Day 203: “My Bonnie Lies Over the Ocean…”
Last night, I mentioned several factors that were inhibiting the development of a tropical depression/storm near the Bahamas. If you read that post before going to bed, I can only imagine your surprise this morning when the National Hurricane Center (NHC) issued a special forecast update (above). Last night the probability of development was 40%, which it was earlier today as well. It was then increased to 70% by mid-morning, before being upgraded to near 100% with the special update. And sure enough, during the day, tropical depression #3 developed and strengthened into tropical storm Bonnie (graphic below).
So what happened? Was I completely wrong in what I said last night? Not exactly. Tropical storm Bonnie is still experiencing a lot of southwesterly mid-and-upper-level shear. This is evident in the image below in that all the cold clouds (tops of the strongest convection) are located to the northeast of the center of circulation. Because of this shear, the latent heat release is still being blow away from the storm, which is a strong argument against rapid development.
So what did happen? The (short)wave trough moved far enough away from Hispaniola (i.e., out over open water) that a low-level center of circulation was able to develop. In other words, the higher terrain of Hispaniola is no longer disrupting the low-level air flow into the now tropical storm that a true “center” was able to develop. This is the first step to strengthening. Now, tropical storm Bonnie must develop thunderstorms encompassing the center of circulation before any significant strengthening can occur. I’ll be watching…
PS… I wonder how many times I’ll have to hear the song referenced in tonight’s title…
