sp10_7a_106_Storms

sp10_7a_106_Storms - It was a dark and stormy night. . ....

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Unformatted text preview: It was a dark and stormy night. . . According to the G/omog/ of Meteorology, a storm is defined as... any disturbed state of the atmosphere, especially as affecting the earth’s surface, implying inclement and possibly destructive weather. Why are there storms? Storms are nature’s way of trying to even out the unequal heat distribution at the Earth’s surface (too much heat at the equator, not enough at the poles). Storms of all types are constantly carrying heat from the tropics toward the polar regions to help even out the Earth’s temperature differences. So in this sense, storms are good and necessarl things. We can speak of many types of storms, but the most damaging are: - Tropical cyclones (hurricanes, etc.) - Severe thunderstorms and their derivatives: > Hail > Microbursts and macrobursts > Lightning > Tornadoes > Flash floods - Mid—latitude cyclones and their derivatives: >Strong Winds >Heavy rain, flooding >Heavy snow, blizzards - Local (micro— and meso—scale) storms >Sand and dust storms >Topographically amplified winds Some storm statistics 99% of presidentially «I -‘ 5% .9,5Asfi5§§7@§ / {an \ . ‘3 - - 0-2007 , declared d1sasters 1n ="_ 1 the US have been weather—related (sorry earthquake loversl). : y. ‘Fi’ - IMPORTANT NOTE The mum-I may by sm- ruled: a mum 01 and. Non doll: mh-mahuW—n nmmmnmulmmummnhwv . mmiu-m.mmmslpm; Number of Events OANw-bO'IONCD Billion Dollar U.S. Weather Disasters 1980 - 2007 { NOAAINESDlS/NCDC —— Actual damage amounts at the time of the event —— Damage amounts normalized to 2007 using a Gross National Produa (GNP) inflation index Number of events per year that exceed a cost of 1 billion . f"! .! .gi‘llliaaiiii 80818283848586878889909192939495969 Years (1980 - 2007) Billion Dollar Weather Disasters 1980 - 2007 w- mums "II-I.” I 11‘) : {MI-I”? I $3.. 1mm: M 7101‘ musu M 2003 I $2.0 Tropic-I Storm Flood Sover- WOIlMI Blizzard Fwa: Nor-um loo Slam Hm Wave/drought Freeze lIIOIH.7iI 1mm; "u, nun,” Ir- 2007/$1.0 2001101,! 1000 l $1.0 1’4 "ulna MIIIIJV; nurse“ A; x»... mam,- 7 “’1' mzfi , mom.- mswu- 1' mm} . g 0 not us I mznu o v‘ 0 ‘ D my“: \ 1mm.- m""-‘musm.l Dollar amounts mm are lnp'uthlle damages/com In S DIHIORI MSIHJ mama l ‘WIIIJ mun mun IIIS‘I $2.5 20001515.! mm” mn‘l‘ 1992/”! 1mm" 0 . "an" Loahon m u the general ma to! ma regional event Severn numwm (“1mm Mm” mode "lqu hm Additional Newton 10: lholl menu It IVIIlObb I! NCDC \MNW llh m nod: non w/ovnwflublnnnx html The U S hu MAW 7e wule Mal-d damn aw: in- int 2!! yum wnh aver-u aunugeuzosu excel,de :10 bdon to: each mm 66 of the amnion mod dunng or my 1990 You! cost: tor the 78 "gnu were 500 Mm uunq a GNP mfllhon mm NOAA’s National Climatic Data Center Damage Amounts in Billions of Dollars Weather Fatalities 200 180 I 30 Year Average-(19772006) 4 - 1OYearAverage(1997-2006) 160 - 140 1 120 3 100 i 80 3 60 i 170 Lightning Hurricane ‘ Cold l Wind Tornado Heat Winter Storm Let’s focus today on... - Tornadoes - Pacific NW Wind storms and floods Terminology: A tornado is a rapidly rotating column of air that blows around a small area of intense low pressure with a circulation that reaches the ground. A funnel cloud is a tornado Whose circulation has not yet reached the ground. A waterspout is a tornado that touches down on water rather than land. Formation: Tornadoes are by— products of severe thunderstorms, especially when such storms are severe, or form “multi—cell” systems such as squall A very unstable lines, dry lines, or atmosphere, with lots mesoscale convective Ofwind Shear is complexes MCCs). flCCCS sary. Typical characteristics: Diameter 100—600 m (300—2000 ft) Ground movement usually SW to NE, typical ground speed 25—50 mph. Usually only a few minutes, but some have lasted hours. Direction of rotation: can rotate either clockwise or counterclockwise, but in the Northern Hemisphere most (but not all) rotate counterclockwise (“cyclonic”). Wind speeds typically 100—200 mph, but can exceed 300 mph. Intensity and Damage: Tornado intensity is rated on the “Enhanced Fujita Scale”. EF-O. ng/Jt damage “Vlad 65 to 85 mp/y. Cat/1e; 507716 damage to .rz'dz'og aod "(biog/es. EF—7. Moderate damage LVz'od 8 6 to 770 mp/o. Comz'derao/e roof damage. Ldex tan aproot tree: and ooertam Jingle—wide moot/e loomex. Flagpoles [re/1d. EF-2. Comtderao/e damage Lde 777 to 735 mp7}. Mort "tingle-wide moot/e loomex dextroJ/ed. Permanent homey eao daft oflfoaodatz'oo. Flagpole; eo/[apxe Softwood tree; deoar/éed. BF}. Set/ere damage le'od 736 to 765 mph. Hardwood treer delaar/éed. All out xmallportz'om of bower dextroyed. EF4. Deoartatmg damage “Vlad 766 to 200 mph. Complete destraetz'oo of well—omit rerz'demex, [age Jeetz'om of reboot lam/diagt EF—i. I oeredz'la/e damage IVz'od above 200 male. Szgmfieaot :traetara/ deformation of mid— and ego—me oat/dz'ogx. When and where? - More tornadoes occur in spring than any other season, but can occur any time of year. - Tornadoes are most frequent in the late afternoon (4:00—6:00 p.m.). - The Great Plains and Midwest areas of the U.S., known as “Tornado Alley”, is hit by more tornadoes than any other place in the world. 3;; _}/1 16 I FIGURE 10.28 Tornado rncrdence by sTaTe The upper Trgure shows The average annual number aT Tornadoes observed In each srale Trom 1953 2004 The Tower Trgure IS The average annual number or Tar- nadoes per T0000 square mrles In each sTaTe durrng The same perrod The darker The shadrng. The grealer The Treauency 01 Tornadoes (NDAA) Tornadoes in Washington? - Tornadoes are rare, but not unheard of in Washington. - Washington lead the nation in tornado deaths in 1972 (six fatalities). - On September 28, 1962. . Not many tornadoes in Washington, but we Q have Wind storms! Wind storms in Washington fall into three categories: 1. Intense mid—latitude cyclones 2. “Arctic” outbreaks 3. “Gap” Winds Intense mid—latitude cyclones are strong low pressure centers that typically approach Washington from the southwest. Occasional 'ormauon noflh. with a straight shot from Ch- wast, CYCLONES THAT MAKE LANDFALL IN OR NORTH OF WASHINGTON Those paths land to produce damaging wmaa In Washington, wl-neh am much Into North Oman. Typical characteristics of intense mid— latitude cyclones: Very low central pressure (950-970 mb) The center of the low usually passes just over the northwestern tip of Washington Rapid development (called “explosive deepening”) Strongest winds occur along the outer coast Usually don’t produce a lot of rain Maximum winds occur several hours after the main cold front passes (skies are often clearing by the time the winds really kick in) Exhibit sustained winds of 50-70 mph, and gusts up to 100 mph Some examples: I Hood Canal Bridge Storm (Feb. 13, 1979) Friday the 13th Storm (Nov. 13—14, 1981) Inauguration Day Storm 0 an. 20, 1993) Hanukkah Eve Storm (Dec. 14—15, 2006) Great Coastal Gale (Dec. 1—3, 2007) And the granddaddy of them all... The “Columbus Day Storm” I October 12, 1962 l Strongest widespread non-hurricane wind storm to hit North America in the last 100 years I Struck from northern California to British Columbia l 46 fatalities and $235 million in property damage I Wind speeds as high as 150 mph Columbus Day Storm Weather Map Smaller scale wind storms in Washington - “Arctic Outbreaks” > Cold dry winds that occasionally flow out of the mountain valleys of British Columbia in winter. > Result in strong and gusty northeasterly winds in the northern part of western Washington (Bellingham, San Juan Islands), and in some cases all the way south to Seattle / Bellevue area. > Wind speeds of 40—60 mph with higher gusts are common. The strongest Arctic Outbreak ever observed was on December 28, 1990. V x ' I I - “Cascade Gap Winds” > Localized strong winds that funnel from east to west through the passes and gaps in the Cascades and affect the lowland outflow areas west of the gaps. > Most commonly affected areas are Enumclaw, Black Diamond, North Bend, Sultan, Monroe, and the Columbia Gorge outflow east of Portland. > Wind speeds of 40—60 mph with higher gusts are common in small areas, while the rest of the Puget Sound region may be experiencing only light winds. The weather pattern that produces Gap Winds: 651/) or P435 [Ufa/{S Pacific Northwest flooding The principal cause of flooding in the Pacific Northwest is heavy rainfall associated with storm systems originating over the Pacific Ocean. Flood—producing storms draw heat and moisture from tropical areas of the Pacific, and the upper level jet stream carries this moisture to us in a flow that has been dubbed the “Pineapple Express”. Heavy rain occurs when the warm moist air is cooled and lifted as it passes over the Olympic and Cascade mountains. Greatest historical flooding events in the Northwest May 1948 — Greatest spring snowmelt flooding event; lasted 45 days. February 1996 — Major flooding on rivers in Washington, Oregon, Idaho; $800 million damage. November 1990 — Record flooding in Washington; $250 million in damage; old I—90 floating bridge sank. November 2006 — Record rainfall and flooding in Oregon and southwest Washington; major damage in Mt. Rainier National Park. December 2007 — Chehalis River and surrounding rivers flood in southwest Washington; I-S closed for four days; damage estimates in excess of $1 billion. January 2009 — Record flooding on the Snoqualmie and Stillaguamish Rivers; emergency declared in 21 counties; 1—5 and the three major highways across the Cascades had to be closed; $96 million in damages. ...
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This note was uploaded on 01/11/2012 for the course GEO 106 taught by Professor Robviens during the Spring '10 term at Bellevue College.

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sp10_7a_106_Storms - It was a dark and stormy night. . ....

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