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Brewing El Niño may mean active Pacific hurricane season


Thursday, June 1, 2017, 10:36 - Hurricane season is here for the eastern and central Pacific, and computer models are working on the final numbers that will define how active the season could be

May 15th marked the beginning of the season in the east Pacific, while the central Pacific started on June 1st. The end of the season in both basins will arrive on November 30th.

So how are things shaping up? Here's what we know so far.

How many storms end up forming in the region depends on several factors, although two of the main ingredients include the potential energy available for these storms, which comes mainly from the ocean surface, and the wind shear characteristics of the atmosphere during the season.

Since 2014, the tropical Pacific has been swinging back and forth between El Niño and La Niña. While 2015 will be remembered for hosting one of the strongest El Niño phenomena on record, 2016 was the opposite, with La Niña taking over although not quite as intense as her predecessor.

Now, El Niño seems to be back at least in the El Niño 1 region, just off the coast of Peru and Ecuador where SST anomalies have been very positive and responsible for torrential rains and major flooding.

Monthly and seasonal SST anomaly forecasts for the tropical Pacific, carried out with a variety of computer models, tend to agree that El Niño will continue to extend from the Peruvian coast westward into the central Pacific El Niño 3-4 region during the summer and fall. 

At this point, it is hard to estimate how strong of El Niño will form, but current data shows that even if it is not as intense as the 2015 El Niño, it will end up coming around. 

With this prediction in mind, and given that things are moving in the expected direction, it is likely that the hurricane season, both in the central and eastern Pacific Ocean basins, will be affected by El Niño.

The warming of the equatorial Pacific waters, tends to favor a stronger, more active hurricane season in the region, although the timing of when the warm waters arrive with respect to the season itself is essential as well.

The enhancement of hurricane activity is mainly caused by changes in vertical wind shear in the region, that is, the wind speed and direction roughly 5,000 to 35,000 feet above the ground.

When vertical wind shear is strong, storms can easily fall apart or not even form. However, with low wind shear values as would be the case in the east and central Pacific during El Niño, hurricanes form and strengthen rapidly leading to a more active season with a higher potential for major hurricanes to develop.

On an average season, the east Pacific sees 15 named storms out which 8 become hurricanes, and 3 end up as major hurricanes. This year, despite the fact that the east and central Pacific are currently in a low activity era of hurricane formation, El Niño could balance things out making this a normal to slightly above normal hurricane season.

For now all we can do is wait and see how El Niño evolves during the coming months. What we do know, is the name of the storms forming in the east Pacific this 2017 season.

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