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Northern Hemisphere hurricane season off to record start, fueled by El Niño

by salesassistant@gopower.com 11. June 2015 04:21

This article was originally published in The Washington Post

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Hurricane activity is expected to be below-average this year in the Atlantic Ocean, but that “quiet” forecast does not translate for other parts of the Northern Hemisphere, where tropical cyclones have been smashing records since late March. North of the equator, typhoon and hurricane season has gotten off to a tenacious start, fueled by a strengthening El Niño in the central Pacific.

To determine how active a hurricane season has been so far, scientists use a tool called accumulated cyclone energy (ACE) — a measure of wind speed over time in each individual storm, which is then added across all storms. This measurement is a rudimentary way to calculate the activity of any given season.

According to Colorado State University hurricane researcher Phil Klotzbach, this measurement of hurricane activity has surged to a new record high in 2015. As of Sunday, the ACE for the Northern Hemisphere was an astonishing 152, while the previous high for the year-to-date was 102.

Not only has the Northern Hemisphere blown away the old record, but it’s done it three weeks prior to the old record of 152, which was on June 28, 2004. In other words, this record is coming three weeks ahead of schedule. The normal ACE at this point in the season is just 41.

The majority of the record-breaking activity is due to a blockbuster West Pacific typhoon season so far this year. Three out of the four typhoons that have formed in the northwest Pacific Ocean have also strengthened into super typhoons — basically the equivalent of category 5 hurricanes.

Typhoon Maysak was a particularly long-lived cyclone after it formed in late March. The monster typhoon eventually grew into a category 5 with winds of 160 mph, and it remained at that intensity for 24 hours. It was the strongest known typhoon to develop so early in the season. Ocean surface temperatures were particularly warm in the western Pacific north of the equator in late March, running around 2 to 4 degrees Fahrenheit above average and fueling the powerful storm.

Maysak is joined in the 2015 season by two other super typhoons, Noul and Dolphin. Noul became the equivalent of a category 5 hurricane in the first half of May, while Super Typhoon Dolphin followed quickly, reaching category 5 status on May 16. Dolphin was monitored closely as it approached the Pacific islands of Guam and Rota, and the storm ended up splitting the difference between the two, tracking right down the middle.

The East Pacific hurricane season technically got underway on May 15 and has been setting records ever since. The season has only produced two hurricanes so far, but each of those has gone on to become a category 4 storm with sustained winds exceeding 130 mph.

Hurricane Andres formed on May 28 and ballooned to a category 4 storm with winds of 150 mph on June 1. According to Weather Underground’s Jeff Masters, it was the first time a major hurricane (category 3 or stronger) had been seen that far west in the month of May.

hurricane season
This graphic shows Hurricane Blanca’s track over the past week, with colors representing the sea surface temperature. Blanca acted to cool the ocean beneath it last week, but it strengthened again as it tracked into cooler waters to the north. (Weather Underground)

Hurricane Blanca followed Andres and took advantage of the extremely warm ocean surface temperatures west of Mexico as it grew into the earliest second major hurricane in the satellite record for the region. Blanca peaked at a category 4 on June 3, but without a strong steering current, it lingered over the same area of ocean for about two days. Staying there cooled the ocean water beneath it, and the lower temperature weakened the storm to a category 1.

Remarkably, though, Blanca was able to re-intensify to category 4 status on Saturday, even though it was over slightly cooler water as it tracked north toward the Baja Peninsula.

On Monday morning, Blanca was a tropical storm with winds of 50 mph as it made landfall near Puerto Cortex, Mexico. According to the National Hurricane Center, Blanca was the earliest tropical cyclone on record to make landfall in Baja since Tropical Depression Calvin in 1993.

The record cyclone activity can be attributed to the current El Niño in one very important way — very warm ocean surface temperatures, which fuel stronger hurricanes. Sea surface temperatures have been running well above average across the tropical Pacific Ocean, and the warmth has strengthened over the past few weeks, NOAA’s Climate Prediction Center said on Monday.

According to Florida’s state climatologist David Zierden, all four regions in which climate researchers measure ocean temperature for El Niño have been running 1 degree Celsius (1.8 degrees Fahrenheit) above average for seven weeks in a row, which is the longest streak of above-average warmth in 25 years.

Interestingly, while El Niño bolsters the tropical cyclone season in the Pacific Ocean, it acts to dampen the season in the Atlantic by increasing hurricane-destroying wind shear in the upper atmosphere. So far, all of the organizations that have issued Atlantic hurricane outlooks for 2015 are forecasting a below-average season.

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