Long-term forecasts show that California could experience a big change in weather in the second half of December, with the storm door possibly swinging wide open. Meteorologists are keeping a close eye on these predictions.
“It has been pretty dry in California for about a month now.” “But I still think that is very likely to change, maybe pretty quickly and dramatically, sometime near the end of December, so sometime in the middle to end of December, and most likely by January,” UCLA climate scientist Daniel Swain said in a recent YouTube weather report.
The National Oceanic and Atmospheric Administration’s most recent forecast says there’s a good chance that California will get more rain than usual from December 20 to 26. As a comparison, NOAA scientist David Roth says that San Francisco gets about 0.15 inches of rain every day in December. That means that from December 20 to 26, the city would usually get about 1.05 inches of total rain.
Roth said it’s too early to get specifics because predictions made more than a week ago are less reliable. “It’s not clear how much rain is expected,” he said.
Matt Mehle, a forecaster for the National Weather Service, said that the change in weather will happen when the jet stream flattens out and spreads across the Pacific Ocean, going from west to east and reaching into California. The jet stream is the high-altitude wind that brings storms. The jet stream has been moving from north to south across the Pacific and the country for the past few weeks, but its path has been less straight.
Because of this trend, storms have hit the Pacific Northwest, where this year’s rainfall records have been broken in some places. The southern edges of some of these storms have hit Northern California. The far northern coast has gotten the most rain, but the rest of the state hasn’t gotten much. For Mehle, there is a good chance that there will be a change in the trend. “We’re pretty sure it’s going to rain; the only question now is how much.”
Another question that still hasn’t been solved is where the jet stream will exactly meet up in California. The location of the storm affects which parts of the state get the most rain.
Even though there is a lot of uncertainty, Swain said that conditions are expected to get better for stronger storms. “What I really want to emphasize is that the autumn tells us next to nothing about what the coming winter is likely to hold,” he stated. “Right now, there is actually a pretty convincing signal that out there in the model jet structure, that toward late December, we’re going to get things that might get interesting in California.”
40 to 60% chance of heavy rain over California and high elevation snow for the Sierras, Wasatch, and central Rockies could impact travel locally. Less storminess is predicted for central and eastern states.https://t.co/1N4GaHhqwK pic.twitter.com/Q7MqGDJaTI
— NWS Climate Prediction Center (@NWSCPC) December 13, 2023
Swain also said that the change in the jet stream fits with what scientists have said about the weather during certain times of the year because of El Niño. An El Niño started to form in August and has been getting stronger ever since. When the Pacific Ocean near the equator warms up and temperatures rise above average, this is called El Niño. According to NOAA, the rise in sea surface temperatures can change the jet stream.