We last spoke with Dr. Steve Smith midway through the 2006 hurricane season three months ago, where he reassessed weather predictions and stated that the season would turn out to be an average one. Now that the 2006 storm season has officially come to a close, Claims' went back to get Smith's overall impressions of activity in both the Atlantic and Pacific, and also ask him about factors influencing next year's activity.

This year was the least costly hurricane season in 10 years. Preseason predictions from the National Oceanic and Atmospheric Administration were significantly over inflated. What happened in the Atlantic?

The expectation at the beginning of the season was that the Atlantic sea surface temperatures (SSTs) would remain high from the 2005 season. Warm waters mean more energy for hurricanes to form. The further expectation was that there wouldn't be an El Nino or a La Nina — El Nino suppresses hurricane formation, La Nina enhances it — so that the El Nino effect was expected to play no part.

On a more technical note, we also expected to see more storms form in the Main Development Region (i.e. more Cape Verde-type storms) given that we were expecting a westerly phase of the Quasi-Biennial Oscillation. What actually happened was that the Atlantic SSTs were warmer than average but they were a full degree cooler than they were in 2005. That meant there wasn't as much energy in the Atlantic as there was in 2005.

However, the main story was the influence of wind shear. Wind shear is the change in wind speed or direction with height and higher wind shear tends to suppress hurricane formation and development. What we saw in the 2006 season was much a higher incidence of high wind shear, especially over the Caribbean. This either stopped storms from forming or snuffed out storms that had formed (Tropical Storm Chris was a classic example of this). Finally, towards the end of the season, a weak El Nino formed. This increased wind shear broadly across the entire Atlantic and hurricane formation was effectively turned off.

One thing forecasters did get right was the expectation of more Cape Verde-type storms. We did see a significant proportion of the storms in 2006 form in the Main Development Region, far to the south and east in the tropical Atlantic. This, combined with a strong Bermuda High oriented well to the east, kept the storms that did form over the open ocean and come nowhere near the U.S. mainland.

With increased intensity projected to last several years, is there a chance that hurricanes will move farther north, endangering the U.S. west coast?

I don't think there is an increased likelihood of Southern California being significantly impacted by a hurricane any time in the near future. It is theoretically feasible for a storm to hit California but given the relatively cool Pacific waters north of Baja, it is highly unlikely. Unlike the Atlantic, where the Gulf Stream current pushes warm water to relative high latitudes along the eastern coast, the U.S. west coast has no such mechanism. As we saw this season, there were storms that formed off the Mexican Pacific coast but these all either passed out to sea or hit the Mexican coast in the Baja region.

In your opinion, can we reasonably expect more of the same in the Atlantic in 2007?

There are two main questions going into next year that will influence the season's activity. The first is, How warm with the Atlantic SSTs be in 2007? It is highly likely that the Atlantic SSTs will be above average, but just how far is open to debate. At this time, there is no good answer.

The second question is, Will the El Nino conditions persist? The answer to this question is very far from certain. El Nino models do not have great skill outside the six-to-nine month range before the next hurricane season. There is a roughly equal likelihood that either the El Nino will remain or it will have faded to neutral. In reality, the answer to this question will not be known much before Spring 2007.

Special Reports /

Speaking Of: 2006 Storm Season

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