Every spring, both Dr. William Grey at Colorado State University and the Climate Prediction Center of the National Oceanic and Atmospheric Administration (NOAA) issue forecasts for the upcoming hurricane season (June 1 through November 30). They predict, among other things, the number of named storms, hurricanes, and major hurricanes (those of Category 3 or higher). Dr. Grey even forecasts probabilities that specific coastal regions will be hit by a named storm.
The science and mathematics behind these forecasts are fairly straightforward. Meteorologists use sea surface temperature (SST) data, in both the Atlantic and Pacific Ocean basins, to measure the distribution of heat and circulation patterns in the oceans. La Nina, which is an extended period of below-average SST in the equatorial east Pacific, is currently in progress, though weakening. Anomalies in the SST affect circulations in the atmosphere, and it has been observed that during a La Nina, thunderstorm activity is suppressed in the Pacific and enhanced in the Atlantic.
Long-term climate trends are also important. Atlantic hurricane activity, like many meteorological phenomena, is cyclic. It just so happens that we’re in the midst of an active period, and have been since the middle 1990s. These cycles are part of what’s called the “multi-decadal signal.” No evidence has shown that the current signal, an active period accompanied by above-average Atlantic SST, will change.
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Statistics are employed to find correlations between certain variables, such as SST and large-scale atmospheric circulations, and hurricane activity from the past. The years for which there were strong correlations provide an example of what this year’s hurricane season might be like. It’s basically just a way to find past years that were “similar” to the current one, meteorologically speaking, and use the hurricane activity of those years as a guide.
Let’s forget the fact that in the last 13 years, Dr. Grey’s forecasts have actually shown less skill than climatology (i.e., the long-term averages). In fact, let’s forget how accurate any of these forecasts have been. On a fundamental level, I question the very need for and use of these forecasts, no matter their accuracy.
A prediction for the number of hurricanes does nothing to actually aid preparedness. People will deal with hurricanes as they come and go. Emergency managers and governments should and probably do always prepare for an active season. Those who live along the East Coast know of the danger. Sure, awareness of the danger can be aided by discussing the upcoming season, but take the focus off such specific and rather non-essential details. A discussion of hurricane safety doesn’t require a doomsday forecast in order to sink in.
These forecasts do, in my opinion, drive media frenzy on primarily economic matters related to hurricanes, namely tourism and the oil business. It’s always funny to see the oil prices jump when a forecast for an active season is released. I’m amazed that economic matters can be so swayed by what is really nothing more than educated speculation.
