Be forewarned, the unusually early start to the Anchorage storm season appears set to continue. Only about a week after one powerful storm blasted the Anchorage area, the National Weather Service is warning the atmosphere appears to be stirring up another tempest capable of carrying tropical rain and hurricane-force energy all the way across the Pacific Ocean to bomb urban Alaska.
The results can be downright soaking. A storm similar in nature to what appears to be approaching dumped almost 9 inches of rain on Cordova in 36 hours back in 2006. Valdez and Seward saw 7 inches or more in 48 hours that time. And Portage, at the head of Turnagain Arm just down the Seward Highway from Alaska's largest city, was drenched with 7.4 inches over the course of 55 hours.
Once called a "Pineapple Express," in honor of Hawaii, near which these storms arise, the monsoon-like flows out of the mid-Pacific caught the attention of meteorologists John Papineau and Eric Holloway, who last summer co-authored a research paper -- "Heavy Rain and Flood Events, A Survey" (.pdf) -- explaining how events that begin thousands of miles from Alaska can end up leaving Alaskans all wet.
Suffice to say, what happens is that a lot of water gets trapped high in the atmosphere, then pushed north by swirling global winds, only to be ripped out of the sky by the Chugach Mountains. What sort of downpour is on the way this weekend, thanks to what are now called "atmospheric rivers" breaking up on Alaska mountains, remains something of a mystery as of this writing. The amount of rain that falls, Papineau observed, depends on the speed with which each individual storm system moves across the Gulf of Alaska.
This storm is, however, moving fast enough that the weather service Wednesday afternoon posted a weather warning for both water and wind.
The winds are not expected to gust as high as those that took out power for tens of thousands of customers around the Anchorage Bowl last week and caused hundreds of thousands of dollars in damage, primarily due to falling trees, the statement said. Still, the weather service report noted, "a higher than normal chance of uprooted trees and resulting power outages."
If the storm brings with it the heavy rainfall that Papineau and some others worry it might, the blowout might be worse. Once the ground gets saturated, tree roots begin to lose their grip, and trees can topple in even relatively moderate -- at least by Anchorage Hillside standards -- winds. The weather service is expecting Hillside winds to peak at 80 mph during this incoming storm, which is fast but compared to the winds of 100 mph and greater last winter, not that fast.
Winds in the city itself are expected to stay below 40 mph, but meteorologists caution that's just a guess. A lot remains in flux. Conditions could be worse, or not so bad. As Papineau points out, it all depends on how fast the system moves across the Gulf. Cross your fingers. Maybe Anchorage residents will get super lucky and the system will stall out.
"Forecast speeds at this time are very preliminary and could change significantly over the next few days," the official weather statement said. Unfortunately, that could also be for the worse as well as the better.
Contact Craig Medred at firstname.lastname@example.org