Tropic wind shear predicted to drop last half of July

[phantom power]

It would have been neat if he'd extended the "average wind shear" line out through January, although the trend is pretty obvious.

Since SSTs are not the limiting factor, our old friend wind shear must be the answer! Let's look at wind shear in the eastern Caribbean, where both Hurricane Dennis and Hurricane Emily intensified into major hurricanes last year. As we can see from Figure 5, wind shear was very low in this region in 2005, and has been near normal or even above normal in 2006. Wind shear is expected to remain near average or above average across the the entire tropical Atlantic for the remainder of this week. While it is possible a tropical storm could form in a "hole" in the wind shear, the chances of it being able to stay together for an extended period and grow into a hurricane are low. So, it appears that the first half of July is shaping up to be a very normal one in the tropics.

What about the last half of July?
The two-week forecast from the GFS computer model has been consistently predicting a steady reduction in the amount of wind shear over the tropical Atlantic for the week of July 15 - July 23. Thus, many more "holes" in the wind shear will be opening up, potentially allowing tropical storms to form. I'll stick with my prediction I made at the end of June that we'll see one or two named storms in July, one of which may be a hurricane (but not a major hurricane). The forecast pressure pattern for the rest of July continues to show a weakness in the Bermuda High near the U.S. East Coast. This favors an above-normal chance of strikes on the U.S. East Coast, and a below-normal chance for the Gulf Coast, for storms forming in the Caribbean or near the Bahama Islands.



Figure 5. Wind shear over the Eastern Caribbean in 2005 (red line) and 2006 (blue line) compared to normal (black line). Wind shear is computed as the difference in wind between the upper atmosphere (200 mb pressure, about 40,000 feet high) and lower atmosphere (850 mb pressure, about 5,000 feet high). Image credit: CIRA

Jeff Masters