By Andrew Freedman From Mashable

It’s only May, which means the tropical cyclone season in the Northern Hemisphere is still in its infancy. The Atlantic season doesn’t officially start until June 1, after all.

Yet already, in just the first four-and-a-half months of the year, the planet has had more Category 5 storms — the most destructive category — than its average annual total of such powerful tempests.

So far, five Category 5 storms have formed. The record was eclipsed over the weekend, when Super Typhoon Dolphin became a Category 5 storm in the Northwest Pacific, with maximum sustained winds estimated to be about 160 miles per hour. (The storm is now dissipating and transitioning into a non-tropical storm system.)

The planet averaged just 4.6 Category 5 storms per year between 1990 and 2014. Using a separate metric, this year also appears to be an outlier so far. The accumulated cyclone energy, or ACE index, shows that the Northwest Pacific alone has been running 483% of its typical activity-to-date. This index measures both the intensity and duration of tropical cyclones.

For the year-to-date (as of May 18), the ACE index in the Northwest Pacific was 106.475, according to statistics made available by WeatherBELL Analytics. This means there has been a high number of storms, and some of these storms have been powerful and long-lasting. The typical ACE index value at this point in the season is just 22.

According to Jeff Masters of Weather Underground, Super Typhoon Dolphin marked the earliest time in the year when a seventh named tropical storm or typhoon formed in the Northwest Pacific. The previous record for this milestone was May 19, which occurred in 1971.

Furthermore, 2015 already has the sixth most Category 5 storms on the planet for any year in at least the past 26 years, Masters wrote.

The formation of three Category 5 storms in the Northwest Pacific through mid-May puts that ocean basin on a record pace for the year, assuming more such storms form. The season is running more than two months ahead of the pace set by the record-breaking year of 1997. During that year, the Northwest Pacific had a total of 10 Category 5 storms.

Like 1997, this year is also proving to be an El Niño year, and the elevated ocean temperatures associated with El Niño is one factor driving these supercharged storms. Ocean temperatures north of the equator in the Western Pacific, a prime typhoon breeding ground, are running nearly four degrees Fahrenheit above average for this time of year.

Most Category 5 storms in the Northwest Pacific tend to form between July and November, which is the peak period of the Northern Hemisphere’s tropical cyclone season. The Northwest Pacific is home to the largest number of Category 5 storms on the planet, with about 60% of them occurring there. It’s likely that there will be more such monster storms this year, particularly considering the ocean temperatures.

Super Typhoon Dolphin
A study published Monday in the journal Nature Climate Change finds that warming ocean temperatures worldwide, which is associated with manmade global warming, are leading to a decrease in the number of tropical cyclones, but an increase in the intensity of the storms that do form. However, this does not prove to be the case every year, as El Niño is known to boost tropical cyclone numbers and intensities in the Northwest Pacific.

Hurricanes and typhoons (which are the same type of storm, just referred to by different names) play a role in the climate system by transporting heat from the tropics to the poles. This heat transport function may help explain why, with sea surface temperatures at an elevated level, there have been an unusually high number of powerful typhoons.

El Niño’s presence does not guarantee a continued string of monster storms in the Pacific, but it does indicate a likelihood for an above average season overall.

IMAGES:
The eye of Super Typhoon Dolphin seen on May 16, 2015. IMAGE: UNIVERSITY OF WISCONSIN
Dolphin ISS Image of Super Typhoon Dolphin taken from the International Space Station. IMAGE: TWITTER/ASTROSAMANTHA

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EDITOR: This could be good news for us here in the Cayman Islands as “While El Niño tends to boost activity in the Pacific Ocean, it clamps down on storm formation in the tropical Atlantic.” – See following story:

El Niño is hanging on: What that means for hurricanes

By Andrea Thompson From Climate Central

Over the next few months, the globe might see an uptick in tropical cyclone activity thanks to an El Niño that is showing signs of asserting itself more forcefully.

That doesn’t mean more hurricanes everywhere, though: While El Niño tends to boost activity in the Pacific Ocean, it clamps down on storm formation in the tropical Atlantic. That link has at least one hurricane forecaster calling for a very quiet Atlantic hurricane season this year — possibly the quietest since the mid-20th century.

While El Niño is a cyclical climate phenomenon in the Pacific Ocean — marked by warmer ocean temperatures in the tropics and a weakening of the usual easterly trade winds — it can impact weather around the globe.

During an El Niño, a domino of atmospheric effects causes a large area of stable, subsiding air to form over the tropical Atlantic. Exactly the opposite of what a fledgling tropical cyclone, which thrives on instability, needs to grow and strengthen. El Niño also tends to bring more wind shear to the region, meaning the speed and direction of the wind changes more between different altitudes, putting the kibosh on a burgeoning storm.

In the Pacific, it’s a different story: There, tropical cyclone activity ramps up during El Niño events. That doesn’t necessarily mean more storms, said Philip Klotzbach, a hurricane researcher at Colorado State University; instead, it might just mean storms form in areas that leave them with plenty of ocean to traverse before they peter out (and can shift the areas more likely to be hit by storms). Such longer-lasting storms are something frequently seen in the Pacific during an El Niño, Klotzbach said.

Forecasters combine the strength of a storm and its duration into a measure called Accumulated Cyclone Energy, or ACE, which can be used to gauge the impact of a single storm or a season’s worth of them. Stronger, longer-lasting storms have higher ACE values.

In an El Niño year, fewer Atlantic storms mean a lower ACE for that basin, while in the eastern and northwest Pacific, longer-lasting storms raise the ACE value. But the changes aren’t equal: The increase in Pacific activity is larger than the decrease in the Atlantic, so “your global activity actually increases in El Niño years,” Klotzbach said.

In particular, activity in the northwest Pacific is a big determinant of global ACE for a given year. There, the tropical cyclone (or typhoon, to use the regional term) season lasts virtually all year, and so there is more opportunity for storms to form.

“The northwestern Pacific drives the bus,” as Klotzbach put it.

Through April 6 of this year, the northwest Pacific’s ACE value was the second highest ACE to date on record, Klotzbach said.

Even though the El Niño didn’t fully emerge until February (by the reckoning of U.S. government forecasters), it is playing a part in this amped-up early season activity, which saw the formation of Category-5 Super Typhoon Maysak, one of only three storms of similar strength to form prior to April 1 in the records.

The tendency towards El Niño-like conditions last year still boosted Pacific activity and tamped down on the Atlantic. Several storms reached Hawaii, while Japan saw several landfalls — other signatures of El Niño-year activity. The global ACE value was also higher than in the previous two years, when neutral conditions were in place.

The most recent El Niño observations and climate model projections suggest the current event is looking a little more textbook and could last through summer, possibly even strengthening. Because of this, Klotzbach thinks that ACE “should actually be high this year,” though he expects only seven tropical storms to form in the Atlantic, compared to the average of about 12. Of those, his forecast calls for only three to become hurricanes, compared to an average of six.

Of course, El Niño activity is notoriously difficult to predict in the springtime, and signs around this time last year of a strong El Niño in the works didn’t pan out. So forecasters are cautious.

Even if activity is below normal in the Atlantic, forecasters are quick to caution, there is still potential for a pocket to open up and bring the right ingredients together to form a devastating storm.

The best example of this is Hurricane Andrew, which barreled into Florida as a Category 5 storm in 1992, during what was otherwise a remarkably quiet year in the Atlantic. The considerable damage from that storm marked it as the costliest Atlantic hurricane on record until Katrina.

IMAGES:
Super Typhoon Maysak seen by the Suomi NPP satellite on April 1, 2015, as it made its way toward the Philippines. Credit: NOAA/NASA
Areas that see more (orange and red) or less (green) tropical cyclone activity during an El Nino. Credit: KNMI
The most recent observations of sea surface temperatures across the tropical Pacific Ocean (top) and how different those temperatures are from normal (bottom).

For more on this story go to: http://www.climatecentral.org/news/el-nino-hurricanes-18887