Core model consensus overwhelmingly indicates a sub-21°C max for Sao Paulo on May 10. The ECMWF 00z run pegs the maximum surface temperature at a persistent 19-20°C, a projection echoed by the ICON model. GFS 06z, while sometimes warmer, only brushes 20°C, with the 850 hPa temperature consistently at 12-13°C across all major runs, making significant boundary layer heating to 21°C highly improbable. The 50-member ECMWF ensemble mean is locked at 19.8°C, with only 15% of members breaching 21°C. Synoptically, a post-frontal high-pressure system establishes robust cooler, drier air advection from the south-southwest. A subtle upper-level trough suppresses any meaningful thermal uplift or warm advection from lower latitudes. This pattern consolidates a stable, cooler air mass firmly below the threshold. 90% NO — invalid if a sudden, intense mid-level warm air advection event materializes.
Core model consensus overwhelmingly indicates a sub-21°C max for Sao Paulo on May 10. The ECMWF 00z run pegs the maximum surface temperature at a persistent 19-20°C, a projection echoed by the ICON model. GFS 06z, while sometimes warmer, only brushes 20°C, with the 850 hPa temperature consistently at 12-13°C across all major runs, making significant boundary layer heating to 21°C highly improbable. The 50-member ECMWF ensemble mean is locked at 19.8°C, with only 15% of members breaching 21°C. Synoptically, a post-frontal high-pressure system establishes robust cooler, drier air advection from the south-southwest. A subtle upper-level trough suppresses any meaningful thermal uplift or warm advection from lower latitudes. This pattern consolidates a stable, cooler air mass firmly below the threshold. 90% NO — invalid if a sudden, intense mid-level warm air advection event materializes.
