Hurricane Document Notes Flashcards
What are very strong tropical systems referred to as in North America?
Hurricanes
What are very strong tropical systems referred to as in China Sea?
Baguio
What are very strong tropical systems referred to as in Eastern Asia?
Typhoons
What are very strong tropical systems referred to as in India and Australia?
Cyclones
What are the conditions necessary for the development of tropical storms?
SST at least 27 degrees Celcius or 80 degrees Fahrenheight
The Coriolis force is outside of 3 to 5 degrees latitude
Very little vertical shear
The temperature is relatively constant over large surface areas
Relatively high mid-tropospheric moisture
A strong disturbance
What do disturbances that lead to tropical cyclone development include?
Decaying extra-tropical systems (MCC’s and fronts), waves in the ITCZ, and easterly waves
The African waves account for what percent of major hurricanes in the Atlantic and the Eastern Pacific?
85%
Atlantic hurricanes which originate directly off the coast of Africa are known as what?
Cape Verde storms
What happens when thunderstorms release large amounts of latent heat?
The latent heat warms the mid and upper troposphere. As a result of this heating, the air begins to diverge consequently by lowering the surface pressure
Surface convergence is enhanced by what?
Friction
Because of warm waters, the adiabatic cooling as the air crosses the isobars is balanced by what?
Conductive heating
What would happen if there were vertical shear associated with a hurricane?
The heat in the core of the hurricane would be transported away from the center, not allowing further strengthening
How does friction balance a tropical systems strength?
By limiting its intensity but maintaining its fuel supply (latent heat)
What can a body have?
Kinetic and potential energy
The internal energy of a body is a result of what?
The potential and kinetic energy of the molecules
The internal energy of the air parcel increases as a result of what?
Latent heat transferring heat to the gas
The potential energy of a parcel is increased by what?
The lifting of the air
What happens when air radiates to space near the top of the troposphere?
It becomes cooler, losing internal energy and subsides, causing a loss in potential energy
The process of a Hadley cell, likewise a Hurricane, likens a Carnot engine because why?
It loses energy at a cooler temperature than it gains back
In a Hadley Cell and Hurricane, what is the source of energy?
Sensible and latent heat from the sea/ocean
What does the First Law of Thermodynamics state?
A measure of heat transferred into a system will result in an increase in temperature and in the system’s ability to do work
What does the Second Law of Thermodynamics state?
Only in transferring heat from a warmer body to a colder body that heat can be converted into work in a cyclical process
What is the ITCZ defined as?
The result of the equatorial Hadley Cell where air converges near the equator, rises and diverges near the tropopause thereby transporting heat away from the equatorial regions in the upper troposphere
Observations have noted that the rate of precipitation greatly exceeds the rate of evaporation from the ocean in the vicinity of what?
The ITCZ
What is the ITCZ?
A distinct number of cloud clusters separated by large areas of clear air
The ITCZ is rarely over what?
The equator
Cloud clusters in the ITCZ propagate westward with weak wave disturbances over a period of how many days?
4 to 5 days
What does mass continuity dictate?
That regions of convergence at low levels must give way to divergence at higher levels
What is important regarding the Level of Non-Divergence (LND)?
The level where the mass divergence is zero
Where is the Level of Non-Divergence located in the tropics?
Near the 400 millibar level
Large scale convergence will occur in what way?
Cyclonically
Large scale divergence will occur in what way?
Anticyclonically
As storms develop in the tropics, there is considerable entrainment of what?
Relatively dry mid-tropospheric air into the incipient storms
Only a large cluster of cumulonimbus clouds can protect the inner core from what?
Evaporational cooling and the resulting negative buoyancy
Large disturbances off of Northern Africa generate what?
Sufficient thunderstorm activity
In April, African wave disturbances begin to occur in association with what?
Intense surface heating over the Sahara Desert
What is the average wavelength of African wave disturbances in April?
About 2500 kilometers with a period of 3 to 4 days
How many waves occur on average over North Africa each year?
About 60
What is currently unknown regarding easterly waves?
How they change from year to year in both intensity and location and how these might relate to the activity in the Atlantic and East Pacific
The convectively-induced waves generated off of Africa are responsible for what?
Much of the tropical storm activity in the Pacific as they continue west past the North American continent
What does CISK stand for?
Conditional Instability of the Second Kind
There are many phenomena in the atmosphere where what happens?
The large scale flow help develop smaller scale convection and in turn, the convection helps drive the larger scale circulations
The cooperative interaction between the cumulus convection and a larger-scale perturbation leads to what?
Unstable growth of the system
Out of the many tropical depressions that develop each year, only what percent intensify?
10%
Under favorable moisture supply, the CISK mechanism leads to what?
The rapid development of a hurricane
Friction usually dissipates what?
Energy
Despite the kinetic energy loss due to frictional convergence in the boundary layer, it is the friction that leads to what?
Increased moisture convergence
Extra-tropical cyclones develop from what?
Baroclinic instability where a small disturbance amplifies as temperature advection changes the pressure field
What is important to note what regarding small disturbances in the tropics?
They rarely strengthen at all. As a result, a large reservoir of potential energy of tropics lays untapped much of the year
The maritime tropical atmosphere is a balance of what?
Turbulent fluxes of sensible and latent heat from the sea surface, cooling of the atmosphere by infrared radiation to space, transport of heat/moisture/momentum by cumulus clouds, and horizontal and vertical transport by large-scale atmospheric motions
The tropics can be divided into how many regions?
Four regions
What is the first region of the tropics?
Cumulus towers pump latent heat high into the cold upper troposphere
What is the second region of the tropics?
Dry air subsides from Region 1 which establishes the trade inversion
What is the third region of the tropics?
Towering cumulus clouds in the lowest 1 to 3 kilometers meet the capping inversion
What is the fourth region of the tropics?
The air in the subcloud layer has relative humidities between 75 and 80%
The CISK-like driving mechanism is not responsible for what?
The tropical atmosphere’s motions
What is the large circulation driven by?
The large temperature differences between Regions 2 and 3 and Region 1 set up by the SST gradient
The latent heat associated with the large cumulus convection has more to do with what?
Maintaining the convective motions than maintaining the entire Hadley Circulation
What is the original idea of cloud clusters or organized convection?
Originally thought to tap into the reserve of potential energy and so it is mistakenly assumed that this is the cause of hurricanes
The actual energy source for hurricanes lies in the difference between what?
The water and the subcloud layer
In a hurricane, the steady-state is the production of what?
Mechanical energy used to balance the frictional dissipation
Tropical cyclones do not what?
Develop spontaneously in the tropical atmosphere
Whatever the mechanmisms resulting in tropical cyclone formation, the Carnot heat engine is a good way to understand what?
How the system maintains itself and strengthens
Work is done to balance what in a tropical system?
Frictional dissipation by the acquisition of heat at a high temperature and a deposit of heat at a low temperature
What is important about the eye of a hurricane?
It is the calm in the middle of the storm where skies are relatively clear and winds subside to near calm in its center
Temperatures are often what in the eye of a hurricane?
Several degrees warmer than the surrounding eyewall, especially at higher levels of the storm
Soundings taken within the eyewall exhibit what?
A layer of warm and moist conditions from the surface to around 1 to 3 kilometers and beneath the inversion
When does the eye of a hurricane typically form?
As the intensity of the storm increases
The winds converging and rotating around the center of the hurricane can what?
No longer be forced toward the center due to the law of the conversation of angular momentum where speeds would quickly rise to supersonic speeds
The eyewall which surrounds the eye contains what?
The most turbulent conditions and the most intense thunderstorms
Convection in tropical cyclones are organized in what way?
Into long, narrow rainbands that converge towards the center of the storm, known as spiral bands
What leads to clearing within the eye of a hurricane?
Subsidence on both sides of the spiral rainbands
What two things lead to the development of the eye of a hurricane?
Subsidence and the centrifuging effect
Some tropical cyclones intensify and develop two or more what?
Concentric eyewalls surrounding the circulation center of the storm
As the inner eyewall forms, what does the convection do?
Organize into distinct rings
With additional subsidence from the outer eyewall, what does the inner eyewall do?
Weakens as the outer eyewall becomes the dominant feature
What happens when the inner eyewall dissipates?
Pressures rise slightly and are only partially compensated by the more rapid pressure falls associated with the intensification of the outer eyewall
A hurricane’s eye can range in size from what to what?
From 5 miles to over 120 miles across
Most hurricane eyes are what size?
20 to 40 miles in diameter
What is known as the most deadly and destructive part of a hurricane?
The storm surge
For every 1 millibar drop of atmospheric pressure, the sea level rises what?
1 centimeter
What can be a serious problem if a hurricane hits at high tide?
Coastal flooding
What is the Dvorak technique?
A methodology to get estimates of tropical cyclone intensity from satellite pictures
How does the Dvorak technique work?
The scheme utilizes the difference between the temperature of the warm eye and the surrounding cold cloud tops. The larger the difference, the more intense the tropical cyclone is estimated to be
Maximum wind speeds based upon the Dvorak technique alone are what?
Prone to some error due to local condition variability
Since a hurricane is in gradient wind balance, the radius also contributes to what?
The speed of the hurricane’s winds
What is a sub-tropical cyclone?
A low-pressure system existing in the tropical or subtropical latitudes that has characteristics of both tropical cyclones and mid-latitude cyclones
Most sub-tropical cyclones exist in what?
A weak to moderate horizontal temperature gradient region
What do most sub-tropical cyclones receive much of their energy from?
Convective clouds
What do most sub-tropical cyclones transform into?
Tropical cyclones
There is no evidence to suggest what?
Tropical cyclones will have any major changes in where they form or occur
The peak intensity of tropical cyclones may increase by what percent in wind speeds?
5 to 10%
Little is known about what?
How the average intensity or size of tropical cyclones may change due to global warming
How do sub-tropical cyclones compare in size to other tropical-related systems?
Sub-tropical cyclones are quite small compared to the observed large natural variability of hurricanes, typhoons, and tropical cyclones
More study is needed to better understand what?
The complex interaction between tropical storms and systems and the tropical atmosphere/ocean
ENSO swings between what stages?
La Nina, Neutral, and El Nino
