The February 24, 1961 Southwest Oregon Windstorm by Wolf Read |
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The February 24, 1961 event is particularly interesting because it produced winds that were nearly equivalent to those that assaulted Eugene during the February 7, 2002 South Valley Storm (SVS). In fact, a glimpse at Figure 1, above, peak gusts during the storm, reveals a damaging event that struck a large part of Southwest Oregon. Wind speed reports for Sexton Summit and Corvallis on the official observation forms are noted as either missing or estimated immediately after the period of peak winds, apparently due to anemometer-deadening power outages. According to a brief note in the National Climatic Data Center's (NCDC) Local Climatological Data monthly publication for Eugene, February 1961, "While the high wind of February 24 was not as strong as that of January 7, 1961, it was unusual for Eugene and considerable property damage resulted." The newspaper headline, "Sudden Wind Storm Batters Eugene Area," on the front page of the February 24, 1961 Eugene Register-Guard has that familiar SVS ring. From the newspaper account (used with permission, © The Register-Guard), trees were the principal victim, with two down on the old University of Oregon campus. These were individuals that had survived an onslaught of earlier storms. Eugene had suffered a steady assault of gale winds during January and February [Footnote 1], with significant blasts occurring on January 7th, February 1st and February 11th [1]. With an average velocity of 58 mph and gusts to 81, the storm of January 7th produced sustained winds a cut above the 54 mph during the February 24th event. The earlier storms were responsible for several toppled trees on the University of Oregon campus [2], leaving slim pickings for the later storm. The February 24th gale repeated the ever-familiar broken trees not just at the U of O campus, but throughout Eugene, with specimens down on 13th and Alder, 12th and Ferry and 1665 Lincoln Street. The tree on Alder appears to have brought down a high-tension line during its fall. South Eugene High School lost some roofing. Eugene Water and Electric Board suffered many outages, and downtown lights wavered with each pounding surge of wind. Lane County Electric Cooperative lost service to 5,000 of its 5,500 total customers. Pacific Telephone-Northwest had 226 phones dead by 16:00. With planes anchored firmly, the airport escaped damage. Southward, at Yoncalla High, a third of the roof sailed from the gym and heavy rain flooded the interior. A 30' by 55' chunk of roof was pulled off of Union High School in Grants Pass. Carried by 70 mph winds, the heavy debris crashed into a classroom. There were no injuries, and the school was expected to be closed for two weeks. A large window was also broken. Along the Pacific shores at Florence [3], an unofficial anemometer registered a gust to 80 mph. This was not a good day for the CAP, as the moorings for their Florence-based single-engine aircraft snapped under the gale's pull. The plane was thrown with devastating effect into the CAP office building, resulting in about $1,600 damage. Moving to the Cascade Mountains, along Highway 58 east of Oakridge more than 40 trees were thrown across the thoroughfare over a distance of just one mile, resulting in closure of the road [4]. Nineteen vehicles were trapped by the collapsed trees, which were described as having fallen "one after another." An ambulance on its way to a heart attack victim was one of those forced to stop. However, the ailing man had been taken to hospital in a truck, and he had passed away during the trip. Moving to the windstorm's details, Figure 2, below, plots the surface observations at Eugene during the February 24th gale, demonstrating the sudden burst of strong winds not unlike 2002 [5]. Duration and velocity are nearly equivalent between the two storms, though the differences in wind measure between the two times periods should be kept in mind (instantaneous gusts in the 2002 storm may have exceeded the 72 mph peak in 1961). |
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Probably the most significant difference between the two sets of observations is that the period of maximum winds in 1961 happened as the pressure declined, with a sudden reduction in velocity at, and after, the barometer's low point. Wind direction was generally south-southwest during the whole-gale period, with a sudden shift to southwest, then west-northwest at and after the low pressure point. Eugene's surface observation form shows temperatures climbing to 59° F during the damaging winds. Heavy showers or thunderstorms are not associated with this gale. Temperatures show a sharp drop to 46° between 12:57 and 13:58, the period when airflow shifted more from the west. The temperature continued to fall, sinking to 42° F by 15:58. This is a fairly dramatic swing for winter, the mark of a strong pool of cold air moving into the region. If Eugene's details were considered alone--with knowledge of the lower peak gusts at Salem and Portland--a case might be made for a weak low moving just north of the station and producing an SVS. However, the early onset of high winds relative to the pressure minimum is evidence that something was probably different in 1961 when compared to 2002, as was the tendency toward a southwest wind direction ahead of the hypothetical low. Study of stations to the north provide more clues. Examination of Salem's surface observation form for February 24, 1961 shows significant correlation with Eugene, save for the powerful gale. Morning-time had fairly light south winds during the pressure drop phase, with temperatures hovering in the 44°-46° F range. Between 09:58 and 10:58, airflow increased to 20 mph gusting to 29, with a temperature escalation to 55° F. By 11:58, there had been a shift of wind direction to the southwest, and a lowering of speed to a steady 17 mph. The temperature was 56° F, and the barometer had started to rise. Then, within the next hour, the wind shifted west-southwest, and velocities reached 21 mph gusting to 29. The temperature fell to 46° F during the one hour ending at 12:58. Moderate, sometimes heavy, precipitation began in the same hour, and continued up to 17:58. Ignoring the difference in wind speeds, the pattern at Salem was pretty much the same as Eugene, with the wind direction changes, and subsequent temperature drops, happening close to the same time. This is evidence of a strong cold front that roughly paralleled the valley. Portland's data provides more support for this conclusion. Strong south winds, reaching 23 gusting to 36 mph at 10:57 accompanied a temperature rise to 57° F. The barometric low point was achieved around this time. By 11:46, rain had begun, and winds shifted due west at 17 mph. The temperature was down to 50° F just eleven minutes later, with west winds down to 14 mph. Apparent frontal passage ("APRNT FROPA") was noted at this time, 11:57. Between 12:57 and 14:57, winds shifted southwesterly, and increased, ranging as high as 21 mph gusting to 30. The temperature continued to fall, along with the dew point, reaching a low of 39° F at 21:57, with a 35° DP. Showers of light rain and snow mixed occurred at this time. Apparent frontal passage was noted at Eugene at 13:11, about 90 minutes after the line moved through Portland. At Salem, FROPA was not noted. Wind direction changes and temperature drops place it between 11:58 and 12:58. It probably happened about halfway between the arrival times at Portland and Eugene--say 12:30. This strong cold front drifted into Oregon, hitting Astoria first around 03:58, most likely moving slowly in out of the west-northwest. This direction of travel puts the cool air arrival later in the day for stations south. Fairly generous precipitation, with a total of 0.68" at Portland, suggests that this front did not dive in straight out of the north (such fronts tend to be quite dry). Judging from the arrival times, the line raced east-southeastward once ashore, approaching relative north-south speeds of 60 mph. The storm's center appears to have made landfall north of Portland, indicated by lower pressures at that station when compared to Salem and Eugene. Figure 3, below, shows the pressure traces for all three locations. With the exception of the hour of frontal passage at Eugene, pressure gradients generally remained positive throughout the entire storm episode. This is in marked contrast to the pre-storm negative gradients that occurred in the 1994 and 2002 events, with a rapid reversal to positive after the cyclones had passed to the east. |
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| There's an even more striking feature in the gradients with the 1961 storm. As shown in Figure 4, below, the maximum winds at Eugene occurred during a time when gradients were decreasing. This is backwards to the typical windstorm scenario. At the time of pressure minimums during this event, gradients were at their most relaxed state of the day. This suggests a broad area of low pressure across the Northwest. |
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| Barometers up north in Seattle and Olympia were also nearly equally depressed, if but a few hundredths of an inch lower. Figure 5, below, a pressure "spectrum" for Eugene, Portland and Seattle, shows slightly deeper barometric minimums up north, but with wider, more gentle curves. It seems that the strong cold front witnessed in the Willamette Valley was the surface manifestation of a broad trough of low pressure that moved inland on the 24th. |
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This trough was cold. Once the front passed through and temperatures plummeted, Portland, Olympia and Seattle's Boeing Field reported snow mixed with rain. At Portland, the rain/snow mix began at 21:39, long after the front had pushed through. At that time, the temperature was 39° F with a dew point of 34°. The temperature at Olympia fell to 36° F with a dew point of 34° during the period of very light rain-snow mix, which began earlier than Portland, around 15:58, but still after the period of minimum pressures that suggest the trough had passed eastward. An estimated (due to melting) 0.1" of snow fell during the following morning and afternoon, and left a trace accumulation on the ground. At Boeing Field, light rain-and-snow mixed started falling around 14:58 on the 24th, when the temperature hit 38° F and dew point 34°. For the two Washington stations, the snow occurred during a period of light north to northeast winds, and then all precipitation ceased after a wind shift to southerly at Seattle, and southwesterly at Olympia. This wind shift likely marks a boundary, and suggests that the surface front hadn't reached these two stations until much later than it did Willamette Valley locations. Portland's snow occurred long after frontal passage, and may be more akin to the snow event at Olympia the following day. Also, the wind at Portland showed a strong shift to southerly long before the arrival of the front and subsequent shift to the west, a marked difference when compared to the Washington stations. The initial north to northeast winds in the Puget Lowlands, and Portland's move to southerly, suggests the possibility that a weak center of circulation might have made landfall with the trough, and passed between Portland and Olympia. Finally, due to the relatively even pressure changes across the region, this trough and associated cold front produced rates of pressure rise that were relatively even up and down the Willamette Valley, with Eugene having a peak climb of 0.08" per hour, Salem 0.10", and Portland 0.07". This contrasts against steadily decreasing rates of pressure climb northward in the Willamette Valley during the 1994 and 2002 SVS events. With the maximum winds occurring at a time when the gradient was 0.5 to 3.3 mb, winds driven solely by pressure differential can be ruled out. A low tracking across the mid-valley has also been ruled out, as are thunderstorm winds. This pretty much leaves only one other possibility for the generation of extreme winds: mid-to-upper-level jetstream winds being mixed down to the surface near the sharp cold frontal boundary. Sometimes, when a front is strong, vertical mixing can bring down the supporting jet stream winds. Often, during winter storms, these winds range from 45 to 75 mph at an altitude of 5,000-10,000 feet, sometimes even faster. If there's enough mixing, then these velocities can be forced to the surface as strong gusts. This typically happens during the southerly winds immediately ahead of the front, with a quick decrease after the boundary has passed, as was the case on February 24, 1961. These boundary winds can be very local. During a similar event on December 16, 2001, the kind of mixing described above prompted a high wind warning for northwest Oregon, including the Willamette valley, for winds of 25-35 mph with possible gusts to 60 as the cold front neared [6]. At Astoria, winds briefly escalated to 64 mph, and knocked out power to the airport, leaving many of the ASOS weather instruments dead, even 24 hours later. Much closer to my former home in Oregon City, a spotter at Canby reported a gust to 60 mph before there was much of a breeze being indicated on my anemometer. When the winds finally struck home, the peak velocity on my gauge amounted to a mere 31 mph! At Portland, Salem and Eugene, peak gusts were 44 mph, 43 and 36 respectively. The maximum EUG-PDX gradient was +4.8 mb. During a trailing front event on December 12, 2002, the pattern of higher winds at Eugene turned up in a manner similar to February 24, 1961, though nowhere as strong. According to the National Weather Service, Portland, peak winds from south to north included Medford SE 31 mph with gusts to 37, Eugene also with S 31 mph with gusts to 37, Salem with S 24 gusting to 29, and Portland with E 24 gusting to 26. Though nowhere at the same magnitude as the 1961 event, higher winds at the south end, including Medford, a place that is often shielded from powerful winds by the mountains that brim the narrow Rogue Valley, are demonstrated. In this scenaro, the incoming strong front was slowed when a wave developed at the base of the system along 40º N, which spared Oregon the high winds that had been forecast had the front continued its rapid progress eastward. One is left speculating what might have happened in Southwest Oregon had this system continued unimpeded and at full strength. Before closing, some of the striking events in the Garden and Rogue Valleys warrant closer scrutiny. At the Medford Airport, winds sustained at 25 to 30 mph from 10:30 to 17:00--a very extended time when compared to places like Eugene [7]. The strongest gusts happened near frontal passage, similar to stations north. Prefrontal winds, probably southeasterly, lifted the temperature from 39° F at 10:00 to 61° F by 11:00, an astounding rise of 22° F. The high was 63° F just before the cold air ushered the mercury back to 39° F by 22:00. A quarter inch of rain fell from this storm. Roseburg's winds lasted for a much shorter period of time, from 13:00 to 15:30 and ended when the rains began. Precipitation almost reached half an inch in a few hours. Due to the extreme conditions at Medford, Grants Pass and Roseburg, with wind velocities comparable to the Columbus Day Storm and even higher, this storm event probably warrants a more detailed study. The February 24, 1961 front meets several of the SVS criteria, including strong winds being confined to the South Willamette Valley, and lowland snowfall. What is missing is a low tracking across the Mid-Willamette Valley, and the associated pressure and wind phenomena that goes with that kind of event. Thus, despite the powerful winds that selected out Eugene, this event is not classed as a SVS--at least not the February 7, 2002 kind. However, this does not make the 1961 storm any less interesting! |
Footnotes 1. This assault of windstorms would continue, especially for the south valley. Examination of the National Climatic Data Center's Local Climatological Data Monthly Summaries for Eugene turns up other significant wind events on March 5th (35 mph 1-minute average), March 19th (40 mph), May 1st (46 mph) and May 26th (40 mph). The February 1st and 11th storms produced sustained winds of 37 and 35 mph respectively. As 1960 drew to a close, there were also events on November 20th (40 mph), and December 18th (37 mph). All these average velocities could easily contain gusts in the 45-55 mph range, and marked a very active winter season for 1960-61. |
References [1] Data from the National Climatic Data Center, Local Climatological Data Monthly Summary, for Eugene Mahlon Sweet Field, January and February 1961. [2] Damages in the interior, including Eugene, Roseburg and Medford, for the February 24, 1961 and earlier events are from the Eugene Register-Guard, February 24, 1961, in "Sudden Wind Storm Batters Eugene Area," front page. February 25, 1961, in "Wind Spills Trees, Cuts Power," and photo caption, both on the front page. [3] Damages along the coast, including Florence and Newport, for the February 24, 1961 and earlier events are from the Eugene Register-Guard, February 25, 1961, in "Wind Spills Trees, Cuts Power," and photo caption, both on the front page. [4] Damages in Cascade Mountain country, and Central Oregon are from the Eugene Register-Guard, February 25, 1961, in "Wind Spills Trees, Cuts Power," front page. [5] Data for the February 24, 1961 section from this paragraph downward, unless otherwise noted, is from the National Climatic Data Center, Unedited Surface Observation Forms, for Eugene Mahlon Sweet Field, Salem McNary Field, and the Portland International Airport, February 24, 1961. [6] Data on the December 16, 2001 cold front was collected online from the National Weather Service, Portland and Seattle offices, and NOAA Weather Radio, Portland. [7] Climate facts in this paragraph are from the Medford Mail Tribune, February 26, 1961, in "Valley Residents Take Inventory Of Wind Damage," front page. The News-Review, Roseburg, February 25, 1961, in "Record-Level Winds Lash Douglas County, Disrupting Service, Inflicting Damage," front page. In the articles, it was noted that the figures came from Roseburg and Medford Weather Bureau officials. |
Last Modified: May 30, 2003 You can reach Wolf via e-mail by clicking here. | Back | |
