Friday, April 23, 2010

The Science Behind Seasonal Hurricane Forecasts

I am almost certain by now you’ve heard the forecast for an extremely active 2010 Atlantic hurricane season. With experts are predicting 15 named storms, including 8 hurricanes, and 4 majors to develop this year, along with a 69 percent chance of at least one hurricane striking the United States coastline, it’s quite obvious atmospheric indicators are pointing towards an above-average season. But what are those indicators? What is the science behind seasonal forecasts?

Well, there needs to be sound physical arguments for how certain predictors impact tropical cyclones. The predictors in place ahead of the 2010 Atlantic hurricane season were in place during the epic hurricane seasons of 1998 and 2005. Interesting, right? Those predictors are:

El Niño – El Niño produces strong wind shear, which suppresses hurricane formation. Created out of an abnormal warming of the Eastern Pacific Ocean, El Niño is forecast to fade before the heart of the 2010 Atlantic hurricane season.

Sea Surface Temperatures – When the tropical Atlantic is abnormally warm, hurricane season likely will be more active. The tropical Atlantic was the warmest ever for March and is expected to continue heating up.

Wind Patterns – High and low pressure systems over the Atlantic work to slow the trade winds. The trade winds are forecast to be relatively light, promoting storm development.

Ocean Circulation – When there is a strong ocean current moving to the north, as is the case this year, hurricane season tends to be busier. This circulation pattern works to draw warm water from southern latitudes into the region where hurricanes form.

Natural Cycle
Because of a natural cycle known as the multi-decadal signal (or oscillation), warm water shifts from the North Atlantic to the tropical region where storms tend to develop. The multi-decadal signal is currently in a warmer phase.

So it seems there is very strong scientific basis supporting the forecasts that have been made thus far. But keep in mind that while one can forecast an active season, there is no real science to predict who will be affected, as this is largely determined by specific atmospheric conditions in place while the storms are actually spinning.

Only time will tell how the 2010 Atlantic hurricane season shapes up! Stay tuned, and be ready…