Big Winds in the West, Possible Wind Gust Record in California
Big Winds in the West, Possible Wind Gust Record in California
A near record-strength high pressure system over the Pacific Northwest slid southeast into the Great Basin on Nov. 30-Dec. 2 creating powerful wind gusts across almost all of the Western states causing considerable damage to many areas. Sustained winds of 148 mph with estimated gusts to 175 mph were recorded on Mammoth Mountain in California’s Sierra Nevada. Herein is a short summary of the wind events.
Winds in California
Around midnight November 30-December 1st the pressure peaked at Seattle-Tacoma Airport at 1043.4 mb (30.80”), the highest on record at that site and only 1 mb short of the all-time record for Seattle (30.83” set on December 3, 1921). Meanwhile a developing low pressure over Arizona caused isobars over California, Nevada, and Utah to tighten dramatically.
Surface map (top) and 500 mb map (bottom) for December 1, 2011 at 7 a.m. EST. Note that the high pressure over the Pacific Northwest had a peak pressure of 1047 mb (30.92”) at that hour.
Powerful Santa Ana winds developed over southern California on the evening of November 30th with the highest measured gust at 97 mph on Whitaker Peak (elev. 4120’) in Los Angeles County. Other unconfirmed reports indicate a gust of 167 mph (suspicious) at Henniger Flats at a site 2,800’ near Pasadena. The Los Angeles Airport was forced to close because 50 mph wind gusts blew debris over the runways. Low elevation wind gusts of 50-70 mph affected the entire southern California region and endured for almost 24 hours. Hundreds of large trees fell, downing power lines and causing small fires. At one point over 200,000 homes lost electricity, most in the San Bernardino Valley towns of Altadena and Pasadena.
A van is crushed by a fallen tree in the Highland Park section of Los Angeles following the high winds of December 1st. Photo by Mike Meadows/AP.
In Central California strong Diablo winds (the equivalent of ‘Santa Anas’ in the San Francisco Bay Area, also caused some damage and power outages, although not on the scale as in Southern California. The peak wind gust was 77 mph on the summit of Mt. Diablo (4100’). Amazing winds were recorded along the Sierra Nevada crests in the Mammoth Lake region with a RAWS site (Mammoth Summit Gondola 2) at 11,053’ reporting sustained winds up to 148 mph. The anemometer only registered up to 150 mph so the highest actual wind gust can only be estimated. Jan Null, a former Lead Forecaster for the NWS and chief meteorologist at Golden Gate Weather Services, calculated that the peak wind gusts would have been around 175 mph. This would be close to the highest wind gust ever reported from California (176 mph at Mt. Ward above the Alpine Valley Ski Resort, date NA).
Winds in Utah, Nevada, Colorado and New Mexico
By December 1st the high winds began to ramp up in the Great Basin and in New Mexico. Kane Springs, Nevada reported a gust to 98 mph (far short of the 141 mph gust, a state record if confirmed, reported from Virginia Peak on Nov. 19 during the wind event that burned dozens of homes in the Reno area).
In Utah, a peak wind of 102 mph was measured in Centreville, just north of Salt Lake City. Tractor-trailer trucks and other high-profile vehicles were blown over along Interstate Hwy 15 and flying debris closed many roads in the Provo-Ogden Salt Lake City corridor.
One of the many vehicles overturned by high winds in the Salt Lake City area where wind gusts as high as 102 mph were recorded on December 1st. Photo by Leah Hogsten, The Salt Lake City Tribune.
In Colorado news reports mentioned wind gusts to 123 mph at some site near Steamboat Springs Ski Resort in the central part of the state.
In Arizona, New Mexico, and Colorado heavy snow developed in the higher elevations (24” fell at Show Low, Navajo County in Arizona) while high winds raked the lower elevations. Peak wind gust in New Mexico was 78 mph at Dripping Springs on December 1st. The El Paso, Texas area was also slammed, with a peak wind gust of 75 mph measured at Mesa Hills, five miles west of El Paso city.
A Note on the Use in the Media of the Term “hurricane-force winds”
Jan Null admonishes the media for the widespread misuse of the term “hurricane-force winds” whenever an event such as this happens. He recently posted, in my opinion important, this statement concerning the issue:
“The ongoing strong wind events in the West are spawning the return of the dreaded "hurricane force winds" and "hurricane force gusts" terminology. Here's how I feel about the topic:
It seems that anytime there is a wind gust over about 60 mph the airwaves and other sources, including NWS statements, are rife with the expression “hurricane force” winds. While this might be good for conveying that it’s windy and might be dangerous, it’s both bad meteorology and bad physics! (And calling it a hurricane force gust doesn’t make it right either).
Let’s start with some basics. The threshold for hurricane winds is when the 1-minute sustained winds equal or exceed 74 miles per hour. Please note the word “sustained”! According to the NOAA Hurricane Research Division , peak 3 to 5-second gusts are approximately 30% higher than their associated sustained winds. This means that a 74 mph sustained wind of a minimal hurricane has gusts in the range of 96 mph. Quite a difference.
But that’s just the wind speed. What about the amount of force from the wind onto a surface that is perpendicular to the wind? From high school physics we remember that the force associated with a given speed is proportional to the square of the wind speed. (For the overachievers out there, the formula to calculate this force is: F = .00256 x V^2, where F is the force in pounds per square foot (psf), and V is the wind velocity in mph) Consequently, the amount of force with a 74 mph gust is 14.0 psf, while the force from a 96 mph gust is 23.6 psf; or 69% higher.
The bottom line is that a gust to 74 mph is NOT even close to hurricane force!"
Certified Consulting Meteorologist
Golden Gate Weather Services
All for now.
Christopher C. Burt
KUDOS: To Jan Null (former Lead Forecaster with the National Weather Service for California and Adjunct Professor and Lecturer at San Francisco State University) and chief meteorologist at Golden State Weather Services for providing information on peak wind gusts in the Sierra Nevada and his comments on ‘hurricane-force' winds.