Storms 5 Flashcards
What is the hurricane eye wall
A circle of thunderstorms around the eye
For a hurricane to fuel itself, it needs to
- Remove heat from the ocean
- Create strong winds that form high waves
To form and strengthen, where must hurricanes be?
- NOT at the equator
- Over the ocean so that sea spray from breaking waves can add humidity to air
Why do hurricanes not form at the equator?
because Coriolis force is zero
Hurricanes don’t hit BC because
sea surface is too cold
(below 26˚C)
Warm core is important for hurricanes because
it causes high pressure at top of storm, which drives an outward spiralling wind at storm top
What is a storm surge
a local rise of sea level as hurricane winds push ocean water to pile up against coastlines
Where is storm surge the greatest
-> right side of the storm track in Northern Hemisphere cuz anti-clockwise rotation
-> left side for Southern Hemisphere cuz clockwise rotation
Other names for hurricane
Typhoon
Tropical cyclone
Compare the size of a hurricane to thunderstorms
Hurricane has much larger diameter (150-300km)
than thunderstorms (15km)
height is the same for both (15km)
Which way do hurricanes turn in the Northern Hemisphere?
Counterclockwise
Which way do hurricanes turn in the Southern Hemisphere?
Clockwise
Hurricanes are made of __1__ that make up the __2__ and __3__
- thunderstorms
- eye wall
- spiral bands that extends out from eye wall
What is the eye of a hurricane?
The center
- relatively clear and calm
- low pressure at sea level
Where is precipitation the heaviest in a hurricane?
At the eye wall
Saffir Simpson Hurricane Scale measures what?
Wind speed - faster means stronger hurricane
Eye pressure - lower as hurricane gets stronger
Storm surge - increases ^^
A category 5 hurricane has ___ eye pressure than a category 1 hurricane
lower
Can hurricanes cross the equator?
No never!
How long can hurricanes (& their tstorms) last? Why?
up to weeks, they’re organized to create their own fuel
- because they manipulate the envo to continually create new fuel of warm/humid air from heat stored in ocean
Supercell thunderstorms can last a long time due to ____.
Favourable wind shear
(normally 15-30 mins, but supercell can last for hours)
- blows fresh fuel into storm
- blows Tstorm to new regions with fuel
What is boundary-layer air?
air in the bottom 1km of atmosphere
How do hurricanes create fuel?
- low pressure in the EYE sucks in boundary-layer air
- air moves faster as it gets closer to the eye
- faster winds create larger ocean waves
- Evaporation from ocean surface + wave spray
- When air reaches base of eye wall, it is warm + near 100% humidity + lots of sensible and latent heat fuel
How does evaporation from the ocean surface help fuel hurricanes?
evaporation and spray from waves adds moisture to boundary-layer air
To form, hurricanes need a sea surface temperature of ___ and warm surface waters that are ___
> 26˚C
> 60m deep
True or false: adding heat to the ocean can fuel a hurricane
false; need to remove heat from the ocean
True or false: strong winds that form high waves help fuel hurricanes
true
Why should the depth of warm surface water be > 60m ?
to avoid reaching a temperature below 26˚C, because hurricanes cause sea surface temperature to cool
(due to wave-induced turbulence)
Hurricane season is ___ because ____
- late summer and early fall
- waters are warmest
Official North Atlantic hurricane season is ____ but most hurricanes occur ____
June - Nov
Aug - Oct !
Where do hurricanes form and not form?
Form in the tropics (near equator has warm SST), but
NOT at the equator (zero Coriolis effect)
Coriolis is ___, its effect is strongest near ____
earth’s rotation, strongest near the poles
Favored hurricane formation latitudes
10˚ and -30˚
To persist, the pressure in the hurricane eye must remain ___
low
(to create wind, waves, suck in humid air, etc)
What can kill a hurricane?
- moving over colder water
- landing
- cold fronts interfere
Westerlies are winds that are near ___ and head ___
poles
east
Trade winds are near ___ and head ___
equator
west
Hurricanes are steered by ___ in the atmosphere
the general circulation of trade winds and westerlies and Bermuda High
Hurricanes strike US at ___
gulf coasts and SE Atlantic states
Why can hurricanes last for weeks despite all air molecules continually being blown into the core?
Heavy condensation and rain from storms in eye wall causes core to become warm relative to surroundings
hurricane core consists of
eye + eye wall
At the top of the hurricane, the air is flowing ___
outflow away from core
At the bottom of the hurricane, the air is flowing ___
inflow towards the core
Hurricanes have a ___ circulation
vertical
Strong updrafts are in the
eye wall of thunderstorms
What was the deadliest hurricane that strikes Florida?
Hurricane Ian, a category 4 that strikes in Sept 2022
What is the direction of the inflow and outflow of a hurricane in the Northern Hemisphere?
Inflow at low levels: counter-clockwise
outflow at high levels: clockwise
What hurricane-caused events cause the most deaths?
coastal flooding due to
-> storm surge (most)
-> rain
What was the deadliest US hurricane
Hurricane Harvey 2017
Why is floodwater so dangerous?
carries disease
- insects breed
- mold
- destroy things, ptsd
advanced warning period of hurricanes compared to tornadoes
hurricanes: several days
tornadoes: couple hours or minutes
True or false: hurricane predictions are accurate
false
hurricane predictions are inaccurate, so forecast is usually probabilities
Canadian hurricane centre
Halifax, Nova Scotia
provides information and warnings on hurricanes in canada
Example of a recent hurricane that occurred in Canada
Hurricane Fiona, Sept 2022
True or false: hurricanes are rare in canada
true
4-5 per decade
if canada gets hurricanes, are they mostly formed here or elsewhere?
formed elsewhere
- mostly hits Nfld and nova scotia
