El Niño years typically result in fewer hurricanes forming in the Atlantic Ocean. But a new study suggests that the form of El Niño may be changing potentially causing not only a greater number of hurricanes than in average years, but also a greater chance of hurricanes making landfall, according to climatologists at the Georgia Institute of Technology. The study appears in the July 3, 2009, edition of the journal Science.
“Normally, El Niño results in diminished hurricanes in the Atlantic, but this new type is resulting in a greater number of hurricanes with greater frequency and more potential to make landfall,” said Peter Webster, professor at Georgia Tech’s School of Earth and Atmospheric Sciences.
That’s because this new type of El Niño, known as El Niño Modoki (from the Japanese meaning “similar, but different”), forms in the Central Pacific, rather than the Eastern Pacific as the typical El Niño event does. Warming in the Central Pacific is associated with a higher storm frequency and a greater potential for making landfall along the Gulf coast and the coast of Central America.
Even though the oceanic circulation pattern of warm water known as El Niño forms in the Pacific, it affects the circulation patterns across the globe, changing the number of hurricanes in the Atlantic. This regular type of El Niño (from the Spanish meaning “little boy” or “Christ child”) is more difficult to forecast, with predictions of the December circulation pattern not coming until May. At first glance, that may seem like plenty of time. However, the summer before El Niño occurs, the storm patterns change, meaning that predictions of El Niño come only one month before the start of hurricane season in June. But El Niño Modoki follows a different prediction pattern.
“This new type of El Niño is more predictable,” said Webster. “We’re not sure why, but this could mean that we get greater warning of hurricanes, probably by a number of months.”
As to why the form of El Niño is changing to El Niño Modoki, that’s not entirely clear yet, said Webster.
“This could be part of a natural oscillation of El Niño,” he said. “Or it could be El Niño’s response to a warming atmosphere. There are hints that the trade winds of the Pacific have become weaker with time and this may lead to the warming occurring further to the west. We need more data before we know for sure.”
In the study, Webster, along with Earth and Atmospheric Sciences Chair Judy Curry and research scientist Hye-Mi Kim used satellite data along with historical tropical storm records and climate models.
The research team is currently looking at La Niña, the cooling of the surface waters in the Eastern and Central Pacific.
"In the past, La Nina has been associated with a greater than average number of North Atlantic hurricanes and La Nina seems to be changing its structure as well,” said Webster. “We’re vitally interested in understanding why El Niño-L Niña has changed. To determine this we need to run a series of numerical experiments with climate models.”
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Monday, July 6, 2009
New Type of El Niño Could Mean More Hurricanes Make Landfall
Tuesday, March 3, 2009
Georgia’s Spring Climate Outlook
Spring will likely be drier than normal for most of Georgia. March will have wide swings in temperature. A late freeze or even a snow or an ice storm isn’t out of the question. Severe thunderstorms and tornadoes are common this time of year.
Through most of this winter, Georgia’s climate was primarily a response to a neutral climate pattern. The neutral pattern is one of three climate patterns that have major influences on Georgia’s climate. The other two and better-known patterns are El Niño and La Niña.
This past winter, Georgians have experienced a classic neutral winter with periods of very cold and very warm weather. Rainfall in neutral winters can be very dry, near normal or very wet. This winter has been a very dry one.
Since the beginning of the year, the climate pattern has gradually shifted to a weak La Niña. This change is expected to have a major influence on the state’s spring climate.
It is important to realize that knowing which climate pattern we are in gives us only the probabilities of what to expect. It can tell us how we might want to hedge our bets, so to speak. It isn’t a guarantee.
Because the climate pattern is now in a weak La Niña, there is a very high chance that the coastal plain will experience a very dry spring. The chances of a very dry spring decrease into the northern piedmont. In the piedmont north of a Carrollton-to-Elberton line, near normal rainfall is the most likely outcome.
In the mountains of north Georgia, there are no clear indications of what to expect rainfall wise over the next three months. If a consistent storm track occurs over the mountains, then the spring may be wet. However, if the storm track is just 50 to 100 miles north of Georgia, then the mountains will experience a dry spring. The good news is that typically under a weak La Niña – like we have now – the storm track has a tendency to be further south, which means the mountains might receive some beneficial rains.
As far as temperatures are concerned, we can expect a continuation of a wide range, especially through the middle of April.
The date of the last killing freeze, or 28 F or below, or the last frost has no relationship with the climate pattern. Knowing that Georgia is currently under the influence of a weak La Niña tells us nothing about when the last freeze will occur.
Just as important, a warm March does not tell us anything about the likelihood of a late freeze. The 2007 Easter freeze is a prime example. March 2007 had been very warm and most plants had broken their dormancy. Then a devastating freeze hit in early April.
Snow and ice storms are not unusual in Georgia during March. Additionally, March through May is a time when severe thunderstorms and tornadoes are common. Because tornadoes can occur at anytime, day or night, all Georgians are encouraged to have a National Oceanic and Atmospheric Administration, or NOAA, weather radio at home. NOAA weather radios can be purchased at most electronic stores, large discount stores and many grocery stores.
By David Stooksbury
University of Georgia
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