Bertha strengthening again, after rapidly falling apart

Hurricane Bertha fell apart yesterday to a minimal Category 1 hurricane about as quickly as her meteoric rise to major hurricane status had come. At Bertha's peak--a Category 3 hurricane with 120 mph winds and 948 mb pressure--Bertha was the third strongest hurricane on record so early in the season. Increased wind shear of about 20 knots plus some dry Saharan air that got injected into the core caused Bertha's sudden demise.

The intensity forecast
Shear is on the wane again over Bertha, down to about 15 knots. The storm is beginning to get a more symmetric cloud pattern and better organization, as seen on visible satellite loops. An eye is reappearing, and with Bertha over warm 28°C water, further intensification is likely today. None of the models are predicting a return to Category 3 status again, but Bertha could become a Category 2 hurricane again before wind shear increases once more later this week.


Figure 1. Bertha at peak intensity: 21:15 GMT Monday July 7, 2008. At this time, satellite estimates of Bertha's strength were 115 kt (135 mph), making the storm a weak Category 4 hurricane. Bertha was the third strongest hurricane on record so early in the season.

The track forecast
Bertha is slowing down and turning northward as it "feels" the approach of a trough of low pressure to the north. All of the computer model turn Bertha northwards east of Bermuda, and it currently appears that the island will feel only peripheral effects of Bertha. However, the trough of low pressure turning Bertha to the north will not be strong enough to fully drag the storm into the far North Atlantic, so Bertha will wander close to Bermuda early next week while it waits for another trough of low pressure to finish the job. It is very unlikely Bertha will threaten the U.S., but it could eventually affect the Maritime Provinces of Canada.

Elsewhere in the tropics
There are no threat areas to discuss in the tropical Atlantic. The GFS model is predicting that a tropical depression may form off the coast of Africa on Monday.

Dramatic temperature difference in California
At 3pm PDT yesterday, the temperature at the Point Sur Light Station was 52°F. A shallow marine layer lay along the coast, keeping temperatures cool. Just 20 miles inland, the temperature was 111°F at Arroyo Seco RAWS! You can check out this remarkable contrast by viewing the Wundermap for the region. We just added a fire layer to the product yesterday, so you can see the smoke density in the region as well. It's another bad day in Big Sur!

I'll post an update Thursday morning.
Jeff Masters