Source: http://www.wired.com/2015/02/noaas-hurri...

Meanwhile, 44,000 feet below us, the P-3 is skimming along the bottom of the clouds. When it reaches the Coast Range where land meets sea, it will spiral up to 10,000 feet and follow the storm over the mountains. Caught in the flow of atmospheric river’s central jet, the plane will see how much of the potential precipitation turns into actual rain. It was, according to later accounts by the crew, an equally turbulent flight. “We were in 80-knot winds, screaming over the mountains,” says Ryan Spackman, CalWater2’s flight operations scientist. He says it feels similar to being in a hurricane.

While the G-IV and the P-3 are offshore, the two other planes fly similar missions in the Sierra Nevada Mountains. But, these have a tighter focus on how particulate matter like pollution and dust help or hinder condensation of water vapor into droplets. The crews on all of the planes chat constantly via an IRC-like client, trading jokes, gripes, and mission updates. When the P-3 found the atmospheric river’s central jet, the techs on the G-IV got the news immediately, annotated with color commentary.

Hours before, finding that central jet was nowhere near assured. When the scientists were still on the ground for Friday’s weather and operations briefing, they weren’t sure the storm was going to come at all. “Bring on the rain! We need it!” said Allen White, one of NOAA’s top on-site scientists. It should have been pouring in Sacramento. But even though the clouds outside were dark, the ground was barely damp. Not only was the storm late—it was forecast to hit Thursday afternoon—it was off target. The models said the storm was supposed to zero in on San Francisco. Instead, it centered on Bodega Bay, 50 miles north.

The models were off, but to be fair, the storm was coming on the tails of an incredibly dry January. These types of transitions are hard to predict. “The air had been so dry before, it takes a while for it to saturate, and the rain to arrive,” says White. In the end, the storm would also run 10 to 20 percent less precipitation than anyone predicted. That’s the kind of thing this research is meant to help figure out. Data from these missions should improve scientists’ ability to forecast atmospheric rivers, which would be a huge boon to water management across the state.

For instance, if the models had been correct, and this atmospheric river had squarely hit San Francisco, the Coast Range would have wrung out less of the storm’s rain. Instead, the majority of the moisture slithered through the Golden Gate and carried on into the Sierra Nevadas. This could recharge the snowpack in the mostly bare mountains, put a greater portion of the rain in the state’s parched reservoirs, and give the Central Valley a much-needed soaking. “We hope that by getting the word out that water resource managers and emergency managers and utilities and power generators can all have better situational awareness for when atmospheric rivers hit and what their impacts are going to be,” says White.