slide1 n.
Skip this Video
Loading SlideShow in 5 Seconds..
Department of Atmospheric Sciences PowerPoint Presentation
Download Presentation
Department of Atmospheric Sciences

Loading in 2 Seconds...

  share
play fullscreen
1 / 98
Download Presentation

Department of Atmospheric Sciences - PowerPoint PPT Presentation

coy
177 Views
Download Presentation

Department of Atmospheric Sciences

- - - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

  1. Department of Atmospheric Sciences Popular Lecture Series

  2. Windstorms of the Pacific Northwest Cliff Mass Atmospheric Sciences University of Washington

  3. Many Believe that Northwest Weather is Benign But beneath the velvet softness of region’s fog and gentle rain, Mediterranean summers, and mild temperatures lurks another reality… the infrequent occurrence of some of the most damaging storms on the planet.

  4. January 29, 1921

  5. Circa 1912 North Head,WA Lighthouse Also a co-located Navy wireless station

  6. North Head Light

  7. The Unexpected • The Weather Bureau believed a storm was approaching the coast, and at 8 AM small craft warnings were posted. • Pressure fell rapidly at North Head until 2 PM, after which it steadied. Winds were from the east between 20 and 30 mph. To the weather observer (Mr. Hill), the worst appeared to be over. • At 2:40 PM the Mr. Hill and his wife left for the town of Ilwaco to pick up mail and supplies… a trip that usually takes about an hour.

  8. Ilwaco • Returning home around 3:15 PM they traveled a road though a dense forest of spruce and hemlock. • Very suddenly, the wind picked up to hurricane force and beyond…

  9. 1921 Windstorm Account: Mr. Mills, U.S. Weather Bureau North Head Observer “On the return trip, a telephone pole across the roadway brought the car to a stop, and a short distance beyond the pole an immense spruce tree lay across the road. We left the machine and started to run down the road toward a space in the forest where the timber was lighter. The southeast wind roared through the forest, the falling trees crashed to the ground in every direction from where we stood. Many were broken off where their diameter was as much as 4 feet. A giant spruce fell across the roadway burying itself within 10 feet of where we stood. Tree tops broke off and sailed through the air, some of the trees fell with a crash, others toppled over slowly as their roots were torn from the earth. In a few minutes there were but two trees standing that were dangerous to us and we watched every movement of their large trunks. The wind shifted from the southeast to the south and the velocity decreased to probably 100 mph or it may have been as low as 90 mph. Shortly after 3:50 p.m. we started toward North Head. We climbed over fallen trunks, crawled under others, and pushed our way through tangled masses of tops that lined the roadway. We supposed that all the houses at North Head had been leveled and the wireless station demolished for we knew that the storm was the most severe that had occurred in the vicinity of the mouth of the Columbia with the last 200 years."

  10. 1921 Historical Photograph Of Tree Blow-Down

  11. An Extraordinary Event • Hurricane-Force Winds Struck the Entire Washington Coast • At North Head sustained (5 minute average) winds reached 126 mph, with a maximum one-minute wind of 150 mph before the sensor failed. • At Tatoosh Island, 150 miles to the north, winds reached 110 mph. • At Astoria, on the south side of the Columbia, there were unofficial reports of gusts to 130 mph.

  12. An Extraordinary Event It was estimated that 80% of the mature timber near North Head was razed during this storm and 7-8 BILLION board feet of timber was downed over coastal Washington– eight times that blown down by Mt. St. Helens, and roughly the entire current annual harvest for the entire Pacific Northwest today.

  13. In some areas over 40% of the trees were blown down As a result, this event has become known as the “The Olympic Blowdown Storm”

  14. And Even More • The North Head wireless tower was demolished and all roofs in the vicinity were lifted from their structures. • At the nearby town of Ilwaco, dozens of boats were torn from their moorings and dashed to pieces on beach bulkheads. Nearly all roads in the area were impassable. • A canvas-back duck was thrown through a 1-inch glass plate window in the nearby town of Chinook. • An entire herd of 200 elk was killed by falling timber. • Power and telephone lines are downed over western Washington. • In Seattle's Elliott Bay twenty one barges broke their mooring lines and were driven into Puget Sound by 50- 70 mph winds, while on land a number of greenhouses were destroyed and several dozen fires were ignited.

  15. Courtesy of Wolf Read The 1921 Storm Track

  16. The Great Northwest Windstorms • The 1921 storm was one of the great windstorms of the Pacific Northwest…but by no means the most intense. • This talk will describe the nature of these storms, review some of the major events, and describe our progress in forecasting their development.

  17. Windstorm 101

  18. Most Northwest Windstorms are Produced by Midlatitude Cyclones • A cyclone is an area of low pressure around which air circulates in a counterclockwise direction (in the northern hemisphere)

  19. Midlatitude Cyclones • The lower the central pressure the stronger the winds. Typical winter low 990-1000 mb. • mb --millibar is a unit of pressure. 1013 mb is equivalent to 29.92 inches--average sea level pressure • Usually associated with areas of large changes in temperature--- fronts. • The energy source of these storms are the temperature changes between relatively warm air from the south and cooler air from the north. • Dominate north of approximately 30N

  20. Weather Satellites Show These Storms As Cloud Swirls

  21. Most Major Northwest Windstorms Are Associated with Lows that Follow a SW to NE Track Western WA Storms

  22. In Contrast: Tropical Cyclones • Also low pressure centers with air rotating around counterclockwise north of the equator. • Range in intensity from tropical depressions to hurricanes. • No fronts or temperature contrasts • Associated with convection…thunderstorms • Their energy source is the heat and moisture of warm tropical oceans. Need water temperatures greater than 80F. • Thus, they weaken rapidly over land or over cooler water. • With cool water offshore of the Northwest coast, tropical cyclones and hurricanes do not reach our shores.

  23. Tropical Cyclones

  24. Hurricane: A tropical system in which the maximum sustained surface wind is 64 knots (74 mph) or greater. The Saffir-Simpson Hurricane Scale Note that 1-minute average winds are used below. • Category One: Winds 74-95 mph, above 980 mb • Category Two: Winds 96-110 mph, 965-980 mb • Category Three: Winds 111-130 mph , 945-965 mb • Category Four: Winds 131-155 mph, 920-945 mb • Category Five: Winds greater than 155 mph, below 920 mb • Category Six: Only in the imagination of TV scriptwriters

  25. The Hybrids • Occasionally, tropical cyclones move northward and get transformed into midlatitude cyclones • Some of the strongest Northwest windstorms had such an origin… such as the 1962 Columbus Day Storm

  26. Other Differences • Midlatitude storms do not weaken as quickly over land as tropical storms. • Midlatitude storms generally move much faster. • Midlatitude storms are generally larger in size. • Midlatitude storms in our neighborhood have a forced multiplier… big trees.

  27. Force Multiplier Professor Bob Houze’s home after a minor windstorm: he was standing outside and had to jump for his life! Easter Sunday, April 97

  28. History

  29. The Thunderbird Native Americans knew about NW windstorms and had several legends regarding their origin.

  30. Early Settlers • As European settlers moved into the Northwest during the later half of the nineteenth century, they also learned that Northwest windstorms were a force to be reckoned with. • Seattle pioneer Arthur Denny noted that "the heaviest windstorm since the settlement of the country" occurred on 16 November 1875 and was "a strong gale, which threw down considerable timber and overturned light structures, such as sheds and outbuildings.” Arthur Denny Seattle

  31. January 9, 1880 • Regarded by the Portland Oregonian as "the most violent storm ...since its occupation by white men", the cyclone swept through northern Oregon and southern Washington toppling thousands of trees, many 5-8 ft in diameter. • Sustained wind of 60 mph with gusts to 73 mph begin in Portland during the early afternoon, with stronger winds to the south, demolishing and unroofing many buildings, uprooting trees, felling telegraph wires, and killing one person. • Scores of buildings throughout the Willamette Valley were destroyed and hundreds more, including large public buildings, were damaged. Part of the roof of the Oregon State Capital in Salem was blown off, allowing snow to accumulate inside the building.

  32. January 9, 1880 • Rail traffic was halted in most of northwest Oregon, virtually all fences in the Willamette Valley that were aligned east-west were downed, and every barn near the coastal town of Newport, Oregon was destroyed. • Wind gusts on the coast were estimated to reach 138 mph. At Coos Bay, a 3-masted schooner dragged its anchor, was blown onto the beach, and broke in two. • Extraordinary deep low, with pressure falling to 955 mb (28.20 inches of mercury)

  33. The 1880 Storm Had Both Wind and Snow Courtesy of Wolf Read

  34. Description of the 1880 Storm by the Portland Oregonian "Not even among the traditions of the native Indian inhabitants of the country is there a record of a tempest so wild and furious or so disastrous and terrible in its results... The scene … was grand and terrible. The creaking of signs and buildings, the crash of falling awnings, the rumbling of tin roofs, the whistling chimes of electric wires, and above all and louder than all the fierce rage and roar of the tornado, united in a fearful and terrifying chorus. Men hurried hither and thither, eager, uncertain and fearful, women with white scared faces peered from the windows of their homes, dreading to remain yet knowing not whether to fly for safety, little children from the schools, ran homeward with frightened haste, horses snorted in helpless fear, and even the dogs were affected with the universal terror."

  35. October 21, 1934 • Wind gusts of 60-70 mph hit the interior of western Oregon and Washington, with higher winds on the coast, including an 87 mph gust at North Head. Winds gusted to 70 mph at Seattle's Boeing Field and 83 mph in Tacoma. • The storm removed roofs, overturned fishing boats, and lifted a hanger at Boeing Field off the ground that fell upon and destroyed four aircraft. Large swaths of forest were downed and waves on Puget Sound and in the Strait of Juan de Fuca reached extraordinary heights of 20 ft.

  36. Loss of power and telephone lines throughout western Washington, as well as numerous fires. Large display signs were ripped from buildings across the city, and dozens of buildings collapsed as a result of the strong winds. • Twenty-two people in Washington and Oregon lost their lives due to the storm.. • On the Seattle waterfront, the Pacific liner President Madison became unmoored, hit and sunk two other ships, and then smashed into a dock before coming to rest. • The smokestack of the central heating plant at the Church of the Immaculate in Seattle toppled and crashed through the dome of the sanctuary, from which parishioners had left only ten minutes before.

  37. The Most Extreme Northwest Windstorm: The Columbus Day Windstorm of 12 October 1962

  38. The Big One • The Columbus Day Storm was the most damaging windstorm to strike the Pacific Northwest in 150 years. • An extensive area, stretching from northern California to southern British Columbia experienced hurricane-force winds, massive treefalls, and power outages. • In Oregon and Washington, 46 died and 317 required hospitalization as a result of the storm. • Fifteen billion board feet of timber worth 750 million $ were downed, 53,000 homes were damaged, thousands of utility poles were toppled, part of the roof of Portland’s Multnomah stadium was torn off, and the twin 520 ft steel towers that carried the main power lines of Portland were crumpled. • At the height of the storm approximately one million homes were without power in the two states, and total damage was conservatively estimated at a quarter of a billion (1962) dollars.

  39. Columbus Day 1962: At Cape Blanco there were 150 mph with gusts to 179! Strongest winds on bluffs and windward slopes of coastal orography

  40. Columbus Day 1962 • Over coastal regions and the offshore waters the winds gusted well over 100 mph, with 60-90 mph gusts over the western interiors of Oregon and Washington. • At the Naselle radar site in the coastal mountains of southwest Washington gusts reached 160 mph, and a 131 mph gust was observed at Oregon's Mount Hebo Air Force Station. • Away from the coast, winds gusted to 116 mph at Portland's Morrison Street Bridge, 90 mph in Salem OR, 100 mph at Renton WA, 80 mph at Whidbey Island Naval Air Station, 80 mph at Paine Field, 113 mph in Bellingham, 88 mph in Tacoma, 89 mph at Toledo WA, and 83 mph at West Point in Seattle. • Even in California fierce winds were observed, with sustained winds of 68 mph in Red Bluff, in the Central Valley, and gusts of 120 mph at Mt. Tamalpais, just north of California.

  41. Max Winds (mph) Columbus Day Storm 1962

  42. Began as Typhoon Frieda and then moved northward and transformed into a midlatitude cyclone.