Remarkable weather weekend ahead as Tropical Storm Rachel approaches San Diego and early

Key Points:

• Southern California experienced one of its worst late-season heatwaves on record in early October, with Downtown Los Angeles hitting over 100°F for five consecutive days, San Diego tying its October record with two days above 100°F, and multiple cities recording their warmest October start ever.
• The heatwave is ending as Tropical Storm Rachel shifts northward toward Southern California, with the National Hurricane Center issuing a rare Tropical Storm Watch from the California-Mexico border to the Orange County/San Diego county line due to the potential for rain, wind, and coastal flooding.
• Rachel may re-strengthen into a strong tropical storm near landfall because of record-warm Pacific Ocean temperatures and favorable upper-level atmospheric conditions, creating a possibility of tropical storm-force winds and significant coastal impacts, especially around San Diego.
• Coastal Southern California is already experiencing elevated ocean water levels and moderate flooding due to thermal expansion and a coastally-trapped Kelvin wave, with the risk of major coastal flooding increasing if Rachel takes a more northerly track.
• Aside from Rachel, a Pacific trough will bring cooler, breezier weather and light showers to parts of California over the weekend, along with a possible fire weather threat in northern California and western Nevada due to drier air and stronger winds.