Geography: Tropical Cyclone and Warm Air Essay

Submitted By dglause2
Words: 718
Pages: 3

Ch. 7 Atmospheric Disturbances
Air Masses
• “air mass”
a homogeneous body of air that takes on and retains the characteristics of the surface over which it formed
• Characteristics o Large (diameter > 1600 km) o Uniform horizontal properties o Recognizable entity; travels as one
• Classification o Lowercase letter indicates moisture content
 c = continental, dry
 m = maritime, humid o uppercase letter indicates source region
 P = polar source region
 T = tropical
 A = arctic
 E = equatorial
• Types o Continental Polar (cP) o Continental Tropical (cT) o Maritime Polar (mP) o Maritime Tropical (mT)
• Clash over midlatitudes between polar and tropical air masses o *especially cP and mT
• “front”
the leading edge of an air mass
• Weather changes behind front o Temperature o Winds o Pressure o Ex: behind a cold front
 Temperature decrease
 Wind direction change
 Air pressure increase
• Primary frontal types o 1. Cold front
 Cold air advancing
 Protruding “nose” of cold air
 Lift warm air ahead of cold fronts
 *fastest moving o 2. Warm front
 Warm air advancing
 Gentle slope of warm air rising above cool air
 Slow cloud formation and precipitation o 3. Stationary front
 No advance of air masses o 4. Occluded front
 Cold front catches and overtakes warm front, removing the energy (warm air) of the storm
 Occlusions mark the end of the cyclone’s life
Midlatitude Cyclones
• Exist between 35-70 degrees latitude
• Roughly 1600 km in size
• Central pressure near 990 to 1000 mb
• Circulation creates fronts
• Occurrence and distribution o Typically 6-15 cyclones exist, at any given point in time, worldwide o More numerous and better developed in winter than in summer o Move more Equatorward during summer
• Life cycle of a cyclone – cyclogenesis (beginning) to occlusion (end)
Midlatitude Anticyclones
• Anticyclones o Subsiding, diverging winds at the surface o Move slightly slower than cyclones
• Relationship to cyclones o Occur independently, but have a functional relationship o Follows a cyclone o Typically reside behind cyclone’s cold front
• Stages leading to a hurricane o 1. Easterly wave
 Oriented N-S
 Little cyclonic circulation
 Convergence behind wave, divergence ahead of wave
 Minor tropical disturbance responsible for thunderstorms in the tropics o 2. Tropical cyclone/disturbance o 3. Tropical depression
 Low reaches Earth’s surface
 Winds < 38 mph o 4. Tropical storm
 Winds 38-74 mph
 *the stage when the hurricane is named o 5. Hurricane
 Winds > 74 mph
• Origin o Over warm water o A few degrees north or south of Equator o Late summer/early fall
• Characteristics o Prominent low pressure center, winds spiral inward o Steep pressure gradient and strong winds o Warm moist air enters storm to form rain and release latent heat o Eye wall and eye o Anticyclonic winds aloft, divergence aloft
• Movement o Irregular tracks within the flow of the trade winds o Typically begin moving east-west, some