Thunderstorms
What are the conditions needed for a thunderstorm’s cumulus stage?
Source of moisture , lifting of the air mass , and unstable atmosphere
What are the characteristics of a severe storm?
• Continuous supply of surface moisture
• Upper-Level low pressure system causing unstable air
• Large temperature differences between air masses
Describe the major wind systems that guide a tropical cyclone as it moves from the tropics to the mid-latitudes.
Initially, move northwestward due to trade winds
Then, controlled by prevailing westerlies
How would relatively light rain potentially cause flooding?
If it rains for a long enough time the ground may become saturated, leading to excessive runoff and flooding.
It measures the wind chill factor, by estimating the heat loss from human skin caused by a combination of wind and cold air
How does a thunderstorm form along a front?
Results when cold air forces warm air to rapidly rise (If the warm air is significantly warmer and has a large amount of moisture, then the storm will be larger)
What are the two characteristics of thunderstorms that lead to hail formation?
1. Strong updrafts and downdrafts circulate the hailstone.
2. Liquid water in freezing parts of the cloud allows for adding layers to the hailstone.
What two conditions must exist for a tropical cyclone to form?
Warm ocean temperatures as a source of energy and disturbance in the atmosphere to provide unstable air (aka low pressure)
Why is the air in a winter high-pressure system is very cold despite compressional warming?
Snow on the ground reflects sunlight so heat is not absorbed.
Low angle of sun means less concentrated light.
Clear skies means that there is not insulating blanket to retain heat.
The eyewall is a band immediately surrounding the eye that contains the strongest winds in a hurricane
What is the difference between a sea-breeze thunderstorm and a mountain thunderstorm?
• Both are air mass thunderstorms; the storm occurs inside one air mass
• Mountain thunderstorm occurs as a result of orographic lifting
• Sea breeze thunderstorm occurs due to difference between land and ocean heating
Strong updrafts and downdrafts keep the hailstone suspended, moving it up and down between freezing and liquid zone and layers of ice.
Moves over land or cold water
In both cases, it loses its source of energy, warm ocean water
Compare the data of the heat-index scale and the wind-chill index. What variables influence each scale?
Heat-Index – Temperature and Relative Humidity
Windchill – Temperature and Wind Speed
What causes a thunderstorm to dissipate?
Convection cells exist as long as there is warm, moist air at Earth’s surface. Once down drafts begin, the updrafts slow and eventually stop, because of surface cooling.
1. Wind shear causes a “rolling pin” of wind over the surface.
2. Passing over a warm place leads to an updraft that turns the “rolling pin” from horizontal to vertical
3. The “rolling pin” stretches out and wind speeds increase to form a tornado
Imagine that you live on the eastern coast of the United States and are advised that the center of a hurricane is moving inland 70km north of your location. Would a storm surge be a major problem in your area? Why or why not?
No, low pressure hurricanes rotate CCW in the Northern hemisphere
So, storm surge would hit north of the eye
A storm stalls over Virginia, dropping 0.75 cm of rain per hour. If the storm lingers for 17 hours, how much rain will accumulate?
17hrs * 0.75 cm/hr
= 12.75 cm of rain
A channel of partially charged air.
What are the similarities and differences of how a cold front creates thunderstorms compared to how a warm front would?
Cold- Rapid uplift creates towering cumulonimbus, intense thunderstorm with concentrated precipitation
Warm- Gentle lifting creates wide spread stratus clouds that produce gentle and wide spread rain. Mild Thunderstorm
It is an extended period of well-below-average rainfall, usually caused by shifts in global wind patterns
What is the definition for Return Stroke?
A branched channel of positively charged particles.