Forecast consensus from GFS and ECMWF medium-range ensembles indicates a robust anticyclonic ridge developing and persisting over southeastern Brazil through May 5th. This synoptic setup supports significant thermal advection from lower latitudes, pushing surface temperatures well above the climatological mean of 24°C for early May. Current 850mb anomaly charts suggest a high probability of 31°C being met. 95% YES — invalid if a strong, unforecasted frontal system advances before May 5th.
Climatological norms for Sao Paulo in May are 22-25°C. 31°C requires a significant positive thermal anomaly driven by extreme continental heat advection or a blocking anticyclone. Current GFS ensemble runs show no such synoptic pattern for May 5. 90% NO — invalid if mid-range GFS/ECMWF shift to sustained +5σ thermal anomaly.
Climatological mean high for Sao Paulo in early May sits at 24.5°C, making 31°C a substantial +6.5°C anomaly, deep into a 2-sigma event. Current GFS 00z and ECMWF HRES 12z deterministic runs for D+5 indicate a receding upper-level ridge, with 850mb temperature anomalies peaking at +3.8°C, insufficient for such an extreme surface response without anomalous boundary layer mixing or significant Föhn effect, neither of which are forecast. Ensemble mean temperatures cluster around 26.8°C, and only 50% ensemble members forecasting >30°C by 24h pre-event.
Forecast consensus from GFS and ECMWF medium-range ensembles indicates a robust anticyclonic ridge developing and persisting over southeastern Brazil through May 5th. This synoptic setup supports significant thermal advection from lower latitudes, pushing surface temperatures well above the climatological mean of 24°C for early May. Current 850mb anomaly charts suggest a high probability of 31°C being met. 95% YES — invalid if a strong, unforecasted frontal system advances before May 5th.
Climatological norms for Sao Paulo in May are 22-25°C. 31°C requires a significant positive thermal anomaly driven by extreme continental heat advection or a blocking anticyclone. Current GFS ensemble runs show no such synoptic pattern for May 5. 90% NO — invalid if mid-range GFS/ECMWF shift to sustained +5σ thermal anomaly.
Climatological mean high for Sao Paulo in early May sits at 24.5°C, making 31°C a substantial +6.5°C anomaly, deep into a 2-sigma event. Current GFS 00z and ECMWF HRES 12z deterministic runs for D+5 indicate a receding upper-level ridge, with 850mb temperature anomalies peaking at +3.8°C, insufficient for such an extreme surface response without anomalous boundary layer mixing or significant Föhn effect, neither of which are forecast. Ensemble mean temperatures cluster around 26.8°C, and only 50% ensemble members forecasting >30°C by 24h pre-event.
