Topic 10 - Storms and Severe Weather

Geostrophic winds

blow parallel to the isobars, more or less horizontal. These are the high altitude winds. Not affected by friction.

Cyclone

also called a Midlatitude cyclone - Convergent flow - wind flows in toward the center of a low pressure system and rises up. Bad weather because air rises and clouds form and condense

Anticyclone

Divergent flow - wind blows outward away from the center of a high pressure system. Good weather because air does not rise, so no clouds form and no ppt.

what are sky rivers aka atmospheric river or AR?

Primary cause of flooding in the West Coast States, called water vapor superhighways

what is a well known example of a sky river?

"Pineapple Express," a strong atmospheric river that is capable of bringing moisture from the tropics near Hawaii over to the U.S. West Coast.

what are midlatitude cyclones?

the storms that form across the U.S. and are moved along with the westerlies. They are steered by the jet stream. Thunderstorms that affect us here in the Midwest

within the midlatitude cyclones, what is the end result ?

end result: cumulonimbus clouds, heavy rain, thunder, lightning, tornado, strong winds, hail

where do thunderstorms form?

In air masses that are warm, lots of water vapor, along a cold front, or in the mountains

What are downbursts?  Why are they dangerous?

These are very violent downdrafts – larger, more water/rain, They can cause windshear so no planes here!!

What is lightning?

Lightning is caused by electrical discharges – 10’s of millions to 100’s of millions of volts, heat the air to temperatures of 15,000 to 30,000 degrees C. Energy builds up inside a cloud and between clouds or the ground and a cloud.

what is sheet lightning?

is reflected by clouds

what is heat lightning?

is sheet lightning near the horizon

what is spider lightning?

crawls across the sky for up to 150 km

what are blue jets and red sprites?

originate in clouds and rise rapidly toward the stratosphere as cones or bursts.

what is the Lightning Imaging Sensor?

satellite that monitors lightning and other weather-related occurrences

what is thunder?

the sound of the air expanding

how do tornadoes form?

Wind is blowing horizontally - starts with a rotating column of air, the wind closest to the ground creates friction between itself and the ground - This air slows down, The wind higher aloft - does not experience this friction and so continues to flow at a faster speed, The air mass begins to roll along like a rolling pin, When this horizontally rolling air mass encounters updrafts that are created by the storms at the front, the axis of rotation shifts to vertical, Now a vertically spinning mass of air is formed - complete with updrafts and thermal energy release, This forms a wall cloud and a mesocyclone, Funnel-shaped clouds that come out of the rotating wall cloud may or may not reach Earth’s surface. These are tornadoes if they do touch down.

what is the diameter of a tornado?

The diameter can range from a few meters to a few hundred meters

how long can a tornado last?

Can last from a few seconds to tens of minutes

what is the home office of tornado occurrence?

Midwest of North America - The topography of north America is perfect for tornado formation – its flat and large, great open space for wind to blow across and the air masses flowing north and south add to the formation

what are the peak months for tornadoes?

May and June, due to the northward migration of the jet stream  

since when has the severity of tornadoes been increasing ?

since the 1950’s, global warming is one reason

what is the doppler radar?

shows the size of the storm and the direction it is moving

what does a hook shape on the end of the doppler radar tell us?

tells us that a tornado is forming, or has formed

what is a debris ball?

shows the exact position of the tornado on the ground

what is the scale for tornadoes?

Enhanced Fujita Scale : EF- 0 (gale) up to an EF - 5 (incredible)

who invented the Enhanced Fujita Scale?

Ted Fujita - University of Chicago

What are tropical cyclones ?

Form entirely within the Tropical Latitudes – between 23.5 N and S (the tropics of Cancer and Capricorn)

what are other names for tropical cyclones and hurricanes?

Hurricane – northern Atlantic and east pacific, Typhoon – West Pacific (coast of Japan), Cyclone – Indian Ocean, Australia

what are the conditions for the formation of a tropical cyclone?

homogeneous air masses - same temp and type of front (there can’t be any cooler air that would cause the storm to lose its strength or slow it down), warm air and warm water – the water is the fuel for the hurricane (the warmer the better for hurricane development)

what is the diameter of a hurricane?

storm diameter can range from 100 miles to about 600 miles, can fill the entire troposphere

what are rain bands?

circle the eye and are heavier on the backside of the hurricane, the most intense rain is around the eyewall

what is the central part of a hurricane?

is the eye. It is calm here, no wind, no rain  

what quadrant of a hurricane can produce tornadoes?

The right front quadrant

what is the hurricane wind scale?

Saffir Simpson Hurricane wind scale, it is based on wind speed. Ranges from category 1 to a category 5

What does the path of a hurricane look like?

They get stronger as they cross the ocean – the larger the ocean, often, the bigger the storm

what does the landfall of a hurricane look like?

As a hurricane makes landfall (meaning it hits the land), the strength of the storm decreases

Why does the storm decrease once it hits land?

No more water to fuel the storm, and friction with the land causes it to slow down

what is storm surge?

flooding due to the high winds pushing the ocean  water inland. Can be very destructive.

what can a tropical cyclone turn into?

hurricane