It's almost June, and those hazy, hot, humid days are just around the corner. Alas, our 2008 summer outlook is here.
The task of doing a summer outlook is no easy one. First, with few exceptions, summer in the D.C. area is mainly hot. Does Joe Public really care if it's 88 and humid or 93 and humid? Second, 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 2008...
Keep reading for our summer outlook. For weather in our more immediate future, see our full forecast through the weekend.
The main methodology in 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 2008. 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. Below are the factors we consider to be of the greatest value in picking analog years.
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:
We are currently experiencing a weakening La Niña event that peaked during the winter. La Niña is an oceanic phenomenon in which the equatorial waters of the Pacific Ocean are anomalously cool (the opposite of El Niño, when the same waters are anomalously warm). Currently, sea-surface temperatures in these waters are quickly approaching normal.
This past winter was a relatively mild one for our region with very little snow. Most of the East Coast experienced warmer-than-normal temperatures, with the coldest areas in the Northern Plains and Desert Southwest. We saw large precipitation deficits in much of the Lower Mid-Atlantic and Deep South, while much of the Ohio Valley and Northeast experienced an abundance of precipitation.
Spring temperatures have been quite warm in our area until the last few weeks. Nonetheless, spring has been quite cool over most of the country with the exception of California, Texas, the Lower Mid-Atlantic and Southeast. Precipitation this spring has been well above normal in the Mid-Atlantic, Ohio Valley and Lower/Western Plains, while the rest of the country (especially the West Coast and Southeast Coast) has been relatively dry. Severe weather has been prominent in the favored areas of the Deep South, Ohio Valley, Midwest and Lower Plains.
*This May will be the first month since April 2007 to finish with below-normal temperatures.
*22 of our last 30 summers have finished with temperatures at or above normal, including the last three in a row.
*8 of our last 10 Augusts have finished with above-normal temperatures.
Primary Analog Year (or best match): 1974
Secondary Analogs (close matches): 1971, 1976, 1985, 1989, 1999, 2000
The weather during the summers of the analog years serves as the basis for our outlook.
June: Normal to 1 degree below normal
August: Normal to 1 degree above normal
Overall: Normal to Slightly Above Normal
As our probabilities shown to the right suggest, confidence is fairly high temperatures will be pretty close to average for the summer.
90-degree days: Normal (about 30)
Precipitation: Slightly Above Normal
We think this summer will be our coolest since 2004, but that isn't saying much considering we've had three consecutive hot summers. At the same time, this probably won't be one of our colder summers, either. As usual, expect plenty of hot, humid days with highs in the upper 80s to low 90s, especially in the heart of summer between mid-June and mid-August. However, this summer may seem more moderate, as the extended heat waves that plagued the last three summers are not as likely.