Can a Volcanic Eruption Occur in Los Angeles?.And heavy rains at higher elevations mean the water has to go somewhere, and that’s always downhill. Hillsides blackened and denuded by fires are the worst possible place for heavy rain to fall. This frequently causes mud and debris flows. This collision and lifting effect means that mountains wring the maximum moisture out of atmospheric rivers. The Santa Barbara area, a bit to the south, has received 12-15 inches of flooding rain.Įven though California has been deluged with rain in recent weeks, it doesn’t compensate for more than two decades of drought, which played a big part in record-shattering fire seasons.Ītmospheric river moisture plumes in the lower and middle levels of the atmosphere, when they encounter mountains, are forced to rise quickly, enhancing the rainfall. For reference, San Luis Obispo sits just north of 35° north latitude, the line that the persistent, elongated Pacific jet stream has followed across the ocean in recent weeks. So La Niña typically means warm, dry conditions in Southern California and the Southwest, but it’s not always the case.Ĭentral California continues to be the primary focus of this El Niño-like jet stream position, and the part of the state that has received the most above-average precipitation. As Tardy points out, snowpack is twice average right now, and about 310 inches has accumulated at Mammoth, which is more than any of the three prior seasons there. La Niña is forecast to persist, with a 50-50 chance of conditions turning neutral in the January-to-March period.Ĭonditions in the state are nevertheless entirely different this year, compared with the previous two La Niña winters. This is the third consecutive winter that’s firmly in La Niña territory, based on conditions in the ocean and atmosphere in the tropical Pacific. Such conditions are more typical of La Niña, the cool phase of the El Niño-Southern Oscillation (abbreviated as “ENSO”) climate pattern. These are called “inside sliders.” This pattern is conducive to Santa Ana winds in Southern California, where winter wildfires broke out in February.

Storms riding along the storm track were shunted inland, moving over the Intermountain West or the Rockies. This is significantly different from the patterns that brought the Southland a wet December 2021, then a a record-dry January and February 2022. Storms on this route tend to grab warmer moisture as they barrel across the ocean in expressway fashion, one after another. 20 found in the jet stream to be in what meteorologists call a zonal pattern, flowing straight west to east, with a region of upper-level lower pressure to the north and an area of high pressure to the south, closer to Hawaii. Weather patterns over the Pacific since Dec. Like trying to fill a champagne glass with a fire hose, to use retired Jet Propulsion Laboratory climatologist Bill Patzert’s analogy. When they arrive in quick succession, as has been the case in recent weeks, it can be overwhelming: Too much of a good thing for a drought-stricken state. But potent ones can cause extreme rainfall with catastrophic flooding and mudslides. On average, about 30% to 50% of annual precipitation on the West Coast comes from a handful of atmospheric rivers. These “rivers in the sky” can transport enormous amounts of often-beneficial moisture. They tap into moisture from areas around Hawaii, sweeping it along in atmospheric rivers as they head toward California.Ītmospheric rivers are concentrated streams of water vapor about 100 to 250 miles wide in the middle and lower levels of the atmosphere. Moisture is plentiful in the western Pacific, where waters are warmer than usual because of La Niña, and storms can easily grab more as they pass by the tropics on their eastward track.

This jet stream is like a moving sidewalk at the airport, where storms can pick up baggage along the way.

It’s the position of that moving belt that has been a key factor this winter. It’s not unusual for storms to move along the jet stream.

Los angeles weather in february 2022