RodneyS

Thanks, Roger. You will note above that in my post of February 20, 2020 I found a similar differential for six other cities in the Mid-Atlantic and Northeast US. There are other temperature differentials in that region during the course of the year, but the January 12-14 to January 20-22 differentials seem to be the most extreme by far.

Yes, although the differences are not quite as extreme. See below table, showing the average daily temperatures for January 12-14 combined and January 20-22 combined for the periods 1872-1983, 1984-2022, 1984-2013, 1991-2020, and 2014-2022: Period Jan 12-14 Jan 20-22 Difference 1872-1983 33.8 36.4 +2.6 1984-2022 39.3 33.6 -5.7 1984-2013 38.6 33.0 -5.6 1991-2020 40.5 33.7 -6.8 2014-2022 41.4 35.6 -5.8

Recent DCA temperatures offer more support for the "January 13th thaw-January 21st freeze" hypothesis, with the former day in 2022 averaging 41.5 degrees and the latter day averaging 23.0 degrees. The new NCDC 1991-2020 DCA normals now reflect a bottoming out of yearly temperatures in the January 18th-22nd time frame (at 37.0 degrees), with January 13th 0.2 degrees higher. The previous 1981-2020 normals showed a bottoming out right around January 13th (at 35.7 degrees), with January 21st 0.2 degrees higher. While this update is a step in the right direction by NCDC, it does not come close to reflecting the reality that during 1991-2020 at DCA January 13th temperatures averaged 9.0 degrees higher than January 21st (41.6 vs. 32.6). What convinces me that this differential is not merely a weird aberration, but rather an unexplained phenomenon, is that I first noticed it nine years ago, and it has continued. Specifically, during the last nine years (2014-2022), January 13th temperatures at DCA have averaged 6.7 degrees higher than January 21st (40.4 vs. 33.7). While this differential is not quite as high as during 1991-2020, my first calculation of the differential was for the period 1984-2013, when it averaged 8.2 degrees (40.3 vs. 32.1). So, the differential actually increased when that 30 year period was moved forward by seven years to 1991-2020, and while it has been somewhat lower during the most recent nine years, it is still for those nine years way beyond what would be expected if 1984-2013 had been an aberration. What is particularly interesting about all of this is that for the first 112 years of official daily temperature recordkeeping in DC (1872-1983), there tended to be a January 13th freeze and a January 21st thaw. Specifically, during that time frame, January 13th averaged 3.5 degrees cooler than January 21st. So, while for the most recent 39 years in DC, January 13th has averaged 7.0 degrees warmer than for the first 112 years (40.3 vs 33.3), January 21st has averaged 4.3 degrees cooler (32.5 vs 36.8). Why the big shift? Inquiring minds want to know.

I did not notice that the IAD snow amount tied a record yesterday, but something seems amiss if the reported hourly precipitation totals are accurate. By the way, today's IAD report shows an additional 0.2 inches of snow on 0.07 inches of precipitation, but that seems reasonable as the temperature was above freezing while that snow was falling. I just made an inquiry of the lwx webmaster, asking someone to look into yesterday's reported snow total.

Yes -- three times, including the first winter IAD was open. 1) 1962-63: DCA 21.4, BWI 19.6, IAD 20.6 (and RIC 16.9) 2) 1987-88: DCA 25.0, BWI 20.4, IAD 16.7 (and RIC 12.6) 3) 2001-02: DCA 3.2, BWI 2.3, IAD 2.6 (and RIC the champ at 8.7) By the way, I'm suspicious of the report of only 2.3 inches of snow at IAD yesterday. I live near there and there was quite a bit of light, flaky snow through late afternoon. IAD reported 0.42 inches of precipitation as of 6:52 PM, and I would have thought that the snow-precipitation ratio would have been at least 10-1, which would mean at least 4.2 inches of snow.

The temperature this morning at DCA made it down to 17 degrees, the lowest there since the 10 degree low of January 31, 2019.

Today's average temperature of 26 at DCA (high of 30, low of 22) was the lowest since February 1, 2019's average of 22 (high of 24, low of 20). The 30 degree high was also the lowest since Feb 1, 2019's high of 24.

It appears that the National Weather Service has reduced yesterday's snowfall at DCA from 2.7 to 2.6 inches and at IAD from 4.5 to 4.0 inches. If those revised figures hold, the current Top Three would be: olafminesaw 7.3, Rickin Baltimore 8.8, and WxWatcher007 and MN Transplant tied at 9.8. Unfortunately for WxWatcher007, he is still closed out by olafminesaw, but olafminesaw now has a little more of a cushion over MN Transplant. The latter would now need BWI to receive an additional 0.2 inches or more, IAD to receive an additional 4.1 inches or more, and RIC to receive an additional 0.5 inches or more to close out olfaminesaw. Alternatively, however, if RIC were to receive 1.6 inches more, olafminesaw would be closed out even if no more snow falls in the Washington-Baltimore area this season.

Another way of looking at this is that if snow at each of the four locations averaged about 85% of George BM's forecasts, snow would total 44.6 inches at BWI, 28.5 inches at DCA, 47.6 inches at IAD, and 24.6 inches at RIC. That would result in George BM's total departure being 26.0 and Idub23's total departure being 26.3. That would close out Idub23 because all of his departures would be negative, whereas all of George BM's departures would be positive. By the way, as good as olafminesaw has been in your contest over the years, he is on shaky ground this year because he already has negative departures at both BWI and DCA. If during the rest of the winter, BWI were to receive an additional 0.2 inches or more, IAD were to receive an additional 3.6 inches or more, and RIC were to receive an additional 0.5 inches or more, MN Transplant would close out olafminesaw.

Very true, and according to my calculation, 12 have been eliminated. That includes WxWatcher007, who is currently tied for second, but is closed out by olafminesaw.

Congratulations, Don, nicely done once again.

DCA _ NYC _ BOS __ ORD _ ATL _ IAH ___ DEN _ PHX _ SEA 1.0 1.5 1.4 -0.5 1.5 2.0 -0.1 0.1 -2.1

Another interesting fact about December 2021 is that there were only 0.63 inches of precipitation at DCA -- the 6th driest December in DC history, with 1889 the driest at 0.19 inches. (1901 was the wettest December in DC at 7.56 inches). Moreover, November and December 2021 combined totaled only 1.61 inches at DCA -- the 2nd driest November-December in DC history, with 1965 the driest November-December at 0.84 inches. (2018 was the wettest November-December in DC at 13.39 inches, and was also the wettest year overall, at 66.28 inches). However, unlike 1965, which was the second driest year overall in DC at 26.94 inches (1930 was the driest, at 21.66), 2021 was relatively wet overall, at 44.09 inches (tied with 1912 for 47th wettest out of 151 years).

December 2021 at DCA could not match December 2015's average of 51.2 degrees, but it was the second warmest December in DC history at 47.6 degrees -- 3.6 degrees cooler, but 2.0 degree warmer than the December record holders prior to 2015, which were December 1889 and 1984 (45.6). That also makes December 2021 the fourth warmest meteorological winter month in DC history, behind only December 2015, January 1950 (48.0), and February 2017 (47.7).

DCA _ NYC _ BOS __ ORD _ ATL _ IAH ___ DEN _ PHX _ SEA 2.1 1.6 1.3 3.2 3.7 4.7 5.6 4.1 0.4 DCA _ NYC _ BOS __ ORD _ DTW _ BUF ___ DEN _ SEA _ BTV 12.8 25.0 45 54 42 91 48 12 75

BWI: 12.2" DCA: 12.8" IAD: 17.8" RIC: 6.0" Tiebreaker SBY: 5.2"

Whoops, I forgot to sign in.

DCA _ NYC _ BOS __ ORD _ ATL _ IAH __ DEN _ PHX _ SEA 2.2 3.1 2.8 3.1 1.6 1.1 1.4 -0.4 -0.4

DCA _ NYC _ BOS __ ORD _ ATL _ IAH __ DEN _ PHX _ SEA -1.0 -0.1 1.3 0.6 0.1 0.6 1.3 -0.9 0.6

And the NHC seemed to tilt heavily toward those models, even though they seemed implausible to most experienced forecasters. I think what NHC did was unwise, as mistakes of this type can cause the general public to be skeptical of future projections that may legitimately forecast a scary scenario requiring an evacuation.

You may want to volunteer to assist the National Hurricane Center. At 5 PM on Saturday (4 hours after you posted), the NHC "Wind Probs" were vastly inflated for just about every location. For example, they showed a 99% probability that Providence, RI would experience sustained tropical force winds over the weekend. The reality: The highest sustained wind at TF Green Providence International Airport was only 35 mph.

DCA _ NYC _ BOS _ ORD _ ATL _ IAH _ DEN _ PHX _ SEA -0.4 -0.1 0.9 1.7 -0.5 -0.7 0.4 -0.8 1.2

-0.3 _ 0.5 _ 0.5 _ 0.9 _ -0.9 _ 0.1 _ 1.1 _ 0.5 _ 2.0

DCA __ NYC __ BOS ___ ORD __ ATL __ IAH ____ DEN __ PHX __ SEA 1.0 1.4 1.8 0.5 0.0 -0.9 0.3 0.9 1.5

Today has an interesting distinction, with a high of 59 at DCA, which was recorded at 12:33 AM. Officially, that is the second lowest DC maximum ever for May 29th, with May 29, 1893 being the record-holder at 58 degrees. However, that record is likely the result of the temperature not being observed when the day dawned, because the official DC temperature range for May 28, 1893 is 60-69 degrees. If that is correct, which I think is likely, May 29th, 1893 had to begin with a temperature of at least 60 degrees. So today's high of 59 is likely the new unofficial record-holder for lowest DC maximum on May 29th.