El Niño Taming the Hurricanes

Patricia Grogg

HAVANA TIMES, Aug. 27 (IPS)  – The cyclical climate phenomenon known as El Niño/Southern Oscillation (ENSO) in the equatorial Pacific Ocean this year is helping weaken cyclone activity in the Northern Atlantic and the Caribbean. But Cuban meteorologists are warning against complacency.

Cyclone activity is reduced in this area when El Niño is on the rise, but that does not mean a complete absence of intense tropical storms.  Jose Rubiera, head of the Forecasting Centre at the Meteorology Institute of Cuba, pointed out to Tierramérica that in 1930 one single hurricane destroyed the capital of the Dominican Republic.

In 1992, another El Niño year, there was very little cyclone activity, but Andrew, one of the few hurricanes that season, achieved category 5 status, the maximum on the Saffir-Simpson scale that measures wind velocity. Andrew devastated the south-eastern U.S. state of Florida.

El Niño, the warm phase of ENSO, occurs when the surface water temperatures of the central and equatorial Pacific Ocean rise above the average.

So far, this season is seeing a “weak” El Niño, but it is expected to intensify towards the end of the year, said Rubiera, who went on to describe the two faces of this naturally recurring phenomenon, which manifests every two to five years.

The “good” El Niño is when it helps neutralize cyclone activity in the Northern Atlantic and Caribbean during the summer hurricane season, due to the increase in wind speeds in the upper atmosphere (at altitudes of 10 to 12 kilometers).

One of the factors that contribute to the formation of a tropical cyclone is wind patterns near the ocean’s surface that make the air flow in a spiral, with weak current in the upper troposphere. Such circumstances foment the development of vast areas of rains and electrical storms.

The Down Side to El Niño

“But this El Niño can also diminish the summer rainfall and increase rains in the northern winter,” added Rubiera. In 2004, this ocean-atmosphere interaction caused one of Cuba’s worst droughts in decades.

El Niño appears when there is a change in the atmospheric pressure in the western equatorial Pacific, off New Guinea and Indonesia, which triggers changes in the direction and normal strength of the Alisios winds, also known as the Trade winds, which blow from the southeast to the northwest, as well as altering the marine currents.

When there is no ENSO, the Trade winds maintain enormous masses of warm water along the western Pacific coasts.  El Niño slowly pushes those masses towards the east, to the coasts of Peru, Ecuador and Colombia, increasing the sea level and sea temperatures.

But Rubiera stressed that no two ENSO events are alike. Now there is talk of the “Modoki” variant – which in Japanese means “similar but different” – in which greater warming occurs in the central equatorial Pacific, and not in the east.

According to some studies, in that case the hurricane activity would be strong in the Atlantic, with harsher cyclones hitting land. “However, we must state that these studies are not conclusive and that all of this is quite new, which is why I would take these conclusions with caution,” said the expert.

He questioned whether the current El Niño could be considered of the Modoki variety, “because the greater warming is occurring in the eastern portion, and not in the central Pacific.”

In Rubiera’s opinion, such an argument is supported by the fact that “there is an active cyclone season in the eastern Pacific, corresponding to the warming that is occurring there, while there is almost nothing happening in the central Pacific.”

Cuba Tracks All Possible Storms

Cuba has yet to recover from the thrashing it took from three hurricanes in 2008 (Gustav, Ike and Paloma), which caused 10 billion dollars in damage, equivalent to 20 percent of GDP, according to President Raúl Castro.

With that price tag in mind, in mid-August the Cuban population closely tracked the paths of Ana, Bill and Claudette, the first named tropical storms of this hurricane season.  Hurricane Bill bypassed Cuba and made its way up the eastern U.S. coast to Canada, weakened to a tropical storm and dissipated in the North Atlantic early this week. Now tropical storm Danny has formed east of the Bahamas.

Rubiera believes that the message to all residents is that they should “always be prepared, whether it’s an active, normal or inactive season, because in the end nobody knows where or when a hurricane that does not yet exist is going to develop.”

“Any long-term forecast is only of relative practical use,” said the expert, who also emphasized that a reduction of cyclone activity does not mean an absence of activity, meaning there will be storms, but not as many as in the last three years.

The hurricane season begins Jun. 1 and ends Nov. 30. In Cuba, the months of highest activity are usually October, September and August, in descending order. Cuba’s disaster prevention system, which can include the massive evacuation of thousands of people, has reduced to a minimum the number of human fatalities, but not the economic losses.

In its report on Aug. 19, the World Meteorological Organization (WMO) predicted that El Niño, described currently as “weak or moderate”, would last until the end of 2009 and likely the first quarter of 2010.

There is no solid data about what will happen after that date, when El Niño could continue, or revert to the cooler phase of ENSO (known as La Niña), or return to the neutral state of early 2009, said WMO expert Rupa Kumar Kolli.

Last year was a dramatic one for the Caribbean region, with the formation of 16 tropical storms, of which eight became hurricanes.

(*This story was originally published by Latin American newspapers that are part of the Tierramérica network. Tierramérica is a specialised news service produced by IPS with the backing of the United Nations Development Program, United Nations Environment Program and the World Bank.)