The Intersection

Concluding Remarks on Alberto

Jeff Masters gives us a useful rundown on Alberto’s life history; here’s the part I find most interesting:

Alberto formed from a tropical wave that moved off of the coast of Africa on May 30. The wave tracked farther north than usual for June, entering the eastern Caribbean on June 5, and the western Caribbean on June 8. The wave interacted with the unsettled weather of the Intertropical Convergence Zone (ITCZ), which has been able to push unusually far north for this time of year. The interaction between the ITCZ and the African wave produced Alberto on June 9. It is uncommon for a June tropical storm to form from an African wave; usually, the left-over remains of a cold front or trough of low pressure serve as the seed for June storms. However, last year’s Tropical Storm Arlene also formed from an African tropical wave at about the same time of year….


If you’ve been closely following the hurricane-global warming debate, this point resonates in the following sense. In public talks at conferences, such as this one, Peter Webster and Greg Holland–co-authors of one of the now famous papers saying that hurricanes are getting stronger–have extended their analysis to focus on why Atlantic hurricane seasons have been so active lately. They place a lot of emphasis on the fact that storms seem to be developing both earlier and later in the season (i.e., in months like July and October), and that more of them are developing from these African easterly waves rather than following other routes to genesis. In general, these scientists add, this means that the storms form closer to the equator (south of 25 N) and tend to be more intense because they’re forming over warmer waters. None of which is good news.

The formation of Alberto–from an African wave, south of 25 N, and early in the season–certainly has many consistencies with the Webster/Holland analysis. Meanwhile, Masters thinks we could see two more named storms this June, once again developing from African easterly waves….