Tropical Disturbance 99L a threat to develop - 8/1/12
Good morning and welcome to my tropical weather update for Wednesday, August 1st, 2012. The tropics is finally producing something interesting with Invest 99L located in the Central Atlantic. Satellite shows a fairly organized disturbance, with spiral banding and outflow beginning to become more prominent in the last few hours. Based on this, the National Hurricane Center has upped the chances for development into 60% in the next 48hrs. A surface circulation is finally starting to become per satellite loops, which appears to be located in the Northwest Quadrant of the convection.
(figure 1. Latest satellite image of Invest 99L)
Forecast for 99L
99L has finally it appears managed to break away from the ITCZ that was connecting it for the last few days and is beginning to sustain it's own convection. However, it needs to stop heading north too much as it will run into a ban of 20-30kt shear that will blast it apart. I don't think that will happen, instead I think that it will manage to actually get ventilated by this as it begins to take a more west course.
(figure 2. Latest shear analysis)
The models have been pretty unreliable with developing this into anything, most of them either started out the system wrong or just flat out refuse to develop it into a Tropical Depression even. The CMC, GFS, and HWRF are the only models wanting to show some sort of development. That being said, the SHIPS shows fairly high humidity and low windshear for the next few days and brings the system to 52 kts in 72 hours. Saying where this system is going to go is fairly simple I believe. Most of the models are saying that this will get into the Caribbean and I think it will too. However it appears the situation has changed with the shear, and there is a better chance for survival if it can get into the Caribbean that there was before. The HWRF and GFS are showing that once it can get past that area of high shear in the Caribbean intensification will occur in the Western Caribbean.
(figure 3. Latest spaghetti plot for Invest 99L)
Based on all this, I believe 99L has a 70% chance of becoming a Tropical Depression in the next 48 hours. I do not believe 99L will become a major system and could very well die over the Eastern Caribbean thanks to high windshear. I will be updating this blog if something drastic occurs later today or tomorrow.
UPDATE 5:30pm EDT.
Invest 99L has become Tropical Depression 5. No change in forecast is necessary, however as of the 5pm update the NHC is predicting a Category 1 hurricane in the Caribbean.