Hurricane Lorenzo and its impact on Ireland

Hurricane Lorenzo weakening as it approaches Ireland.

On September 28, 2019, Hurricane Lorenzo made history.

According to the National Hurricane Center, the category 5 hurricane travelled farther east and north in the Atlantic Ocean than any previous storm of the same strength. By October 2, the hurricane had weakened to a category 1, but it still brought winds of 145 kilometers (90 miles) per hour to the Azores archipelago. The storm is expected to bring heavy rain to Ireland later this week.

The image above shows Lorenzo on October 2, 2019, shortly after passing the Azores. The image below shows the hurricane on September 28, when it was a category 5 storm. The images were acquired by the Moderate Resolution Imaging Spectroradiometer (MODIS) instruments on NASA’s Terra and Aqua satellites, respectively.

Lorenzo moved toward colder North Atlantic waters and the storm became an extratropical cyclone. The Irish Meteorological Service recorded heavy rainfall over Ireland in early October.  Disruption was minimal with the weather warnings lifted by October 4. Parts of Donegal however, did experience localised flooding causing damage to homes in parts of the county after rivers burst their banks.

From Ireland, the remnants of Lorenzo turned toward Britain and then continental Europe.
Lorenzo on on September 28, when it was a category 5 storm.

Lorenzo was the second category 5 hurricane in the Atlantic Ocean this year; the first was Hurricane Dorian. Hurricanes typically do not reach this strength in the northeastern Atlantic Ocean because water temperatures are usually too cold and wind shear conditions can hinder hurricane development. However, satellite measurements of sea surface temperature anomalies showed that the water under the storm was warm enough to give it an energy boost.

Hurricanes rarely travel this far east or north in the Atlantic; the last storm to brush the Azores archipelago was tropical storm Alex in 2016. In this case, news outlets noted that a large high pressure area in the western Atlantic blocked the storm from traveling toward North America.

Research has shown that the average latitude at which tropical cyclones reach their peak intensity has been shifting closer to the poles over the past 30 years. In other words, hurricanes in the northern hemisphere are reaching their maximum intensity at latitudes farther north than decades ago.

“It’s basically consistent with the oceans warming,” said Tim Hall, a hurricane climatologist at NASA’s Goddard Institute for Space Studies. “There’s a larger area of temperatures that can sustain intense hurricanes pushing further north.”

Hall also noted that hurricanes in the North Atlantic naturally recurve eastward as they move north into mid-latitudes; this suggests that intense storms of the future could form further east in the Atlantic because they will be traveling farther north.

Reporting: Earth Observatory