Ch 18 - Fronts And Frontal Depressions Flashcards
Frontogenesis
The formation of a front
Frontolysis
Dissipation of a front
Front
Narrow area where a front is passing through that covers a few miles
Transitional Zone
An area where a front is moving though can be 100’s of miles - ITCZ
Quasi-Stationary Front
Very little movement (5kt)
Flowing parallel to the friction layer
Could interact with the surface and create clouds, SHRA and DZ
Usually there is no weather but depends on the level of instability
Can be around for long periods of time
Polar Font
Where the polar air and the warmer Ferrell masses meet at ~50 degrees N/S
Tropical maritime and polar maritime
Always there
Circumnavigated the globe
Mediterranean Front
Usually occurs in winter
Where the is low pressure moving from east to west
Can be strengthened by the wind coming off the N. African coast
Because the ocean temp is higher than the land, there is low pressure on the sea, strong wind coming off the land which can lead to MEDICONES - storms along the front
Usually has increment weather
In the summer, the ITCZ moves north and brings with it high pressure - Med Weather
ITCZ
The intertropical convergence zone (the heat equator)
A transitional area over a very large area
Is the meeting of air masses that causes the trade winds (a low pressure belt)
North in summer and further south in winter
Can bring with it intense TS and TRS that go up to 45,000ft
It moves
Polar Front Examples
Between 40-60 degrees north and south
Summer it can be found over new found land or Norway and north Scotland
In winter it moves down towards Florida or the SW UK
A Polar Front depression
Forms at the polar front when the sub tropical warm air starts to mix with the cooler polar air
Starts as a disturbance and forms into a wedge shaped depression
(Westerly waves also known as the westerly situation + travelling lows)
Comprised of a Warm front, Warm sector and a cold front
Warm Front
Polar air in front with tropical air behind
Can bring with it frontal fog
Ci seen first, slowly gets worse and worse until a NS
May see Virga
Will have Ra and decreasing vis as it passes
Spans over 6/700nm with speeds of 2/3 of the 2000ft wind
1:150 slope
Warm Sector
Can have ST, FWX CU low level cloud with little vertical development
Usually no RA
Can have DZ, -RA and Fog in winter
If cT: little cloud development with clear good WX
Cold Front
Has a cold nose
Possible TS
CU CB EMB CB NS AS
Gusts as it approaches, RA
1:50
50/100nm
Travels at 100% of the 2000ft wind
SPD and Direction of a polar front depression
Isobars extended out from the warm sector will show you the direction
Speed can be determined by using the geostrophic wind scale in the corner
Depression Hazards: Warm Front
FzRA Low cloud Icing in cloud Poor Vis. Cloud/RA/FG Aquaplaning on RW CAT around jet stream