Destructive Windstorm Rips across Northwest U.S.; TS Rick Forms in Northeast Pacific

One of the most widespread and damaging bouts of high wind to strike the Northwest U.S. in years tore down trees and power lines and knocked vehicles off roadways from Washington to the northern Great Plains from Tuesday into Wednesday. At one point, high wind warnings covered nearly 1 million square kilometers, or more than 10% of the contiguous United States (thanks to Stu Ostro at The Weather Channel for this tidbit). Washington governor Jay Inslee declared a state of emergency for all counties in the state on Wednesday. According to weather.com, at least four deaths were reported, and more than 1 million people in several states have been affected by power outages, in some cases for hours or days. Avista, the utility that serves the Spokane, Washington, area, said the windstorm was "the most devastating natural disaster the utility has faced in its 126 year history," with more than 100,000 customers still without power as of Thursday afternoon (thanks to WU member fred37 for calling this to our attention). A sampling of the most impressive wind reports:

Spokane, WA: 71 mph. This was the strongest wind ever recorded at Spokane International Airport apart from thunderstorms.
Mission Ridge Ski Area, WA: 137 mph
Colburn, ID (5 miles west): 101 mph
Chadron, NE: 75 mph



Figure 1. Eastbound traffic lanes, right, on Interstate 90 are dampened by wind-driven waves from the south as the floating bridge calms Lake Washington to the north, left, Tuesday, Nov. 17, 2015, in Seattle. Image credit: AP Photo/Elaine Thompson.


Figure 2. Jay Bly checks out the damage to his home in Spokane, Wash., Wednesday, Nov. 18, 2015, after a Norway spruce fell on his house the day before. Image credit: Colin Mulvany/The Spokesman-Review via AP.


Figure 3. Wind trace from atop the Mesa Laboratory at the National Center for Atmospheric Research in Boulder, CO, from 7:49 am MDT Tuesday, November 18, 2015, to 7:49 am MDT Wednesday. The peak gust was 94.4 mph just after 7 am Wednesday. Image credit: NCAR/RAL Real-Time Weather Data.


The wind-prone areas of Colorado’s Front Range, between Interstate 25 and the foothills of the Rockies, got hammered by this windstorm, with a number of car windows left shattered. Wind gusted to 95 mph in Lyons; 94 mph at the National Center for Atmospheric Research’s Mesa Laboratory, which sits just above Boulder; and to 102 mph at (fittingly) the National Wind Technology Center, a few miles to the south of Boulder. At Colorado State University in Fort Collins, a gust to 77 mph was the second-strongest since records began in 1997, behind only 84 mph on December 30, 2008, according to Dan Lindsey (CSU/CIRA). I don’t have a wind report from my own place in Louisville, just east of Boulder, but my frame house was groaning during the peak of the storm!

El Niño not strongly linked with major Northwest windstorms
Boulder is one of the largest U.S. cities prone to extreme downslope winds (warm chinooks and cold boras). An informal catalog of high wind events in Boulder since the 1960s, maintained by NOAA’s Earth System Research Laboratory, shows that major windstorms have occurred in both El Niño and La Niña years. The “super” El Niño winters of 1982-83 and 1997-98 were both skimpy on high-wind events in Boulder. Likewise, El Niño is not typically associated with damaging windstorms over the Northwest U.S. Data compiled by the University of Washington’s Cliff Mass show that the eight years from 1860 to 2000 associated with the most destructive Pacific Northwest windstorms all had Niño3.4 anomalies between +1.0°C and -1.0°C for the November-to-February period. In other words, these were either neutral, weak El Niño, or weak La Niña years. “Big windstorms AVOID strong El Nino years. Similar to vampires and garlic,” says Mass. “But there can be moderate storms in El Nino years and it appears that the very strongest years (like 97-98) had plenty of coastal storms.” Although eastern Washington experienced some of its highest winds on record this week, Mass dubbed the winds in the Puget Sound area of western Washington (gusts to 30-45 mph over land and 40-60 mph over water) “substantial but not record breaking.”

The culprit for this large-scale high wind event was an extremely powerful jet stream (see Figure 4 below) that arrived in Washington from the west, then angled east-southeast as it arced toward the Plains north of a strong ridge of high pressure off the California coast. The anticyclonic orientation of the flow favored downward motion that allowed very strong upper-level winds to mix toward the surface, especially in the lee of mountain ranges. Ahead of this strong jet, the powerful upper-level storm that fueled severe weather over the central and southeastern United States over the last several days has lifted northeast into Canada, leaving behind a front that remains remarkably well-defined on satellite near the Appalachians (see Figure 5 below).


Figure 4. WunderMap depiction of winds at 12Z (7:00 am EDT) Thursday, November 19, 2015, at the 200-millibar level, or about 38,000 feet. A powerful jet continues to arc across the western United States.


Figure 5. Visible GOES-13 satellite image from 1600Z (11:00 am EDT) Thursday, November 19, 2015. Image credit: NOAA-NASA Goes Project.


Rainy night in Nunavut
The channel of warm, moist southerly flow ahead of the front and upper-level storm shown in Figures 4 and 5 will bring a rare night of November rain to Iqaluit, the capitol of Nunavut, Canada. Located about 200 miles south of the Arctic Circle (see Figure 6), Iqaluit averages 59” of snow but just 0.03” of rainfall from November through April. Its average daily high on November 19 is 12°F. On Thursday night, after a sunset at 2:26 pm, Iqaluit is expecting rain and temperatures in the upper 30s.


Figure 6. Departures from average temperature at 12Z Thursday, November 19, 2015. Image credit: Climate Reanalyzer/University of Maine.


Late-season Tropical Storm Rick forms in Eastern Pacific
Tropical Storm Rick formed on Thursday morning in the record-warm Pacific waters off the southwest coast of Mexico, becoming one of the latest-forming tropical storms in the history of the Eastern Pacific. Since accurate records began in 1949 (with higher-quality satellite records beginning in 1971), the Eastern Pacific has seen only four tropical storms form after November 18: December 5, 1983 (Winnie), November 27, 1971 (Sharon), November 27, 1951 (Unnamed), and November 20, 2011 (Kenneth.) None of these storms hit land. Rick is also not expected to hit land; after a two-day period of intensification on Thursday and Friday, wind shear will increase over Rick this weekend, likely destroying the storm by Monday. Both the GFS and European models are advertising the possibility of another tropical storm forming in a similar location early next week.


Figure 7. MODIS image of Typhoon In-fa taken at 03:00 UTC November 18, 2015. At the time, In-fa was a Category 1 storm with 75 mph winds. Image credit: NASA.

Typhoon In-fa expected to pass south of Guam
In the Western Pacific, Typhoon In-fa is tracking west-northwest on a path that is expected to take the storm about 200 miles south of Guam on Saturday. In-fa became a typhoon on Wednesday unusually far to the south--at 5.8°N. According to wunderblogger Dr. Phil Klotzbach, this is the farthest south that a typhoon has formed since Typhoon Bopha of 2012 (3.8°N). In-fa is not expected to hit any land areas, and the Joint Typhoon Warning Center forecasts that the storm will top out at Category 3 strength this weekend.

The Atlantic is quiet with no tropical cyclone formation expected for the next five days.

Bob Henson (windstorm), Jeff Masters (tropical)