Global models on Thursday have generally become more optimistic with Gulf of Mexico development and less optimistic with deep tropics development. At 2:00 PM EDT Thursday afternoon, the National Hurricane Center (NHC) gave a near zero percent chance of a tropical cyclone forming from a monsoonal low in the Gulf of Mexico within 48 hours, and a 50 percent chance within five days. This is up from yesterday at this time, at which NHC only gave a 20 percent chance of development within five days. 

The 12z Thursday ECMWF and CMC models predicted that Tropical Storm Bret would form in the Gulf of Mexico by next Tuesday. The 12z Thursday GFS model, in contrast, just predicts a disorganized tropical low that struggles to consolidate. The most likely track evolution is that a circulation closes off just north of the Yucatán Peninsula and tracks to the west, making landfall in Northern Mexico. However, the unreliable CMC model disagrees, showing tropical cyclogenesis much faster and a landfall in Northwestern Florida. Because of the monsoon gyre nature of the system, if a tropical cyclone does form, it will likely be large and will struggle to organize quickly. It is very unlikely that this system will be able to reach hurricane strength if t develops. It should be noted that large monsoonal gyres tend to have heavy rain as their primary threat. Based on the fact that the ECMWF model has fared better in tropical cyclogenesis the past few years than the GFS, I give a 60 percent chance of development occurring with this system over the next five days, which is slightly higher than the NHC’s 50 percent chance. 

The tropical wave in the Atlantic Main Development Region (MDR) has struggled today, with minimal deep convection near its center. None of the 12z Thursday GFS, ECMWF or CMC runs predicted development of a tropical depression from this system. In fact, most GEFS ensembles, which were previously quite bullish in predicting development, are not predicting development of this wave anymore. I give this tropical wave a 10% chance of development in five days, lower than the NHC’s 20% chance, and this might even be a little generous considering model support has been largely dropped for this system today. There is still a slight chance that a small low-level circulation forms along with persistent convection, but the most likely scenario is this tropical wave crashes into Northern South America without a chance to develop. Two other tropical waves, one to the east and one to the west of the wave on the NHC Tropical Weather Outlook, actually have more thunderstorm activity than the area of interest, but lack model support and are not expected to develop at this time. 

I will be back for another blog post tomorrow discussing our two Atlantic areas of interest. I give a 60 percent chance that we will see Tropical Storm Bret form during the next ten days, most likely in the Gulf of Mexico.