Editor’s note: A version of this article originally appeared in the CNN Weather Brief weekly weather bulletin, which is published every Monday. You can sign up here to receive them every week and during major storms.
CNN
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NOAA’s hurricane hunters could be just as busy now as they were during hurricane season. However, it is not the hurricanes that pass through, but the atmospheric river systems that have plagued California since Christmas week.
Atmospheric rivers may not make headlines in the same way that hurricanes do, but they can have extreme consequences.
“Atmospheric rivers can span the entire Pacific. They are long and narrow, but much larger than hurricanes,” said Anna Wilson, atmospheric river reconnaissance coordinator.
They are crucial to the west coast. Half of the rain and snow the West receives comes from atmospheric rivers, which are plumes of moisture from the Pacific Ocean. And they cross an area with very few observing sites, making it difficult to forecast.
Until recent years, forecasters had to rely solely on satellites and forecast models to forecast atmospheric rivers, which can get very muddy without really knowing what’s going on inside the storms.
The University of California-San Diego, the Scripps Institution of Oceanography, and the Center for Western Climate and Water Extremes have partnered with NOAA Hurricane Hunters who can launch instruments called “dropsondes” into an atmospheric river, to transmit live weather data. The information is immediately put into weather forecast models, dramatically improving forecast accuracy.
“With the probes launched by the Hurricane Hunters, we get profiles of humidity, temperature and winds in the lower part of the atmosphere, which are really critical to understanding the structure of the atmospheric river,” Wilson said.
The information not only improves the general understanding of what atmospheric rivers are capable of, but also improves nowcasting.
“NOAA aircraft are flying into these weather systems and validating the models,” said Capt. Jason Mansour, pilot and commanding officer of NOAA’s Hurricane Hunter Gulfstream IV aircraft. “So NOAA’s National Weather Service is better equipped to predict where and when these systems will impact, and how much impact it will impact.”
Mansour is a seasoned veteran of the Hurricane Hunters. He says the ride could be a little less bumpy for atmospheric rivers, but the mission is the same.
“We are effectively part of the early warning system for atmospheric rivers across the board,” Mansour explained.
Parts of California have seen almost a foot of rain since Christmas weekend. San Francisco has received more than nine inches of rain, while Lake Tahoe has seen more than 11 inches. At the higher elevations, the snow totals have also been staggering. Parts of the Sierra have more than double the snow cover than you would normally see this time of year. Mammoth Mountain has seen almost 120” of snow since December 26. And that’s not all.
This week will begin the fourth consecutive week of rain and snow for California. Experts refer to the series of atmospheric river events, which occur in rapid succession, as a “family of atmospheric rivers.”
“Which basically means a series of them one after the other with maybe a day or so in between,” Wilson explained. “If it came on its own, it wouldn’t have a huge impact, but because it came right after three others, it has much higher hydrological impacts than otherwise.”
The West has been at the forefront of hydrological problems. Experiencing a megadrought, resulting in dry lakes and riverbeds, intense wildfires, and potential water shortages. The pendulum has now swung and California now faces extreme drought and extreme flooding simultaneously as the current rains will not solve California’s drought.
“What we need to get out of the drought is not an incredibly wet month where a lot of that water can’t be stored because of runoff,” Wilson explained. “What we need is a couple of consistent wet years, and it’s coming in a way where more of it can seep into the ground.”
Wilson added that he has seen the pendulum swing many times in California, but not like this.
“The swing back and forth is potentially widening,” Wilson said. “California is known for its volatile climate changes, but it seems that in recent years, like now, we are going from this new record for drought to this new record for rainfall.”
Rain will continue this week to the west, with no real cut in available moisture in the near future.
