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Any more 80+ days?, Stats included for last 30 years at DCA for September 20th and after.

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Posted
Posted

1981-2010, 80 degree days from 9/20 forward

Average: 7.2

Median: 6

High: 23 (2007)

Low: 2 (1992, 1996, 1999, 2004)

Latest: 11/15 (1993)

Chance of getting at least 1 80 degree day: 100%

Chance of getting at least 4 80 degree days: 80%

Chance of getting at least 8 80 degree days: 40%

Chance of getting at least 12 80 degree days: 10%

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Ian

Ian

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There is probably a stats based answer. Probably 97% range? I don't know how to calculate it but there is probably a formula based on sample size and sample.

yeah probably.. dunno. didnt even realize the avg was still 78 on the 20th either.

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ORH_wxman

ORH_wxman

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There is probably a stats based answer. Probably 97% range? I don't know how to calculate it but there is probably a formula based on sample size and sample.

30 year sample size given the median and min/max, I'd say without doing the actual calculations that the chance is in the 98-99% range. If you can go back further like a whole century, then we could probably get it in the high 99% range...enough to just round it to 100%. But for this thread's purpose, 100% is probably just fine.

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RodneyS

RodneyS

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30 year sample size given the median and min/max, I'd say without doing the actual calculations that the chance is in the 98-99% range. If you can go back further like a whole century, then we could probably get it in the high 99% range...enough to just round it to 100%. But for this thread's purpose, 100% is probably just fine.

A complicated question, considering that temperatures have generally been rising in recent years. However, as recently as 1966, there were no 80+ days at DCA after September 12. The high temperature on September 12, 1966 was 81 and the highest temperature after that was 79 -- on September 15 and 30, and October 4 and 10.

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RodneyS

RodneyS

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A complicated question, considering that temperatures have generally been rising in recent years. However, as recently as 1966, there were no 80+ days at DCA after September 12. The high temperature on September 12, 1966 was 81 and the highest temperature after that was 79 -- on September 15 and 30, and October 4 and 10.

I have now reviewed the daily temperature record of DC in its entirety (back to 1872), and found four other years in which the temperature did not reach at least 80 on or after September 20. They are 1875, 1876, 1888, and 1896. In 1875, the temperature reached 80 on September 15, but then got no higher than 79 (on October 25). In 1876, the temperature reached 88 on September 9, but then got no higher than 78 (on October 6). In 1888, the temperature reached 80 on September 19, but then got no higher than 79 (on September 20). In 1896, the temperature reached 80 on September 19, but then got no higher than 79 (on September 27).

So, that's five times out of 139 years in which the temperature did not reach at least 80 on or after September 20, which equals 3.6%. However, since 1897, it's just one out of 114 years, or 0.9%; and it's zero out of the most recent 44 years. So, given the rise in autumn temperatures over the period of record (Relative to 1872-1900 high temperature averages, 1981-2010 high temperature averages have risen 1.7 degrees in September, 2.2 degrees in October, and 4.3 degrees in November), the probability of having at least one 80 degree high temperature on or after September 20 would appear to be at least 99% at present. Still, as recently as 2004, the last 80 degree plus day was recorded on September 23. Further, in 1996, the last September day to reach at least 80 was the 10th, and the only days to reach at least 80 after that were October 17 (81) and October 30 (82). So, it wouldn't have taken much to have missed in either of those two years.

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Ian

Ian

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I just hope the EML doesn't cause it to bust. :whistle:

-----

For cereal... climo's still upper 70s, and we should get at least a couple next week unless clouds come in stronger and/or the troughing digs in further than expected.

Ahh the tornado prediction.. I'm dense.

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RodneyS

RodneyS

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BTW, from today on we're right around 1 90+ on avg.

From the 20th on it's closer to once every other yr.

I strongly doubt we have another.. had 5 more from this pt last yr.

If we don't have another 90+ day this year at DCA, the final one will have occurred on August 26th, which was the 50th 90+ day of the year. Last year as of August 26th we had 54 such days, but then had another 13 through September 25th, including the hottest (astronomical) autumn day ever here, at 99 on September 24th. The earliest final 90+ day of the year was August 3rd, in 1890; but we almost equaled that in 2004, when the final 90+ day occurred on August 4th. The latest 90+ day of the year occurred on October 11th, in 1919.

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Ian

Ian

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Channel 5 met (FOXDC) said he bets that there will be one more day of 90 degree temps in DCA... I would likely bet against that happening

Probably stealing stats from CWG on climo.

I haven't looks far out but the odds drop extremely fast day by day at this pt. Pattern of recent doesn't seem to support it.

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uncle W

uncle W

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looking at climo from the threaded extreme site I'd bet DC has a few more warm days before mid October...How warm/hot is the question...

http://threadex.rcc-acis.org/

9/17 96 in 1991 93 in 1958 92 in 1915

9/18 91 in 1927 91 in 1921 91 in 1898

9/19 96 in 1895 94 in 1978 94 in 1896

9/20 94 in 1895 91 in 1965 90 in 2005+

9/21 96 in 1895 95 in 1931 92 in 1998+

9/22 98 in 1895 97 in 1931 95 in 2010+

9/23 98 in 1895 96 in 1970 93 in 2010+

9/24 99 in 2010 94 in 1970 92 in 1930

9/25 95 in 1930 94 in 1970 93 in 2010

9/26 96 in 1930 95 in 1881 94 in 1895

9/27 95 in 1998 92 in 1900 92 in 1881

9/28 91 in 1886 90 in 1941 90 in 1881

9/29 93 in 1954 91 in 1945 91 in 1881

9/30 91 in 1986 91 in 1954 89 in 1881

10/1 93 in 1941 93 in 1927 92 in 1881

10/2 89 in 1986 89 in 1881 88 in 1968+

10/3 92 in 1879 91 in 1919 88 in 2002+

10/4 94 in 1954 91 in 1941 90 in 1919+

10/5 96 in 1941 94 in 1951 91 in 1967

10/6 93 in 1941 90 in 1997 89 in 1959+

10/7 95 in 1941 92 in 2007 87 in 1997+

10/8 91 in 2007 88 in 1931 87 in 1916

10/9 94 in 2007 90 in 1939 87 in 1879

10/10 92 in 1939 87 in 1997 87 in 1958+

10/11 90 in 1919 88 in 2010 88 in 1954

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RodneyS

RodneyS

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Probably stealing stats from CWG on climo.

I haven't looks far out but the odds drop extremely fast day by day at this pt. Pattern of recent doesn't seem to support it.

I agree, but a possible analog could be 1986. That year, as of this date, it looked as if the last 90+ day at DCA would be August 16. The high temperature was only 69 on September 17, 1986, and reached only 73 the next day. However, the temperature then rose to 93 on September 26, and reached 91 on both September 30 and October 1.

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Ian

Ian

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I agree, but a possible analog could be 1986. That year, as of this date, it looked as if the last 90+ day at DCA would be August 16. The high temperature was only 69 on September 17, 1986, and reached only 73 the next day. However, the temperature then rose to 93 on September 26, and reached 91 on both September 30 and October 1.

Well I guess we can't write it off 'til October. You never know. I just think the pattern switched up a bit sometime in August and we have not really been that warm since. Just the drop in odds over 5 days from y-day through the 20th suggests it will be increasingly difficult to do. I would not be surprised at all to get a stretch of warm weather again though. And as noted the avg is still 78 on the 20th so still getting 80s at that point or beyond is normal.

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H2O

H2O

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Going off memory here but doesn't Oct typically have amped up ridges and troughs as Canadian fronts start driving further south? We almost always get a toasty day or two in front of the strong cold fronts.

i seem to think the same thing as well. Warm days with a showery front that dropped temps 5-10 degrees.

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WVclimo

WVclimo

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I'm starting to wonder if we can crack 70.

Today was the 5th day in a row that MRB failed to reach 70. That's pretty much unprecedented for this early. The last time MRB had 5 days in a row below 70 in September was 2001, but that was from the 25th-30th. 1975 did have 5 of 6 days from the 13th-18th, but all the other streaks were later in the month.

For anyone looking for what it means for the upcoming winter: some pretty lackluster winters for snow lovers followed a lot of these September streaks, along with a few decent seasons:

1971: 6 days (9/22-27)

1966: 7 days (9/24-30)

1962: 5 days (9/25-29)

1950: 11 days (9/20-30)

1949: 6 days (9/22-27)

1929: 5 days (9/19-23)

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uncle W

uncle W

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Today was the 5th day in a row that MRB failed to reach 70. That's pretty much unprecedented for this early. The last time MRB had 5 days in a row below 70 in September was 2001, but that was from the 25th-30th. 1975 did have 5 of 6 days from the 13th-18th, but all the other streaks were later in the month.

For anyone looking for what it means for the upcoming winter: some pretty lackluster winters for snow lovers followed a lot of these September streaks, along with a few decent seasons:

1971: 6 days (9/22-27).....85 11/2

1966: 6 days (9/24-30).....no 80's

1962: 5 days (9/25-29).....89 10/12

1950: 11 days ( 9/20-30)..85 11/1

1949: 6 days (9/22-27).....86 10/10

1929: 5 days (9/19-23).....83 11/2

only 1966 saw no 80's .....

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