Watching Invest 99L for the threat of development - 7/30/12
Good morning and welcome to my tropical weather update for Monday, July 30th, 2012. The tropics have finally ignited in activity with Invest 99L currently located in the Atlantic with a chance to develop into a tropical cyclone. Satellite reveals a relatively disorganized system, thanks to an abundance of Saharan Air entering into the system. However that being said it appears that this system will be able to create a moisture field around itself and be able to fend off the dry air as most Cape Verde systems are able to do.
(figure 1. Current satellite image of Invest 99L)
The CMC, GFS, NOGAPS, and UKMET have all been showing some consistency on developing this system. The past few days, most noticeably the GFS and CMC, have had the models drop the system and then only to pick it up again with the next run. However, the last 36 hours or so the models have finally become more consistent on development with the GFS only predicted a moderate tropical storm from this before meeting its death in the Caribbean. The CMC believes this will go north of the islands and become your typical Cape Verde hurricane. I somewhat favor the CMC track, as it appears that there will be a shortwave trough situated off the US Coast during this time. If 99L manages to separate itself from the ITCZ and begin to intensify it will probably go north of the islands. However, if it takes the GFS path it will face a wall of shear in the Caribbean and meet it's death without becoming anything more than a 50mph tropical storm. Right now, it's hard to say where exactly this might go as usual, all we need is patience.
(figure 2. Current model runs on Invest 99L)
The intensity forecast is going to be problematic. The CMC and GFS both show two totally different situations, the CMC is showing that if it goes north of the islands it will be able to intensify into a major system. However if it takes the GFS track it will die in the Caribbean, thanks to strong easterlies in the Caribbean due to the development of the El Nino in the Eastern Pacific. Based on what we know so far, I will not make an intensity forecast and it would be much rather to my liking just to sit back and watch the next few days.
(figure 3. Current shear over the Atlantic, note the high trade winds over the Caribbean)
Based on all this, I will not give a specific forecast yet on 99L given that there are too many factors coming into play. This situation will probably be no where near as tough as Debby was last month to forecast, and we have a lot of time to watch this system. Cape Verde season is now in effect, it's all a matter of time before we get another system.