MAR110 LECTURE #18 Hurricane Dynamics

MAR 110: Lecture 18 Outline – Hurricane Dynamics
MAR110 LECTURE #18
Hurricane Dynamics
Hurricane and Typhoon Distribution
The locations of historical hurricanes/typhoons (red dots) and the tropical
regions where they are formed and found most frequently. (ItO)
Geostrophic Flow – A REVIEW
With geostrophic flow (red), the pressure gradient force (blue) and Coriolis
force (aqua) are perpendicular to the flow and in balance.
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MAR 110: Lecture 18 Outline – Hurricane Dynamics
Geostrophic Ocean Flow
With geostrophic Gulf Stream (red), the sea surface slope induces the
pressure gradient force (blue) which balances the Coriolis force (aqua) .
Geostrophic Atmospheric Winds
With geostrophic Jet Stream (red), the temperature contrasts induce the
pressure gradient force (blue) which balances the Coriolis force (aqua) .
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MAR 110: Lecture 18 Outline – Hurricane Dynamics
Cloud Structure of a Typical Hurricane and Earth Rotation
(a) Warm (pink), wet air spirals inwards over the warm ocean towards the eye of the hurricane, where
it begins spirals upward around the outside of the eye - called the “eyewall”.
(b) Because the rising air cools, it becomes increasingly more humid (that is the air becomes
saturated with water vapor - a gas).
(c) At 100% humidity the water vapor condenses to form water droplets (liquid) that make up the
clouds and rain.
(c) At the top of the troposphere the very cool (blue), dry air spirals outward and begins to descend
toward the sea surface.
(d)This cool, dry air descends in the eye and the various spiral bands, warming and becoming even
less humid (i.e. dryer) as it encounters the higher pressures at lower levels.
(e) Upon reaching the sea surface this very warm and dry air able to absorb both heat and moisture
from the ocean – re-energizing it so that it can feed the heat engine (i.e., power) of the hurricane.
(??)
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MAR 110: Lecture 18 Outline – Hurricane Dynamics
Temperature Structure of a Typical Hurricane
Warm moist air heated by the ocean rises through the center of the hurricane through
convection and spreads out once it reaches a certain elevation where it cools and the
moisture in the air condenses and becomes rain. (??, NH)
Hurricane Wind Dynamics
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MAR 110: Lecture 18 Outline – Hurricane Dynamics
Hurricane Trajectories
Hurricane Wind Structure
In the northern hemisphere the highest winds are on the right hand side
of the leading edge of the hurricane (here the upper right quadrant).
The speed of the hurricane itself is added to the speed of the wind
around the storm when they are both going in the same direction while
it is subtracted when going in opposite directions as on the left side of
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MAR 110: Lecture 18 Outline – Hurricane Dynamics
Saffir-Simpson Scale
Ocassionally a extratropical coastal storm will interact with a tropical storm and morph into
a powerful hybrid –such as the so-called “Perfect Storm” that stayed relatively stationary
off the northeast coast for several days in and around Halloween October 1991.
(NH)
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MAR 110: Lecture 18 Outline – Hurricane Dynamics
Hurricane Measurements
The “Hurricane Hunter” trajectories are indicated in the
schematics of the spiral-banded hurricanes.
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MAR 110: Lecture 18 Outline – Hurricane Dynamics
Hurricane Rita (2005) Evolution
(ABOVE) A time series composite of wind speed and air pressure
measurements are compared to an inverted version of the trajectory .
Note the color-coded Saffir Simpson scale categories.
Hurricane Rita (2005) Wind Structure
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MAR 110: Lecture 18 Outline – Hurricane Dynamics
Hurricane Rita (2005) Rain
Hurricane Sizes
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MAR 110: Lecture 18 Outline – Hurricane Dynamics
Hurricane Damage
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