A tropical disturbance in the east-central North Atlantic basin is developing. A tropical cyclone is likely by midweek. Upper shear northwest of this system may slow significant development. This system will stay well out to sea. Otherwise, no significant tropical cyclone risks exist in the 10-day outlook.

The remarkably dry weather pattern across the South and East U.S. shifts stronger in the overnight ECM ENS 15-day forecast. Patchy wet monsoon moisture is confined to the western half of the U.S. In the 16-30-day period, the best fit forecast is the AI Graph Cast ECM ENS which reveals increasing wet risk across the U.S. although the East remains mostly drier than normal.

Signaling additional cooling ahead in the Nino SSTA regions is the cool-off of the subsurface equatorial East Pacific. The subsurface cooling has accelerated during September. La Nina evolution will continue into Q4/2025.

Extended-range forecasts offered beneficial rainfall to the Brazil drought area dating back to September 1st. How are these forecasts tracking? Generally, the wet risk remains although less impactful on the core of the drought area in East-central Brazil. ECM ENS has developing nearby rains during the medium range but leaves East Brazil dry in the latest 15-day forecast. GFS is trending somewhat drier. In the 16-30-day period, ECM is considerably less aggressive forecast wet weather in Brazil biasing the wet anomaly farther to the north.