ATM 10 Severe and Unusual Weather Prof. Richard Grotjahn L 18/19 http://canvas.ucdavis.edu Lecture 18 topics: • Hurricanes – what is a hurricane – what conditions favor their formation? – what is the internal hurricane structure? – where do they occur? – why are they important? – when are those conditions met? – what are they called? – What are their life stages? – What does the ranking mean? – What causes the damage? Time lapse of the – (Reading) Some notorious 2005 Hurricane Season – How to stay safe? Note the water temperature • Video clips (colors) change behind hurricanes (black tracks) (Hurricane-2005_summer_clouds-SST.mpg) Reading: Notorious Storms • Atlantic hurricanes are referred to by name. – Why? • Notorious storms have their name ‘retired’

© AFP Notorious storms: progress and setbacks • August-September 1900 Galveston, : 8,000 dead, the deadliest in U.S. history. • September 1906 Hong Kong: 10,000 dead. • September 1928 South Florida: 1,836 dead. • September 1959 Central : 4,466 dead. • August 1969 Hurricane Camille, Southeast U.S.: 256 dead. • November 1970 Bangladesh: 300,000 dead. • April 1991 Bangladesh: 70,000 dead. • August 1992 Hurricane Andrew, Florida and Louisiana: 24 dead, $25 billion in damage. • October/November 1998 Hurricane Mitch, Honduras: ~20,000 dead. • August 2005 Hurricane Katrina, FL, AL, MS, LA: >1800 dead, >$133 billion in damage • May 2008 Nargis, Burma (Myanmar): >146,000 dead.

Some Notorious (Atlantic) Storms Tracks

• Camille • Gilbert • Mitch • Andrew • Not shown: – 2004 season (Charley, Frances, Ivan, Jeanne) – Katrina (Wilma & Rita) (2005) – Sandy (2012), Harvey (2017), Florence & Michael (2018) Hurricane Camille • 14-19 August 1969 • Category 5 at – for 24 hours – peak winds 165 kts (190mph @ landfall) – winds >155kts for 18 hrs – min SLP 905 mb (26.73”) – 143 perished along gulf coast, – another 113 in Virginia

Hurricane Andrew • 23-26 August 1992 • Category 5 at landfall • first Category 5 to hit US since Camille • affected S. Florida & Louisiana – 1.4 M families without electricity – 107,800 homes damaged – 49,000 homes destroyed – 250,000 people homeless – $30 B economic loss

Hurricane Mitch • 23Oct – 6 Nov 1998 • Category 5 – for 33 hours – peak winds 155 kts for 15 hrs – min SLP 905 mb – wave hts ~44’ at some spots – up to 75” of rain fell! • devastated Central America – 11,000+ deaths (that many more missing) – worst loss of life (W. Hemis.) since 1780 – 2.4 million people affected – 124,068 homes damaged or destroyed • Honduras – 20% of population homeless – 70-80% of transport infrastructure destroyed – 1/3 of capitol (Tegucigalpa) buildings destroyed – 70% of crops destroyed ($900M) Cyclone Nargis • 2-3 May 2008 • Category 4 – peak winds 115 kts – min SLP 962 mb – up to 50” of rain fell! • Devastated Burma (Myanmar) – >146,000+ deaths (estimate) – >2M people homeless – >10B (U.S.$) damage – Irrawaddy delta very low elevation with a large population

Typhoon Haiyan • 3-11 November 2013 • ‘Super ’ Cat 5: 170+ knots 195 mph, (gusts est. to 235 mph) • Largest since Typhoon Tip (1979) • Possibly strongest ever at time of landfall (3 were stronger at sea) • >5,500 fatalities 2005 Atlantic season • 3 major hurricanes hit US • Largest number (26) of named storms in prior 156 years! (since detailed records kept) • Wilma set new Atlantic SLP record (882 mb) • Katrina (well forecast) was the most destructive natural event in US history (>$133B)

Willma at max intensity. gif loop with Katrina images Hurricane Sandy • 24-30 October 2012 • Category 2 at landfall, hurricane force winds across 1,150 mile diameter. • at high tide, flooded parts of NJ shore and southern parts of NYC. • Heavy precipitation (snow in WV) as tropical air interacted with cold arctic air. At landfall: hurricane status was changed to frontal system. • 159 fatalities (72 direct, 87 indirect) • ~$65B in losses

Hurricane Harvey • 17 August – 2 September 2017 • First major hurricane to hit US in12 years • Category 4 at landfall – ‘tied’ for costliest with Katrina – Why? stalled near Houston for ~3 days – Dumping >40” of rain over a wide area – peak winds 130 mph – min SLP 937 mb (27.67”) – 106 perished in the US Hurricane Irma

• 30 August – 13 September 2017 • Category 4 at US landfall – peak winds 175 mph. – Category 5 for 60+ hours – min SLP 914 mb (26.99”) at landfall – 92 perished in the US – >$53 B in damages

• 2017 had 18 named storms (10 hurricanes, 6 category 3 or higher) in Maria (Puerto Rico)

• 16 Sept. – 2 Oct. 2017 • Category 5 • peak winds 175 mph (130 @ US landfall) • min SLP 908 mb • Devastated Puerto Rico • 2 weeks after Irma • >2,975+ Deaths (Puerto Rico Governor estimate) • 450,000-1.2 million without power ~ 4 months later • >91B (U.S.$) damage • Also hit several other islands Hurricane Michael

• 7 – 12 October 2018 • Category 4 at landfall – peak winds 155 mph strongest winds at landfall since Andrew (1992) – min SLP 919 mb (27.14”) at landfall – 17 perished in the US – >$15B in damages – Photo shows a house on the beach built to withstand 200 mph winds and with breakaway walls on the ground floor. Atlantic Hurricanes affecting the US

• Summarizing just a few is illustrative, many others have been devastating. • How to summarize? – By cost? – By storm intensity at landfall? Andrew (1992) vs Irma (2017) Video of the day: Hurricane Safety - 1 Katrina damage (Gulfport, MS)

• Nova-Gilbert – Camille: Surge 1:38 – Camille: Survivor 3:06

Hurricane Safety - 2 • “Earlier we [had] evacuated for Hurricane Dennis and that was ‘nothing’. So about 30 of us decided to stay at the [apartment] complex and ride this one out… As it was getting dark we could see water coming under the front door. There was several inches in the room. Then a wave broke through the window and we decided we had to get out of there…As we swam away we could see the apartments pancake into the water… Insulation, wood, furniture, wires were everywhere…We grabbed what we could to stay afloat”

AnotherKatrina Camille survivor, (1969) survivor? 2005 Reading: Hurricane Safety - 3 • FYI: Flyer prepared by NOAA: (no, you don’t have to memorize all this for the final) Test your understanding: Hurricane Safety - 4 • A mandatory evacuation is given for a hurricane approaching your area, you should: 1. quickly check that you have food & water to survive at home 2. board up windows and stay home to guard your stuff 3. put towels around the outside door jambs to keep out the water 4. all of the above 5. none of the above • Why was Katrina so bad?

• The measure of its power was deceptive. – The strongest winds and (corresponding) central sea level pressure determine category, on that basis Katrina was category 4 at landfall (Mississippi mouth; cat 3, 127mph at Ms coast) – But, Katrina covered unusually large area, (earlier slide) – And, the large kept the winds down (recall the conservation of angular momentum argument). – So, peak winds (apparently) not as catastrophic as Andrew or Camille, but storm surge was larger than Camille in height, and it covered a wider area (longer length of shoreline). – Thus, Katrina’s total power was much larger than recent hurricanes. • Another key reason: There was a breakdown of emergency response – some examples: – Lessons & procedures from planning exercises were not followed: – Lessons from actual experiences were not heeded

Camille & Katrina Storm Surge compared

6m

B&W line: Camille surge 3m (U.S. Army Corps of Engineers) Color squares: Katrina surge (preliminary estimates,Tim Marshall) U.S. Army Corps of Engineers

Are hurricanes getting worse? • Hard to know: atmosphere has inherent variability (Atlantic only shown) • Climate models predict…increase in top wind speeds (~10% over the next 25 years) Same or fewer number of storms. • No notable increase in total number of storms over the whole globe, but an observed increase in numbers of category 4 & 5 storms. • Accumulated cyclone energy (ACE) used to measure net energy in tropical cyclones • ACE varies in basins, but no obvious trend What is it like? • MORE VIDEOS OF THE DAY • Wind – Hurricane Charley gas station (Hurricane_Charley_Gas_Station_Strea m.mnv) • Storm Surge – Typhoon Yuri (Typhoon_Yuri_Storm_Surge_Stream.w mv) • Both during Katrina storm either – Gulfport (Hurricane_Katrina_Stream.wmv – Biloxi (biloxi-civic-center- katrina2.wmv) • Flooding (next lecture)

Lecture 18 Summary: • Hurricanes – Part 2 – Development stages: tropical disturbance, tropical depression, tropical storm, then hurricane (alt: typhoon, or tropical cyclone) – Hurricanes typically ~500 km wide, sustained winds must be >64 kts – Hurricane intensity ranked by Saffir-Simpson scale: • Category 1 is weaker, 5 is strongest – Air spiraling in towards the eye wall gains speed by conserving angular momentum (radius * wind speed = a constant) – Highest winds where motion of storm adds to wind blowing around eye. – Damage from: 1) high winds, 2) flooding from heavy rain, 3) storm surge – Storm surge is high sea level at coast • water driven onshore by 1) high winds, 2) extremely low SLP, 3) coastline shape and magnified by 4) high wave heights and 5) timing of tides • usually most destructive element of hurricane undermines, & batters structures – Hurricane Safety – heed the warnings! Seek appropriate shelter, etc. – Hurricane trends • Number of most severe hurricanes has been increasing globally in last 30 years, though total number of hurricanes of all types has not changed. (apparently) • In the future? Some models predict generally stronger storms. Unclear if there will be more or fewer of them. Increasing wind shear may suppress storms in the Caribbean. Lecture 19 topics: • Hurricane flooding – (Reading) Lessons from Hurricane Katrina • From New Orleans • For us, here… • Non-Hurricane flooding Taiwan, after 80 inches of rain From Typhoon Morakot – Frontal cyclone (“” on W. coast) – Persistent convective weather patterns • Pakistan 2010 • US Midwest 1993, CO/NM 2013

– Flash flooding (severe Interstate 5, SW Washington, or MCC) Nov. 2007 Reading: Lessons from Hurricane Katrina

• Summary map (courtesy of CNN) Reading: ‘Everyone knew it would happen’ • N.O. sits in a bowl, much of it below sea level • N.O. has twin threats: – hurricane storm surge – catastrophic flooding by Mississippi River.

Source: Times Picayune, 2002 Reading: ‘Everyone knew it would happen’ • On smaller scale, it has happened before. • For years, researchers, engineers, weather forecasters, and emergency preparedness officials warned that N.O. was in precarious position. • In 2002, the main N.O. newspaper ran series of prophetic articles projecting what might happen to N.O. in a devastating hurricane, reasons for concern, costs of protecting against the disaster. It predicted what Katrina wrought. See: http://www.nola.com/hurricane/?/washingaway/ • In the summer 2004, a fictional ‘hurricane Pam’ scenario tested readiness of local & state agencies (Readiness was lacking) • October 2004, National Geographic article (The Big Uneasy) foretold the Katrina story.

• Which is better? Levee upgrades (~$14B) plus annual maintenance (~$200M / year) versus >$130B cost of Katrina (and no new protection New Orleans after Betsy, 1965 and not to mention lives & property lost) Were people caught ‘off guard’ by poor forecast guidance? (No!) • On FRIDAY 26 August: – NHC 60-hour forecast, valid at 8 AM Mon. 29 Aug: 30.5N, 89.5W 115 kts – Actual MS landfall: 10 AM Mon. 29 Aug. 30.2N, 89.6W 110 kts – Track error (E-W): 10 km – Intensity error: 5 kts • Forecasts 60 hours before were essentially perfect in location and strength. Public forecast 60hrs (2.5 days!) before landfall Reading: Why was Katrina an American tragedy? • Poor preparation & inadequate response made it worse. • Breakdowns of emergency response – a few examples: – Lessons, planning, & procedures were not followed: • New Orleans had detailed plan to evacuate 300,000 (source: CNN) using busses that were left in an area that flooded, rendering them useless. Time • White house staff saw LA Governor’s request for specific supplies on the 12 Sept. 2005 Governor’s website, but needed an ‘original letter’ before responding delaying supplies for 4 days (source: CNN) It is unclear if White House saw Governor’s request for assistance 2 days before landfall. No response until 5 days after landfall. • When FEMA was placed under HSD, FEMA’s budget for levee upgrades and maintenance was slashed 90% (source: TIME) • FEMA staff may have used Accuweather instead of NHC guidance! • FEMA top administrators out of sync with field personnel – Lessons from actual experiences were not heeded • Hurricane Ivan threatened N.O. in 2004, many evacuated, BUT, it was noticed that many poor were not. (Many poor did not have their own transport.) • People who evacuated to the Superdome during hurricane Georges (1998) were assaulted and robbed. Same thing after Katrina (2005) • MAJOR bridges that failed in Camille (1969) and again in Ivan (2004) were rebuilt to the same standard – and failed again.

Reading: What’s FEMA?

• Federal Agency • Created by Pres. Carter 1979. • Charged with providing federal assistance during emergencies, including natural • Few disasters occurred in the early 1980’s so subsequent directors became political appointments. • Ironically, FEMA’s response to hurricane Andrew (August, 1992) was heavily criticized and that helped Pres. Bush (Sr.) loose Florida, and loose re-election that fall. • FEMA is a large agency that was removed from the Cabinet level and placed underneath the umbrella of the Homeland Security Department (HSD) after the attacks of 11 Sept. 2001. • FEMA’s response to hurricane Katrina was heavily criticized. Its then director, Mr. Michael D. Brown was sacked a month after. Reading: 2005 FEMA head, Michael Brown . • Mr. Brown’s primary qualification to head FEMA? His friendship with Mr. Allbaugh, President Bush (Jr.) 2000 campaign manager. (source CNN, 3 Nov. 2005) • The day Katrina struck, Mr. Brown: – dismissed reports that there was flooding – ignored requests of staff of where to send supplies – focused on how he looked on TV & finding a dog sitter • On 27 September 2005, Michael Brown testified that he only made two mistakes: 1. He didn’t hold enough press conferences 2. He couldn’t get the LA Governor and NO major to ‘sit down and get over their differences’ – In short, more press conferences would have facilitated aid delivery. Would press conferences have evacuated thousands of people? The politicians have to meet? – weren’t they busy coordinating relief/rescue? • He rejected any notion that he was incompetent. • This was scandalous: 10’s of thousands of people were trapped, nearly a thousand lost their lives in the after Katrina was well past. Hundreds were rescued from attics and rooftops. 1 House Select Bipartisan Committee to Investigate the Preparation for and Response to Hurricane Katrina, Testimony of Michael D. Brown, Hurricane Katrina: The Role of the Federal Emergency Management Agency, 109th Cong. (Sept. 27, 2005). What lessons can we learn?

1. Emergency services should not be headed by a political appointee, or at least not one with no relevant management experience.

2. Emergency personnel in the field are dedicated and hard working.

3. Assistance will come but it may take time. Take a hint from the URL of the emergency preparedness website: www.72hours.org (Plan to be on your own for at least the first 3 days) This is my motivation for your term project. 4. If an area is unsafe, don’t build there, don’t buy a home built there. Was that learned? Reading: N.O. & Biloxi 5+years later • >$114B federal aid distributed Lakeview New Orleans – All the construction meant no recession there. • New Orleans. – Population 60% of ‘pre-K’ level (273,000 in 2008 versus 452,000 before) – 23% of LA assistance paid (2007) – In absence of political will, people make decisions to live & rebuild in harms way. – Most feel that this their best option, though it has danger and much hardship. • Biloxi: – Population ~90% of ‘pre-K’ amount – Casinos had record $$ income July 07 • 2007 Poll: – 55% of Americans think New Orleans will never fully recover. – 52% of Americans think federal gov’t did not do enough

Permits to rebuild (2007): 45% of East New Orleans 29% of Lower 9th ward

Lower Ninth ward (July 2015) many abandoned lots, many are rebuilding homes raised on pilings. On the relevance of Katrina

• New Orleans was the 2nd most vulnerable large metropolitan area in the country to flooding. • The most vulnerable is the 26th largest metro area in the US (~2 million pop.) It is located at the confluence of 2 major rivers. In 1986 and 1997 it was nearly flooded catastrophically by high waters that were well below the 1 in 100 year flood protection thought to be in place (assuming the levies are maintained). • The name of this city? …. •Sacramento. (view of homes below water level behind a levy, Greenhaven neighborhood) Photo: Sacramento Bee, 2005 • Confluence of 2 major rivers draining large watersheds including high elevations (large volumes of water possible) • Sacramento river flows range from low of 15,000 cfs (typical in autumn) to 500,000 cfs during high rainfall Reading: events of 1986 and 1997. • Flows can increase 10x in as few as 3 days Sacramento • Much of city is below level of levees and rivers at flood stage: main commercial area and state capitol. (Other river cities sit on high ground) Geography • Folsom dam in 2006 was #1 safety priority of Bur. Reclamation (overtopping would erode dam’s base catastrophically. Fixes raised it, added big side spillway) • Unlike New Orleans, higher ground is much closer, <10 miles to escape any danger zone.

Source: Sacramento Bee articles, Fall 2005 • Much new development is in flood-prone areas protected by minimal levees • How can that be? Sacramento – Agencies (e.g. Corps of Engineers) tasked with maintaining the levees do not decide Development whether development is allowed! – Agencies responsible if a levee fails (the state and federal government) do not decide whether development is allowed! – Cities & counties approve permits! (and no liability … until 2008 legislation)

Source: Sacramento Bee articles, Fall 2005 • In 1986, one more inch of Sacramento precipitation in American River basin would have caused Folsom dam to be overtopped. Protection • Flows in several recent events have exceeded the dam’s engineered capacity. • The level of protection by the dam has been downgraded over the years.

Source: Sacramento Bee articles, Fall 2005 Reading: Sacramento Protection • Sacramento levees offer less protection than many other river cities (~100 year vs ~500 year in St. Louis, ~250 year in New Orleans & Omaha) • & high water in 1997 uncovered deep seepage that *may* cause internal levee and unforeseen failures. (The section of levee pictured at right failed in 1997; that was “once in 63 year” flood. ) • Water flows in excess of the 100 year flood level might not be withstood. • As of 2005, several major hospitals are in flood prone areas (emergency generators in basements) • Much new development is occurring in flood-prone areas protected by minimal levees

Source: Sacramento Bee articles, Fall 2005 What is a 100 year flood? • Means high water as might occur, on average, once in a hundred years. • It could happen this winter, it could happen many years from now, a larger event could happen first. • The likelihood of a catastrophic flood somewhere in the central valley during the next 14 years is about 1 in 3. (Prof. Mount) • Considered a minimal standard. • Numerous levee sites did not meet even that standard in 2005 • 2018: worst spots have been fixed.

Source: Sacramento Bee articles, Fall 2005 Reading: Sacramento Flood maps • Flooding would not be localized, but spread for miles • Flooding would reach rooftop depths over large areas • 300,000 people, 140,000 structures at serious flood risk • Worst case: multiple levee breaches.

Source: Sacramento Bee articles, Fall 2005 Reading: Sacramento Flood maps • Flooding would not be localized, but spread for miles • Flooding would reach rooftop depths over large areas • 300,000 people, 140,000 structures at serious flood risk • Flooding can be worst far from the breach. • Levees become dams

Source: Sacramento Bee articles, Fall 2005 Reading: Sacramento Flood maps • What happens depends on where the breach occurs.

Source: Sacramento Bee articles, Fall 2005 Reading: Update on Sacramento Levees

• Problems identified in 2005-6 have 2015 begun to be addressed. • 29 March 2015 status

2010 Reading: Update on Folsom Dam

• Goal is 200yr flood safety. • Dam road closed to public • Upgrades to the spillways • Construction of $962M auxiliary spillway in 2010- 2017. • Raising of dam height 3.5 ft.

Sources: Sacramento Bee, 27April2012 USBR.gov/mp/jfp Reading: Sacramento area evacuation • Warning of potential breaches would be 6-24 hours in advance of an event. • People would have as little as 12 minutes or up to several hours to evacuate after an actual breach. • Roads with more than a foot of water are considered impassable by most vehicles. (Even with higher clearance, you can’t see the road)

• ~51,000 people live in Sacramento households without a Photo, car, they would need busing. M.J. Leddy • 7-13 % of those facing evacuation won’t have access to 1997 transportation. • >120,000 people evacuated Yuba & Sutter counties in 1997 event • The evacuation route to take depends on where breach is

Source: Sacramento Bee articles, Fall 2005

What should you do?

• Assess your risk at locations: where you work, live, and elsewhere as applicable (e.g. other family members locations) • Consider purchasing flood insurance • Choose to avoid areas of potentially deep flooding. • Have sufficient emergency provisions • Have an emergency contact • Have an evacuation plan

Source: Sacramento Bee articles, Fall 2005 Non-hurricane Flooding Weather & Safety

• Working down in scale: • Frontal cyclone flooding (potentially catastrophic) in • Persistent large convective patterns (The great flood of 1993, 2009 & 2010, Pakistan 2010) • Isolated thunderstorm flash floods (the Big Thompson disaster) (Non-Hurricane) US Floods are costly • (‘Severe weather’ includes tornadoes, , lightning, downbursts.) Frontal Cyclone Flooding • This is the main concern for the Central Valley • On west coast: “” ‘atmos. River’ – moisture drawn from subtropics & tropics: area of for W. coast – warm, moderate to heavy rainfall – floods amplified if melts snowpack, falls on saturated soils, and/or pattern persists • California examples: – Jan.-Mar. 1995: $3B in losses & 27 fatalities – Feb. 1986: levee break floods Linda CA – April 1982: Big Sur highway 1 slide, road closed for 2 years 1997 Western U.S. Flooding • New years eve storm • Highest peak flow measured on American river (3-day ave) • Historical pattern irregular, recent peak events somewhat larger than the past (when flood control structures were designed & built) Hypothetical: California ‘ARkStorm’ • Analogy to 1861-2 winter • Combined: preconditioning of 1969 + followed by the stalled atmospheric river of 1986. • Widespread flooding: an inland sea. Reading: 3 Dec.2007 Severe Frontal Cyclone

• AFFECTED: NORTHWEST U.S. • I-5 closed at Chehalis. • All-time record flooding: Chelhalis River, Centralia, Wash. Monday's measurement: 74.8 feet Previous record: 74.3 feet Flood stage: 65 feet • Skokomish River, near Potlach, Wash. Monday's measurement: 18.1 feet Previous record: 17.8 Flood stage: 16 feet • Wind gusts during storm: Bay City, Ore.: 129 mph Lincoln City, Ore.: 125 mph Cape Disappointment, Wash.: 104 mph Rockaway Beach, Ore.: 104 mph • All-time 24-hour precipitation records, from Monday (3 Dec.): Plain, Wash. 3.00 inches (previous record: 2.10 inches, 1943) Winthrop, Wash. 1.65 inches (previous record: 1.11 inches, 1915) • Daily rainfall records from Monday (3 Dec.): Seattle-Tacoma Airport: 3.46 inches (previous record: 1.85 inches, 1968) Olympia: 2.80 inches (previous record 2.77 inches, 1982) • Notable rainfall totals (from Sat. a.m - Mon. p.m, 1-3 Dec.): Lees Camp, Ore.: 13.3 inches Bremerton, Wash.: 12.06 inches South Fork, Ore.: 11.06 inches • Notable snowfall totals (from Sat. a.m. - Mon. p.m. , 1-3 Dec.): June Lake, Wash.: 27 inches Island Park, Idaho: 22.5 inches Swift Lake, Wash.: 20 inches • Source: National Weather Service & USA Today Convection: The Great Flood of 1993 • Once in 500 yr event • Unusual in these respects: – persistent daily summer , – wide spread: 400k mi2 covering 9 states – 17,000 mi2 under water – >1,000 levees topped or failed – long duration, nearly 200 days some places – precipitation 200-350% of normal saturated soils – $15B damage – 50 fatalities – ¼ M people in Des Moines without tap water 19days – 26.5M sandbags used

• 2008 had a once in 200 yr event over similar region Northern Pakistan: 1 August 2009 Reading: Convection: And 31 July 2010 Great Pakistan Flood 2010 • Worst event in living memory (BBC; in past 80 years) – Oddly persistent strong monsoon rains 27-30 July. – Possibly related to / over Russia – Totals at several stations >15 inches in N and NW mtns. • Unusual in these respects: – Covered 17M ac (1/5 of country) – 2+ months to reach the sea. – 1,750 fatalities (21 October) – >1.2M livestock died – 20 M people affected – ~10M people sought relief. – >43B US$ damage

Local Flash Floods • Thunderstorm (typically) – Intense rain on hard surfaces or saturated ground – Much dangerous debris picked up • Miscellaneous lessons: – DON’T try to outrun the flood, – DO climb to safety – re-development restricted – burned, lightly vegetated areas shed water magnifying flood : Big Thompson, CO • Once in 200 yr event, 31 July 1976 • Stationary severe thunderstorm – up to 10” rain – 137CFS  31,200 CFS in 3 hrs – 10:30 pm highest water – 144 lives lost, $36M damage

CO & NM floods: 9-15 Sept. 2013

• 1000 year event (source: climate central) – Note: just 37 years after a 1 in 200 year event, though 2013 event covered much larger region. (Big Thompson flow at least a foot higher than in 1976) – Several extreme storms spread over several days • Repeated severe thunderstorms – Trough stalled over Great Basin, moist upslope – up to 17” rain, in 1 week one of drier years became the wettest on record – 8 lives lost, – >$40M damage – 27 highways closed in CO

Flash Flood Safety • If you are driving in a canyon and see a flash flood approaching, you should 1. stay in the car and try outrunning the flash flood 2. stay in the car but pull over and park on the shoulder of the road 3. leave your car and go under the nearest tree (to hold onto if needed) 4. leave your car and lie flat in a ditch 5. leave your car and climb up the side of the canyon • Reading: World’s Worst Flash Flood? • Vargas,Venezuela • Stationary heavy rain – 14-16 December 1999 – 1000 year event (USGS) – 90-480mm (3.5”-19”) rain – Along 300km of coast – 2M m3 debris flows among largest in history (USGS) – numerous – ~30,000 lives lost, – $1.8-3.5B damage

Videos of the day • Antelope canyon flash flood • UT flash flood ‘fun’ • CO rescue scenes

Lecture Summary: • Hurricanes – Part 3 – What can we learn from hurricane Katrina? • Plenty of blame to go around, management of the crisis was poor at high levels, thwarting efforts of dedicated staff ‘in the field’. • take control of your fate: (1) have a plan to survive for at least 72 hours, (2) stockpile emergency supplies, and (3) heed warnings. • (Non-hurricane) Flooding – frontal cyclone flooding (“pineapple express/ atmos. river” on W. Coast) • moist air from subtropics & tropics (near Hawaii) unleashes heavy precipitation on a region of the W. Coast visible as thick cloud band • major California floods have been from this cause • when warm rain falls on snowpack, melting magnifies flooding, ditto for a persistent pattern, and for rain on saturated soils. • Sacramento is a city presently at great risk. – persistent weather patterns • midwest floods summer 1993 one of worst floods in US history • once in 500 year event overwhelmed some flood controls, • Notable floods in: 2008 (250 year event, IA), 2011(Missouri, lower Miss. rivers), 2013 (1000 year event, CO & NM) – flash flooding from isolated thunderstorm or MCC • saturated or lightly vegetated ground (including burned) shed water quickly • if in canyon, climb to safety, don’t try to outrun the water

Thanks for taking ATM 10 ! • I hope you’ve enjoyed the course! – 19 lectures – 21 demonstrations – >60 videos

• Final exam: Thursday 13 Dec. 10:30am – 12:30pm – Review in discussion this week. Topics based on two feedbacks – Format similar to midterm (2/3 of final on stuff since midterm)

• If you like this subject consider the Atmospheric Science major – Small classes – interact a lot with faculty and fellow students – Students in major about half male, half female – Our BS degree meets all NWS & AMS standards – Good job prospects when you graduate – Contact me or staff advisors in 1152 PES or email [email protected] for more information.