90s to Start September?

After a brief cooldown during this upcoming week (Aug 23-27), when our high temperatures Tue-Thu will likely hold in the 80s, a return the 90s is expected by next weekend. These conditions, which will be several degrees above normal, should last into early September with less than usual chances for significant rains.

This is all a result of the redevelopment … after taking a brief break this week … of one of the characteristic patterns we’ve seen during the last 6 months. This pattern, where an upper-level ridge of high pressure sits over the southeastern United States, is a typical byproduct of the La Nina condition we are currently in. La Nina, which is a phase of the El Nino/Southern Oscillation phenomenon that affects sea-surface temperature patterns in the Pacific Ocean and atmospheric weather patterns worldwide, is defined by a cooling of the near-surface water temperatures across much of the equatorial Pacific Ocean. Through a complicated interaction with the overlying atmosphere, this ocean water cooling is often related to a global weather pattern that favors warmer-than-average temperatures over the Southeastern and Southcentral U.S.

Strikingly unlike Summer 09 and last Winter, when we were firmly in the midst of an El Nino that played a role in allowing cool/cold air to routinely invade the Central U.S., this relatively warm and humid pattern for much of the country (east of the Rockies) began to take shape early this Spring. It is indeed likely that La Nina has played a significant role in giving this part of the world a hot summer.

Looking ahead, long-range forecasts expect La Nina to continue through the upcoming fall and winter. It wouldn’t surprise me to see our month-to-month temperature anomalies continue to follow the warm theme for the next several months at least. If nothing else, the atmosphere is in an entirely different mode than it was a year ago, and a repeat of last winter seems highly unlikely.