Personally, I think we may observe more organization within the next 24 hours. I would not be surprised if we observe the formation of a tropical storm over the next two to three days. Latest visible images indicate a persistent convective burst has been occurring very near (or over) the LLC. Additionally, low-level inflow has been becoming much better defined in all quadrants, including the eastern sides (where dry air and easterly shear initially inhibited convection). This indicates a slower forward motion as the fast easterly flow relaxes across the area. I think it represents an increasingly favorable environment ahead of TD 4.
http://www.ssd.noaa.gov/goes/east/tatl/loop-vis.htmlIts presentation has been drastically improving over the past few hours.
You can clearly detect the changing structure of TD 4. Note the larger expanse of the circulation. This trend can precede the formation of a conducive upper-air and low-level environment, which would allow sfc convergence and convection over the LLC. This is the first key step toward a mature tropical cyclone, and it is a classic representative of the "favorable" deep tropics regime during the peak CV months (August and September). I think we could see Dean very soon - additionally, the larger structure could affect the rate of development, especially if conditions improve (very likely) over the next 24 hours.
I think the larger size could play a role in TD 4's eventual path, too. The reduction in its forward speed could allow the trough to move out of the area. On the other hand, the larger size could initiate a larger weakness in the mid-level ridge. It largely depends on the influence of shortwaves and the strength/expanse of the Plains ridge over the next several days.
What do you think?