GEOG 140 Exam 2 Review

Where in a hurricane is the lowest atmospheric pressure found, and what does lower pressure indicate?

Found in the eye; lower central pressure creates a steeper pressure gradient, driving stronger winds.

Which millibar reading indicates the strongest hurricane among 997, 986, 993, and 984 mb?

984 mb (lowest pressure corresponds to the strongest winds).

Where and why do Atlantic hurricanes normally form, and in what season and direction do they move?

Form over warm tropical ocean waters (heating the air and driving convection). They occur in summer/fall and generally move west/northwest.

Put these in order of development: tropical storm, hurricane with eye, small tropical disturbance.

1. Small tropical disturbance over the sea

2. Tropical cyclone/storm

3. Hurricane with a central eye.

Does every tropical disturbance become a hurricane? Explain.

No; most lack favorable conditions like warm water, high humidity, or low wind shear.

What single factor can tear apart a developing storm and prevent it from becoming a hurricane?

Vertical wind shear; it tilts the storm's vertical column and disperses its heat engine.

What are three reasons a fully developed hurricane weakens or dies?

Moving over cold water, moving over land (cutting off moisture/heat), and encountering high wind shear.

A 135-mph hurricane spends 4 hours crossing a large island. Will its winds increase, decrease, or stay the same?

Decrease, because friction with land and lack of warm ocean moisture weaken the storm.

How many categories are on the Saffir-Simpson Hurricane Wind Scale?

5 categories (Category 1 through Category 5).

How could forward speed explain why City A has more damage than City B from identical category 3 storms?

A slower-moving storm dumps more rain and batters an area longer, increasing total damage.

What factors sustained Hurricane Sandy in cooler waters in late October?

Interaction with the Gulf Stream, extra-tropical transition (combining thermal energy), and warm anomaly waters.

What caused Hurricane Sandy to make its sharp left turn into the East Coast?

A blocking high-pressure zone (atmospheric ridge) that steered the storm westward into the coast.

Why was Hurricane Sandy's coastal flooding so severe despite being only a Category 1 storm?

It had an exceptionally massive wind field and combined with a full moon high tide.

What made Hurricane Katrina strengthen rapidly in the Gulf of Mexico?

Extremely warm deep waters (Loop Current) and low wind shear.

Why did Hurricane Katrina weaken as it neared the Louisiana coast?

Land interaction, dry air entrainment, and the eye wall replacement cycle.

What are the primary reasons New Orleans' levees are slowly sinking?

Levees prevent natural sediment deposition from the Mississippi River, while underlying soils compact and sea level rises.

Define overland flow and a stream, and state their key difference.

Overland flow is unchanneled sheet water moving down a slope; a stream is water confined to a distinct channel.

Does all rain and snowfall in a watershed end up in streams? Where else can it go?

No; water can also infiltrate into groundwater, evaporate, transpire through plants, or be stored in lakes/depressions.

Which factor is least likely to change how fast overland flow moves: vegetation, slope steepness, stream shape, or precipitation type?

Stream shape, because overland flow occurs before water enters a stream channel.

Two equal-sized basins receive the same rain, but Basin A carries more water. What characteristics could explain this?

Less vegetation, less permeable soil, and higher amounts of paved/impervious surfaces.

Name factors that increase stream discharge and one that decreases it.

Increases: heavy rain, snowmelt, urban paving. Decreases: high evaporation or heavy groundwater infiltration.

Why do road networks and urban areas increase stream discharge?

Impervious surfaces prevent infiltration, accelerating runoff into storm drains and streams.

Define a flood in terms of stream volume and floodplain.

A flood occurs when stream water significantly increases so the channel can no longer hold its volume, spilling onto the floodplain.

What is the fundamental difference between a flash flood and a regular flood?

Flash floods happen rapidly (hours or minutes) due to intense localized rainfall, whereas regular floods develop more slowly over larger basins.

What caused the Great Midwest Flood of 1993?

Saturated soils from a wet previous fall, heavy winter snowpack, and a persistent weather pattern locking a jet stream over the Midwest with continuous spring/summer rain.

Why was the near-continuous rain in summer 1993 so critical regarding percolation and saturation?

The soils reached full saturation, meaning zero further percolation could occur and all extra rain immediately became surface runoff.

What is the primary economic reason people live on floodplains despite the risks?

Fertile agricultural soil, flat land for development, and access to water transportation.

What is the usual temporary measure for patching a levee breach, and why is it practical?

Sandbagging; it uses local, flexible materials that can be rapidly deployed during an emergency.