hurricanes

Q: What are the main hazards from hurricanes?

A: Storm surges, high winds, heavy rain, inland flooding.

Q: Which cyclones were among the deadliest disasters 1970–2011?

A: Cyclones in Bangladesh (1970, 400,000 fatalities; 1991, 140,000 fatalities) and Myanmar (2008, 140,000 fatalities).

Q: What was the costliest insured disaster 1970–2010 and its cost?

A: Hurricane Katrina (2005, USA) was the costliest insurance disaster at $50.85 billion (2010 US$).

Q: Which notable Atlantic hurricanes affected Canada 1900–2011?

A: Hazel (1954, 81 fatalities), Juan (2003, 8 fatalities).

Q: Which notable Pacific tropical storms/hurricanes affected Canada (often as extratropical remnants)?

A: Freda (1962, 7 fatalities), Ogden (1984, 5 fatalities).

Q: What is the North Atlantic hurricane season and its peak?

A: June 1 to November 30. Peak: mid‑August to late October.

Q: How do the terms hurricane, typhoon, and cyclone relate?

A: Hurricane: tropical cyclone in Atlantic/Pacific with one‑minute sustained winds >119 km/hr. Typhoon: same phenomenon in the Pacific. Cyclone: same phenomenon in the Indian Ocean.

Q: What sea surface temperature and atmospheric conditions are required for hurricane formation?

A: Warm sea surface temperatures (>27°C in upper 60 m). Warm, humid, unstable air. Weak upper‑level winds. Coriolis force from Earth's rotation. Driven by summer heating of tropical oceans.

Q: How does the Coriolis force affect hurricane formation and where is it ineffective?

A: Coriolis deflects moving objects to the right in the Northern Hemisphere and left in the Southern Hemisphere; it is zero at the equator and increases toward the poles. Lack of Coriolis force near the equator (<10° N) prevents hurricane formation there.

Q: What forces produce cyclonic flow in a hurricane?

A: Pressure gradient (inward toward low pressure), Coriolis force (perpendicular to motion), centrifugal force (radially outward), and friction (opposes motion). Net motion spirals into the low‑pressure eye; flow is counter‑clockwise in the Northern Hemisphere.

Q: What are the four stages of hurricane formation and their wind thresholds/identification?

A: Tropical Disturbance: thunderstorms drawn into a low‑pressure zone, weak winds (<36 km/hr), not named/numbered.

Tropical Depression: Winds 37–63 km/hr, cyclonic flow begins, identified by number.

Tropical Storm: Winds 64–119 km/hr, identified by name.

Hurricane: Winds >119 km/hr, strong rotational flow, eye forms, identified by name.

Q: What is the hurricane eye and eyewall, and what safety warning applies during eye passage?

A: Eye: Circular calm region (30–65 km diameter) at the low‑pressure center.

Eyewall: Cylindrical area of upward spiraling winds around the eye with the strongest winds.

Safety: Do not leave shelter during eye passage; winds die down in the eye but intense eyewall winds resume suddenly from the opposite direction.

Q: How and why do hurricanes decline in strength?

A: Hurricanes decline when cut off from warm water energy: by landfall (traveling over land) or moving over colder waters.

Most hurricanes reaching Canada are greatly weakened, though they can unexpectedly gain strength interacting with other mid‑latitude weather systems.

Q: Where do North Atlantic hurricanes typically form and what general steering patterns affect their paths?

A: Usually start at 10–20° N. Trade winds push them west at low latitudes; Coriolis force pushes them north (to the right of motion); westerly winds push them east at 30–60° N.

Paths are often influenced by the size and shape of the Bermuda High (a high‑pressure zone over the central Atlantic).

Q: What causes storm surges?

A: Rise in sea level due to: Strong onshore winds pushing on ocean surface. Low atmospheric pressure beneath the eye creating a mound of seawater.

Q: When are storm surges most damaging?

A: Most damaging if coinciding with high tide.

Q: How large can storm surges be for major hurricanes and what is the record mentioned?

A: Major hurricanes: commonly > 5.5 m (record: 13 m in Australia, 1899).

Q: What are storm surges a major cause of in North America and in low-lying countries?

A: Major cause of property damage in North America. Major cause of death in low-lying countries (e.g., Bangladesh).

Q: What facts about Bangladesh increase its storm-surge hazard?

A: Deltas are low-lying (30 cm above sea level), 35% of country < 6 m above sea level.

Seven of the nine deadliest 20th-century weather events were cyclone storm surges; increasing future hazard due to population growth and sea-level rise.

Q: Where do maximum storm surges occur in the Northern Hemisphere relative to the eye path and why?

A: In the Northern Hemisphere, maximum storm surges occur 15–30 km to the right of the eye path due to strongest winds.

Q: How strong can hurricane winds be and what hazards do they cause?

A: Often 200+ km/hr over large areas (record: 345 km/hr). Hazards: Damage/destroy buildings (roofs blown off), flying debris, uprooted trees, dangerous ocean waves/surf/rip currents, extensive power outages.

Q: How is wind speed affected by the hurricane’s motion along its track?

A: Speed of hurricane motion along its track is added/subtracted from internal wind speed. Example: 160 km/hr internal wind, moving NW at 30 km/hr → NE side: 160 + 30 = 190 km/hr; SW side: 160 − 30 = 130 km/hr.

Q: How much rain and inland flooding can hurricanes produce?

A: Often 10s of cm (record: 150 cm). Huge warm, moist air mass holds enormous water; rising air condenses, producing heavy rains for prolonged periods (days to weeks), causing flooding and associated hazards.

Q: What is identified as the greatest hazard of hurricanes and what do most evacuation orders address?

A: Greatest Hazard: Water (storm surges, rain), not wind. Most evacuation orders are for flooding.

Q: What does the Saffir‑Simpson Hurricane Scale measure and what are category effects?

A: Saffir‑Simpson Hurricane Scale (Categories 1–5) measures strength and damage.

Category 1 (Minimal Damage): Winds damage trees, unanchored mobile homes.

Category 2 (Moderate Damage): Some trees blown down, major damage to mobile homes and some roofs.

Category 3 (Extensive Damage): Large trees blown down, foliage stripped, mobile homes destroyed, structural damage to small buildings/homes.

Category 4 (Extreme Damage): All signs blown down, heavy damage to windows/doors/roofs, coastal buildings suffer major damage, flooding kilometers inland.

Category 5 (Catastrophic Damage): Severe damage to windows/doors/roofs, small buildings overturned/blown away, major damage to all buildings < 500 m from shoreline and < 5 m above sea level.

Q: Give an example of a Category 5 hurricane and its impacts?

A: Hurricane Camille (1969, Florida): Category 5, winds > 320 km/hr, storm surge 7.3 m, killed 256.

Q: How are hurricane names selected and retired?

A: 1953–1979: Only female names. Since 1979: WMO uses preselected lists of alternating female and male names, recycled every 6 years. Names of extreme hurricanes are retired and replaced (e.g., Katrina replaced by Katia, Juan replaced by Joaquin).

Q: What safety actions should be taken before a hurricane?

A: Before: Stay informed on forecasts/warnings (radio/TV/online). Evacuate from exposed coastal/flood-prone areas to higher ground. Park vehicles safely (not under trees). Take cover in a well-built home: close/shutter/board windows, remove/secure outdoor items (lawn furniture, tools, bicycles). Stock food/water, have flashlights, battery-powered radio, extra batteries.

Q: What should you do during a hurricane?

A: During: Stay informed (battery-operated radio most reliable). Stay in basement or secure inner room without windows. Stay inside during eye passage (winds may cease, but eyewall winds resume suddenly). Use phone only for emergencies.

Q: What steps are recommended after a hurricane?

A: After: Inspect house/property for damage. Report downed power lines and stay away. Clean up debris. Take photos of damage for insurance. If evacuated, return only when authorized.

Q: What land-use and building-code mitigation measures reduce hurricane impacts?

A: Hurricane Mitigation: Land Use Planning: Avoid population centers in low‑lying coastal lands; designate hazard-prone areas for farms, parks, golf courses. Building Codes: Stronger codes for mobile homes. Eliminate/strengthen eaves, strap roofs to walls, ban thin asphalt roofing (easily torn off, become projectiles).
Q: What was the context and overall impact of Hurricane Katrina (2005)?

Q: Why was New Orleans especially hard hit by Katrina?

A: Much of city below sea level and below levels of Lake Pontchartrain and Mississippi River. Protected by levees (raised embankments).

Q: What was Katrina’s timeline and key events?

A: Aug 25: Achieved hurricane status before Florida landfall (14 killed), weakened over land, gained strength over warm Gulf waters.

Aug 26: Models predicted 17% chance of direct hit on New Orleans with 8.5 m storm surge (levees max 7 m).

Aug 28: Reached Category 5 over Gulf (unusually warm waters, 28–32°C). New Orleans mandatory evacuation began.

Aug 29: Landfall in Gulfport (55 km E of New Orleans) as Category 3 (195 km/hr winds). Storm surge and winds devastated Mississippi (238 killed) and Alabama coasts. New Orleans experienced Category 1–2 winds. Storm surge of 8 m breached levees in 53 places, flooding ~80% of New Orleans (1500 killed).

Q: What rainfall accompanied Katrina and how far did its effects reach?

A: Extremely heavy rains on landfall (up to 42 cm in Florida, 38 cm in Louisiana, 25 cm in Mississippi). Heavy rains as far north as Canada (up to 10 cm in Ontario, causing flooding in Ontario and Quebec).

Q: What were Hurricane Juan’s classification, impact, and significance (2003)?

A: Impact: Category 2 hurricane with sustained winds of 160 km/hr at landfall near Halifax.

Extensive wind damage to Nova Scotia and PEI. 8 killed, $300 M damage.

2 m storm surge (Halifax record).

Worst storm to hit Halifax in >100 years.

Q: What specific wind and forest impacts did Hurricane Juan cause?

A: 31% of homes in Halifax damaged.

Millions of trees damaged/downed (e.g., 70% of 60,000 trees in Mt Pleasant Park). Trees/branches blocked streets, knocked down power lines (300,000 without power, some for 2 weeks).
Extensive damage/grounding of small boats, damaged wharves.

Q: What administrative action followed Hurricane Juan’s impacts?

A: Name Retirement: Juan was retired in April 2004 due to its effects in Canada (first time Meteorological Service of Canada requested retirement).

Q: What was Typhoon Freda / Hurricane Freda (1962) and its overall impacts in Canada and the US?

A: Context: Extra-tropical remains of Typhoon Freda. Most powerful storm to strike Pacific Northwest in 20th century. Impact: Killed 7 in Canada, 46 in US. BC Damage: ~$500 M. Total Damage: ~$7 B (including lost timber). Known as "Hurricane Freda" in Canada (not a true hurricane) and "Columbus Day Storm" in US.

Q: What was Freda’s track and evolution before striking the Pacific Northwest?

A: Sept 28: Tropical depression in Philippine Sea. Oct 4: Grew to Cat 1 typhoon (Freda) near Wake Island, heading NE. Oct 8–10: Declined to tropical storm, then tropical depression. Oct 11: Merged with another depression between Hawaii and California, rapidly grew into a huge extra-tropical cyclone (lacked warm core of true hurricane). Oct 12: Struck California, turned NE up coast with high winds, rain, flooding. Oct 12/13: Hit Vancouver Island.

Q: What wind, wave, and local impacts occurred when Freda hit the Pacific Northwest and BC?

A: Oct 12: Struck California with record rain (11.5 cm in Oakland). Max sustained wind 180 km/hr, gusts 220 km/hr. Oct 12/13: Hit Vancouver Island. Victoria: sustained winds 90 km/hr, gusts 145 km/hr. Trees/power lines downed, boats broke moorings, store windows shattered, ferries cancelled. Vancouver: Church steeples downed, Stanley Park lost 1/3 of its trees (3,000). Peak Gusts: 270 km/hr in northern Oregon, 260 km/hr in southern Washington, 140 km/hr in BC