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Showers in the Central Atlantic

A tropical wave that moved off the African coast two days ago is kicking up thunderstorms over the Central Atlantic this afternoon. The National Hurricane Center is cautioning that slow development may occur with this system over the next day or two. Sea-surface temperatures are roughly 28-29┬║C where the cyclone is located, so it is warm enough. There are three major inhibiting factors right now: shear, dry air to the north, and its position. Shear, while high now (Figure 1), is forecast to decrease over the next day or two over the Central Atlantic. Also, the shear is easterly, which is more conducive to cyclone formation than westerly shear. The other two factors are tied together. The storm is located so far to the south that the rotation of the earth is not helping the system become organized. However, if it moves any further to the north, it will encounter very dry air at the mid-levels (Figure 2), which will suppress the thunderstorms. However, I think as this storm moves further to the west, into a more favorable environment, the storm will become better organized and eventually become a tropical depression, our third of the season. Stay tuned to the StormTrack over the weekend for updates.

Figure 1. Shear over the Central Atlantic. Currently, Invest 99L is under 15 knot shear, which is a little high for cyclone formation
Figure 2. An enhanced satellite image showing dry air at the mid- to upper-levels. Hotter colors indicate drier air.

Posted by Adam Moyer | Permalink