Monday, September 2, 2013

KDCA, KBWI, and KIAD Climatological Summer 2013 Temperature & Precipitation Recap

Dusk as seen from 17th and S Streets NW, Washington, D.C., 7:37PM August 31, 2013 (the last day of climatological summer).

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Here is a climatological summer recap for the three regional civilian airport climate stations including Ronald Reagan Washington National Airport (KDCA); Baltimore/Washington International Thurgood Marshall Airport (KBWI); and Washington Dulles International Airport (KIAD).  The information is from the Sterling LWX website including the local climate / observed weather page and Sterling's discussion from 759AM on Sept. 1st.

To be clear, climatological summer runs from June 1st to August 31st. Astronomical (seasonal) summer runs from roughly June 21st to roughly September 21st, though this year it ends on Sept. 22nd at 2044 UTC / 4:44PM EDT). Also, "normal" refers to the current 30-year average period of 1981 - 2010.

The KDCA climograph (or climate plot) through September 1st, 2013. The 28.33" amount reflects an additional 0.01" on September 1st. There was another 0.11" this morning bringing the yearly total to 28.44".

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For climatological summer at KDCA, the temperature averaged 78.3F or +0.6F. This includes +1.3F at 76.5F for June; +1.4F at 81.2F for July; and -1.0F at 77.1F for August. The August temp. was the first summer month below normal at KDCA since July 2009.

It was the 25th warmest summer on record -- but it FELT much cooler relative to the last three hellishly hot summers.

In all, there were 23 days of 90F or higher at KDCA, which is below the 26 average for the full climate record back to 1871. By contrast, there were 52 such days in 2010; 47 in 2011; and 48 in 2012. There were only 5 days of 95F or higher with the highest temp. of 97F on July 17th. The average number of 95F+ days is 6. In 2012, there were 28 such days and 22 such days in both 2011 and 2010.

Of note, it surpassed 90F at KDCA on both September 1st (93F high) and 2nd (92F high), but those are not included in the climatological summer average.

Most unusually, there was a record long stretch where temps. never went below 80F from July 16th - 21st, the longest such stretch ever (surpassing the 4 day stretch in July 2011).

Precipitation-wise, KDCA ends August with 1.34" or -1.59" below normal for August, but for climatological summer starting June 1st and ending August 31st it is well above normal, specifically, +5.30" at 15.74" (which is nearly double last climo. summer's 7.97" total and the wettest summer since 2006). Most of this rainfall occurred in June (9.97" or +6.19" above normal), which was the 4th wettest June on record.

For the year, KDCA is a bit above normal, specifically, +1.92" at 28.32" (and well above last year's total at this point of 18.71").

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The KBWI climograph (or climate plot) through September 1st, 2013.

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For climatological summer at KBWI, the summer averaged 75.8F or +1.0F (of note, I calculated it as 75.7F or +0.9F but I'll defer to Sterling LWX on this). This includes +1.5F at 73.9F for June; +2.0F at 79.0F for July; and -0.9F at 74.2F for August. The August temp. was the first summer month below normal at KBWI since July 2009.

Once again, while it was somewhat above normal at KBWI, it FELT much cooler relative to the last three hellishly hot summers.

In all, there were 19 days of 90F or higher at KBWI, which is below the 23 average for the full climate record back to 1872. By contrast, there were 47 such days in 2010; 37 in 2011; and 40 in 2012. There were only 5 days of 95F or higher with the highest temp. of 97F on July 18th. The average number of 95F+ days is 6. In 2012, there were 20 such days, in 2011 there were 16 days, and in 2010 there were 19 days.

Of note, it surpassed 90F at KBWI on both September 1st (91F high) and 2nd (92F high), but those are not included in the climatological summer average.

Precipitation-wise, KBWI ends August at 1.13" or -2.16" below normal, while for climatological summer starting June 1st and ending August 31st it is a bit above normal, specifically, +0.89" at 11.71" (which is also almost exactly equal to last summer's 11.77" total).

(Of note, the Sterling LWX discussion gave a number of 12.16" for the full summer but that does not add up to the June, July, and August tallies on its page, so I am discounting it.)

For the year, KBWI is -2.28" below normal at 25.57" (though somewhat above last year's total at this point of 22.47").

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The KIAD climograph (or climate plot) through September 1st, 2013. The 27.88" amount reflects an additional 0.03" on September 1st. There was another 0.18" this morning bringing the yearly total to 28.06".

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Sterling LWX did not provide a full climatological summer temperature summary for KIAD but it was +0.8F for June at 73.2F, +1.6F for July at 78.3F, and -1.8F for August 73.6F, which by my calculations works out to 75.0F or +0.2F for the full summer. The hottest temperature of the summer was 96F on July 18th.

Of note, it surpassed 90F at KIAD on both September 1st (92F high) and 2nd (91F high), but those are not included in the climatological summer average.

Precipitation-wise, KIAD ends August at 1.95" or -1.58" below normal, but for climatological summer starting June 1st and ending August 31st it is 13.86" or +2.68" above normal (which as with KDCA is also nearly double last climatological summer's 7.24" total).

Year to date, it is almost average at 27.85" or -0.15" below normal (and significantly above the 20.05" at this point last year).

By contrast, it has been unusually wet down around Charlottesville this month with KCHO recording 6.12" or +2.50" for August, and for the climatological summer starting June 1st and August 31st it is +5.22" above normal at 16.89" (which is above last summer's 12.50" total and which is actually slightly LESS than KDCA's climatological summer precipitation departure (see above)).

Year to date through August 31st it was at 33.52" or +5.38" (and also well above last year's total at this point of 26.58").

--Regulus

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