Steve Smith says the science points to a hurricane season in line with the heightened risk period – or worse.
As the 2008 Atlantic hurricane season opens, the industry will yet again be deluged with forecasts and prognostications of hurricane activity. Pre-season forecasts are unreliable, and when presented numerically, can mislead end users that precise and accurate predictions are possible when they are not. However, by relying on the underlying science to interpret climatic conditions, we can provide a valuable lens through which to view the potential for activity in 2008. That is not to say that our “lens” is distortion-free. While the climatic conditions may set up the right environment for an active or benign hurricane season, the actual season may be very different due to unanticipated factors or just the simple fact that hurricanes are essentially random events.
Recent work at Pennsylvania State University has shown that roughly 50% of year-on-year hurricane activity is predictable by looking at climate variables. However, the remaining 50% is entirely random and unpredictable.
So what, if anything, can we say about the potential for hurricane activity in 2008? Right now, we are expecting the following climatic conditions:
• Atlantic sea surface temperatures (SSTs) are in line with the warm temperatures seen since 1995, and similar to 2006. However, the extent of water in the Atlantic just below 26.5 degrees C (which is able to support hurricanes) could potentially be larger than in 2006 and 2007.
• A neutral El Niño state is likely to be in place for the summer. While this will neither decrease nor increase wind shear over the Atlantic Basin, the hold-over from the recently decayed La Niña will potentially lead to decreased wind shear for at least the first few months of the season.
• A westerly phase of the Quasi-Biennial Oscillation will be in place, decreasing wind shear locally over the Equator.
• Lastly, given wetter conditions over the Sahel region of Africa, it is somewhat likely that dust loading over the Atlantic will be less than that seen in 2006 and 2007.
Given these factors, we think it is likely that hurricane activity in the Atlantic Basin will be at least average for the current period of heightened activity, or above average if one takes the last 100 years of activity as a baseline. There are no indications that the Atlantic is moving out of the period of enhanced hurricane activity.