Bertha heads towards Bermuda

Hurricane Bertha continues trundling along towards Bermuda, but is not in a hurry to get there. The storm has a rather sloppy appearance on satellite loops, thanks to the fact that the eyewall dissolved last night, with a new, much larger eye taking its place. Bertha will probably start to intensify today now that this Eyewall Replacement Cycle (ERC) is done. Wind shear is low (less than 10 knots) and water temperatures are warm (28°C). Shear if forecast to remain below 10 knots until Sunday, but the water temperatures will gradually cool to 26°C by the time Bertha reaches Bermuda's latitude on Sunday. Intensification back to Category 2 status seems probable, and Bertha still has an outside chance at reaching Category 3 status again. The Air Force Hurricane Hunters will make their first flight into Bertha this afternoon to check on the storm's strength.

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Figure 1. Forecast of wave heights for 8am EDT (12 GMT) on Saturday, July 12, from the World Wave Model. Wave heights in excess of 4 meters (13-14 feet) are likely near the center of Bertha.

High surf is already beginning to affect Bermuda, and the World Wave Model (Figure 1) predicts that waves will continue to build at Bermuda through Sunday as the storm approaches. The Bermuda Weather Service is predicting waves of 9-13 feet in the island's outer waters by Sunday. There is about a 47% chance the island will experience sustained winds of tropical storm force (40 mph), according to the latest tropical storm wind probability forecast by NHC. None of the computer models currently foresee that hurricane force winds will impact the island, but given the very weak and unpredictable steering currents forecast to affect Bertha by Sunday, the storm could easily approach closer to the island than the current official forecast. Wind shear is expected to rise above 20 knots on Sunday and Monday, and this could knock Bertha down to tropical storm strength by Monday. Bertha could affect Newfoundland as a tropical storm in a week's time, as predicted by the GFDL model.

Elsewhere in the tropics
There are no threat areas to discuss in the tropical Atlantic. Three out of four of our reliable computer models are predicting that a tropical depression may form between Africa and the Lesser Antilles Islands 5-7 day from now. These models did a pretty good job forecasting the formation of Bertha this far in advance, so the potential of another Cape Verdes-type storm forming next week needs to be taken seriously.

I'll post an update Saturday morning.
Jeff Masters