Written at 12:21 pm CDT…
I continue to monitor what’s going on in the tropics. Right now, surface observations in southern Mexico show a broad area of circulation coming from the southern tip of the Bay of Campeche. Computer forecasting models continue to struggle with where this area of low pressure will end up and when it will end up there. The 12Z North American Model (NAM) has this broad area of circulation becoming a little more organized and striking central Mexico in the next 48 hours, or around Wednesday afternoon. It is hinting that it will develop into a tropical depression or a weak tropical storm.
Another model, Global Forecast System (GFS) at 12Z this morning suggests that the low will not develop much more than it already is, and has an abundance of rain just south of the Rio Grande Valley Wednesday evening into Thursday morning. However, GFS still suggests that the RGV will get its share of rain from this system, starting Tuesday (6/28) afternoon through the weekend.
Finally, looking at the Euro Model (ECMWF) at 00Z, it suggests that it will be a little more organized and making landfall by Thursday morning, a little further north than the 12Z GFS run has it. If this model is correct, it will be our best chance at rain here in the Rio Grande Valley.
Overall, no matter which model is correct, there is still a decent shot that the Valley will be getting some rain beginning on Tuesday afternoon through the weekend, with the best shot of rain coming on Wednesday and Thursday. There is a chance that this system will become a tropical depression or even a tropical storm, but nothing more developed than that is expected. If I had to put a percentage on the chance of rain for the week it would be:
The National Hurricane Center just issued a 30% chance of this area of low pressure developing into a tropical cyclone within the next 48 hours. Up 10% from 6 hours ago. I will continue to monitor this.