The summer of 2011 brought the Mid-Atlantic region hotter-than-normal weather and was quite active in the tropical Atlantic in terms of the number of named tropical storms. There are some differences, however, to this year’s sea surface temperature anomalies in both the Atlantic and Pacific Oceans that should result in a noticeable change from last summer. To begin with, there are now some cooler-than-normal waters off of the western African coast as well as in the western Atlantic nearer to the US east coast. Also, the current La Nina phase in the tropical Pacific (i.e. cooler-than-normal water), which was persistent all of last summer, appears to be transitioning towards a neutral signal and then will likely develop into a weak El Nino (warmer-than-normal water) by mid-summer. These two factors should tend to inhibit tropical activity somewhat this summer; especially, during the 1st half of tropical season (Jun-mid Aug) when “African-based” storms dominate the Atlantic Basin tropical scene. During the 2nd half of the tropical season (late Aug-Oct), however, the warmer-than-normal Gulf of Mexico waters may lead to a more active period for the US when tropical systems are usually more “home-grown” and tend to develop closer to home. As far as the Mid-Atlantic summer is concerned, several analog years suggest that it may be quite normal temperature-wise or perhaps even a tad cooler-than-normal along with slightly higher rainfall amounts.
In summary, the current oceanic conditions and the expected near term changes suggest the following: 1) Normal to slightly-below normal Atlantic tropical season a. 10-11 named tropical storms b. 5-7 hurricanes
2) The most active period for the US in terms of tropical systems should occur during the 2nd half of the season (late Aug-Oct) after a relatively slow start
3) Normal to slightly cooler-than-normal temperatures are expected for the Mid-Atlantic this summer (June-Sept) with slightly higher-than-normal rainfall amounts