After 2010 and 2011 produced the two hottest summers on record back-to-back, I am sure almost everybody is hoping for some relief this summer. Unfortunately, we don’t think that will be the case. Even our normal summers are mostly hot and humid and we believe this summer will exceed normal with ease.
We think the summer of 2012 has a 50-50 chance of cracking the top 10 warmest on record in Washington, D.C. (since 1871). While the incredible record heat of the last two summers is unlikely to be “three-peated”, the signals we’ve examined portend another oppressive summer.
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 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 (relative to average) that we sometimes see in advance of winter. As such, our outlook is of low-medium confidence. .
This kind of seasonal forecasting is experimental and large errors are possible. Nevertheless, we’ll do our best to convey what we expect for summer 2012 based on factors we’ve analyzed...
Signals favor a historically hot summer with a strong chance of breaking into the top 25 hottest on record. Chances of cracking the top 10 are about even.
Heat has certainly been the narrative in recent years, with only two below normal summer months (June, July 2009) dating back to the summer of 2005.
If there is any silver lining, we believe that July has a 50-50 chance of being below normal. But with July being our hottest month, slightly below average is still plenty hot.
We find the extremely dry conditions that have persisted this year are likely to continue. That means drought conditions may well develop and worsen.
Of course, an anomalous localized thunderstorm complex or remnants of a tropical system could alter this, so our precipitation prediction like our temperature prediction is based on a tendency and can certainly be wrong.
June: 2 to 3 degrees above average
August: 1 to 2 degrees above average
Overall: 1 to 2 degrees above average
Number of 90-degree days for June/July/August: 40-45 (Normal is 31)
Number of 100-degree days: 1-2
Longest Streak of 90+: 9-12 days
Somewhat below normal (75-80% of normal)
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 2012. 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
We are currently in the waning weeks of an almost two year La Nina episode (cooler than average waters in the equatorial Pacific Ocean). Observations and models suggest that the tail end of La Nina conditions should continue to move toward neutral conditions, though a tendency toward El Nino conditions (warmer than average waters) may start to emerge as we progress through summer.
Winter and spring conditions
The near record warmth of winter persisted into spring with our warmest March on record and it was hot across most of the country. April has been a bit cooler across the East but still finished 1-2 degrees above normal. And the heat has returned for the first week of May. Additionally with a few localized exceptions, this spring has been dry in most of the Ohio Valley, South and East Coast.
The analog years, or the years where the above factors were present to some extent, are: 1939, 1976, 1989, and 2002.
The weather during these summers served as general guidance for our outlook along with the persistent warm weather we have experienced the last year (The only below average month in the last year was October 2011).
Try to enjoy the summer despite the heat and humidity. There are always going to be some cooler respites, though they are likely to be of short duration, and it least the heat shouldn’t be as punishing as the last two summers (hopefully).