Figure 1.1 above Peak gusts (mph and km/h) for the March 10, 2016 windstorm. Wind speeds are largely from long-term surface airways weather observation sites, data buoys, lighthouses and C-MAN stations, with limited data from other networks (e.g. RAWS). Stations with long histories are preferred because of the research focus on intercomparison of historic storms. Numbers preceded by a tilde (~) represent the highest gust report in a dataset that has been interrupted at the height of the storm--usually data loss is from power outages. Values in italics are gusts estimated from peak wind, usually 2-minute or 5-minute, using a 1.3 gust factor. Stations with high-wind criteria gusts (≥58 mph or 93 km/h) are denoted with white-filled circles. Isotachs depicting ≥60 mph (~100 km/h) gusts are included to highlight the regions that had concentrations of the indicated magnitudes. The track of the extratropical cyclone center is shown (yellow arrow). Click on the map to see a larger version. Here is a map listing the station names.

Figure 2.1 above Storm track estimation largely based on surface maps provided by the US. NOAA Weather Prediction Center, and satellite photo interpretation. Faded blue track depicts a secondary low-pressure center that followed very close to the primary low. Date and time in PST and central pressure in hPa (mb).

The extratropical cyclone developed in the Northeast Pacific far off of the northern California coast (Figure 2.1) and moved northeast to 130ºW off of the coast of Washington. The low intensified approximately 18 hPa (0.53" Hg) over nine hours on its approach to the Washington offshore waters, then deepend another eight hPa (0.24" Hg) over the next six hours to 965 hPa (28.50" Hg) as it turned north and tracked just inside 130ºW toward the Queen Charlotte Sound. Deepening at ≥24 hPa in 24 hours puts this storm in the cyclogenic bomb category. Continuing on a nearly due north track, the storm system maintained its intense depth for several hours. This persistence of depth may have contributed to the strong winds over parts of southwest British Columbia as the low moved into the Queen Charlotte Sound, a position that supports strong SE winds along the Georgia and Queen Charlotte Straits. The storm did not begin filling until it passed the north end of Vancouver Island, likely due to increasing terrain interaction as the mature low neared the British Columbia mainland. The low lost 11 hPa (0.32" Hg) of central pressure in the six hours before landfall, and then nine (0.27" Hg) more in the next three hours after reaching the coast.

Interestingly, a secondary low-pressure center developed to the southwest of the primary one. As the primary tracked northeast and then north along 130ºW, this new low rotated counter-clockwise around the base of the initial cyclone. In some ways, this is reminiscent of the December 15, 2002 storm mentioned in the introduction, though the secondary low on March 10, 2016 seems more associated with the primary's bent-back front as opposed to developing along a frontal triple-point. Indeed, the March 10th secondary low appears to merge with the bent-back front of the primary just before reaching the south Vancouver Island coast. Unlike on December 15, 2002 when the secondary low landed in Oregon causing a relaxation of pressure gradients most especially in those areas between the primary and secondary lows, the March 10, 2016 secondary low stayed far offshore and may have enhanced surface pressure gradients along the coast over northwest Oregon and southwest Washington, helping support the observed extreme winds. The pressure gradient over the North Interior and Lower Mainland may also have been enhanced by this secondary low, or at least energy contributed to the bent-back front as it swept inland. The northeast to north-northeast trend of strongest winds (i.e. Astoria to Bellingahm) is reminiscent of Olympic or south Vancouver Island lows on a northeast track--this is comparable to the direction of motion of the secondary low and subsequently the large bent-back front of the primary after the absorption of the secondary. Remnants of the secondary low may have had enough influence on pressure gradients to reduce peak gust speeds over much of southern Vancouver Island, while helping enhance winds from the south Washington coast to the Lower Mainland and southward about a hundred or so miles (~150 km).

Figure 2.2 above Satellite photo composite of: a) four km resolution visible; b) four km water vapor; c) four km enhanced infrared; and d) 1 km visible for 2330 UTC (1530 PST) on March 09, 2016 for the first three and 1500 UTC (0700 PST) March 10, 2016 for the 1 km visible.

Figure 2.3 above Satellite photo composite showing four km resolution water vapor images for: a) 1530 UTC (0700 PST) on March 09, 2016; b) 1300 UTC; c) 0300 UTC on March 10, 2016; and d) 0830 UTC.

Table 3.1 above For 24 key stations in the study region, peak wind and gust (knots, mph and km/h), with direction (º) and time of occurrence (PST). Regional and overall maximums, minimums and averages are provided, along with the legacy 11-station average. Average gust ratios (average wind/average gust), or AGR, are also included. Wind direction average is based on vector components.

Figure 3.1 above Peak wind (mph), peak gust and peak wind direction (º) for coastal stations arranged by latitude.

Figure 3.2 above Peak wind (mph), peak gust and peak wind direction (º) for interior stations arranged by latitude.

Figure 3.3 above Peak wind (mph) and peak wind direction (º) for coastal and interior stations arranged by latitude.

With a 24-station average peak wind of 32.7 mph (53 km/h) and average peak gust of 49.7 mph (80 km/h) from the S, the March 10, 2016 windstorm in overall terms performed about average for Northwest windstorms (Table 3.1, Figure 3.1). However, given a relatively distant track near 130ºW as the low-pressure center moved northward, the wind speeds were actually rather strong and indeed quite unusually so in some locations.

The region of intense winds on the northwest Oregon and southwest Washington coasts is reminiscent of the Great Coastal Gale of December 2007. As with the earlier storm, a coastally trapped jet contributed to the high readings. Also, as noted above, the secondary low that swung around the base of the primary appears to have helped strengthen pressure gradients in the region afflicted by the intense wind gusts. The main low of the December 2007 event also tracked through the Queen Charlotte Sound--perhaps this is a repeating pattern for extreme winds for the region from approximately Newport, OR, to Hoquiam, WA.

In the interior, winds were particularly intense north of Seattle (Figure 3.2), the standard outcome for a classic "southeast sucker" and typically the result of extratropical cyclones following tracking far from the coast. In the main strike zone, some stations were dramatically favored over others for high winds, not an entirely unusual situation among the rugged terrain of the Pacific Northwest. This is looked at more below.

Peak gusts on the coast were markedly higher than in the interior up to about the latitude of Seattle, then the situation reversed to some extent (Figure 3.3). The secondary low appears to have relaxed pressure gradients enough on the central and southern coast of Vancouver Island to prevent more extreme winds from occurring, while at the same time supporting intense southeasterly winds in the Georgia Strait and Northern Inland Waters. Northern Vancouver Island, overrun by the intense pressure gradient surrounding the core of the intense March 10, 2016 extratropical cyclone, was not spared intense winds like the southern 2/3 of the Island.

Figure 3.4 above For 24 southeasterly high windstorms that affected the Victoria, Vancouver and Abbotsford region from 1994-2015, the peak gusts (knots) at Vancouver and Abbotsford. The majority of the storms are depicted in gray to show the range of variability. The average peak gust at the two locations for all the storms is highlighted in black. The outcomes of a windstorm on November 8, 1994 and March 10, 2016 are accented in blue and orange respectively.

During the March 10, 2016 windstorm, Vancouver and Abbotsford reported dramatically different peak gusts, 40 mph (65 km/h) verses 66 mph (106 km/h) (Table 3.1). These two locations are just 37.6 straight-line miles (60.6 km) apart. On average, Abbotsford tends to have higher readings than Vancouver during southeasters, so the peak gust outcome on March 10, 2016 is not entirely unusual (Figure 3.4). However, this is the largest exceedance of Vancouver's peak gust for the 22 years 1994-2015. Interestingly, during southeasters, Vancouver sometimes receives stronger peak winds than Abbotsford. The "Looper Storm" of November 8, 1994 resulted in what appears to be the most dramatic difference in peak gusts between the two locations, with Vancouver being slammed by a 55 mph (89 km/h) gust while Abbotsford received a meager 20 mph (31 km/h).

I have not yet encountered a meteorologist to date that can provide a mechanism for the favoring of one station over the other during a specific storm, this despite being an important forecasting issue in the Lower Mainland. Anticipating the region to be most strongly afflicted by an incoming storm would be useful to interests such as electrical utilities, as it would allow them to strategically place damage-control assets ahead of an incoming extratropical cyclone with confidence.

As for a mechanism, my suspicion is that the favoring of one location, more often Abbotsford, has to do with the tendency of a cold surface layer sourced from the Fraser Valley to be emplaced over the Lower Mainland ahead of southeasterly windstorms. SE winds tend to arrive with warmer, more buoyant air that can simply lift right over any emplaced cold air. The resistance of the cold surface airmass to being eroded by increasing S to SE winds likely determines outcomes: Abbotsford is often affected by downsloping winds off of the Cascades during southeasters, and perhaps these winds are often strong and turbulent enough to break up the cold surface layer in the region sooner than Vancouver in many instances--this despite Abby being closer to the source of the cold, dense air. In Vancouver, the North Shore Mountains probably act as an air dam, leaving the region under a shield that directs the wind above the city. The depth of the cold surface layer, combined with the strength of the attacking SE winds, may determine to some extent how long it takes for the warm winds to reach the surface. If it takes long enough, strong SE winds may not hit Vancouver as the center of a given storm moves far enough away to relax local pressure gradients by the time the cold air layer has been removed. Sometimes the surface layer is weak, leaving both locations exposed early during an approaching storm. The pressure gradient orientation (pressure slope) ahead of the storm and during the SE wind onslaught may have a key role in outcomes, too. If E to NE winds are favored, then the cold surface layer can be continually reinforced. In contrast, if the pressure gradient orientation is more in favor of ESE to SE winds ahead of the storm, the source of the cold air may be cut off, allowing for a quicker erosion of the boundary layer. These are just ideas. This topic is just waiting for a detailed study--it would be a nice PhD project.

The March 10, 2016 extratropical cyclone developed far off of the West Coast and followed a recurving path that took the center northward near 130ºW and just west of the north end of Vancouver Island. Tracks this far from the mainland generally do not cause high winds in the interior sections of Oregon and Washington (e.g. December 15, 2002). For the most part this was the case on March 10, 2016, save north of Seattle where intense 60 to 70 mph (95 to 115 km/h) wind gusts occurred. The development of a secondary low center that tracked closer to the Washington coast, and the passage of the primary low's bent-back front likely contributed to the strong interior winds, and also gusts of 70 to 85 mph (115 to 135 km/h) on the coast. A coastally-trapped low-level jet also contributed to the coastal wind speeds. In some ways, the March 10, 2016 windstorm behaved like a lesser version of the 2007 Great Coastal Gale.

Figure 5.1 above Intense southerly winds at the Pitt Meadows Airport flipped this airplane. The vehicle had been anchored before the storm. Photo by Trevor Batstone.

Figure 5.2 above A toppled tree is suspended on utility lines in Woodinville, WA, after gale-force gusts swept through the Puget Lowlands. Photo by Brie Hawkins.