Here are a few excerpts:

Q: We’re currently in an El Niño period. Is this expected to change the climate outlook for Haitians?

Tony Barnston: Haiti’s rainy season is long. As I mentioned above, it actually has two peaks, with a brief period in July that has relatively lower rainfall. We expect the current El Niño to persist through at least March, and possibly through May. During times of El Niño, the region around Port-au-Prince tends to get above-normal rainfall from late winter to around May. But we can’t be sure the El Niño will still exist in May. We’ll have a better idea in the coming months.

Alessandra Giannini: Let’s remember that we are talking about the impact of the El Niño-Southern Oscillation (ENSO) in its weakening phase, which is different from that in its growing phase. Right now, El Niño’s impact on Haiti is mostly indirect, resulting from warming in the tropical North Atlantic over the past six months. That’s why we also need to consider North Atlantic atmospheric circulation, captured in something called the North Atlantic Oscillation. The NAO was in its negative phase in December 2009, meaning that trade winds were weakened. This situation contributed to ocean warming, because there was less evaporation happening on the surface waters. So if the NAO lasts in its negative state from December to March, it will favor the continuation of these warm conditions, which are the basis for the above-normal rainfall predictions that Tony mentioned above.

Q: And what about the second half of the rainy season– after July?

Tony Barnston: The rainfall expectation for the second half of Haiti’s rainy season will depend in part on the direction of the ENSO state this summer– will it be toward another El Niño, La Niña or neutral? At this time of year we currently have poor predictability for ENSO beyond about May or June. An unfavorable scenario for Haiti would be for the development of La Niña during the summer. It would not only imply a wet second half of its rainy season, but also the chances for a tropical hurricane in the vicinity, or even a hurricane hit. As these maps show, La Niña conditions tend to not only increase the total number of hurricanes in the Atlantic, but also increase the number that cut across the Caribbean. In 2008, Tropical Storm Fay, Hurricane Gustav, Hurricane Hanna and Hurricane Ike pounded Haiti, leaving widespread destruction and displacing hundreds of thousands of people.

Read the rest on the IRI’s web site.

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