Tempest strengthens to Category 3 storm

MIAMI—Hurricane Irma continued its rapid power grab Thursday, with wind speeds increasing by more than 55 mph since Wednesday to become a major Category 3 storm.

In a 5 p.m. advisory, National Hurricane Center forecasters said sustained winds had climbed to 115 mph as the storm headed to the west, northwest at 12 mph. Irma remains in the far east Atlantic, just over 1,700 miles east of the Leeward Islands. Up and down changes in intensity are possible over the next few days, forecasters said, but the storm is expected to remain a major hurricane that could become a Category 4 storm in four days.

What impacts Irma poses to land remain unclear. Models are notoriously unreliable more than five days away, and Irma is not expected to near the Leeward Islands until sometime next week.

Thursday afternoon, forecasters said Irma became an “impressive” hurricane with a tight spin around its small center eye. The storm underwent a remarkable 57 mph increase in wind speed since Wednesday, they said, and satellite images indicate the storm may already be undergoing an eyewall replacement, a shift that occurs in intense storms.

Forecasters said they suspect the eyewall replacement will be the first of many, which could help broaden the storm’s reach. Over the next several days, they expect wind shear to remain weak and ocean temperatures moderate. Because of that, the storm’s deepening intensity could level off for the next two days.

After the weekend, the storm will likely cross much warmer water and again strengthen.

They expect the storm to begin turning west and south over the next few days as a high pressure ridge in the central Atlantic begins steering it. However, models disagree on how much influence the ridge will play, leaving its future path less clear.