BFB Mid-latitude Cyclones By Rick Garuckas and Andrew Calvi

Role of Mid-latitude Cyclones Reduce temperature gradients/baroclinicity. Convert potential energy to kinetic energy 1. Although these processes bring the atmosphere closer to a balanced state, a perfectly balanced state is never achieved.

The Location of Mid-latitude Cyclones Around the World (Northern Hemisphere) Most frequently track across eastern North America, the north Atlantic, near Japan, and across the North Pacific. (Lackmann 2012) (Southern Hemisphere) More continuous storm track due to less landmasses which reduce topography ( Lackmann 2012)

Locations Relative to the USA. Form most frequently in three places Lee Side of the Rocky Mountains, off the East Coast, and along the Gulf Coast. Can also form in Southwest Canada. 1. Alberta Clippers.

Map of Most Common Cyclone Tracks

Formation of Mid-Latitude Cyclones Near Surface Features: Typically form along a frontal boundary such as a cold front or stationary front. these boundaries have preexisting cyclonic vorticity and convergence Q: What is vorticity??? A: spin about an axis!!!

Formation of Mid-Latitude Cyclones Cont. Upper-Level Features: Divergence in the jet steam pattern. 1) this is where the winds are diffluent in the upper levels. 2) helps to increase the convergence at the surface. Q: Where does upper-level divergence occur? A: Generally on the east side of a trough in the jet stream.

Map of Surface and Upper Level Formation

500 MB map( heights, vorticity) Any guess where a surface area of low pressure might develop?

Structure of Mid-Latitude Cyclones Cold-core systems. Strengthen with height. Thermally direct Circulation. Generally larger than tropical systems. Contain frontal boundaries, sometimes large boundaries. Intense mid-latitude cyclones can contain dry slots. (Reak havoc for the forecaster.) Tend to have tight pressure gradients. Can sometimes transfer into tropical systems if they linger over tropical regions long enough.( rare) Adiabatic cooling.

Textbook Mid-Latitude Cyclone

Famous Mid Latitude Cyclones 29-30 October 2011 Historic early season snowfall for Eastern New York and New England. Partially foliated trees lead to extensive damage and power outages. Adiabatic cooling underdone by the models.

Famous Mid Latitude Cyclones con’t 23-27 Oct 2010 Strongest non-tropical storm in USA ever recorded at 953 mb. Significant severe weather outbreak in IN, IL, MI, OH. Pulled dry air down from the stratosphere.

Famous Mid Latitude Cyclones con’t 12-15 March 1993 Produced widespread heavy snowfall( Syracuse , NY 43 in. Mobile , AL 3 in. Affected two-thirds of the country. Produced an extreme-damaging squall line of storms in Florida.