Meteorology Ch 12

Cyclogenesis: the development of a cyclone

  • Explosive cyclogenesis Bombing - central pressure falls more than 24 mb in 24 hours

types of cyclones

tropical cyclones - occur between 0-30 degrees lattitudes

  • warm cores

Extra tropical

  • cold cores

  • betweem 30 and 60 degrees

  • As hurricanes move more north they become more extra tropical

    Hurricane Sandy

  • had the largest TC diameter on record

  • more on the synoptic scale

how is a mid lattitude cyclone formed

  • parallel winds going in opposite directions

  • open wave - precipitation is more impactful

  • mature - strongest part of the hurricane

  • advance collusion - colluded front means the cyclone is dying

  • cut off cyclone

Source regions for extra tropical cyclone

Leeward side of Rocky Mountains

  • Alberta Clipper (affect ND the most)

  • Colorado low (affect ND the most)

  • cyclones spin faster coming off the mountains

Nor’easter

  • when winds come from the northeast they thought the wind would pick up and weather would get worse

  • brings heavy snow

  • cause damage along the beach

Mid lattidude Cyclone

  • mT behind warm front

  • cP behind cold front

  • mP in front of warm front

  • Sleet in front of warm front

  • east winds in front of warm front

  • storms in front of cold front

  • blizzard in the wrap around area

  • Isobars are the tightest at the wrap around area

Parameters that determine a cyclones strenght

temperature -

  • warming the air can contribute to a decrease in surface air pressure (strengthening)

  • cooling the air can contribute to an increase in surface air pressure (weakening)

Moisture

  • more moisture (strengthening)

  • less moisture (weakening)

low pressure system

  • surface level convergence = upper level divergence

  • the system is nor weakening or strengthening

  • the pressure will remain constant

surface level convergence > upper level divergence

  • the pressure of the column is increasing

  • the system is weakening

  • no longer a low

  • the pressure is getting higher

surface level convergence < upper level divergence

  • the pressure of the column is decreasing

  • the system is strengthening

  • the low is getting lower

vertical structure

  • downstream of a trough is upper level divergence

  • upstream of a trough is upper level convergence (the surface low and high happen under these areas)

  • cyclone tilts westward with height (know this)

The occluded cyclone

  • at the occlusion stage, the cyclone has reached its maxmum intensity

  • upper level low has a closed circulation

  • no upper level divergence

  • low begins to fill (filling in the low)

Jet Streams

  • they will strengthen cyclones

Jet streaks

  • left entrance, right exit

  • look at 200/250/300 mb maps

  • four quadrant jet theory

  • upper level divergence, right entrance, left exit

  • upper level convergence, left entrance, right exit

  • tilt your head to the right, upper level divergence

  • tilt your head to the left, upper level convergence

four quadrants of a jet stream

CD

DC