ECMWF points toward tomorrow as the hottest day of many consecutive extremely hot days which last through this week. Thunderstorms caused by Tropical Cyclone Kay can cause local flooding late this week/next weekend as the heat wave erodes. Short-term thunderstorm activity is likely over the Sierra Nevada and southwest California mountains.

Presence of an upper-level low-pressure trough in the upper troposphere developed late last spring and lingered through meteorological summer. The upper trough is weaker in late August but still evident stretching from the Bahamas southwestward. The last time a tropical upper tropospheric trough was present during August in a vivid character was 2013 and during a weak La Nina climate.

Category-4 Typhoon Hinnamnor just-misses China to the east this weekend as intense drought continues. The immense California heatwave ahead peaks in strength next Tuesday. NOAA 30-day forecasts widen Midwest and Northeast drought while implicating Louisiana for September hurricanes.

ECMWF indicates the most likely location for tropical cyclones to develop that can become hurricanes and make landfall on the U.S. Coast is in the Gulf of Mexico for the last third of September and into early October. This season's core activity arrives late and lasts longer than usual!