Sunday, August 22, 2010

Summer of Simmer: August Week 3 Update

8 PM Update: The high temperature reached 89° around the 6:00 hour.

Original post:
Today's preliminary high of 88° and low of 77° average out to 6° above the long-term normal.

As the final week of August (and meteorological summer) approaches, Washington temperatures have continued above average overall. There were 2 more 90°+ temperatures in the past week (91° on the 16th and 92° on the 20th). This brings the total for the summer to 49 and for 2010 as a whole to 54. This is within 2 of the 56 in 2002, although still well below the record of 67 90°+ days in 1980.

The summer average temperature of 81.6° continues well above the all-time record hottest summer of 80.0° in 1980. If temperatures for the remaining 9 days of August merely equal the long-term average, the final summer average will be 81.0° (up from 80.8° last week). This is a full 1° above the old record, a margin equivalent to the difference between the current record and the 9th hottest summer.

The histogram of summer temperatures shows how far this year deviates from the past 140 years of records. Each bar shows the number of summers with average temperatures within 0.5° intervals. The 2 light orange boxes on the far right of the chart show the current season average to date and the projected result based on average conditions for the rest of August.

The August average of 80.9° is unchanged from last week's value. Although not a record, if it were to hold, it would be the 6th warmest August on record.

So far this season, the only days failing to reach 80° or higher were the 7th, 8th, and 9th of June, so today is now the 74th consecutive day of 80°+ temperatures. The latest forecast indicates that this string could break on Tuesday with a high of 76°. Although the current record summer of 1980 finished with a strong run of mid and upper 90s, it had already seen 2 days in August below 80° by this date.

Images (click to enlarge):
  • Washington, DC average summer temperatures to date for 2010 and previous record years 1980, 1991, 2002, and climatological period 1971-2000
  • Summer 2010 to date and projected temperatures vs. top 10 hottest summers in Washington
  • Daily high temperatures, summer 2010 (portion above 90° in dark red)
  • Distribution of Washington, DC summer average temperatures from 1871 to 2010 (number of occurrences in 0.5° intervals)
  • Number of 90°+ days per calendar year
CapitalClimate charts from National Weather Service data, background photo from Kevin Ambrose

No comments:

Seasonal Outlook

Latest seasonal forecast: Click here.

Latest 3-month temperature outlook from Climate Prediction Center/NWS/NOAA.