Mid-latitude cyclone

Whatis a mid-latitude cyclone?

-Themid-latitude cyclone is a synoptic range low push system that has cyclonic(counter-clockwise in north hemisphere) circulation that is discovered in the middlelatitudes (i.e., 30�N-55�N)


o Tbelow is a place (tropics vs.mid-latitudes) and also size distinction in between hurricane and also mid-latitude cyclone

�Typicaldimension of mid-latitude cyclone = 1500-5000km in diameter

�Typicalsize of a hurricane or tropical storm = 200-1000kilometres in diameter

Here is a snapshot of a typical mid-latitudecyclone and also hurricane. Notice the dimension difference.

You are watching: When an upper-level low lies directly above a surface low:


How does the mid-latitudecyclone form (for a much longer summary read pages 219-228)

1.Frompolar front concept, we recognize that in the mid-latitudes tright here is a boundary betweencold dry (cP) air to the north and warmth moist (mT) air to the south

2.Alongthis boundary a counter-clockwise circulation have the right to set up at the surconfront, whichacts to take warmth air up from the south and cold air dvery own from the north. Thisis called cyclogenesis.

3.Inthe facility of this circulation, tright here is mass convergence (all the air isrelocating in towards the facility of the circulation much favor as soon as you make a whirl-poolin a pool, all the leaves and stuff floating around moves toward the center).When all that air hits the center, we have rising motion because it has nowhereelse to go.

4.Ifthe upper levels are favorable for cyclone advancement, then tbelow is a regionof divergence aloft above the developing Low-pressure facility. This will certainly helppull the air that is converging at the surface upward and also proceed to construct thesurchallenge cyclone. (The upper levels also steer the device and make it progresseast (prefer we learned earlier)).

a.Ifthe upper levels aren�t favorable for cyclone advancement, the cyclone won�tgrow and also the mass convergence into the Low at the surconfront will simply pile up andfill in the Low and it will degeneration.

b.Referto the second figure below for the optimal instance.

5.Ifthe upper levels are favorable, then the mid-latitude cyclone will continue todevelop and lug up mT air in the heat sector and lug down cP air in thecold sector.

a.ThemT air rises as it moves out ahead of the low helping to deepen the Lowpressure facility to the east and assist it move along

b.ThecP air sinks behind the system and also fills in the Low on the backside alsohelping to relocate the device along

i.Itis this carry of power that both strengthens and also propaentrances themid-latitude cyclone!

6.Oncethe mid-latitude cyclone is completely arisen, well-identified fronts show up.

7.Asthe mid-latitude cyclone reaches maturity, the central press will certainly be at itslowest and also the occluded front will start to create (as the cold front catches upto the warmth front).

8.Oncethe mechanism is occluded (all the heat air is above the cold air) the mass convergenceacts to fill in the Low and therefore the press rises in the Low and thedevice decays.

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Evolution of a mid-latitude cyclone. Each figureadheres to the summary over 1-8



Theabove numbers were taken from www.u.arizona.edu/~korine/230/chap10_figs.htm


Diagram of circulation (circulation) throughout thedepth of the troposphere


Whereperform mid-latitude cyclones commonly form (in North America in winter)? (Remember that cycloneschoose to develop along air mass boundaries)

-Leeside of the Rockies = Lee Cyclones

o Alberta Clippers

�FASTMOVING and normally don�t have as well a lot precip connected through them because theyare much from a moisture source


�IntenseLow, with solid warm air advection in the heat sector, very cold temps in thecold sector. If tright here is most gulf moisture to occupational with, they tbelow istypically sleet, freezing rain and also rain connected with the warmth front, solid thunderstormsalengthy the southerly edge of the cold front and scurrently along the backside and tothe NW of the Low (even BLIZZARDS)

-Alongthe East Coast

o Gulf Low

�Formalong the southerly coast wbelow tbelow is a thermal boundary in between the warmsea and cool land also. Generally have actually many precip linked with them because theyare so close to the ocean

oHatterasLow and Nor�easters (aka ��bomb�cyclones)

�Theseare the MOST INTENSE units and also they form alengthy the thermal boundary betweenthe warmth Gulf Stream and the cold Atlantic coastline. They deserve to carry flooding rainsalong the coast and a number of feet of snow additionally inland as they use the oceanas a substantial resource of the moisture. These also build very conveniently and also sometimeshave push drops of 24mb in a solitary day. With a pressure drop of thismagnitude you deserve to imagine how rapid the winds are approximately these things.

What are their typical tracks? See diagrambelow


Precip patterns (and types),winds, temperatures, fronts, upper level flow and also clouds that are about a typicalmid-latitude cyclone in winter.