-windy-today-before-chillier-weather-settles

DCA _ NYC _ BOS __ ORD _ ATL _ IAH ___ DEN _ PHX _ SEA 0.1 0.9 1.7 2.3 0.0 2.1 -0.6 0.9 0.5

BWI: 6.7 DCA: 4.4 IAD: 7.6 RIC: 8.0 SBY: 5.5

DCA _ NYC _ BOS __ ORD _ ATL _ IAH ___ DEN _ PHX _ SEA 0.7 0.3 0.6 2.5 2.0 0.9 0.3 1.0 1.1 Snowfall DCA: 4.4" NYC: 8.5" BOS: 20.0" ORD: 31.6" DTW: 38.0" BUF: 78.9" DEN: 55.5" BTV: 66.6" SEA: 5.1"

DCA _ NYC _ BOS __ ORD _ ATL _ IAH ___ DEN _ PHX _ SEA 0.2 0.4 1.0 0.9 0.0 0.7 1.8 2.0 1.5

DCA _ NYC _ BOS __ ORD _ ATL _ IAH ___ DEN _ PHX _ SEA 1.0 1.3 2.0 1.5 0.1 1.2 1.4 3.0 3.6

Time for an update. Not much has happened to change the picture during the last two years. In 2019, August 12th had no precipitation at DCA, whereas August 15th had 0.20 inches. This year, August 12th had 0.26, whereas August 15th had 0.21. So the updated 150-year totals for DC, 1871-2020, are: August 12: 43.69 inches total; 21 days with a trace, 55 days with measurable, 12 days with at least an inch, 5 days with 2+ inches. August 15: 12.86 inches total; 16 days with a trace, 49 days with measurable, 5 days with at least an inch, no days with 2+ inches.

DCA _ NYC _ BOS __ ORD _ ATL _ IAH ___ DEN _ PHX _ SEA 0.9 1.3 2.2 0.9 0.0 -0.4 1.5 2.7 0.3

DCA recorded 28 90-degree-plus days this month, breaking the DC record of 25 set in July 2011. However, the longest streak at 20 days fell one-day short of the 1980 and 1988 record streaks of 21 days. Also, the July 2020 average temperature of 83.9 at DCA fell short of the July 2011 record average monthly temperature of 84.8, as well as the July 2012 average of 84.0.

DCA _ NYC _ BOS __ ORD _ ATL _ IAH ___ DEN _ PHX _ SEA 1.8 2.2 1.2 2.8 -0.8 1.2 3.1 0.7 -0.8

DCA _ NYC _ BOS __ ORD _ ATL _ IAH ___ DEN _ PHX _ SEA 1.1 0.7 1.3 1.9 0.6 1.0 3.9 2.2 -0.5 99 98 97 96 99 103 98 118 93

Based on the metric I was using, 1917 wasn't quite as cold as this year in DC, with an average maximum temperature of 63.8 during April 14-May 13. However, May 1917 maximums averaged only 68.8, 4th coldest of all time. And the overall average May 1917 temperature was only 59.6, just 0.4 degrees above the all-time coldest DC May, which was 1907.

In response to a comment on the Capital Weather Gang webpage arguing that we had a normal Spring, I posted this reply at https://www.washingtonpost.com/weather/2020/05/13/warm-weather-arrive-abruptly-east-this-week-may-just-be-tease-some: I wouldn't exactly call this Spring normal, particularly for the last 30 days. The maximum temperature at DCA during April 14-May 13 averaged 63.6 degrees, the 6th coldest all-time in DC for that period and the coldest since 1882, which averaged 62.2. The coldest all-time was 1875, which averaged 60.8; and the warmest was 1985, which averaged 79.0.

April 2020 at DCA averaged 55.3 degrees -- the same as the 1871-2019 historical average. However, precipitation at 6.30 inches was double the DC April historical average of 3.15 inches. In fact, it was the 7th rainiest April in DC history, with the rainiest being 9.13 inches in 1889.

DCA _ NYC _ BOS __ ORD _ ATL _ IAH ___ DEN _ PHX _ SEA -1.7 -1.7 -1.2 -2.4 -0.3 1.6 3.0 3.4 1.4

I just posted this on the Capital Weather Gang webpage, in response to Ian Livingston's article at https://www.washingtonpost.com/weather/2020/04/28/pm-update-some-more-showers-tonight-much-warmer-wednesday Today marked the 15th consecutive day at DCA without a 70+ degree reading. The only other April 14-28 period where that happened in DC weather history was 1875. However, as Ian notes, the current run appears over, as tomorrow is forecast to be at least 70. In 1875, the run ended one day later, on April 30th, with a reading of 72. Still, there is a big difference between these two Aprils. April 1875 averaged only 48.0 degrees, the second coldest April in DC history, whereas this April has averaged 54.8 so far, only slightly below the 1871-2019 historical April average of 55.3. By the way, 1874 was the coldest April in DC history, at 47.1, and the only April day that reached 70+ that year was the 15th, at 72 degrees.

Eight years ago today, I posted on this thread -- http://www.americanw...h-on-record-dca: "The final numbers for the 2011/12 astronomical and composite winters are 45.9 and 45.6 degrees, respectively. Thus, the record for the warmest astronomical winter was broken by 2.2 degrees and the record for the warmest composite winter was broken by 1.6 degrees. When the astronomical winter warm record was last broken (in 1989-90), it was only by 0.2 degrees, and when the composite winter warm record was last broken (in 2001-02), it was only by 0.9 degrees." This season, the astronomical winter (December 21-March 20, on average) averaged 45.5 at DCA , and so it fell only 0.4 degrees short of 2011/12. And the composite winter (December 1-March 20, on average) averaged 44.6 at DCA, and so it fell 1.0 degree short of 2011/12. Both averages are good enough for second warmest in DC history.

February 2020 averaged 43.8 degrees at DCA, with the meteorological winter there at 42.8 degrees, each 7th on the all-time DC list, although February 1984 also averaged 43.8.

I have now done some additional analysis that shows that in several other eastern cities January temperatures during the most recent 30 years have peaked on or about January 13th and bottomed on or about January 21st: Raleigh-Durham: 46.9 vs 37.7 degrees Richmond: 43.6 vs 34.0 degrees Philadelphia: 38.4 vs 29.3 degrees New York: 37.3 vs 28.9 degrees Boston: 34.1 vs 26.2 degrees Portland: 26.4 vs 19.5 degrees

Time for another update. Once again this year at DCA, January 13th was much warmer than January 21st (48.5 degrees vs 31.5). So, for the most recent 30 years (1991-2020) at DCA, January 13th has averaged 41.6 degrees vs. 32.6 degrees on January 21st. A two-tailed T-Test shows that the odds of this being a random variation are less than 1 in 18,500. So, how will the NCDC handle this inconvenient fact when it calculates its new daily 30-year January temperature normals at DCA? The 1981-2010 January temperature normals there show temperatures bottoming out in mid-January, not January 21st. Further, even if the new DCA normals were to reflect a bottoming out on January 21st, the January 13th normal would likely be calculated using standard methodology as only 0.2-0.3 degrees higher than January 21st, and not the actual 9 degrees higher. Could someone at NCDC think way outside of the box and develop a radically new January temperature model, showing an annual thaw at DCA occurring around January 13th? And if s/he did, would s/he be given an award or fired? A thorny problem for NCDC, it seems to me.