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EAS 212: The Oceans > 17. Hurricanes > Flashcards

17. Hurricanes Flashcards

1
Q

Storms=

A

disturbances with strong winds and precipitation

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2
Q

Air Masses=

A

large volumes of air with distinct properties

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3
Q

Land air masses are ___(dry/ moist) and marine air masses are ___

A

land= dry
marine= moist

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4
Q

Front=

A

a boundary between air masses

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5
Q

Warm front=

A

contact where warm air mass moves to colder area

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6
Q

Cold front=

A

contact where cold air mass moves to warmer area

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7
Q

Where do storms typically develop?

A

at fronts

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8
Q

Jet stream=

  • where is it?
A

narrow, fast-moving, easterly air flow
- may cause unusual weather by steering air masses

  • at middle lats just below the top of troposphere
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9
Q

Hurricane=

How are they classified?

A

A large rotating mass of low pressure, bringing strong winds and torrential rain. Defined by having sustained winds of 120km/hr or more

classified by max sustained wind speed

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10
Q

Hurricanes require 3 things:

A
  • ocean water warmer than 26C
  • warm, moist air
  • The Coriolis Effect
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11
Q

Hurricane winds need water vapor. What provides the energy?

A

latent heat of condensation

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12
Q

Explain the difference between a hurricane, typhoon, and cyclone

A

Hurricane= extreme tropical storm over Atlantic & Eastern Pacific Oceans
Typhoon= over western pacific ocean
Cyclone= over Indian ocean & Australasia

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13
Q

Why are hurricanes inhibited near the equator?

A

Because they need the impact of the Coriolis effect, which is not at the equator

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14
Q

Hurricanes depend on the availability of ___ water as an energy source

A

warm

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15
Q

T/F
Tropical cyclones are rare in the south atlantic

A

true

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16
Q

There are __ categories of hurricanes. What do larger numbers indicate?

A

5

larger numbers= lower central pressure, greater winds, and stronger storm surges

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17
Q

What is the typical central pressure of a hurricane system?

A

950hPa

As low as 870hPa

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18
Q

T/F
The energy release by a single hurricane can exceed the annual electricity consumption of the US and Canada

A

true

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19
Q

What’s the approx diameter of a hurricane?
How does this compare to the size of a mid-latitude cyclone?

A

100-400+km

1/3 of the size of a mid lat cyclone

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20
Q

Hurricanes occur where a ____(deep/shallow) layer of warm eater exists and during times of ____(highest/ lowest) SSTs

A

deep
highest

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21
Q

What’s the hurricane season in NH vs SH?

A

NH: august and sept

SH: Jan-March

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22
Q

Tropical disturbance=

A

clusters of small thunderstorms

Can lead to a hurricane

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23
Q

Tropical depression=

A

when at least 1 closed isobar is present

Can lead to a hurricane

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24
Q

Tropical storm=

A

further intensification of a tropical depression: winds speeds must reach 60km/hr

At this point, the system is named. Becomes classified as a hurricane once wind speeds of 120km/hr are reached

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25
Q

Most tropical disturbances develop from ______ waves .

Some also form from ____-related convection or in association with mid-latitude ____

A

easterly

ITZC
troughs (migrating toward lower lats)

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26
Q

Easterly waves=

A

undulations in the trade wind pattern

  • spawn hurricanes in the Atlantic
27
Q

~__% of tropical disturbances intensify into more organized rotating storms

A

10%

28
Q

Between which latitudes do hurricanes typically form? Why?

A

Between 5 and 20 degrees

Optimal formation coniditions here
- Between 0 and 5 degrees, can’t form because no coriolis
- higher than 20 degrees= the water is not warm enough

29
Q

Hurricane formation requires an atmosphere which cools fast enough w/ height so that it’s potentially unstable to:

Where is this available

A

moist convection

Available in the western tropical oceans but not in the eastern parts of the ocean

30
Q

Hurricane formation requires relatively moist air near which part of the atmosphere? Why?

A

Mid-level of the troposphere (4900m)

For latent heat release

31
Q

What kind of vertical wind shear b/w the sfc and upper troposphere is required for hurricane formation?

A

Low values (less than 37km/hr) of vertical wind shear

32
Q

vertical wind shear=

A

the change in wind speed with height

33
Q

Fully developed hurricanes move ____

A

poleward

34
Q

tropical disturbances and depressions are largely regulated by:

Which direction do they therefore move?

A

trade wind flow

simply move westward

35
Q

T/F

Upper level winds and ocean temperatures are more important for tropical disturbances/ depressions than for tropical storms/ hurricanes

A

false

for tropical storms/ hurricanes, upper-level winds and ocean temp gain importance (not just trade wind flow)

36
Q

The low pressure center of a hurricane is called:

A

the eye of the hurricane

37
Q

Hurricane diameter is typically less than ___km

Up to:

A

200km

800km

38
Q

In a hurricane, does the horizontal pressure gradient increase or decrease with altitude?

A

decreases (slowly)

39
Q

At what hPa are pressures within the hurricane approx = to pressure outside the storm

A

400hPa

40
Q

Where in a hurricane is there cyclonic circulation?
Anticyclonic?

A

From the surface up to 400hPa= cyclonic

From the 400hPa level to the tropopause= anticyclonic

41
Q

The upper portions of a hurricane storm are blanketed by what? Why?

A

a cirrus cloud cap due to overall low temps

42
Q

Describe the eye of a hurricane:
- what is the air/ weather doing?
- Diameter of the eye?
- What is indicated by a shrinking eye?
- How fast does the eye move?

A
  • an area of descending air, relatively clear sky & light winds
  • 25km ish
  • shrinking eye= storm intensifying
  • 20km/hr
43
Q

Hurricane Eye wall=

A

The area just outside the eye, where the air ascends from the sfc to the tropopause
- the winds are strongest here
- Largest clouds & highest precipitation (100 inches/day!)

44
Q

T/F
The sinking air in a hurricane eye warms adiabatically, making the eye much warmer than the rest of the hurricane

A

true

45
Q

How quickly does air in the hurricane eye sink?

A

Most of it descends very slowly, taking days to traverse the eye’s depth

46
Q

Where in a hurricane is the pressure gradient strongest?

A

near the eye wall, where the most violent winds are produced

47
Q

Where do the strongest storm surges occur in relation to the hurricane?

A

to the right of the hurricane

48
Q

There are 4 main causes of hurricane dissipation:

A
  • Passing over land or cold water: this removed warm water source, which is the basic fuel driving the storm
  • The storm meets vertical wind shear
  • Dry, cool air is pulled into the storm system: this reduces the deep convection that keeps the storm going
  • Low pressure develops above the storm in the higher part of the atmosphere
49
Q

Describe what happens when there’s an area of high pressure above a hurricane vs an area of low pressure

A

High: helps move out the buildup of air above the storm, so the storm can keep drawing in new air at the surface (keeps the storm alive)

Low: causes inward flow above the storm. The rising air within the storm then has no escape –> storm collapses in on itself!

50
Q

T/F

Even as a hurricane weakens, it can still bring huge amount of rainfall 100s of km inland

A

true

51
Q

storm surge=

A

abnormal increase in shoreline sea level generated by a storm

  • greatest threat to life & property from a hurricane
52
Q

Give 4 main ways hurricanes are destructive

A

high winds
intense rainfall
storm surges
tornadoes

53
Q

Where are winds and surge typically most intense? Why?

A

In the right front quadrant of the storm
- b/c this is where wind speeds combine with the speed of the storm’s movement to create the area of highest potential impact

54
Q

There are 2 processes that can cause storm surges:

A
  1. hurricane winds drag surface waters forward and pileup the waters near coasts
  2. lower atmospheric pressure raises sea level (1mb decrease= 1cm increase of sea level)
55
Q

Storm surges raise coastal sea level by __-__m typically, but can be as much as __m

A

1-2
7

56
Q

most hurricanes contain clusters of tornados.
- where do they occur?
- How do they form?

A

The right front quarter of the hurricane’s movement

The slowing of the wind by friction at landfall= tornado formation

57
Q

The Fujita intensity scale for tornados goes from ___ to____

A

F0 (light)

F6 (inconceivable damage)

58
Q

Give up to 5 historical tropical storms/ hurricanes that were very destructive

A

Andrew, 1992
Mitch, 1998
Katrina, 2005
Irene, 2011
Sandy, 2012

59
Q

A hurricane watch is issued if:

A

an approaching hurricane is predicted to reach land in more than 24hrs

60
Q

A hurricane warning is issued if:

A

an approaching hurricane is predicted to reach land in less than 24hrs

61
Q

Hurricane ____ is the largest Atlantic hurricane on record. What category?

What did it cause? Why did it cause so much damage?

A

Sandy, cat 1

  • severe coastal erosion, extreme flooding
  • 233 deaths & $68 billion in damages
  • a storm surge coincided with peak high tides in heavily populated New York & New Jersey
62
Q

Which hurricane was the costliest & deadliest US hurricane?
Where did it flood?

A

Katrina, Cat 3
New Orleans

63
Q
A

EAS 212: The Oceans (18 decks)

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