Windstorms of the Pacific Northwest

Note: this post concerns regional windstorms, as opposed to localized windstorm that also occur in many Pacific Northwest locations.

Much of information and images in this post was gathered from a few key sources:

• An excellent book by University of Washington professor Cliff Mass, The Weather of the Pacific Northwest (2008)
• A related journal article: Mass and Dotson (2010): Major Extratropical Cyclones of the Northwest United States: Historical Review, Climatology, and Synoptic Environment. Mon. Wea. Rev., 138, 2499-2527, doi: 10.1175/2010MWR3213.1. 
• Visit Mass' weather blog here.

Figure 1: The University of Washington Atmospheric Sciences Department's logo: a depiction of the Thunderbird capturing an Orca.

The Thunderbird. According to the Quileute Tribe of the Washington State coast, the Thunderbird (figure 1) was a giant bird with wings twice as long as a war canoe and talons the size of oars who hunted Orca. With every flap of its wings, great winds would be unleashed. Clearly, The Quileute, along with other coastal tribes, knew the power of windstorms, something that is reflected in their practice of moving away from the coast during the winter months. As a hazard, Pacific Northwest windstorms pose a significant and common threat. The coastline from Oregon through British Columbia experiences hurricane-force winds as often (if not more often) than the Atlantic and Gulf coasts experience them from actual hurricanes. Based on NOAA’s Storm Data publication, it has been conservatively estimated that these storms have caused between 10 and 20 billion dollars in damage since 1950. Despite this, relatively little research or media attention has been paid to these storms relative to the East Coast's tropical cyclones. As a result, windstorms have a long history of surprising the region with little or no warning.

Aside from Native legends of great windstorms, written accounts from non-native settlers goes back to the Lewis and Clark expedition in 1805. Since, then many significant storms have been recorded (figure 2), with a few outlined below.

Figure 2: Some tracks of historical windstorms, from Mass and Dotson (2010).

The Windstorm of 1880
The first well documented major windstorm occurred on 9 January, 1880. The storm, which was described by newspapers as being “the most violent storm…since its occupation by white men”, killed one person and destroyed or severely damaged hundreds of buildings, uprooted trees, and damaged telegraph lines throughout Oregon’s Willamette Valley. Near the coastal town of Newport, every barn was destroyed, and in Coos Bay, a schooner dragged its anchor, was blown onto the beach, and broke in two.

The Great Olympic Blowdown
A few decades later, another major windstorm swept through the region, although this one’s damage was focused in Washington instead of Oregon. The Great Olympic Blowdown of 29 January, 1921 was notable for bringing hurricane force winds to a long stretch of Washington and Oregon coasts. The North Head Weather Bureau station, located on the northern tip of the mouth of the Columbia River measured a peak gust of 130 kt before the anemometer was destroyed. The exact wind speed will never be known since at the time, wind was measured using four cup anemometers, instead of the now standard three cup versions. Along the entire coast of the Olympic Peninsula at least 20% of all trees were blown down, with some areas seeing as much as a 40% loss (figure 3). Due to the devastation, roads into the backcountry became impassible, resulting in billions of board feet of timber being unable to be salvaged by the logging industry. By comparison, the 1980 eruption of Mount Saint Helens leveled only an eighth as much forest.

Figure 3: Olympic Peninsula timber damage from the 1921 windstorm from Mass and Dotson (2010).

The Windstorm of 1934

Over the course of the next few decades, two more historical windstorms impacted not just the coast, but also the interior regions of the Pacific Northwest; the Puget Sound region in particular. The 21 October, 1934 windstorm brought gusts of 50-60 kt to Puget Sound where it kicked up waves 6 m high and brought down roofs across the Seattle area. At Boeing Field, four aircraft were destroyed when winds lifted a hanger which then landed upon them. Fires occurred throughout the interior cities and spread rapidly by the wind, resulting in the busiest day in the Seattle Fire Department’s history up until then. A total of twenty-two fatalities were attributed to the storm.


The Windstorm of 1958
On 3-4 November 1958, a storm tracked through the region near Olympia, WA, and Mt. Rainier. This unusual westerly track resulted in one of the few windstorms to produce both northerly and southerly high winds. Northerly winds of 40 to 55 kt occurred over the central and northern Puget Sound region, while southwesterly winds of 60 to 75 kt were observed in areas south of Olympia. Along Oregon’s coast, nearly every major roadway was blocked by downed trees.

The Columbus Day Storm
In early October, 1962, Typhoon Freda (figure 4) formed east of the Philippines and recurved to the northeast while undergoing extratropical transition. After heading east across the Pacific during the following days, it made a sharp turn northward while roughly 1900 km northwest of Los Angeles and began to rapidly intensify. On 12 October, the storm reached its lowest pressure of 956 hPa (1 hPa equals 1 mb) while 480 km southwest of Brookings, OR. Over the next 18 h, the storm tracked nearly parallel to the coast before making landfall (figure 5) on the northwest tip of the Olympic Peninsula without any significant change in intensity. Heavy winds were experienced from northern CA, to southern BC, with wind gusts reaching 179 kt at Cape Blanco's Loran Station in southern OR, and 139 kt at the Naselle radar site in southwest WA. Meanwhile, the interior regions of the Willamette Valley and Puget Sound experienced gusts between 80 and 110 kt.

The Columbus Day Storm was likely the most damaging windstorm since the arrival of European settlers and quite possibly the strongest non-tropical storm to strike the contiguous US in the past century. In total, 46 people died and another 317 required hospitalization, while one million homes lost power. Along with the direct effects on humans, 15 billion board feet of timber was downed, 53,000 homes were damaged, and thousands of utility poles were toppled. The total damage was about a quarter of a billion 1962 dollars; if the storm were to strike today’s Pacific Northwest, the damage would likely be in the billions or tens of billions. The Columbus Day Storm also highlighted another significant difference between Pacific Northwest windstorms and tropical cyclones: inland wind speed. While even the strongest tropical cyclones typically do not produce heavy winds very far inland, the Columbus Day Storm (along with some other windstorms) produced winds greater than 85 kt at sites at least 80 km from the coast.

Figure 4: Path of the Typhoon Freda/the Columbus Day Storm. The triangle points are when the storm was extratropical. Insert is a satellite image of Typhoon Freda.

Figure 5: Surface analysis of the Columbus Day Storm, from Mass and Dotson (2010).

The Hood Canal Storm of 1979
On occasion, the terrain can even induce mesoscale-like lows in their lee. This was the case on 13 February, 1979 when a rather typical large scale winter windstorm caused a localized low center to form near Port Townsend. The low resulted in a small area of very high southerly winds over the Hood Canal that reached over 85 kt. A 975 m section of the Hood Canal floating bridge (figure 6) was lost (at the cost of 140 million 1979 dollars) and up to 80% of timber in the area was blown down.

Figure 6: The Hood Canal Bridge after its collapse in 1979.

The Twin Storms of 1981
On 13-15 November, 1981, a series of two windstorms followed near identical paths, making landfall on central Vancouver Island. The first storm (figure 7), which was by far the stronger one, brought high winds to locations along the Oregon coast, including an unofficial gust of 100 kt. Offshore, two ships reported gusts of 85 kt and another ship reported 10 m seas. In the Seattle area, the Evergreen floating bridge (SR 520) recorded gusts up to 65 kt and received thousands of dollars worth of damage that required an eleven hour closure. The second, much weaker storm (figure 8) brought lower wind speeds overall, but, strangely, caused far more damage to trees. In total, thirteen fatalities were attributed to the storms, while four thousand residents lost power.

What these two storms highlighted was the incredible difficulty in forecasting massive windstorms. Even just 24 hours before the first storm, NWS forecasts had little indication that an incredibly rapid intensification would occur. The only warning came eight hours before the storm when a local television meteorologist rushed a videotape of an animation of satellite images showing the intensifying storm over to the Seattle NWS office. Thankfully, weather forecast offices have since been equipped to make their own animation loops.

Figure 7: A visible image from about 14 November, 0000 UTC of the first of the two 1981 storms. This was captured soon after the storm's explosive intensification.

Figure 8: A visible image from about 15 November, 2100 UTC of the second of the two 1981 storms.

The Inauguration Day Storm
On 20 January, 1993, the day of President Bill Clinton’s inauguration, a storm blasted through Oregon and Washington that has been considered to be the third most damaging in the past 50 years. At 0000 UTC on the 20th, the low was located roughly 1000 km west of northern California. By 1500 UTC (figures 9 and 10), while the low was offshore the Columbia River outlet, the pressure had dropped 14 hPa to its lowest value of 976 hPa. The storm brought hurricane force winds to the Puget Sound area and the atmospheric sciences building at the University of Washington in Seattle measured a record wind speed of 76 kt. In Washington, six people died from the storm, while about 870,000 people lost power. The insured losses from the storm were estimated at 159 million 1993 dollars, with 79 homes and 4 apartment buildings being destroyed, and another 581 dwellings were severely damaged.

One of the aspects that made the Inauguration Day Storm significant was that it was the first major windstorm to be skillfully forecasted. As a result, the National Weather Service was able to issue a high-wind watch at 2130 UTC on 19 January and a high-wind warning 0600 UTC on the 20th. As is typical of most Pacific Northwest windstorms, however, the forecast was widely ignored by the media at large.

Figure 9: IR image of the Inauguration Day Storm at 1500 UTC on 20 January as it was making landfall on the Washington coast.

Figure 10: This the surface analysis of the storm, also at 1500 UTC, from Mass and Dotson (2010).

The Windstorm of 1995
Possibly the most skillfully forecasted windstorm occurred on 12 December, 1995 (figure 11). The storm brought hurricane-force gusts along a stretch of the west coast extending from San Francisco all the way to southern British Columbia. Five fatalities and over 200 hundred million dollars in damages were attributed to the storm, along with the loss of power to a total of over 1.3 million people.
What was fortunate about the storm was that forecast models predicted it up to four days in advance. Furthermore, it occurred during a major research program, COAST (Coastal Observation And Simulation with Topography experiment), which included surveillance of the storm's structure by one of the planes (a P-3 Orion) typically used for hurricane reconnaissance.

Figure 11: A visible image of the 1995 storm at 1930 UTC on 12 December.

The South Valley Surprise
Unfortunately, forecasts are still far from perfect, as was made evident on 7 February 2002, when a rapidly developed storm (figure 12) brought strong winds to Southern Oregon with practically no warning. The system resulted in the toppling of thousands of trees and power lines. The winds experienced in the southern Willamette Valley were likely the strongest since the Columbus Day storm.

Figure 12: A visible image of the South Valley Surprise at 2300 UTC on 7 February.

The Hanukkah Eve Storm
The strongest windstorm to strike the region since the Columbus Day Storm occurred on 14-15 December, 2006. This storm took a much more westerly track than most windstorms, making landfall (figure 13) along the central coast of Vancouver Island. Most of the damage from the Hanukkah Eve Storm occurred in western Washington, where 1.3 million people lost power, some for well over a week. Across Washington and Oregon, at least 13 fatalities were recorded and the total damage was estimated to be between 500 million and one billion 2006 dollars. In magnitude, this storm was comparable to the Inauguration Day Storm, yet the damage in western Washington was significantly greater. Much of this increase in damage was due to the record breaking amount of precipitation during the preceding November that left soils highly saturated, allowing trees to be uprooted far easier. Another factor influencing the damage total was the incredible amount of population growth that had occurred in the Seattle area since 1993, leaving far more people vulnerable.

Figure 13: An IR image of the Hanukkah Eve Storm at 0300 UTC on 15 December. Note the scale of the storm compared to most of the others

The Summer Windstorm of 2015
While windstorms of various intensities typically occur at least once a year, the 23 August, 2015 storm (figure 14) stands out by being the only recorded windstorm to occur during the summer. Most Pacific Northwest storms occur between November and March, when large extratropical cyclones dominate the region's weather. During the summer, high pressure usually sets up, bringing very dry conditions and clear skies. While the storm was far weaker than the other historic storms covered here, gusts over 35 kt were recorded at the Evergreen floating bridge before its instruments went offline. Like many early season storms, this oddity likely began its life as a tropical system that then became extratropical.

Figure 14: A visible image of the 2015 summer storm at 1600 UTC on 29 August.

Meteorologically speaking, there are several factors contribute to intensity of Pacific Northwest windstorms. Perhaps the most important is the effect of local topography. The many mountain ranges of the region often channel or enhance wind speed. It is for this reason that many of the record wind measurements, such as those at North Head (figure 15), were made at sites atop mountains or along the coast, where coastal mountains enhance winds along their windward slopes. This is especially true of the southwest flank of the Olympic Mountains, which receives the full force of the southwesterly winds. 

Figure 15: The North Head Lighthouse, where many of the record winds have been recorded. Notice how it sticks out from the coast and at the top of a pronounced slope.

A second major factor in Pacific Northwest windstorms is the location of highest winds relative to the low center. Unlike tropical cyclones whose maximum winds are found adjacent to the eye, or inland mid-latitude cyclones whose wind maxima are often found associated with a cold front, studies have found that these lows have maximum winds near a trough, well behind the cold/occluded front. This structure, sometimes called the poisonous tail of the bent-back occlusion (figures 16 and 17) typically rotates cyclonically around the south side of the low in the unstable air of the cold sector.

Figure 16: A surface model of the Hanukkah Eve Storm from the same time as figure 13 showing the bent-back trough extending south from the low’s center with very closely spaced isobars. From Mass and Dotson (2010).

Figure 17: A model of  near surface wind speed from the same time as figure 13 and 16. The black, red, and white areas show the strong winds associated with the bent-back trough. From Mass and Dotson (2010).

During a Pacific Northwest windstorm, the greatest danger to both lives and property are falling trees and branches. This type of damage is so prevalent, that tree damage, as inferred via tree ring width data, has been used to estimate the timing of major windstorms as far back 1701. A study in 2009 found that between 1995 and 2007, non-convective winds were associated with 143 fatalities, or 35% of all deaths due to wind related tree failures in the United States (figure 18). Of these, 28 were in Washington alone, making the state the second deadliest (after New York) in terms of all fatalities associated with tree failures due to high wind.

Figure 18: Fatalities due to non-convective wind tree failures between 1995 and 2007.

Trees typically fail in a windstorm either by snapping off the upper portions and branches or by being uprooted altogether (figures 19 and 20). In the Pacific Northwest, trees regularly reach 50 m or higher and are fast growing. These factors make them highly susceptible to windsnap due to their large exposure to the wind. The wet autumns and winters of the region often cause the soil to become saturated, making the ground less able to hold the trees’ roots. In more recent decades, tree failures have become more common as developers clear land for buildings. In doing so, they expose parts of the forest that had previously been protected by surrounding trees; the long-time structure of the forest having grown shorter, hardier trees along the edges and weaker, taller trees in the interior. Perhaps an even greater issue is that a few trees are often left standing as scenic backdrop. These isolated groups of trees are highly susceptible to wind damage. Since this pattern is often found in neighborhoods, it is not uncommon for roofs to be heavily damaged by large pieces of failing trees. In cases where trees become completely uprooted (figure 21), the heavy trunks can literally slice a house in two.

Figure 19: Extensive tree damage from a smaller scale windstorm in 2007. From Mass and Dotson (2010).

Figure 20: This picture (and the remaining images) is of damage caused by the 2006 Hanukkah Eve Storm.

Figure 21: A house has been sliced in half by an uprooted tree.

Finally, there is the issue with electrical power. In the Pacific Northwest, most power lines are above ground and thus easily broken by falling trees (figure 22). This is such an issue that most power lines are equipped with explosive charges that cut-off power when large current is created due to the grounded line. The flashes and booms accompanying these explosions can travel for miles and thus are often heard and/or seen repeatedly throughout a windstorm. Since above ground power lines pose such an issue, why are they not placed underground? The answer is: nobody knows. After every windstorm, the suggestion is commonly made by the public, but after a few months, it seems to be forgotten...until the next windstorm.

Figure 22: Trees brought down countless power lines during the 2006 storm.

Windstorms in the Pacific Northwest are a fact of life. Most residents keep multiple battery-powered lamps available; some even invest in personal electrical generators. As regular as these events may be, it is important to remember that they are both dangerous and expensive, with an estimated average cost of 112 million dollars per event, based on data from 1952-2006. Despite this, they are too often underestimated and under-researched; only since the 1990s has there been any real skill in forecasting these storms. Clearly, much still has to be done in understanding, and mitigating the effects of the windstorms of the Pacific Northwest. Until then, the Thunderbird will continue to dominate its domain.