Hot, dry summer anticipated
After an epic, record-breaking winter, can we expect similar extremes this summer? We present our annual Summer Outlook. This summer we're predicting above average temperatures. While not historic, the heat this summer should be classically D.C., similar to the summers of 2005-2008: consistently hot, and perhaps quite dry.
The task of doing a summer outlook is no easy one. First, with few exceptions, summer in the D.C. area is mainly hot. Do we really care if it's 88 and humid or 93 and humid? Also, the weather varies less during the summer than it does during the the rest of the year (especially compared to winter), with the vast majority of summer months finishing within a few degrees of normal. So, it follows that when putting together a summer outlook we're less likely to see the signals for extreme warmth or cold that we sometimes see in advance of winter.
Nevertheless, we will do our best to convey what we expect for summer 2010...
Keep reading for the full summer outlook, but first vote in our 90-degree poll. On average, we get 31 days at or above 90. Last year we had only 21 and in 2008 we had 29. By comparison, we had 55 in 1988.
This summer is likely to be similarly hot to the summers of 2005-2008 and may be quite dry as well like the summers of the late 1980s. There will be long stretches of oppressive heat and humidity. While there will be occasional reprieves, there is likely to be a handful of heat waves (maximum temperatures of 90 or higher for 3+ days), with perhaps 2 or 3 lasting more than a week. It is quite hard to predict precipitation totals as a day of heavy thunderstorms or remnants of a tropical storm can skew the statistics, but overall we expect a dry summer with long stretches of no rain. This will be a classic D.C. summer: hazy, hot and humid.
June: 1 to 2 degrees above average
July: 1 degree above average
August: 1 degree above average
Overall: 1 to 2 degrees above average
Number of 90-degree days for June/July/August: 40-45 (Normal is 31.3)
Number of 100-degree days: 1-2
Longest Streak of 90+: 10-12 Days
Below normal. Perhaps, well below.
The main methodology for creating the outlook was the use of analog years. Analog years are past years in which conditions leading up to summer most closely resemble conditions leading up to summer 2010. Analog years are far from a perfect predictor due to the complexities of weather, as no two years are exactly alike. However, they can be of considerable value in giving us a general idea of what to expect.
The following factors were given the most consideration in preparing the outlook. It should be noted that any one factor does not necessarily correlate with a particular kind of summer (e.g., warm, cool, dry or wet).
El Niño/La Niña:
After a moderate El Niño episode this past winter, we have rapidly transitioned to neutral conditions this spring. Modeling suggests we may transition to a La Niña episode as we head towards the fall. We are operating under the assumption that conditions will be in a neutral or weak La Nina state throughout the summer.
This Spring's Conditions:
For most of April and May there has been a significant trough in the west and a ridge in the east. As such, temperatures have been well above normal in DC. Indications are that this pattern will persist through much of June, though the warmest temperature anomalies for the summer overall are likely to be in the center of the country from the Northern Plains down through Texas.
The Analog Years, or the years where many of the above factors were also apparent, are: 1964 and 1970
The weather during these summers served as the basis for our outlook.
Enjoy summer 2010. Hope your A/C is working!